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What criteria should be evaluated in assessing the comparative
advantages and disadvantages of different renewable energy
types within the EU?
How should these factors influence energy policy and energy
mix across the EU?
What role does increased energy efficiency have to offer?
1. Introduction
Climate change is an increasing concern globally; the recent acceleration in the
process has been unequivocally attributed to human activity on Earth.
Climate change is defined as variations in the mean properties of the
environment that are sustained over a long period of time, minimally decades. It
is principally attributed to an increase in greenhouse gas levels, which include
carbon dioxide (CO2), methane, nitrogen dioxide (NO2) and ozone, in the
atmosphere as they have a ‘warming effect’ on the planet. Also, particulates and
soot in the air absorb infrared radiation from the Sun, heating the atmosphere to
cause further global warming.
Two major human activities resulting in this warming effect are the burning of
fossil fuels and deforestation. Firstly, burning fossil fuels (oil, coal and gas)
release greenhouse gases. Furthermore, these dirty resources release
particulates, especially coal, which adds to the issue. Secondly, deforestation or a
change in land use means that there are fewer trees to absorb CO2, reducing
natural sequestration and therefore, when combusted, more is released into the
atmosphere. The production of palm oil is a big issue as large amounts of the
jungle are being chopped down. It is a renewable energy source but the way it is
handled means that there is little or no reforestation and trees are burned
without thought of the CO2 released in the process.
Figures show that, by the end of the 21st century, the planet’s average
temperature will have increased by 4 OC if the Earth continues to heat up at the
current rate. This would have catastrophic environmental effects, causing
extreme weather conditions across the world, such as major flooding, hurricanes
and droughts. This problem has been recognised globally, as shown by the
United Nations Conference of Parties (COP): an annual event that will be held in
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Paris towards the end of 2015. This will be the 21st meeting of its kind and aims
to achieve “a universal, legally binding agreement that will enable us to combat
climate change effectively and boost the transition towards resilient, low-carbon
societies and economies1.1”.
Generally, it has been recognised that energy generation and consumption needs
to move away from fossil fuels and to alternative, cleaner sources. Many
technologies have been developed in an attempt to address/solve this problem,
using renewable sources.
The European Union (EU) has already taken steps towards cleaner power,
utilising its diverse environment and resources in five main areas: wind, solar,
hydro, geothermal and biomass. In the EU, 2013, 24.3% of primary energy
production – the amount of useable energy that can be extracted from a resource
- and 15% of gross final consumption – the amount of energy consumed by the
EU’s member states - came from renewable resources1.2. The EU has set a target
that would result in gross final consumption due to renewable sources increase
to 20% by 2020.
Technology is being continuously developed to utilise renewable power sources
to their full potential. It is important to understand that the ability for humans to
generate power from renewable resources isn’t a new concept – burning wood
to heat a room isn’t revolutionary – however the current technologies aren’t
efficient enough at generating power to meet the population’s demand, both in
terms of energy and cost. There are two components to energy productivity:
efficiency and capacity (load) factor. Efficiency is the amount of electrical energy
produced from the mechanical energy put in to a system – it is a case of output
versus input. Capacity factor is how much time a system will spend in operation
per year. It is a measure of the intermittency of a resource; this is most relevant
when the resource can’t be stored, like in wind and solar power. Cost efficiency is
a balance between the price of the energy generated for installation, operation
and maintenance (O&M) of the machinery, plus the added cost of fuel in some
cases, and the price at which the energy produced can be sold at, including any
government funding i.e. grants and feed-in tariffs.
Generally, the prices paid for renewable energy are dropping as the market
becomes more competitive. However, when considering different types of
renewable energy, particularly with regards to cost efficiency, it is important to
remember the variable landscape in different countries across the EU, both
politically and geographically. For example, solar energy will be a much more
viable resource in the south of Spain compared to the United Kingdom (UK) due
to levels of irradiation.
This will affect the energy mix of a country, varied by resources available. Whilst
the move towards renewable energy is occurring, there is still a call for fossil
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fuels when there aren’t sufficient resources available. For example, in the UK,
wind is a good source of energy but is intermittent, so needs to be paired with
another fuel source to be sufficient. This is often gas; it makes economic sense in
the UK, as there are large volumes of it in the North Sea and is a transitional fuel
from fossil fuels to renewable. This is because it has a higher power output for a
lower amount of carbon emission.
Further factors to consider are the effect this will have on government policies,
social impacts and the impact this will have on the other power industries,
namely fossil fuel and nuclear plants.
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2.1. Wind
Wind power is the conversion of the air’s kinetic energy (wind) to electrical or
mechanical power. This has been done for centuries – using sails to power ships
is a prime example.
The development of modern technology has seen the utilisation of wind turbines
to produce electricity. There are two types of wind farms – onshore and offshore
– and each have certain advantages and disadvantages compared to the other. In
February 2015, there was approximately 120.6 GW of onshore wind energy
installed and just over 8 GW offshore throughout the EU 2.1.1.
There are four main parts to a turbine. The blades capture the wind’s energy,
which spins a generator inside the nacelle. The nacelle also houses the gearbox –
this is used to change the rotational speed of the blades to the speed of the
generator (around 1500 rpm). The tower and base stabilise the structure and
contain conductors to transfer the generated electricity for use. A typical turbine
is approximately 150 to 200 feet tall but their height has increased over the past
few years and continues to grow. The estimated lifetime for a turbine is 20 years
– lifetime means the period before any major overhaul work is required;
however, maintenance is done over this time.
It is obvious from the table that offshore wind is much more expensive than
onshore wind with only a slightly higher capacity factor. However, there are
other advantages of offshore wind, which come under social and environmental
impacts.
Figure 1: A diagram showing the different parts of a standard wind turbine 2.1.2
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ONSHORE OFFSHORE
INSTALLATION COSTS (€/kW) 1450 3600 - 4000
O&M (€/kWh) 0.01 - 0.02 0.02 - 0.04
FUEL COSTS (€/kWh) 0 0
CAPACITY FACTOR (%) 30 - 45 40 - 50
EFFICIENCY (%) 2.1.4 45 45
Over a turbine’s lifetime, installation costs amount to around 75% of the overall
costs. Approximately 75% of this is due to purchasing and constructing the
turbine; the rest due to various components including grid connection,
foundation and land rent 2.1.5.
Much of the remaining costs are through O&M. These are due to a variety of
components including insurance, regular maintenance, repair, spare parts and
administration. This is a major issue for offshore wind as they require more
attention (due to erosion from the sea) and access/transport of parts to the
stations is much harder and more costly, and downtime is generally greater as a
result.
The share of costs due to O&M is only 10% to 15% for a newly installed turbine
but increase to between 20% and 35% towards the end of its lifetime 2.1.6.
However, it is very difficult to predict accurately the O&M costs over the lifetime
of a turbine as there are very few that have lived their expected lifetime of 20
years, due to the relative youth of the industry. The rotor blades on wind
turbines have increased in diameter over time, which has led to an increase in
the power output. This has led to a decrease in the O&M costs per kWh for newer
turbines, as shown in Figure 2 below.
Table 1: A table showing the various costs associated with onshore and
onshore wind energy, alongside the capacity factor and efficiency 2.1.3
Graph 1: A graph showing a breakdown of the O&M costs for wind
turbines, depending on their age and expected power output 2.1.7
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A further point to consider is that, in theory, it doesn’t require any fuel – wind is
the source of the energy and is converted straight to electrical energy by the
generator. I say in theory because, in reality, the wind blows intermittently.
To counteract this issue, wind farms are often built around existing natural gas
stations so that, when the wind isn’t producing power, it can pick up on any
deficit in generating capacity or can be used to rotate the turbines (rotating
reserves). This solution reduces wind’s green credentials as CO2 is released in
the process.
This isn’t ideal in the long run if we are to move towards a completely green
energy system and so the future of wind energy relies on the development of
batteries. Currently, large amounts of power can’t be stored for long periods of
time, hence the low capacity factor of wind power. Another option is the use of
compressed air energy storage. Air is pumped in to a high-pressure chamber for
storage and released when required. However, this takes power to pump the air
into the chamber so reduces the efficiency of wind. This is probably a temporary
solution until such time as battery technology is developed sufficiently.
At this point, the capacity factor of wind farms becomes important to consider.
The average turbine begins to generate electricity at wind speeds of 3.5 m/s, has
a maximum output at speeds higher than 14 m/s until it must be shut down at 25
m/s 2.1.8. So, there is only a window ranging 11 m/s where the turbines will
function at maximum output. Capacity factor varies greatly from country to
country, depending on the average wind speed.
Efficiency is related to the capacity factor as it shows how effective a piece of
technology is at producing as close to maximum output as possible. In wind
power, it is affected by how much kinetic energy can be converted to electrical
energy whilst obeying the law of mass conservation – the same mass of air that
enters the turbine must exit it. However, as the fuel is free, efficiency is of less
concern.
Finally on wind, I will discuss the social and environmental impacts. This point,
while less directly related to cost efficiency, is still relevant as it impacts
government policy, government funding and planning regulations. There is also a
certain level of opinion making involved.
The two major social impacts are noise pollution and visual effects. To build a
wind farm requires a lot of land – just one blade of a turbine is 30 metres or
longer. So, they have to be put in isolated areas: in most cases, the countryside.
This is generally unpopular as it affects the view of the landscape, which is not
only a problem for the locals but also the country’s tourism. Also, turbines are
very noisy and so the problem is increased. Health problems can occur due to the
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flicker caused by a setting sun behind a rotating turbine: a particular issue if a
local in the nearby community has a health difficulty like epilepsy. These issues
have sparked many local debates and companies have struggled to gain planning
permission because of this. Offshore wind solves this issue but has other
separate issues of its own.
Furthermore, the fact that building these large, land-consuming structures can
affect the local ecosystems and also are a danger to birds, particularly during
migration season. These factors are more of a consideration when choosing the
location of the wind farms and can cause problems when obtaining planning
permission.
Whenever considering environmental impacts, the carbon footprint that the
industry leaves is hugely relevant. Wind has one of the lowest carbon footprints
of ‘low carbon’ technology, second only to nuclear; however, with nuclear, the
waste product is a major biohazard. Onshore and offshore wind systems both
emit around 5 g of CO2 per kWh, with offshore having a slightly larger carbon
footprint. 98% of this emission comes from construction – producing steel to
build the tower, concrete for foundations and fibreglass for the blades, not to
mention the emissions produced by vehicles transporting the parts to the site.
The remaining 2% comes from regular maintenance 2.1.9.
These considerations don’t account for rotating reserves, which releases a large
volume of CO2, rendering the plant carbon positive. Also, it doesn’t consider the
transmission of the produced electricity from sites – a major issue in offshore
wind. In isolated areas, transmission lines haven’t been designed to large
currents so there is also the problem of efficiency here too.
Wind is a useful source of energy, particularly for countries like the UK where it
is in abundance. In 2014, wind contributed 9.3% of the UK’s electricity
requirements 2.1.10. However, there are many problems surrounding
intermittency and transmission that need to be addressed to unleash its full
potential.
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2.2. Solar
Solar poweris the use of radiation from the Sun (light and heat) to generate electricity;
this can be done passively or actively.
Passive solar poweris when something is designed in a specific way to utilise the Sun’s
energy without any mechanical or electrical equipment. For example, in hot countries,
houses are painted white because the colourreflects electromagnetic waves (radiation)
so acts as a natural coolant.
Much of the time, passive solar power is insufficient when used alone. So, technologies
have been developed to generate power directly fromsunlight using mechanical or
electrical equipment. This is activesolar power. An example of this is solar panels on the
roof of a house; they generate and supply electricity,whichis fed back into the grid.
There are twomain methods of generating utility-scale power using solar: photovoltaic
(PV)systems and concentrated solar power(CSP). PVsystems can be used on either a
residential (solar panels on house roofs) or industrial scale.
PhotovoltaicSystems
PVsystems can be found in the formof solar farms – huge numbers of PVpanels in an
array – or as individual panels on house roofs. In either circumstance, they work in the
same way.Solar panels are normally used to generate electricity forhomes but the
power produced can be sold back to the grid. In the UK, there is a feed-in tariff scheme
to help promote the use of roofedsolar panels in an effortto move towards EU’s goal of
20% renewable energy generation by 2020. A lifetime of a typicalPV panel – meaning
they willproduce at least 80% of their peak output - is 20 to 25 years 2.2.1.
PVsystems have three main components. The solar cell is the area that collects the
sunlight and convertsits energy to electricity;they are normally made out of the
common semi-conductor silicon. The electricity produced is a direct current (DC) and
must be converted to alternating current (AC) for use in the grid by an inverter. The
utility meter measures how much power is used in the process and how much power
has been generated before it is fed into the grid. There can be additional components
like a fuse box and/or a battery. The fuse box allowsthe electricity to be generated
directly to the house (in the case of roofed solar panels) and the battery is used to store
energy to be utilised when the PV cells stop generating power i.e. when it is dark.
The PV cells have been designed to generate electricity fromlight that has been
refracted off particulates in the atmosphere so will still function when it is overcast.
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PV
INSTALLATION COSTS (€/kW) 3200 - 4500
O&M (€/kWh) 2.2.5 0.005 – 0.006
FUEL COSTS (€/kWh) 0
CAPACITY FACTOR (%) 2.2.6 21
EFFICIENCY (%) 8 - 9
The installation cost coversa number of different areas including installation and
development, electricalhardware, the racking and mounting of the PVcells and the
purchase of the inverter. This cost varies fromcountry tocountry, depending
predominantly on the manufacturing costs and incentive levels (i.e. feed-in tariffs).
The range of values in the installation cost is due to the purchasing of PV panels. On an
individual basis, the panels will cost a lot more than if bought in bulk due to the
economy of scale and standardisation. So, it is cheaper to install a large solar farm of 500
panels compared to putting six on your roof.
To drive prices of solar panels further down,the Chinese government unfairly
subsidised manufactures so they couldsell their products in the European market,
knocking off European competitors, whocouldn’t compete withthe low prices. This is
called dumping – a predatory pricing where manufacturers sell products in another
country at a price lower than the price sold by home-grown companies. The EU
introduced an anti-dumping tax to prevent this happening, whichhas led to a shortage
in panels as the prices rose again and Chinese manufacturers are less inclined to sell in
Figure 3: The difference between a cell, module
and array in PV systems 2.2.2
Figure 4: An image of a PV array 2.2.3
Table 2: A table showing the costs, efficiency and capacity
factor of utility-scale PV systems, built using thin-film
amorphous silicon 2.2.4
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Europe. But, it does prevent international companies having an unfair advantage and
means that wewould be relying on foreign manufacturers forsolar energy supply.
PVsystems require very little maintenance. The panels need cleaning from time to time
to ensure they workefficiently,regular inspections are required to checkfor faulty cells
and the inverter may need fixing/replacing. These are all fixed O&M costs – the variable
costs actually accountforless than 5% of the overall O&M costs.
Like wind, the fuel for solar is free – it is sunlight – so the factthat the efficiency is so low
is less important; however, this is one area that solar power couldcertainly be improved
upon. The statistics shown are the average but a panel’s efficiency actually decreases
throughout its lifetime by about 1% a year. A major issue is due to PV panels heating up
– forevery 1OC temperature increase, efficiency decreases by about 0.5%.
For PVsystems, the capacity factoris calculatedby dividing the number of hours per day
of peak sun by 24 (hours in a day) 2.2.7. This throwsup a number of variables: the time of
the year and the direction the panel is facing being the twomain ones. So, 21% is a very
rough estimate – a fixed array can reach a capacity factorof greater than 35%.
The use of a tracking system willboost efficiency/capacity factor.Thisenables the
panels to follow the Sun’s trajectory,meaning that maximum light willbe received.
However,as this needs moving parts, the costs increase, particularly O&M.
PVpanels are seen as the future of renewable energy in the EU as it is a fairly
inexpensive method forresidents to generate energy fromtheir house. However,it is
not as ‘green’ as many people would believe. Yes, once the systems are in place, it
produces electricity from sunlight but, in the constructionprocess, there are major
environmental impacts. The purificationof silicon foruse in PVcells releases waste
chemicals, like aluminium and carbon, and the process is energy intensive 2.2.8.
The social impacts of solar power are similar to those of wind – they can take up a lot of
land and can be an eyesore. Solar farms are required for utility-scale power– not
enough energy is generated from roof-based for transmission levelgeneration – but this
takes up a lot of land, whichcan often affectagriculture. A balance must be found when
building the farms between accessibility, isolation and proximity of demand.
ConcentratedSolarPower
CSP is important to produce electricity and thermal energy foruse in heating systems.
CSP systems come in four varieties: parabolic troughs, solar towers, parabolic dishes
and linear Fresnel reflectors.Currently, the parabolic trough dominates the CSP
landscape, with 80% of all systems in operation or under development coming from this
technology.
The general idea behind CSP is that an array of mirrors is set up to focusthe sunlight
onto a receiver. Water is heated, as in a normal power plant, and converted to steam,
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whichrotates turbines to generate electricity.Due to the need for a high intensity of
sunlight required, many of these systems (certainly the largest) are found in deserts.
Unlike most PV systems, CSP uses thermal energy to generate electricity.High
temperature collectors also use these systems and transfer heat energy for use in
industrial processes that require high temperatures.
There are low and medium temperature collectorsin the same system that transfer heat
energy to heating systems for houses. They use flat plates that absorb the sunlight.
Within these flat plates, there is a heat-transport fluid to remove heat energy fromthe
absorber and to transfer it to an insulated tank.
The Linear Fresnel Reflectoruses long thin mirrors to reflect light (up to 30 times its
normal intensity) onto an absorber, which transfers the energy to a thermal fluid foruse
in steam generators.
The parabolic dish uses 3D parabolic mirrors to reflect and focus sunlight onto a power
conversion unit.
The parabolic trough is similar to the parabolic dish in method, but is parabolic-shaped
in 2 dimensions and linear in the third. Sunlight is reflected onto an absorber tube.
A solar towerconsists of an array of flat mirrors (heliostats) that focusthe sunlight onto
a receiver at the top of a central tower.
Figure 5: An image of a Linear Fresnel Reflector
with one absorber 2.2.9 Figure 6: An image of a parabolic
dish 2.2.10
Figure 7: An image of a parabolic trough 2.2.11 Figure 8: An image of a solar tower 2.2.12
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The only country in the EU to have multiple operating CSP plants is Spain with 850 in
20112.2.13. So, it is very difficultto compare each of the factorswhen considering CSP
systems across the EU.However,this very factemphasizes that different mixes of
technology will be appropriate fordifferent areas/geographies.
The table below shows the range of values forCSP, based on parabolic troughs and solar
power towersystems*.
The range of values for installation costs is due to the different types of CSP. The most
abundant type – parabolic troughs – costs €4100/kW, whichis the cheapest of the four.
However,they also have the lowest efficiency (aslow as 15%) because the technique
heats the receiver to a comparatively low temperature. A more efficient method is the
use of solar power towers.Currently, there are only a few commercial solar power
towers in operation in the EU – all based in Spain. This is because the installation costs
are greater (between €6000/kW and €9500/kW) and they use large amounts of land –
2 square miles per tower.
The increase in costis largely due to how much storage is implemented; this can be
between 6 and 15 hours. These thermal energy storage systems are made possible by
the use of specific thermal fluids, namely molten salt and synthetic oils. They limit the
length of time energy can be stored. There is also the potential for power tobe stored as
electricity but, like wind, battery technology is not yetdeveloped enough for this to be a
viable option.
The benefit of storage is an increase in capacity factor;at 15 hours of storage, solar
power towersystems can reach a capacity factorof 80%. It is possible to integrate up to
6 hours of storage into parabolic trough systems but this isn’t cost effective – it can cost
between €6400/kW and €8900/kW fora capacity factorof up to 53%.
* Linear Fresnel reflectors and parabolic dishes currently don’t exist on a utility-
scale but can be used in conjunction with PV systems.
CSP
INSTALLATION COSTS (€/kW) 4100 - 9500
O&M (€/kWh) 0.02 - 0.03
FUEL COSTS (€/kWh) 0
CAPACITY FACTOR (%) 20 - 80
EFFICIENCY (%) 2.2.15 15 - 30
Table 3: A table showing the costs, efficiency and capacity
factors 2.2.14
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Tracking systems are common amongst CSP systems, which further improves the
capacity factor.Heliostats often track the sun’s trajectory to maximise the amount of
light received.
Parabolic troughs are normally built on a north-south axis and rotate with the sun from
east to west. Sometimes, troughs are orientated in an east-west direction because then
they only need to be rotated by seasons, requiring less moving parts and thus lowering
the installation and O&M costs but also decreasing the capacity factor.
The O&M costs for CSP are relatively high but are expected to fall as technology
develops. Mirrors require regular attention – they must be cleaned on a regular basis to
ensure they operate at maximum efficiency and routine checksare needed to ensure
there is nothing broken. CSP systems require a large amount of land and areas with a lot
of sunlight and very little cover.Deserts are an ideal place for this but are isolated,
whichincreases the O&M due to the need fortransport. Also, deserts are dusty and
prone to sandstorms; there is the potential formirrors to be covered by large volumes
of sand.
So, in reality, deserts aren’t as ideal as they first seem; however, they do solvethe social
issues that are commonamongst renewable energy – the fact that they blockthe view
and ruin the landscape. CSP systems can actually cause health issues in local
communities because the glare fromthe mirrors can be blinding – they can reflectup to
30 times the intensity of sunlight on the receivers.
Space-based solar poweris another thing to consider forthe future – it removes limiting
factorslike cloudcoverand atmospheric interference and can provide power all year
round by ensuring the satellite has a geostationary orbit. The difficulty withthis form of
power is transferring the energy back on to Earth for use but there is research being
done in an attempt to find a wireless method of transmission.
Solar poweris unique in the factthat it is readily available on both a residential and
industrial scale. Currently, PVpanels are the most accessible formof power forthe
general public to power their ownhomes. It will be important to have a mix of industrial
and residential power for the EU’s energy mix and solar power is leading the way on
that front. However,its productivity level is low and there is no way to store a lot of
thermal energy for a long period of time. Battery development is onceagain essential for
the prolonged success of this formof power.
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2.3. Hydro
Hydropoweris the conversion of the kinetic energy from flowing/falling waterinto
electrical/mechanical energy. Again, this isn’t a new concept – watermills have used this
technique to grind wheat into floursince Imperial Rome.
Hydropowercan be split into a number of categories: conventional, run-of-the-river,
conduit and pumped-storage hydroelectricity.
Conventional hydropower is done through the use of dams to store water foruse. The
benefit of this approach is that the plant can generate electricity more flexibly;the fuel is
readily available.
Run-of-the-riverhydropower captures the kinetic energy of natural streams or rivers
without the use of reservoirs and dams.
Conduit hydropoweruses water systems that have been diverted foruse elsewhere e.g.
as a man-made canal.
Pumped-storage hydropowerpumps water uphill to store in reservoirs. This will
increase the flexibility of the plant but requires power to movethe water.
All of these use the same concept;moving water rotates a turbine, which drives a
generator to produce electricity.The difference between each technique is the source. In
a system involving a hydroelectric dam, water is stored in a reservoir until needed. At
this point gates are opened and water flowsthrough the penstock to rotate the turbine.
There are also small and micro hydroelectric systems, whichcan be used on a
residential basis.
Using basic physics principles, the amount of power available in moving water can be
calculated using the equation , where P is the power (Watts), is the density
of water (kg m-3), Q is the flow rate (m3 s-1), g is the gravitational acceleration (9.8 m s-2)
and h is the verticalheight difference between the inlet and outlet (m) 2.3.1.This assumes
there is 100% efficiency,whichis never the case so the actual power output is calculated
by multiplying the final value by an efficiency factor – a number between 0 and 1 –,
whichvaries depending on the efficiency of the turbines.
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SMALL LARGE
INSTALLATION COSTS (€/kW) 950 - 7000 1200 - 7200
O&M (€/kWh) 0.22 – 5.33 0.32 – 2.33
FUEL COSTS (€/kWh) 0 0
CAPACITY FACTOR (%) 25 - 90 20 - 95
EFFICIENCY (%) 2.3.4 80 – 85 95
Installation costs vary greatly in hydropowerdepending to the size of the dam required
(or if a dam is required at all), whether or not a reservoir needs to be built or if a natural
lake can be used and whether or not water pumps need to be implemented. This largely
depends on the type of hydropowerused: pump-storage systems will be the most
expensive but allow a high level of flexibility whereas low-costrun-of-the-river
hydropowerhas very little flexibility.Small systems are more expensive per unit of
power output because they still need to coverthe costs of project management,
transport of materials and insurance, whilst the end result produces a lower total power
output.
O&M costs forhydropower are very high, averaging at about 2% of the installation costs
per year forlarge plants. Small hydropowersystems have a slightly higher O&M costof
up to 6% of the installation costs per year, as they don’t have the same economies of
scale as large systems. The main costs are due to regular checks on the systems to
Table 4: The costs, capacity factor and efficiency of small and large
hydropower plants 2.3.3
Figure 9: A diagram showing the different sections of a hydroelectric
dam 2.3.2
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ensure maximum efficiency isoccurring and that there are no mechanical failures,
particularly formoving parts e.g. turbines.
The flexibility of accumulation hydropoweris a huge benefit over wind and solar power.
Not only is the fuel free, but it can also be stored physically in reservoirs. This means
that power stations can control the power output to match the demand. This is why the
capacity factorvaries a lot for hydropowerbut it is a controlled variation – not due to
intermittency in the resource like wind and solar.
The efficiency of hydropoweris excellent – the highest of all renewable energy sources –
with up to 95% in large plants. For systems with an output powerof less than 5 MW,
this value drops to between 80% and 85%. Such high numbers are due to the fact that
hydropowerdoesn’t require thermodynamic or chemical processes, where energy can
easily be lost as heat. In water,the loss is largely from as sound energy.
The statistics for hydropowerare promising but a major issue is that it requires a high
flow rate to produce power.So, pumped-storage systems are often used and these
require power to function,whichincur higher installation costs. However,this doesn’t
prevent hydropower frombeing the leading source of renewable energy, generating
60% of electricity from renewable resources and contributing 11.7% of the total energy
generation in Europe 2.3.5.
Whilst hydropoweris a clean energy source – it doesn’t pollute the water or air – it does
have significant environmental impacts, largely due to the dams and reservoirs. Tobuild
a reservoir, an area must be flooded, disrupting the local ecosystems, forests and areas
of agriculture. Natural lakes can be used but this can affectthe local tourism – beautiful
lakes are converted into hydroelectric sites with large, man-made dams. It is an area of
still water– a storage space – so is generally more stagnant than naturally flowingrivers
and lakes. Also, animals (particularly fish) can be killed or injured by the turbines,
although measures have been installed to reduce this e.g. fish ladders.
The volume of waterstored in the reservoirs must be monitored and limited. If there is
too much water, connecting rivers can dry out reducing the fresh supply forthe
reservoir. In extreme cases, dams can burst, whichhas disastrous consequences on the
surrounding environment and its local communities.
Hydropowerhas become a leading source of renewable energy throughout the world.
Its key benefit is the flexibility of the resource; the factthat the fuel is free plus can be
stored physically,forvirtually unlimited periods of time, is a huge bonus.
17
2.4. Biomass
Biomass energy is stored within living things. Powercan be obtained from this resource
by releasing this energy and converting it to electrical or thermal energy, normally
through combustion.
Trees and plants are burned to release thermal energy, which is used to convert water
to steam for use in a turbine, generating electricity.This process is the same as a coal or
oil plant but is more sustainable and, in a well-designed plant, can actually be carbon
neutral. There are other thermo-chemical processes called gasification and pyrolysis
and a bio-chemical process named anaerobic digestion that can also be used.
Combustion (i.e. burning) is the oxidation of molecules in biomass, usually carbon and
hydrogen in the form of hydrocarbons, to produce steam and CO2. Other molecules
existing in the biomass are also oxidised, producing flue gases – gases released into the
atmosphere via a fluepipe - ash or residual slag.
Gasification is the process of partial oxidation of the molecules. This releases carbon
monoxide, hydrogen, CO2 and possibly some hydrocarbons, depending on the
temperature of the reaction. Low temperature gasification (700 OC – 1000 OC) produces
a high level of hydrocarbons,which can then be burned to release energy. This can be an
easier way to transport the energy for widespread use. At higher temperatures (1200 OC
– 1600 OC), a higher proportion of hydrogen and carbon monoxide is produced,
releasing a synthesis gas (syngas) – it can synthesise hydrocarbons – and, if there is a
Figure 10: A diagram of a combustion process using biomass 2.4.1
18
2:1 ratio of hydrogen to carbon monoxide, it can be convertedto a high quality diesel
biofuel 2.4.2.
Pyrolysisis the thermal decomposition of biomass in the absence of oxygen, producing a
gas, liquid and solid char. At higher temperatures (~500 OC), more liquid will be
produced (bio-oil):a dark brown, mobile liquid withhalf the heating value of
conventional fuel oil. This is again useful for distribution into smaller areas for energy
generation.
Both the last two processes are intermediate stages – the products require combusting
to release energy. The main benefit of them is that it allows for easier transport of the
energy, but in a more readily available formthan as a tree/plant.
Anaerobic digestion of biomass is done naturally, but we can synthetically create
conditions where it willoccur.It is the decomposition of organic matter by
microorganisms, producing a biogas and a solid digestate, all done in the absence of
oxygen. Biogas is composed predominantly methane and CO2 – the methane can be
burned forenergy. However,the biogas often requires refining before use.
There are twomain types of boilers used in biomass power plants: stoker and fluidised
bed. Stoker boilers burn fuel on a grate to produce hot fluegases, whichheat the water
into steam. Fluidised bed boilers suspend the fuel, by blowing jets of air from
underneath, and it is burned from here.
STOKER BOILER FLUIDISED BED BOILERS
INSTALLATION COSTS (€/kW) 2.4.3 1700 - 3925 2000 - 4150
O&M (€/kWh) 2.4.3 0.57 – 4.58 0.67 – 4.83
FUEL COSTS (c€/kWh) 2.4.4 2.17 - 12.25 2.17 - 12.25
CAPACITY FACTOR (%) 2.4.5 84 84
THERMAL EFFICIENCY (%) 2.4.6 30 - 35 30 - 35
These boilers are also used in coalplants, so the installation costs are fairly similar. They
can be used for combustion or gasification, although plants must be specifically set up
for one or the other – they are not interchangeable. Pyrolysisuses the same process as
gasification but is limited to temperatures between 300 OC and 600 OC.
Burning biomass in these boilers is not the only way of releasing power. Combined heat
and power(CHP) stations can be installed using biomass, whichreach higher levels of
efficiency than their independent counterparts but are more expensive to install and
operate. Furthermore, biomass can be mixed with coalto produce electricity, called co-
Table 5: A table showing the comparative costs, thermal efficiencies and capacity factors of
the stoker boiler and fluidised bed boiler
19
firing, which is advantageous because it normally produces powerat a higher efficiency
than a biomass-only plant.
The vast majority of O&Mcosts are fixed prices, due to the transportation of fuel and
general checks and maintenance of the machinery, particularly moving parts. These
prices accumulate to between 2% and 7% of the installation costs for the boilers. There
is an additional average variable cost, whichis c€0.46/kWh.
O&M costs vary hugely but are still much higher than all other sources of renewable
energy (apart from hydro),largely due to the number of processes involved in biomass
power generation. The plants are generally bigger and yield a greater output per year
than other sources. The addition of a CCS system also increases these costs significantly.
One element that reduces O&M costs is if the biomass is dried beforetransportation.
Otherwise, there is the cost of transporting moisture, which is useless forpower
generation.
The above fuel cost (forwoodpellets) shows a range of values depending on the price
per tonne of biomass and the moisture content, from 0% to 65%. The lowerthe
moisture content, the lower the cost per kWhof the fuel. So, systems must be put in
place in order to minimise the biomass’ moisture content. The reason the efficiency is
greater when the biomass is dry is because there is more combustible mass in use,
yielding a greater power output for the same price of biomass.
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
0 10 20 30 40 50 60 70
Cost(p/kWh)
Moisture Content (%)
Moisture Content against Cost/kWh
Graph 2: A graph showing the cost per kWh of biomass purchased at £120
per tonne with varying levels of moisture content 2.4.4
20
A major disadvantage of biomass compared to other renewables is that the fuel is not
free. This is for a number of reasons – paying forthe use of/purchasing the land and
transportation cost being the main two.
However,I believe that, because the combustion of biomass is very similar to that of
coal, it is important to draw comparisons between them – why are companies moving
towards biomass plants? For example, the UK power station, Drax, is converting its fuel
from coalto wood chips.
There is a reason that coalhas been utilised so much more than biomass overthe years.
It has a much higher net calorific value;coal contains approximately 29 MJ/kgcompared
to woodpellets/chips (variedby their moisture content),whichhave between 14 MJ/kg
and 17 MJ/kg.
There are plenty of advantages to biomass. Transportation has always been an issue
with coal.Even if the plant is built next to a site, there will alwaysbe problems in the
future, when the supply runs out and another site has to be found. Many plants close
down when this happens because it isn’t financially viable to transport the resources
such long distances – an issue that is apparent in the Western Balkans withtheir lignite
shortage. Biomass solves this problem because it is renewable – forests are replanted to
replenish the source – so this problem is reduced.
Biomass is a sustainable fuel but requires us to nurture it – unlike solar and wind, which
are outwithour control. This raises questions on the impact of afforestation,
reforestation, growth rate and harvesting. Afforestation is the growth of a forest in an
area where there was previously none; reforestation is the restocking of a forest where
there is regular growth. By recyclingCO2 released in the combustion process back into
these forests, we can help increase the growth rate and move the plant towards a carbon
neutral state. However,this needs to be handled with care. Too much forcedgrowth will
destroy the soil as nutrients are used up by the trees, meaning that it will destroy the
ecosystems and render the area useless as a fuel source. This can be avoided by
controlling growth and using fertilisers. CE has the ability to use the waste nitrogen
from its combustion process within a fertiliser plant. Harvesting doesn’t directly impact
the nutrients in the soil but the factthat the trees that absorb the nutrients are being cut
down means that fertilisers are needed to be used to retain a balance.
Coal is a very dirty resource and is a forerunner as a cause of increased global warming.
Carbon content in biomass is less (up to 45% compared to 75% for coal),so there are
less carbon emissions when burning biomass. Government incentives have been put in
place to reward companies for lowering their carbon emissions, whichneed to be cutto
meet the global climate change goal. Furthermore, biomass burns cleanlier than coal,
producing virtually no nitrous or sulphurous oxides in the flue gases.
The factthat biomass is more environmentally friendly to burn than coal does not mean
that it should just be burned without regard. It still produces carbon dioxide and other
unhealthy chemicals. Systems should still be put in place to regulate the release of the
by-products of the combustion process. Carbon capture and storage (CCS) technology is
developing and will be a major step towards reducing carbon emissions and meeting the
global targets. They will also help make coal plants more eco-friendly but does nothing
21
to prevent the release of nasties in the flue gas. However,CCS is currently very
expensive to install so many plants don’t have them.
The land use to grow the biomass has a social impact on surrounding populations.
Agriculture can be affectedas good soil is used to grow fuel forthe plants where it could
be used for foodproduction. The demand forelectricity means that large fields may be
required for a large power station that many people wouldotherwise use for farmland.
Biomass can be almost as damaging as coal if not handled correctly as a product of the
combustion process is CO2. On the other hand, it has the potential to be carbon negative,
particularly with the added use of CCS systems. If handled carefully,biomass could be
the strongest of all the sources of renewable energy. Many of the systems required for
the combustion process are already in place, thanks to fossil fuel power generation, and
it is a reliable, flexible and sustainable resource.
22
2.5. Geothermal
Geothermal energy is the thermal energy generated and stored in the Earth. As the core
is much hotter than the surface, there is a constant heat flow that can be utilised. Hot
springs are an example of geothermal energy and have been used in heating systems
since Ancient Rome.
Now,power is generated by drilling wells into the Earth and extracting heated
water/steam to the surface for use, most often in heating homes. For lower
temperatures, it is used to heat swimming pools. At high temperatures, it can be used to
produce electricity through steam turbines.
Geothermal plants are either liquid-dominated or vapour-dominated.
Vapour-dominated sites, also knownas binary cyclesystems, produce superheated
steam that can be used to power turbines forenergy generation. Underground vapour-
dominated reservoirs are exploited by drilling a well and using water to forcethe steam
up. This technique normally doesn’t require pumps.
Figure 12: A diagram of a flash steam power plant alongside a picture of a
functioning plant in Japan 2.5.2
Figure 12: A diagram of a vapour-dominated power plant 2.5.1
23
Liquid-dominated sites, most often foundas flash plants, generate energy from
underground fluid reservoirs. Fluid is sprayed into a tank held at a lower pressure,
whichcauses the fluid torapidly vaporise (‘flash’) for use in turbines forpower
generation. Any liquid left in the tank can either be vaporised in a second tank or
returned to the reservoir forreheating. The fluid is at a much cooler temperature than
vapour-dominated reservoirs and is oftenlocated near volcanoes.
Both reservoirs are reheated by the heat flow from the core, whichmakes this a
renewable source of energy. The rate of heat flow is 44 TW – which is easily a sufficient
amount of energy to powerthe entire population.
There is also a forcedgeothermal process – enhanced geothermal – whichmeans water
is pumped into the ground to be heated. It is pumped in at high pressures to increase the
width of existing rockfissures to allow for free flow,as there is not necessarily an area
under the surface for water to gather.
VAPOUR-DOMINATED LIQUID-DOMINATED
INSTALLATION COSTS (€/kW) 2.5.3 1800 - 3700 2200 - 5400
O&M (€/kWh) 2.5.4 0.13 - 0.18 0.13 - 0.18
FUEL COSTS (€/kWh) 0 0
CAPACITY FACTOR (%) 2.5.5 95 90
EFFICIENCY (%) 2.5.6 1 - 9 5 - 15
Installation costs forgeothermal power has actually risen over the last few years due to
the increase in prices of drills. Other costs include land rent and construction of power
generators. In a binary cyclesystem, excess steam (steam not used in the turbine) is
condensed into water and recycledbackinto the original process. This increases the
installation cost but also increases the efficiency.
Overall, the efficiency of geothermal powerplants is very poor – the worst of all thermal
conversion plants; coal,oil, gas and nuclear all have an average of above 30% 2.5.7.This is
largely due to heat loss in equipment and the removal of non-condensable gases (NCG).
However,as the source of fuel is free (excluding land rent), the efficiency is not a major
issue.
Like in biomass, the fuel in geothermal can be overused. If the rate of vapour extraction
is toohigh, there willnot be enough time forthe waterto heat up to be converted to
steam. Powergeneration must be regulated to maintain the stability of the plant. This
can be a problem in times of peak demand, as there is no way of storing the power
generated. Like the other forms of renewable energy, and much of technology today, the
Table 6: A table showing the costs, capacity factor and efficiency of vapour-
dominated and liquid-dominated geothermal sites
24
plant efficiency and flexibility will be improved by the development of batteries and
heat storage systems.
On the opposite end of the spectrum to efficiency,the capacity factorfor geothermal
plants is the highest of all renewable resources. It is a constant source of power and is
very flexible, particularly in vapour-dominated systems. The volume of steam extracted
from the reservoir can be varied by changing the rate of water flow so the power
generation can be altered to satisfy the demand.
The O&M costs increase over time, as the plant ages because more maintenance or
replacement of equipment is required. Further costs come from the pay-off of the drill
and steamfield maintenance. There are also significant costs associated withlabour – up
to 32%.
A common misconception is that the billowing clouds of gas from a geothermal plant are
polluting the environment i.e. geothermal isn’t green. This is false; the gas clouds are
steam with very few harmful gases being released. It does contain some CO2 and
hydrogen sulphide but, compared to fossil fuel plants, the carbon emission is minimal.
This excess steam isn’t always released and can be condensed back to water forfurther
use in a binary cyclesystem.
However,it can impact on the waterquality in surrounding areas. Hot water extracted
from the ground contains high levels of sulphur, salt and other minerals. In binary cycle
systems, this water is never released, as it is recycledback in at the start of the process,
so this issue is removed.
Land use is another point of consideration in geothermal power. Drilling holes in the
Earth disrupts local ecosystems and will ruin potential areas of agriculture, particularly
areas around volcanoes,which are renowned forbeing fertile. Furthermore, geothermal
plants are oftenbuilt in areas with a high earthquake risk and the drilling process can
increase their frequency, or cause small earthquakes. Safety measures must be put in
place because an earthquake could potentially wipe out a site, which wouldbe a huge
waste in time, money and resources, not to mention the health risks.
The drilling process requires power, so some carbon emissions will be released. Once
the plant is set up, there should be very little carbon emissions but the installation
process does use power that must be generated from somewhere – more often than not
from fossil fuel plants.
There is a lot of power available from geothermal but it is a long way from reaching its
full potential. When functioning, it is a green resource but the set up surrounding it does
release carbon emissions. The environmental and social impacts are a major concern,
particularly those regarding earthquakes – these couldbe a real danger to the
surrounding population. However,there is a lot of poweravailable in the Earth that can
be utilised cleanly and effectively,particularly as this area advances.
25
3. ComparisonsandEnergyMix
While these are not the only factorsto be taken into consideration when discussing the
EU’s future energy mix, I believe it is important to compare the costs, capacity factors
and efficienciesof each typeof renewable resource directly,to highlight the advantages
and disadvantages of each against the other^.
^ The values in the graphs are the highest from the range shown in the tables
ONSHORE
PV
SMALL
STOKER
VAPOUR
OFFSHORE
CSP
LARGE
FLUIDISEDBED
LIQUIDISED
0
2000
4000
6000
8000
10000
WIND SOLAR HYDRO BIOMASS GEOTHERMAL
Costs(€/kW)
Renewable Source Type
Installation Costs
ONSHORE
PV
SMALL
STOKER
VAPOUR
OFFSHORE
CSP
LARGE
FLUIDISEDBED
LIQUIDISED
0
1
2
3
4
5
6
WIND SOLAR HYDRO BIOMASS GEOTHERMAL
Costs(€/kWh)
Renewable Source Type
O&M Costs
Graph 3: A graph comparing the installation costs of each renewable source
Graph 4: A graph comparing the O&M costs of each renewable source
26
It is obviousthat no one power source will dominate the world, as coal and oil have
done. Eachresource is more suited to individual circumstances that vary depending on
the geography, terrain and climate in an area. Resources like wind and solar will be
more effectiveat different times of the year than others.
ONSHORE
PV
SMALL
STOKER
VAPOUR
OFFSHORE
CSP
LARGE
FLUIDISEDBED
LIQUIDISED
0
10
20
30
40
50
60
70
80
90
100
WIND SOLAR HYDRO BIOMASS GEOTHERMAL
CapacityFactor(%)
Renewable Source Type
Capacity Factor
ONSHORE
PV
SMALL
STOKER
VAPOUR
OFFSHORE
CSP
LARGE
FLUIDISEDBED
LIQUIDISED
0
10
20
30
40
50
60
70
80
90
100
WIND SOLAR HYDRO BIOMASS GEOTHERMAL
Efficiency(%)
Renewable Source Type
Efficiency
Graph 6: A graph comparing the efficiencies of each renewable source
Graph 5: A graph comparing the capacity factors of each renewable source
27
Ultimately, it will be important to mix resources in a country/region. Not only will this
allow forthe optimisation of each power source, but this diversity leads to a security of
the supply – the region is not relying on one technology/fuelsource. Currently, natural
gas plants are oftenpaired with wind power to make up forintermittencies – why not
use a biomass plant instead? With hydropower, in storage-pump systems, power is
needed to pump the water uphill to a reservoir. This power could be generated by
another source of power – solar perhaps.
Intermittent resources are a liability if used as backup forother plants (as described
above with hydro).Our ability to forecastthe weather is a discerning factorin the
success of the solar and wind industries. While it is slightly less significant forsolar –
power can be generated during cloud cover,albeit less effectively – predicting wind
speed and direction will help to plan for powerlapses. Our weather forecasttechnology
is already pretty good but must constantly be improved – getting the prediction wrong
could costthe company a serious amount of money.
Being able to predict the weather accurately is useful but willbe far more effectivewith
better powerstorage systems. As I have stated throughout this report, battery
technology improvements are essential to the success of the renewable energy,
especially for solar and wind.
As an added note, the introduction of renewable energy doesn’t necessarily spell the
death of coal, oil and natural gas as a powersource. These industries are all very good at
producing electricity but their main problem is the environmental impact. CCS systems
will help to reduce carbon emissions from these plants and other technology should be
investigated further to reduce the number of other harmful gases emitted into the
atmosphere from the process. It is a common misconception that these resources are
running out; there is an abundance of oil and gas in the North Sea and with improved
drilling techniques, like fracking, these areas are becoming more easily accessible.
However,an area like this is far less economicalcompared to onshore extraction
locations: in the Middle East forexample.
28
4. EnergyEfficiency
The final point I willaddress is energy efficiency ona grander scale. This not only relates
to energy generation but also energy transmission and consumption.
Currently, around 65% of the world’s powercomes fromburning fossil fuels. These
plants generate electricity at an efficiency levelof just under 40%. Wind and biomass
plants are of a similar efficiency,hydrowithsignificantly more and solar and geothermal
significantly less 4.1.
When considering efficiency,it is important to consider the cost of the fuel,as improving
efficiency willmean less fuel is required to generate the same power output. In this
regard, hydropoweris unequivocally the best; it has a very high efficiency (plus,
pumped-storage systems are very flexible) and the fuel is free. However,with all
renewable energy, except for biomass, the fuel is free so efficiency in terms of energy
generation will, in the future, reduce in relevance. However,this is decades away and
efficiency is seen as an essential step in abating climate change in the near future.
Efficiency isalways going to be a factorthat can continue to improve (particularly for
biomass) but, with a move towards renewable energy in progress, storage systems are
of great importance, as it allows formore flexibility.After all, demand fluctuates so the
ability to store electricity for immediate use would be useful forboth suppliers and
consumers alike.
Once this electricity is generated, it must then be distributed across the country/region.
This is done through the grid, where further energy losses occur.
The main transmission is through power lines. Ideally, these should be perfect
conductors but, in reality, there is no such thing: all conductors willhave some
resistance. Energy losses occurdue to this resistance – resistive losses – and increasing
the voltage of the electricity transmitted willreduce these losses. The electricity
generated by the plant and the electricity required forconsumption don’t function at
these high voltages, so step-up and step-down transformers are used to change the
voltage.
However,these transformers incur losses of their own, usually through heat.
Transformers are the most efficientof electrical devices to date, at highs of 98%, so it is
worth changing the voltages to reduce losses, particularly if the electricity is being
transport over long distances.
Powertransmission efficiency couldbe improved by switching from alternate current
(AC) to direct current (DC). The reason the AC system is in place is due to the
requirement to step-up and step-down the voltage at the beginning and end of the
transmission. Transformers only workwith an AC – to do this witha DC requires a
motor-generator, whichrequires an AC circuit. The grid, and other large-scale electrical
systems, uses AC so it would require a nationwide shift to convertto DC and, withstep-
29
up/step-down technology not yet feasible for DC circuits, there willbe no huge shift in
the foreseeable future. An interesting point to note is that a lot of household electrical
systems use DC, so there is a conversion here, which incurs further losses.
There is then energy loss in these household items. Boilers can be over90% efficient,
depending on their rating, but can be as low as 55%. Actually,more efficient boilers are
now cheaper to purchase, as the technology becomes more readily accessible and there
is a cry for a greater efficiency.
However,there is still use of low efficiency cookers.Gas systems are particularly
inefficientbut there are far more electrical cookers in place now. The AGA is another
cookerthat is deeply inefficient as it is alwaysswitched on. It is a very old-fashioned
piece of machinery in this respect as it is also used to heat the rest of the house – much
less effectively than a regular heating system.
Smaller items make a differenceto a household’s efficiency.This is apparent in the move
from filament to gas-filled light bulbs. About 90% of the energy in a filament bulb is
converted into heat, not light, compared to the gas-filled light bulbs, whichcan produce
up to 90% of the energy as light. These are commonplace now and were really the
beginning of a movetowards more efficienthousehold objects. Furthermore, the
development of highly efficientLEDs could replace gas-filled bulbs in the future.
Cars, and transport in general, is another source of inefficiency.There is a need for
cleaner transportation as many greenhouses gases are released fromexhaust pipes due
to diesel/petrol run vehicles. Electric cars are in development and I believe will be the
future of mass, ground-based transport. Currently, they convert between 59% and 62%
of power to the wheels – fargreater than conventional petrol power cars (17% - 21%);
howeverthere is not enough financial incentivefor people to start using them. Also,
charging stations are not yetin abundance and their mileage is very low – there is still a
lot of work to do before they become mainstream. As an extra not, electric vehicles are
already used in large-scale mass transit systems, like the London Underground. Also,
liquid natural gas (LNG) is used as a fuel source (for example, in ships and lorries),
whichis a step in the right direction – a technique that can be used in the interim.
Planes are an increasing concernas their carbon emission is awful.There is not the
technology to get these planes running on electricity yet,largely (onceagain) due to the
inability to store it in a useable form. This is another area of great inefficiency butmore
concerning is the carbon emissions – it accountsfor 2% of the global CO2 emission.
There are movements towards more efficientairplanes – an objectiveis to reduce the
carbon emissions fromaviation by 50% by 2050 4.2.
I think efficiency is always a point to consider in all aspects of energy. Most importantly,
I think an improvement must be made in the efficiency of the grid – it is a waste of
money to generate electricity at a station forit to be lost in transmission. Of course,
there willalways be some loss but it can certainly be improved; perhaps, in the future, a
move to DC would be more economically and technically viable. However, I believe that
efficiency is less important now due to the unlimited and free supply of so many fuels.
What is more important is to ensure that all areas of electricity generation, transmission
and consumption reduce carbonemissions and slow downthe effectsof climate change.
30
5. Conclusion
There is no perfect source of renewable energy. Having discussed each of their
advantages and disadvantages, I think that it is fairly obvious that no one will be
dominant. There are plenty of other factorsthat I have not considered in this report,
most noticeably the political impacts from country-specific governments, EU policies
and global policies.
Location is important for renewable energy. I think it will be necessary fora super grid
to be implemented in the future across the EU to make use of the varying landscapes. By
combining resources, the EU willhave a stronger, more stable energy supply. However,
this requires political cohesion.
Currently, offshore wind is only feasible forcountries with a coastline, unless land-
lockedcountries transmit the generated power through another country’s grid. This is a
risk as it means they are relying on the other country not to shut off their power. A
super grid wouldreduce this threat because all participating countries would be doing
it.
Furthermore, a super grid would incur lowercost of plants as it allowsthe countries
involvedto benefit fromthe most efficientplants. Geothermal requires very specific
areas to function witha decent output, so willbe scarce in a place like the UK with few
hotspots. However,the UK would balance for this by bringing large amounts of wind
energy to the table. In other words, all countries wouldfeel the benefit of all resources.
It also means that a resource like biomass could be carefully considered. Biomass can be
any living organism and, as I mentioned before, is optimal with fast growing plants.
These sites couldbe used to their full potential and the power generated distributed,
rather than building many smaller plants that use biomass that is not as suitable e.g. has
a lower energy content.
This ideal needs to be driven by government policy and there are plenty of other areas
of politics that governments have to consider alongside energy. Humans’ ability tobe
involvedin conflict– in waror in conflictsof opinion – detracts from their ability to
achieve. Differentpolitical views and changing governments mean it is very hard for
there to be a global agreement on any matter, especially not one as important as energy
generation. Climate change is a current problem but we are still far from global unity in
tackling this area.
Currently, there is a move towards renewable, sustainable energy but it is still on an
individual basis. The Paris CoP at the end of the year will hopeful unite the worldunder
one banner, with clear objectives, but what those will be and even if they come into
being is yetto be revealed. It is certainly a step in the right direction and will hopefully
make a move towards a world where countries worktogether to solve the global
problem that is climate change.

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Renewable Energy Report

  • 1. 1 What criteria should be evaluated in assessing the comparative advantages and disadvantages of different renewable energy types within the EU? How should these factors influence energy policy and energy mix across the EU? What role does increased energy efficiency have to offer? 1. Introduction Climate change is an increasing concern globally; the recent acceleration in the process has been unequivocally attributed to human activity on Earth. Climate change is defined as variations in the mean properties of the environment that are sustained over a long period of time, minimally decades. It is principally attributed to an increase in greenhouse gas levels, which include carbon dioxide (CO2), methane, nitrogen dioxide (NO2) and ozone, in the atmosphere as they have a ‘warming effect’ on the planet. Also, particulates and soot in the air absorb infrared radiation from the Sun, heating the atmosphere to cause further global warming. Two major human activities resulting in this warming effect are the burning of fossil fuels and deforestation. Firstly, burning fossil fuels (oil, coal and gas) release greenhouse gases. Furthermore, these dirty resources release particulates, especially coal, which adds to the issue. Secondly, deforestation or a change in land use means that there are fewer trees to absorb CO2, reducing natural sequestration and therefore, when combusted, more is released into the atmosphere. The production of palm oil is a big issue as large amounts of the jungle are being chopped down. It is a renewable energy source but the way it is handled means that there is little or no reforestation and trees are burned without thought of the CO2 released in the process. Figures show that, by the end of the 21st century, the planet’s average temperature will have increased by 4 OC if the Earth continues to heat up at the current rate. This would have catastrophic environmental effects, causing extreme weather conditions across the world, such as major flooding, hurricanes and droughts. This problem has been recognised globally, as shown by the United Nations Conference of Parties (COP): an annual event that will be held in
  • 2. 2 Paris towards the end of 2015. This will be the 21st meeting of its kind and aims to achieve “a universal, legally binding agreement that will enable us to combat climate change effectively and boost the transition towards resilient, low-carbon societies and economies1.1”. Generally, it has been recognised that energy generation and consumption needs to move away from fossil fuels and to alternative, cleaner sources. Many technologies have been developed in an attempt to address/solve this problem, using renewable sources. The European Union (EU) has already taken steps towards cleaner power, utilising its diverse environment and resources in five main areas: wind, solar, hydro, geothermal and biomass. In the EU, 2013, 24.3% of primary energy production – the amount of useable energy that can be extracted from a resource - and 15% of gross final consumption – the amount of energy consumed by the EU’s member states - came from renewable resources1.2. The EU has set a target that would result in gross final consumption due to renewable sources increase to 20% by 2020. Technology is being continuously developed to utilise renewable power sources to their full potential. It is important to understand that the ability for humans to generate power from renewable resources isn’t a new concept – burning wood to heat a room isn’t revolutionary – however the current technologies aren’t efficient enough at generating power to meet the population’s demand, both in terms of energy and cost. There are two components to energy productivity: efficiency and capacity (load) factor. Efficiency is the amount of electrical energy produced from the mechanical energy put in to a system – it is a case of output versus input. Capacity factor is how much time a system will spend in operation per year. It is a measure of the intermittency of a resource; this is most relevant when the resource can’t be stored, like in wind and solar power. Cost efficiency is a balance between the price of the energy generated for installation, operation and maintenance (O&M) of the machinery, plus the added cost of fuel in some cases, and the price at which the energy produced can be sold at, including any government funding i.e. grants and feed-in tariffs. Generally, the prices paid for renewable energy are dropping as the market becomes more competitive. However, when considering different types of renewable energy, particularly with regards to cost efficiency, it is important to remember the variable landscape in different countries across the EU, both politically and geographically. For example, solar energy will be a much more viable resource in the south of Spain compared to the United Kingdom (UK) due to levels of irradiation. This will affect the energy mix of a country, varied by resources available. Whilst the move towards renewable energy is occurring, there is still a call for fossil
  • 3. 3 fuels when there aren’t sufficient resources available. For example, in the UK, wind is a good source of energy but is intermittent, so needs to be paired with another fuel source to be sufficient. This is often gas; it makes economic sense in the UK, as there are large volumes of it in the North Sea and is a transitional fuel from fossil fuels to renewable. This is because it has a higher power output for a lower amount of carbon emission. Further factors to consider are the effect this will have on government policies, social impacts and the impact this will have on the other power industries, namely fossil fuel and nuclear plants.
  • 4. 4 2.1. Wind Wind power is the conversion of the air’s kinetic energy (wind) to electrical or mechanical power. This has been done for centuries – using sails to power ships is a prime example. The development of modern technology has seen the utilisation of wind turbines to produce electricity. There are two types of wind farms – onshore and offshore – and each have certain advantages and disadvantages compared to the other. In February 2015, there was approximately 120.6 GW of onshore wind energy installed and just over 8 GW offshore throughout the EU 2.1.1. There are four main parts to a turbine. The blades capture the wind’s energy, which spins a generator inside the nacelle. The nacelle also houses the gearbox – this is used to change the rotational speed of the blades to the speed of the generator (around 1500 rpm). The tower and base stabilise the structure and contain conductors to transfer the generated electricity for use. A typical turbine is approximately 150 to 200 feet tall but their height has increased over the past few years and continues to grow. The estimated lifetime for a turbine is 20 years – lifetime means the period before any major overhaul work is required; however, maintenance is done over this time. It is obvious from the table that offshore wind is much more expensive than onshore wind with only a slightly higher capacity factor. However, there are other advantages of offshore wind, which come under social and environmental impacts. Figure 1: A diagram showing the different parts of a standard wind turbine 2.1.2
  • 5. 5 ONSHORE OFFSHORE INSTALLATION COSTS (€/kW) 1450 3600 - 4000 O&M (€/kWh) 0.01 - 0.02 0.02 - 0.04 FUEL COSTS (€/kWh) 0 0 CAPACITY FACTOR (%) 30 - 45 40 - 50 EFFICIENCY (%) 2.1.4 45 45 Over a turbine’s lifetime, installation costs amount to around 75% of the overall costs. Approximately 75% of this is due to purchasing and constructing the turbine; the rest due to various components including grid connection, foundation and land rent 2.1.5. Much of the remaining costs are through O&M. These are due to a variety of components including insurance, regular maintenance, repair, spare parts and administration. This is a major issue for offshore wind as they require more attention (due to erosion from the sea) and access/transport of parts to the stations is much harder and more costly, and downtime is generally greater as a result. The share of costs due to O&M is only 10% to 15% for a newly installed turbine but increase to between 20% and 35% towards the end of its lifetime 2.1.6. However, it is very difficult to predict accurately the O&M costs over the lifetime of a turbine as there are very few that have lived their expected lifetime of 20 years, due to the relative youth of the industry. The rotor blades on wind turbines have increased in diameter over time, which has led to an increase in the power output. This has led to a decrease in the O&M costs per kWh for newer turbines, as shown in Figure 2 below. Table 1: A table showing the various costs associated with onshore and onshore wind energy, alongside the capacity factor and efficiency 2.1.3 Graph 1: A graph showing a breakdown of the O&M costs for wind turbines, depending on their age and expected power output 2.1.7
  • 6. 6 A further point to consider is that, in theory, it doesn’t require any fuel – wind is the source of the energy and is converted straight to electrical energy by the generator. I say in theory because, in reality, the wind blows intermittently. To counteract this issue, wind farms are often built around existing natural gas stations so that, when the wind isn’t producing power, it can pick up on any deficit in generating capacity or can be used to rotate the turbines (rotating reserves). This solution reduces wind’s green credentials as CO2 is released in the process. This isn’t ideal in the long run if we are to move towards a completely green energy system and so the future of wind energy relies on the development of batteries. Currently, large amounts of power can’t be stored for long periods of time, hence the low capacity factor of wind power. Another option is the use of compressed air energy storage. Air is pumped in to a high-pressure chamber for storage and released when required. However, this takes power to pump the air into the chamber so reduces the efficiency of wind. This is probably a temporary solution until such time as battery technology is developed sufficiently. At this point, the capacity factor of wind farms becomes important to consider. The average turbine begins to generate electricity at wind speeds of 3.5 m/s, has a maximum output at speeds higher than 14 m/s until it must be shut down at 25 m/s 2.1.8. So, there is only a window ranging 11 m/s where the turbines will function at maximum output. Capacity factor varies greatly from country to country, depending on the average wind speed. Efficiency is related to the capacity factor as it shows how effective a piece of technology is at producing as close to maximum output as possible. In wind power, it is affected by how much kinetic energy can be converted to electrical energy whilst obeying the law of mass conservation – the same mass of air that enters the turbine must exit it. However, as the fuel is free, efficiency is of less concern. Finally on wind, I will discuss the social and environmental impacts. This point, while less directly related to cost efficiency, is still relevant as it impacts government policy, government funding and planning regulations. There is also a certain level of opinion making involved. The two major social impacts are noise pollution and visual effects. To build a wind farm requires a lot of land – just one blade of a turbine is 30 metres or longer. So, they have to be put in isolated areas: in most cases, the countryside. This is generally unpopular as it affects the view of the landscape, which is not only a problem for the locals but also the country’s tourism. Also, turbines are very noisy and so the problem is increased. Health problems can occur due to the
  • 7. 7 flicker caused by a setting sun behind a rotating turbine: a particular issue if a local in the nearby community has a health difficulty like epilepsy. These issues have sparked many local debates and companies have struggled to gain planning permission because of this. Offshore wind solves this issue but has other separate issues of its own. Furthermore, the fact that building these large, land-consuming structures can affect the local ecosystems and also are a danger to birds, particularly during migration season. These factors are more of a consideration when choosing the location of the wind farms and can cause problems when obtaining planning permission. Whenever considering environmental impacts, the carbon footprint that the industry leaves is hugely relevant. Wind has one of the lowest carbon footprints of ‘low carbon’ technology, second only to nuclear; however, with nuclear, the waste product is a major biohazard. Onshore and offshore wind systems both emit around 5 g of CO2 per kWh, with offshore having a slightly larger carbon footprint. 98% of this emission comes from construction – producing steel to build the tower, concrete for foundations and fibreglass for the blades, not to mention the emissions produced by vehicles transporting the parts to the site. The remaining 2% comes from regular maintenance 2.1.9. These considerations don’t account for rotating reserves, which releases a large volume of CO2, rendering the plant carbon positive. Also, it doesn’t consider the transmission of the produced electricity from sites – a major issue in offshore wind. In isolated areas, transmission lines haven’t been designed to large currents so there is also the problem of efficiency here too. Wind is a useful source of energy, particularly for countries like the UK where it is in abundance. In 2014, wind contributed 9.3% of the UK’s electricity requirements 2.1.10. However, there are many problems surrounding intermittency and transmission that need to be addressed to unleash its full potential.
  • 8. 8 2.2. Solar Solar poweris the use of radiation from the Sun (light and heat) to generate electricity; this can be done passively or actively. Passive solar poweris when something is designed in a specific way to utilise the Sun’s energy without any mechanical or electrical equipment. For example, in hot countries, houses are painted white because the colourreflects electromagnetic waves (radiation) so acts as a natural coolant. Much of the time, passive solar power is insufficient when used alone. So, technologies have been developed to generate power directly fromsunlight using mechanical or electrical equipment. This is activesolar power. An example of this is solar panels on the roof of a house; they generate and supply electricity,whichis fed back into the grid. There are twomain methods of generating utility-scale power using solar: photovoltaic (PV)systems and concentrated solar power(CSP). PVsystems can be used on either a residential (solar panels on house roofs) or industrial scale. PhotovoltaicSystems PVsystems can be found in the formof solar farms – huge numbers of PVpanels in an array – or as individual panels on house roofs. In either circumstance, they work in the same way.Solar panels are normally used to generate electricity forhomes but the power produced can be sold back to the grid. In the UK, there is a feed-in tariff scheme to help promote the use of roofedsolar panels in an effortto move towards EU’s goal of 20% renewable energy generation by 2020. A lifetime of a typicalPV panel – meaning they willproduce at least 80% of their peak output - is 20 to 25 years 2.2.1. PVsystems have three main components. The solar cell is the area that collects the sunlight and convertsits energy to electricity;they are normally made out of the common semi-conductor silicon. The electricity produced is a direct current (DC) and must be converted to alternating current (AC) for use in the grid by an inverter. The utility meter measures how much power is used in the process and how much power has been generated before it is fed into the grid. There can be additional components like a fuse box and/or a battery. The fuse box allowsthe electricity to be generated directly to the house (in the case of roofed solar panels) and the battery is used to store energy to be utilised when the PV cells stop generating power i.e. when it is dark. The PV cells have been designed to generate electricity fromlight that has been refracted off particulates in the atmosphere so will still function when it is overcast.
  • 9. 9 PV INSTALLATION COSTS (€/kW) 3200 - 4500 O&M (€/kWh) 2.2.5 0.005 – 0.006 FUEL COSTS (€/kWh) 0 CAPACITY FACTOR (%) 2.2.6 21 EFFICIENCY (%) 8 - 9 The installation cost coversa number of different areas including installation and development, electricalhardware, the racking and mounting of the PVcells and the purchase of the inverter. This cost varies fromcountry tocountry, depending predominantly on the manufacturing costs and incentive levels (i.e. feed-in tariffs). The range of values in the installation cost is due to the purchasing of PV panels. On an individual basis, the panels will cost a lot more than if bought in bulk due to the economy of scale and standardisation. So, it is cheaper to install a large solar farm of 500 panels compared to putting six on your roof. To drive prices of solar panels further down,the Chinese government unfairly subsidised manufactures so they couldsell their products in the European market, knocking off European competitors, whocouldn’t compete withthe low prices. This is called dumping – a predatory pricing where manufacturers sell products in another country at a price lower than the price sold by home-grown companies. The EU introduced an anti-dumping tax to prevent this happening, whichhas led to a shortage in panels as the prices rose again and Chinese manufacturers are less inclined to sell in Figure 3: The difference between a cell, module and array in PV systems 2.2.2 Figure 4: An image of a PV array 2.2.3 Table 2: A table showing the costs, efficiency and capacity factor of utility-scale PV systems, built using thin-film amorphous silicon 2.2.4
  • 10. 10 Europe. But, it does prevent international companies having an unfair advantage and means that wewould be relying on foreign manufacturers forsolar energy supply. PVsystems require very little maintenance. The panels need cleaning from time to time to ensure they workefficiently,regular inspections are required to checkfor faulty cells and the inverter may need fixing/replacing. These are all fixed O&M costs – the variable costs actually accountforless than 5% of the overall O&M costs. Like wind, the fuel for solar is free – it is sunlight – so the factthat the efficiency is so low is less important; however, this is one area that solar power couldcertainly be improved upon. The statistics shown are the average but a panel’s efficiency actually decreases throughout its lifetime by about 1% a year. A major issue is due to PV panels heating up – forevery 1OC temperature increase, efficiency decreases by about 0.5%. For PVsystems, the capacity factoris calculatedby dividing the number of hours per day of peak sun by 24 (hours in a day) 2.2.7. This throwsup a number of variables: the time of the year and the direction the panel is facing being the twomain ones. So, 21% is a very rough estimate – a fixed array can reach a capacity factorof greater than 35%. The use of a tracking system willboost efficiency/capacity factor.Thisenables the panels to follow the Sun’s trajectory,meaning that maximum light willbe received. However,as this needs moving parts, the costs increase, particularly O&M. PVpanels are seen as the future of renewable energy in the EU as it is a fairly inexpensive method forresidents to generate energy fromtheir house. However,it is not as ‘green’ as many people would believe. Yes, once the systems are in place, it produces electricity from sunlight but, in the constructionprocess, there are major environmental impacts. The purificationof silicon foruse in PVcells releases waste chemicals, like aluminium and carbon, and the process is energy intensive 2.2.8. The social impacts of solar power are similar to those of wind – they can take up a lot of land and can be an eyesore. Solar farms are required for utility-scale power– not enough energy is generated from roof-based for transmission levelgeneration – but this takes up a lot of land, whichcan often affectagriculture. A balance must be found when building the farms between accessibility, isolation and proximity of demand. ConcentratedSolarPower CSP is important to produce electricity and thermal energy foruse in heating systems. CSP systems come in four varieties: parabolic troughs, solar towers, parabolic dishes and linear Fresnel reflectors.Currently, the parabolic trough dominates the CSP landscape, with 80% of all systems in operation or under development coming from this technology. The general idea behind CSP is that an array of mirrors is set up to focusthe sunlight onto a receiver. Water is heated, as in a normal power plant, and converted to steam,
  • 11. 11 whichrotates turbines to generate electricity.Due to the need for a high intensity of sunlight required, many of these systems (certainly the largest) are found in deserts. Unlike most PV systems, CSP uses thermal energy to generate electricity.High temperature collectors also use these systems and transfer heat energy for use in industrial processes that require high temperatures. There are low and medium temperature collectorsin the same system that transfer heat energy to heating systems for houses. They use flat plates that absorb the sunlight. Within these flat plates, there is a heat-transport fluid to remove heat energy fromthe absorber and to transfer it to an insulated tank. The Linear Fresnel Reflectoruses long thin mirrors to reflect light (up to 30 times its normal intensity) onto an absorber, which transfers the energy to a thermal fluid foruse in steam generators. The parabolic dish uses 3D parabolic mirrors to reflect and focus sunlight onto a power conversion unit. The parabolic trough is similar to the parabolic dish in method, but is parabolic-shaped in 2 dimensions and linear in the third. Sunlight is reflected onto an absorber tube. A solar towerconsists of an array of flat mirrors (heliostats) that focusthe sunlight onto a receiver at the top of a central tower. Figure 5: An image of a Linear Fresnel Reflector with one absorber 2.2.9 Figure 6: An image of a parabolic dish 2.2.10 Figure 7: An image of a parabolic trough 2.2.11 Figure 8: An image of a solar tower 2.2.12
  • 12. 12 The only country in the EU to have multiple operating CSP plants is Spain with 850 in 20112.2.13. So, it is very difficultto compare each of the factorswhen considering CSP systems across the EU.However,this very factemphasizes that different mixes of technology will be appropriate fordifferent areas/geographies. The table below shows the range of values forCSP, based on parabolic troughs and solar power towersystems*. The range of values for installation costs is due to the different types of CSP. The most abundant type – parabolic troughs – costs €4100/kW, whichis the cheapest of the four. However,they also have the lowest efficiency (aslow as 15%) because the technique heats the receiver to a comparatively low temperature. A more efficient method is the use of solar power towers.Currently, there are only a few commercial solar power towers in operation in the EU – all based in Spain. This is because the installation costs are greater (between €6000/kW and €9500/kW) and they use large amounts of land – 2 square miles per tower. The increase in costis largely due to how much storage is implemented; this can be between 6 and 15 hours. These thermal energy storage systems are made possible by the use of specific thermal fluids, namely molten salt and synthetic oils. They limit the length of time energy can be stored. There is also the potential for power tobe stored as electricity but, like wind, battery technology is not yetdeveloped enough for this to be a viable option. The benefit of storage is an increase in capacity factor;at 15 hours of storage, solar power towersystems can reach a capacity factorof 80%. It is possible to integrate up to 6 hours of storage into parabolic trough systems but this isn’t cost effective – it can cost between €6400/kW and €8900/kW fora capacity factorof up to 53%. * Linear Fresnel reflectors and parabolic dishes currently don’t exist on a utility- scale but can be used in conjunction with PV systems. CSP INSTALLATION COSTS (€/kW) 4100 - 9500 O&M (€/kWh) 0.02 - 0.03 FUEL COSTS (€/kWh) 0 CAPACITY FACTOR (%) 20 - 80 EFFICIENCY (%) 2.2.15 15 - 30 Table 3: A table showing the costs, efficiency and capacity factors 2.2.14
  • 13. 13 Tracking systems are common amongst CSP systems, which further improves the capacity factor.Heliostats often track the sun’s trajectory to maximise the amount of light received. Parabolic troughs are normally built on a north-south axis and rotate with the sun from east to west. Sometimes, troughs are orientated in an east-west direction because then they only need to be rotated by seasons, requiring less moving parts and thus lowering the installation and O&M costs but also decreasing the capacity factor. The O&M costs for CSP are relatively high but are expected to fall as technology develops. Mirrors require regular attention – they must be cleaned on a regular basis to ensure they operate at maximum efficiency and routine checksare needed to ensure there is nothing broken. CSP systems require a large amount of land and areas with a lot of sunlight and very little cover.Deserts are an ideal place for this but are isolated, whichincreases the O&M due to the need fortransport. Also, deserts are dusty and prone to sandstorms; there is the potential formirrors to be covered by large volumes of sand. So, in reality, deserts aren’t as ideal as they first seem; however, they do solvethe social issues that are commonamongst renewable energy – the fact that they blockthe view and ruin the landscape. CSP systems can actually cause health issues in local communities because the glare fromthe mirrors can be blinding – they can reflectup to 30 times the intensity of sunlight on the receivers. Space-based solar poweris another thing to consider forthe future – it removes limiting factorslike cloudcoverand atmospheric interference and can provide power all year round by ensuring the satellite has a geostationary orbit. The difficulty withthis form of power is transferring the energy back on to Earth for use but there is research being done in an attempt to find a wireless method of transmission. Solar poweris unique in the factthat it is readily available on both a residential and industrial scale. Currently, PVpanels are the most accessible formof power forthe general public to power their ownhomes. It will be important to have a mix of industrial and residential power for the EU’s energy mix and solar power is leading the way on that front. However,its productivity level is low and there is no way to store a lot of thermal energy for a long period of time. Battery development is onceagain essential for the prolonged success of this formof power.
  • 14. 14 2.3. Hydro Hydropoweris the conversion of the kinetic energy from flowing/falling waterinto electrical/mechanical energy. Again, this isn’t a new concept – watermills have used this technique to grind wheat into floursince Imperial Rome. Hydropowercan be split into a number of categories: conventional, run-of-the-river, conduit and pumped-storage hydroelectricity. Conventional hydropower is done through the use of dams to store water foruse. The benefit of this approach is that the plant can generate electricity more flexibly;the fuel is readily available. Run-of-the-riverhydropower captures the kinetic energy of natural streams or rivers without the use of reservoirs and dams. Conduit hydropoweruses water systems that have been diverted foruse elsewhere e.g. as a man-made canal. Pumped-storage hydropowerpumps water uphill to store in reservoirs. This will increase the flexibility of the plant but requires power to movethe water. All of these use the same concept;moving water rotates a turbine, which drives a generator to produce electricity.The difference between each technique is the source. In a system involving a hydroelectric dam, water is stored in a reservoir until needed. At this point gates are opened and water flowsthrough the penstock to rotate the turbine. There are also small and micro hydroelectric systems, whichcan be used on a residential basis. Using basic physics principles, the amount of power available in moving water can be calculated using the equation , where P is the power (Watts), is the density of water (kg m-3), Q is the flow rate (m3 s-1), g is the gravitational acceleration (9.8 m s-2) and h is the verticalheight difference between the inlet and outlet (m) 2.3.1.This assumes there is 100% efficiency,whichis never the case so the actual power output is calculated by multiplying the final value by an efficiency factor – a number between 0 and 1 –, whichvaries depending on the efficiency of the turbines.
  • 15. 15 SMALL LARGE INSTALLATION COSTS (€/kW) 950 - 7000 1200 - 7200 O&M (€/kWh) 0.22 – 5.33 0.32 – 2.33 FUEL COSTS (€/kWh) 0 0 CAPACITY FACTOR (%) 25 - 90 20 - 95 EFFICIENCY (%) 2.3.4 80 – 85 95 Installation costs vary greatly in hydropowerdepending to the size of the dam required (or if a dam is required at all), whether or not a reservoir needs to be built or if a natural lake can be used and whether or not water pumps need to be implemented. This largely depends on the type of hydropowerused: pump-storage systems will be the most expensive but allow a high level of flexibility whereas low-costrun-of-the-river hydropowerhas very little flexibility.Small systems are more expensive per unit of power output because they still need to coverthe costs of project management, transport of materials and insurance, whilst the end result produces a lower total power output. O&M costs forhydropower are very high, averaging at about 2% of the installation costs per year forlarge plants. Small hydropowersystems have a slightly higher O&M costof up to 6% of the installation costs per year, as they don’t have the same economies of scale as large systems. The main costs are due to regular checks on the systems to Table 4: The costs, capacity factor and efficiency of small and large hydropower plants 2.3.3 Figure 9: A diagram showing the different sections of a hydroelectric dam 2.3.2
  • 16. 16 ensure maximum efficiency isoccurring and that there are no mechanical failures, particularly formoving parts e.g. turbines. The flexibility of accumulation hydropoweris a huge benefit over wind and solar power. Not only is the fuel free, but it can also be stored physically in reservoirs. This means that power stations can control the power output to match the demand. This is why the capacity factorvaries a lot for hydropowerbut it is a controlled variation – not due to intermittency in the resource like wind and solar. The efficiency of hydropoweris excellent – the highest of all renewable energy sources – with up to 95% in large plants. For systems with an output powerof less than 5 MW, this value drops to between 80% and 85%. Such high numbers are due to the fact that hydropowerdoesn’t require thermodynamic or chemical processes, where energy can easily be lost as heat. In water,the loss is largely from as sound energy. The statistics for hydropowerare promising but a major issue is that it requires a high flow rate to produce power.So, pumped-storage systems are often used and these require power to function,whichincur higher installation costs. However,this doesn’t prevent hydropower frombeing the leading source of renewable energy, generating 60% of electricity from renewable resources and contributing 11.7% of the total energy generation in Europe 2.3.5. Whilst hydropoweris a clean energy source – it doesn’t pollute the water or air – it does have significant environmental impacts, largely due to the dams and reservoirs. Tobuild a reservoir, an area must be flooded, disrupting the local ecosystems, forests and areas of agriculture. Natural lakes can be used but this can affectthe local tourism – beautiful lakes are converted into hydroelectric sites with large, man-made dams. It is an area of still water– a storage space – so is generally more stagnant than naturally flowingrivers and lakes. Also, animals (particularly fish) can be killed or injured by the turbines, although measures have been installed to reduce this e.g. fish ladders. The volume of waterstored in the reservoirs must be monitored and limited. If there is too much water, connecting rivers can dry out reducing the fresh supply forthe reservoir. In extreme cases, dams can burst, whichhas disastrous consequences on the surrounding environment and its local communities. Hydropowerhas become a leading source of renewable energy throughout the world. Its key benefit is the flexibility of the resource; the factthat the fuel is free plus can be stored physically,forvirtually unlimited periods of time, is a huge bonus.
  • 17. 17 2.4. Biomass Biomass energy is stored within living things. Powercan be obtained from this resource by releasing this energy and converting it to electrical or thermal energy, normally through combustion. Trees and plants are burned to release thermal energy, which is used to convert water to steam for use in a turbine, generating electricity.This process is the same as a coal or oil plant but is more sustainable and, in a well-designed plant, can actually be carbon neutral. There are other thermo-chemical processes called gasification and pyrolysis and a bio-chemical process named anaerobic digestion that can also be used. Combustion (i.e. burning) is the oxidation of molecules in biomass, usually carbon and hydrogen in the form of hydrocarbons, to produce steam and CO2. Other molecules existing in the biomass are also oxidised, producing flue gases – gases released into the atmosphere via a fluepipe - ash or residual slag. Gasification is the process of partial oxidation of the molecules. This releases carbon monoxide, hydrogen, CO2 and possibly some hydrocarbons, depending on the temperature of the reaction. Low temperature gasification (700 OC – 1000 OC) produces a high level of hydrocarbons,which can then be burned to release energy. This can be an easier way to transport the energy for widespread use. At higher temperatures (1200 OC – 1600 OC), a higher proportion of hydrogen and carbon monoxide is produced, releasing a synthesis gas (syngas) – it can synthesise hydrocarbons – and, if there is a Figure 10: A diagram of a combustion process using biomass 2.4.1
  • 18. 18 2:1 ratio of hydrogen to carbon monoxide, it can be convertedto a high quality diesel biofuel 2.4.2. Pyrolysisis the thermal decomposition of biomass in the absence of oxygen, producing a gas, liquid and solid char. At higher temperatures (~500 OC), more liquid will be produced (bio-oil):a dark brown, mobile liquid withhalf the heating value of conventional fuel oil. This is again useful for distribution into smaller areas for energy generation. Both the last two processes are intermediate stages – the products require combusting to release energy. The main benefit of them is that it allows for easier transport of the energy, but in a more readily available formthan as a tree/plant. Anaerobic digestion of biomass is done naturally, but we can synthetically create conditions where it willoccur.It is the decomposition of organic matter by microorganisms, producing a biogas and a solid digestate, all done in the absence of oxygen. Biogas is composed predominantly methane and CO2 – the methane can be burned forenergy. However,the biogas often requires refining before use. There are twomain types of boilers used in biomass power plants: stoker and fluidised bed. Stoker boilers burn fuel on a grate to produce hot fluegases, whichheat the water into steam. Fluidised bed boilers suspend the fuel, by blowing jets of air from underneath, and it is burned from here. STOKER BOILER FLUIDISED BED BOILERS INSTALLATION COSTS (€/kW) 2.4.3 1700 - 3925 2000 - 4150 O&M (€/kWh) 2.4.3 0.57 – 4.58 0.67 – 4.83 FUEL COSTS (c€/kWh) 2.4.4 2.17 - 12.25 2.17 - 12.25 CAPACITY FACTOR (%) 2.4.5 84 84 THERMAL EFFICIENCY (%) 2.4.6 30 - 35 30 - 35 These boilers are also used in coalplants, so the installation costs are fairly similar. They can be used for combustion or gasification, although plants must be specifically set up for one or the other – they are not interchangeable. Pyrolysisuses the same process as gasification but is limited to temperatures between 300 OC and 600 OC. Burning biomass in these boilers is not the only way of releasing power. Combined heat and power(CHP) stations can be installed using biomass, whichreach higher levels of efficiency than their independent counterparts but are more expensive to install and operate. Furthermore, biomass can be mixed with coalto produce electricity, called co- Table 5: A table showing the comparative costs, thermal efficiencies and capacity factors of the stoker boiler and fluidised bed boiler
  • 19. 19 firing, which is advantageous because it normally produces powerat a higher efficiency than a biomass-only plant. The vast majority of O&Mcosts are fixed prices, due to the transportation of fuel and general checks and maintenance of the machinery, particularly moving parts. These prices accumulate to between 2% and 7% of the installation costs for the boilers. There is an additional average variable cost, whichis c€0.46/kWh. O&M costs vary hugely but are still much higher than all other sources of renewable energy (apart from hydro),largely due to the number of processes involved in biomass power generation. The plants are generally bigger and yield a greater output per year than other sources. The addition of a CCS system also increases these costs significantly. One element that reduces O&M costs is if the biomass is dried beforetransportation. Otherwise, there is the cost of transporting moisture, which is useless forpower generation. The above fuel cost (forwoodpellets) shows a range of values depending on the price per tonne of biomass and the moisture content, from 0% to 65%. The lowerthe moisture content, the lower the cost per kWhof the fuel. So, systems must be put in place in order to minimise the biomass’ moisture content. The reason the efficiency is greater when the biomass is dry is because there is more combustible mass in use, yielding a greater power output for the same price of biomass. 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 0 10 20 30 40 50 60 70 Cost(p/kWh) Moisture Content (%) Moisture Content against Cost/kWh Graph 2: A graph showing the cost per kWh of biomass purchased at £120 per tonne with varying levels of moisture content 2.4.4
  • 20. 20 A major disadvantage of biomass compared to other renewables is that the fuel is not free. This is for a number of reasons – paying forthe use of/purchasing the land and transportation cost being the main two. However,I believe that, because the combustion of biomass is very similar to that of coal, it is important to draw comparisons between them – why are companies moving towards biomass plants? For example, the UK power station, Drax, is converting its fuel from coalto wood chips. There is a reason that coalhas been utilised so much more than biomass overthe years. It has a much higher net calorific value;coal contains approximately 29 MJ/kgcompared to woodpellets/chips (variedby their moisture content),whichhave between 14 MJ/kg and 17 MJ/kg. There are plenty of advantages to biomass. Transportation has always been an issue with coal.Even if the plant is built next to a site, there will alwaysbe problems in the future, when the supply runs out and another site has to be found. Many plants close down when this happens because it isn’t financially viable to transport the resources such long distances – an issue that is apparent in the Western Balkans withtheir lignite shortage. Biomass solves this problem because it is renewable – forests are replanted to replenish the source – so this problem is reduced. Biomass is a sustainable fuel but requires us to nurture it – unlike solar and wind, which are outwithour control. This raises questions on the impact of afforestation, reforestation, growth rate and harvesting. Afforestation is the growth of a forest in an area where there was previously none; reforestation is the restocking of a forest where there is regular growth. By recyclingCO2 released in the combustion process back into these forests, we can help increase the growth rate and move the plant towards a carbon neutral state. However,this needs to be handled with care. Too much forcedgrowth will destroy the soil as nutrients are used up by the trees, meaning that it will destroy the ecosystems and render the area useless as a fuel source. This can be avoided by controlling growth and using fertilisers. CE has the ability to use the waste nitrogen from its combustion process within a fertiliser plant. Harvesting doesn’t directly impact the nutrients in the soil but the factthat the trees that absorb the nutrients are being cut down means that fertilisers are needed to be used to retain a balance. Coal is a very dirty resource and is a forerunner as a cause of increased global warming. Carbon content in biomass is less (up to 45% compared to 75% for coal),so there are less carbon emissions when burning biomass. Government incentives have been put in place to reward companies for lowering their carbon emissions, whichneed to be cutto meet the global climate change goal. Furthermore, biomass burns cleanlier than coal, producing virtually no nitrous or sulphurous oxides in the flue gases. The factthat biomass is more environmentally friendly to burn than coal does not mean that it should just be burned without regard. It still produces carbon dioxide and other unhealthy chemicals. Systems should still be put in place to regulate the release of the by-products of the combustion process. Carbon capture and storage (CCS) technology is developing and will be a major step towards reducing carbon emissions and meeting the global targets. They will also help make coal plants more eco-friendly but does nothing
  • 21. 21 to prevent the release of nasties in the flue gas. However,CCS is currently very expensive to install so many plants don’t have them. The land use to grow the biomass has a social impact on surrounding populations. Agriculture can be affectedas good soil is used to grow fuel forthe plants where it could be used for foodproduction. The demand forelectricity means that large fields may be required for a large power station that many people wouldotherwise use for farmland. Biomass can be almost as damaging as coal if not handled correctly as a product of the combustion process is CO2. On the other hand, it has the potential to be carbon negative, particularly with the added use of CCS systems. If handled carefully,biomass could be the strongest of all the sources of renewable energy. Many of the systems required for the combustion process are already in place, thanks to fossil fuel power generation, and it is a reliable, flexible and sustainable resource.
  • 22. 22 2.5. Geothermal Geothermal energy is the thermal energy generated and stored in the Earth. As the core is much hotter than the surface, there is a constant heat flow that can be utilised. Hot springs are an example of geothermal energy and have been used in heating systems since Ancient Rome. Now,power is generated by drilling wells into the Earth and extracting heated water/steam to the surface for use, most often in heating homes. For lower temperatures, it is used to heat swimming pools. At high temperatures, it can be used to produce electricity through steam turbines. Geothermal plants are either liquid-dominated or vapour-dominated. Vapour-dominated sites, also knownas binary cyclesystems, produce superheated steam that can be used to power turbines forenergy generation. Underground vapour- dominated reservoirs are exploited by drilling a well and using water to forcethe steam up. This technique normally doesn’t require pumps. Figure 12: A diagram of a flash steam power plant alongside a picture of a functioning plant in Japan 2.5.2 Figure 12: A diagram of a vapour-dominated power plant 2.5.1
  • 23. 23 Liquid-dominated sites, most often foundas flash plants, generate energy from underground fluid reservoirs. Fluid is sprayed into a tank held at a lower pressure, whichcauses the fluid torapidly vaporise (‘flash’) for use in turbines forpower generation. Any liquid left in the tank can either be vaporised in a second tank or returned to the reservoir forreheating. The fluid is at a much cooler temperature than vapour-dominated reservoirs and is oftenlocated near volcanoes. Both reservoirs are reheated by the heat flow from the core, whichmakes this a renewable source of energy. The rate of heat flow is 44 TW – which is easily a sufficient amount of energy to powerthe entire population. There is also a forcedgeothermal process – enhanced geothermal – whichmeans water is pumped into the ground to be heated. It is pumped in at high pressures to increase the width of existing rockfissures to allow for free flow,as there is not necessarily an area under the surface for water to gather. VAPOUR-DOMINATED LIQUID-DOMINATED INSTALLATION COSTS (€/kW) 2.5.3 1800 - 3700 2200 - 5400 O&M (€/kWh) 2.5.4 0.13 - 0.18 0.13 - 0.18 FUEL COSTS (€/kWh) 0 0 CAPACITY FACTOR (%) 2.5.5 95 90 EFFICIENCY (%) 2.5.6 1 - 9 5 - 15 Installation costs forgeothermal power has actually risen over the last few years due to the increase in prices of drills. Other costs include land rent and construction of power generators. In a binary cyclesystem, excess steam (steam not used in the turbine) is condensed into water and recycledbackinto the original process. This increases the installation cost but also increases the efficiency. Overall, the efficiency of geothermal powerplants is very poor – the worst of all thermal conversion plants; coal,oil, gas and nuclear all have an average of above 30% 2.5.7.This is largely due to heat loss in equipment and the removal of non-condensable gases (NCG). However,as the source of fuel is free (excluding land rent), the efficiency is not a major issue. Like in biomass, the fuel in geothermal can be overused. If the rate of vapour extraction is toohigh, there willnot be enough time forthe waterto heat up to be converted to steam. Powergeneration must be regulated to maintain the stability of the plant. This can be a problem in times of peak demand, as there is no way of storing the power generated. Like the other forms of renewable energy, and much of technology today, the Table 6: A table showing the costs, capacity factor and efficiency of vapour- dominated and liquid-dominated geothermal sites
  • 24. 24 plant efficiency and flexibility will be improved by the development of batteries and heat storage systems. On the opposite end of the spectrum to efficiency,the capacity factorfor geothermal plants is the highest of all renewable resources. It is a constant source of power and is very flexible, particularly in vapour-dominated systems. The volume of steam extracted from the reservoir can be varied by changing the rate of water flow so the power generation can be altered to satisfy the demand. The O&M costs increase over time, as the plant ages because more maintenance or replacement of equipment is required. Further costs come from the pay-off of the drill and steamfield maintenance. There are also significant costs associated withlabour – up to 32%. A common misconception is that the billowing clouds of gas from a geothermal plant are polluting the environment i.e. geothermal isn’t green. This is false; the gas clouds are steam with very few harmful gases being released. It does contain some CO2 and hydrogen sulphide but, compared to fossil fuel plants, the carbon emission is minimal. This excess steam isn’t always released and can be condensed back to water forfurther use in a binary cyclesystem. However,it can impact on the waterquality in surrounding areas. Hot water extracted from the ground contains high levels of sulphur, salt and other minerals. In binary cycle systems, this water is never released, as it is recycledback in at the start of the process, so this issue is removed. Land use is another point of consideration in geothermal power. Drilling holes in the Earth disrupts local ecosystems and will ruin potential areas of agriculture, particularly areas around volcanoes,which are renowned forbeing fertile. Furthermore, geothermal plants are oftenbuilt in areas with a high earthquake risk and the drilling process can increase their frequency, or cause small earthquakes. Safety measures must be put in place because an earthquake could potentially wipe out a site, which wouldbe a huge waste in time, money and resources, not to mention the health risks. The drilling process requires power, so some carbon emissions will be released. Once the plant is set up, there should be very little carbon emissions but the installation process does use power that must be generated from somewhere – more often than not from fossil fuel plants. There is a lot of power available from geothermal but it is a long way from reaching its full potential. When functioning, it is a green resource but the set up surrounding it does release carbon emissions. The environmental and social impacts are a major concern, particularly those regarding earthquakes – these couldbe a real danger to the surrounding population. However,there is a lot of poweravailable in the Earth that can be utilised cleanly and effectively,particularly as this area advances.
  • 25. 25 3. ComparisonsandEnergyMix While these are not the only factorsto be taken into consideration when discussing the EU’s future energy mix, I believe it is important to compare the costs, capacity factors and efficienciesof each typeof renewable resource directly,to highlight the advantages and disadvantages of each against the other^. ^ The values in the graphs are the highest from the range shown in the tables ONSHORE PV SMALL STOKER VAPOUR OFFSHORE CSP LARGE FLUIDISEDBED LIQUIDISED 0 2000 4000 6000 8000 10000 WIND SOLAR HYDRO BIOMASS GEOTHERMAL Costs(€/kW) Renewable Source Type Installation Costs ONSHORE PV SMALL STOKER VAPOUR OFFSHORE CSP LARGE FLUIDISEDBED LIQUIDISED 0 1 2 3 4 5 6 WIND SOLAR HYDRO BIOMASS GEOTHERMAL Costs(€/kWh) Renewable Source Type O&M Costs Graph 3: A graph comparing the installation costs of each renewable source Graph 4: A graph comparing the O&M costs of each renewable source
  • 26. 26 It is obviousthat no one power source will dominate the world, as coal and oil have done. Eachresource is more suited to individual circumstances that vary depending on the geography, terrain and climate in an area. Resources like wind and solar will be more effectiveat different times of the year than others. ONSHORE PV SMALL STOKER VAPOUR OFFSHORE CSP LARGE FLUIDISEDBED LIQUIDISED 0 10 20 30 40 50 60 70 80 90 100 WIND SOLAR HYDRO BIOMASS GEOTHERMAL CapacityFactor(%) Renewable Source Type Capacity Factor ONSHORE PV SMALL STOKER VAPOUR OFFSHORE CSP LARGE FLUIDISEDBED LIQUIDISED 0 10 20 30 40 50 60 70 80 90 100 WIND SOLAR HYDRO BIOMASS GEOTHERMAL Efficiency(%) Renewable Source Type Efficiency Graph 6: A graph comparing the efficiencies of each renewable source Graph 5: A graph comparing the capacity factors of each renewable source
  • 27. 27 Ultimately, it will be important to mix resources in a country/region. Not only will this allow forthe optimisation of each power source, but this diversity leads to a security of the supply – the region is not relying on one technology/fuelsource. Currently, natural gas plants are oftenpaired with wind power to make up forintermittencies – why not use a biomass plant instead? With hydropower, in storage-pump systems, power is needed to pump the water uphill to a reservoir. This power could be generated by another source of power – solar perhaps. Intermittent resources are a liability if used as backup forother plants (as described above with hydro).Our ability to forecastthe weather is a discerning factorin the success of the solar and wind industries. While it is slightly less significant forsolar – power can be generated during cloud cover,albeit less effectively – predicting wind speed and direction will help to plan for powerlapses. Our weather forecasttechnology is already pretty good but must constantly be improved – getting the prediction wrong could costthe company a serious amount of money. Being able to predict the weather accurately is useful but willbe far more effectivewith better powerstorage systems. As I have stated throughout this report, battery technology improvements are essential to the success of the renewable energy, especially for solar and wind. As an added note, the introduction of renewable energy doesn’t necessarily spell the death of coal, oil and natural gas as a powersource. These industries are all very good at producing electricity but their main problem is the environmental impact. CCS systems will help to reduce carbon emissions from these plants and other technology should be investigated further to reduce the number of other harmful gases emitted into the atmosphere from the process. It is a common misconception that these resources are running out; there is an abundance of oil and gas in the North Sea and with improved drilling techniques, like fracking, these areas are becoming more easily accessible. However,an area like this is far less economicalcompared to onshore extraction locations: in the Middle East forexample.
  • 28. 28 4. EnergyEfficiency The final point I willaddress is energy efficiency ona grander scale. This not only relates to energy generation but also energy transmission and consumption. Currently, around 65% of the world’s powercomes fromburning fossil fuels. These plants generate electricity at an efficiency levelof just under 40%. Wind and biomass plants are of a similar efficiency,hydrowithsignificantly more and solar and geothermal significantly less 4.1. When considering efficiency,it is important to consider the cost of the fuel,as improving efficiency willmean less fuel is required to generate the same power output. In this regard, hydropoweris unequivocally the best; it has a very high efficiency (plus, pumped-storage systems are very flexible) and the fuel is free. However,with all renewable energy, except for biomass, the fuel is free so efficiency in terms of energy generation will, in the future, reduce in relevance. However,this is decades away and efficiency is seen as an essential step in abating climate change in the near future. Efficiency isalways going to be a factorthat can continue to improve (particularly for biomass) but, with a move towards renewable energy in progress, storage systems are of great importance, as it allows formore flexibility.After all, demand fluctuates so the ability to store electricity for immediate use would be useful forboth suppliers and consumers alike. Once this electricity is generated, it must then be distributed across the country/region. This is done through the grid, where further energy losses occur. The main transmission is through power lines. Ideally, these should be perfect conductors but, in reality, there is no such thing: all conductors willhave some resistance. Energy losses occurdue to this resistance – resistive losses – and increasing the voltage of the electricity transmitted willreduce these losses. The electricity generated by the plant and the electricity required forconsumption don’t function at these high voltages, so step-up and step-down transformers are used to change the voltage. However,these transformers incur losses of their own, usually through heat. Transformers are the most efficientof electrical devices to date, at highs of 98%, so it is worth changing the voltages to reduce losses, particularly if the electricity is being transport over long distances. Powertransmission efficiency couldbe improved by switching from alternate current (AC) to direct current (DC). The reason the AC system is in place is due to the requirement to step-up and step-down the voltage at the beginning and end of the transmission. Transformers only workwith an AC – to do this witha DC requires a motor-generator, whichrequires an AC circuit. The grid, and other large-scale electrical systems, uses AC so it would require a nationwide shift to convertto DC and, withstep-
  • 29. 29 up/step-down technology not yet feasible for DC circuits, there willbe no huge shift in the foreseeable future. An interesting point to note is that a lot of household electrical systems use DC, so there is a conversion here, which incurs further losses. There is then energy loss in these household items. Boilers can be over90% efficient, depending on their rating, but can be as low as 55%. Actually,more efficient boilers are now cheaper to purchase, as the technology becomes more readily accessible and there is a cry for a greater efficiency. However,there is still use of low efficiency cookers.Gas systems are particularly inefficientbut there are far more electrical cookers in place now. The AGA is another cookerthat is deeply inefficient as it is alwaysswitched on. It is a very old-fashioned piece of machinery in this respect as it is also used to heat the rest of the house – much less effectively than a regular heating system. Smaller items make a differenceto a household’s efficiency.This is apparent in the move from filament to gas-filled light bulbs. About 90% of the energy in a filament bulb is converted into heat, not light, compared to the gas-filled light bulbs, whichcan produce up to 90% of the energy as light. These are commonplace now and were really the beginning of a movetowards more efficienthousehold objects. Furthermore, the development of highly efficientLEDs could replace gas-filled bulbs in the future. Cars, and transport in general, is another source of inefficiency.There is a need for cleaner transportation as many greenhouses gases are released fromexhaust pipes due to diesel/petrol run vehicles. Electric cars are in development and I believe will be the future of mass, ground-based transport. Currently, they convert between 59% and 62% of power to the wheels – fargreater than conventional petrol power cars (17% - 21%); howeverthere is not enough financial incentivefor people to start using them. Also, charging stations are not yetin abundance and their mileage is very low – there is still a lot of work to do before they become mainstream. As an extra not, electric vehicles are already used in large-scale mass transit systems, like the London Underground. Also, liquid natural gas (LNG) is used as a fuel source (for example, in ships and lorries), whichis a step in the right direction – a technique that can be used in the interim. Planes are an increasing concernas their carbon emission is awful.There is not the technology to get these planes running on electricity yet,largely (onceagain) due to the inability to store it in a useable form. This is another area of great inefficiency butmore concerning is the carbon emissions – it accountsfor 2% of the global CO2 emission. There are movements towards more efficientairplanes – an objectiveis to reduce the carbon emissions fromaviation by 50% by 2050 4.2. I think efficiency is always a point to consider in all aspects of energy. Most importantly, I think an improvement must be made in the efficiency of the grid – it is a waste of money to generate electricity at a station forit to be lost in transmission. Of course, there willalways be some loss but it can certainly be improved; perhaps, in the future, a move to DC would be more economically and technically viable. However, I believe that efficiency is less important now due to the unlimited and free supply of so many fuels. What is more important is to ensure that all areas of electricity generation, transmission and consumption reduce carbonemissions and slow downthe effectsof climate change.
  • 30. 30 5. Conclusion There is no perfect source of renewable energy. Having discussed each of their advantages and disadvantages, I think that it is fairly obvious that no one will be dominant. There are plenty of other factorsthat I have not considered in this report, most noticeably the political impacts from country-specific governments, EU policies and global policies. Location is important for renewable energy. I think it will be necessary fora super grid to be implemented in the future across the EU to make use of the varying landscapes. By combining resources, the EU willhave a stronger, more stable energy supply. However, this requires political cohesion. Currently, offshore wind is only feasible forcountries with a coastline, unless land- lockedcountries transmit the generated power through another country’s grid. This is a risk as it means they are relying on the other country not to shut off their power. A super grid wouldreduce this threat because all participating countries would be doing it. Furthermore, a super grid would incur lowercost of plants as it allowsthe countries involvedto benefit fromthe most efficientplants. Geothermal requires very specific areas to function witha decent output, so willbe scarce in a place like the UK with few hotspots. However,the UK would balance for this by bringing large amounts of wind energy to the table. In other words, all countries wouldfeel the benefit of all resources. It also means that a resource like biomass could be carefully considered. Biomass can be any living organism and, as I mentioned before, is optimal with fast growing plants. These sites couldbe used to their full potential and the power generated distributed, rather than building many smaller plants that use biomass that is not as suitable e.g. has a lower energy content. This ideal needs to be driven by government policy and there are plenty of other areas of politics that governments have to consider alongside energy. Humans’ ability tobe involvedin conflict– in waror in conflictsof opinion – detracts from their ability to achieve. Differentpolitical views and changing governments mean it is very hard for there to be a global agreement on any matter, especially not one as important as energy generation. Climate change is a current problem but we are still far from global unity in tackling this area. Currently, there is a move towards renewable, sustainable energy but it is still on an individual basis. The Paris CoP at the end of the year will hopeful unite the worldunder one banner, with clear objectives, but what those will be and even if they come into being is yetto be revealed. It is certainly a step in the right direction and will hopefully make a move towards a world where countries worktogether to solve the global problem that is climate change.