The paper gives an in depth view onrenewable energy sources: Hydroelectric, Wind, Solar, Biomasses

1. THE RENEWABLE ENERGY SOURCES
Hydroelectric
Wind
Solar
Biomasses
Renewable energy sources are called such way as they’re able to regenerate themselves over a
relatively short period of time. The main renewables are: solar energy (photovoltaic and thermal),
wind energy, hydroelectric energy, geothermal energy, energy derived from biomasses and energy
generated by the motion of sea waves and tides.
HYDROELECTRIC ENERGY
For the most part, it is obtained by channeling water into special pipes (penstocks) and dropping it
from a sufficient height to turn turbines that generate electric power. Depending on the height of
the drop and the flow rate, different types of turbines can be used to generate electric power.
In Italy, the largest hydroelectric power plants were built in the first half of the 20th Century. These
facilities, which are still in operation today, are for all intents and purposes the equivalent of an
energy gold mine. Moreover, Edison’s oldest power plants are truly outstanding examples of
industrial architecture. Today, the growth potential of the hydroelectric segment can be realized by
exploiting small/medium-height river drops to power so-called mini-hydro systems.
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3. WIND ENERGY
Wind energy is contained in the wind’s kinetic energy. It is one of the sources that are attracting the
most attention from energy producers, who are making large capital investments in this area
throughout the world.
The wind machine is one of the oldest systems for the production of mechanical energy.
Following the oil crisis of the 1970s, research of alternative technologies based on renewable
sources enjoyed considerable development.
Today, wind powered generation is considered one of the most promising green technologies.
However, costs continue to be higher than those of fossil-fuel power plants. The cost of respecting
the environment continues to rise, even when the “fuel” is free.
Exploiting the wind is not easy: unpredictability of the weather, variability from location to location,
variability in intensity, connections with the power grid and noise have been thus far the main
issues in the design of new wind farms.
The power that may be derived from an aerogenerator depends on the sweep of the blades. The
bigger the radius of the blades, the more power will be available. Power also depends on the cube
of wind speed, which makes knowledge of anemological conditions at the site where an
aerogenerator is to be installed essential.
General Configuration of an Aerogenerator
The blades are installed on a hub to form a rotor. The hub is connected to a shaft (the slower shaft)
that rotates at the same speed as the rotor. Through a gearbox, which is not always present in
some recent aerogenerator models, the slow shaft is connected to a fast shaft equipped with a
safety and control brake, downstream of which an electric generator is installed. These
components are usually placed inside a housing called a nacelle, which is positioned on a yaw ring
and can thus be easily oriented according to the wind’s direction.
The control system of a wind machine can perform different functions (at the design stage,
builders decide which systems to implement, based on the budgeted cost target):
• Pitch regulation,
• Stall regulation,
• Yaw control.
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4. Hub with
blade pitch Rotor brake
actutator Gear box
Generator
Control
system
Nacelle
Yaw system
Rotor
Support tower
Transformer box
Pitch regulation is implemented by rotating the blades on their main axis to increase or reduce the
area exposed to the wind, depending on the wind’s velocity. It is thus possible to optimize the
angle of attack at any wind velocity and cut wind velocity at startup. With high wind velocity, the
pitch angle is changed to reduce the attack angle and, consequently, reduce stress on the blades.
This regulation system thus makes it possible to maintain a constant power output even with high
wind velocity.
Stall regulation can be achieved, during the design phase, by selecting an appropriate
aerodynamic profile for the blades.
The purpose of the yaw control system is to orient the nacelle and, thus, the entire rotor assembly,
depending on the wind’s direction. When appropriately programmed, it can also be used to control
power output.
The first two of the abovementioned systems are most commonly used in aerogenerators. While
the pitch regulation system is the most effective, the stall regulation system is less expensive.
In Italy, the best locations are in Sardinia and the southernmost part of Southern Italy. It is
important that these facilities are appropriately sited, to minimize their impact on local ecosystems
and native fauna.
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5. EDISON’S WIND FARMS
Number of Power of MW Year when
aerogenerators aerogenerators installed commissioned
MW
EMILIA ROMAGNA
San Benedetto Val di Sambro 10 0.35 3.50 1999
(BO) - Monte del Galletto
location
TUSCANY
Montemignaio (AR) 3 0.60 1.80 2001
ABRUZZO
Castiglione Messer Marino 44 0.60 26.40 2001
(CH)
Castiglione Messer Marino 24 0.66 15.84 2004
Expansion (CH)
Fraine (CH) 15 0.60 9.00 2002
Monteferrante (CH) 41 0.60 24.60 2001
Montazzoli (CH) 16 0.60 9.60 2001
Roccaspinalveti (CH) 23 0.60 13.80 2001
Roio del Sangro (CH) 10 0.60 6.00 2001
Schiavi d’Abruzzo (CH) 15 0.60 9.00 2002
MOLISE
Ripabottoni (CB) 24 0.66 15.84 2005
Lucito (CB) 17 2.00 34.00 2008
CAMPANIA
Castelnuovo di Conza (SA) 8 0.60 4.80 (*) 2000
Castelnuovo Conza (SA) 6 1.67 10.02 2007
Foiano (BN) - Monte Barbato 11 0.60 6.60 2001
and Toppo Grosso locations
Foiano (BN) - Piano del 16 0.60 9.60 2001
Casino location
San Giorgio la Molara (BN) – 20 0.50 10.00 1999
Polero location
APULIA
Castelnuovo della Daunia 10 0.25 and 0.35 2.60 1995
(FG) - Casone Romano
location
Celle San Vito 1 (FG) - La 9 0.35 3.15 1999
Montagna location.
Celle San Vito 2 (FG) 7 0.60 4.20 2001
Faeto (FG) 44 0.60 26.40 2002
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6. Orsara la Montagna (FG) 30 0.60 18.00 2001
Rocchetta S. Antonio (FG) 15 0.35 5.25 2000
Volturara Appula anf Motta 19 0.60 11.40 2001
Montecorvino (FG)
Volturino (FG) 20 0.66 and 0.60 13.08 2004
BASILICATA
Vaglio di Basilicata (PZ) 20 0.60 12.00 2003
CALABRIA
Melissa (KR), Strongoli (KR) 25 2.00 50.0 2009
Parco Eolico San 13 2.00 26.00 Under
Francesco construction
SICILY
Mistretta (ME) 15 2.00 30.00 2010
(*): 50% with PE Castelnuovo
SOLAR ENERGY
Solar energy is the energy produced by solar radiation. It can be divided into two main
classifications:
Thermal solar energy, which involves producing heat by exposing to sunlight piping
systems where water reaches a high temperature and is then used heat homes or produce
electric power.
Photovoltaic solar energy, which involves the use of special photovoltaic panels to
transform the sun’s energy into electric power.
Photovoltaic technology makes it possible to transform the sun’s rays into a continuous electric
current without using any moving parts.
After finding widespread applications to produce electric power on satellites, it now seems to have
reached a turning point, becoming suitable for installation in homes or industrial facilities or at
large-scale power plants, thanks to improved conversion efficiency, lower costs and modular
design. Undoubtedly, photovoltaic technology’s immediate application is in distributed power
generation.
Technology Description
Photovoltaic cells, which are the building blocks of solar energy conversion systems, are made of
semiconducting materials. Semiconductors allow the concurrent occurrence of two processes: the
absorption of light and the separation of the electrical charges created by the excitement of the
electrons reached by the light radiation. The semiconducting material must be extremely pure and
free of defects, and, consequently, expensive, in order to avoid that a portion of these free charges
recombine (i.e., return to their original state).
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7. The solar-to-power conversion efficiency of photovoltaic modules currently commercially available
is 14%-15% for crystalline silicon panels and reaches 19% for monocrystalline silicon systems.
Thin-film modules, which have an efficiency of up to 11%, are made with materials that can mimic
the behavior of semiconductors (e.g., cadmium telluride – CdTe, or copper indium gallium
(di)selenide – CIGS).
Because solar cells produce a continuous electric current, the overall conversion efficiency is
reduced by a few percentage points due to the use of power electronics (inverter, power
conditioning and maximum power point tracker) for conversion to alternate current.
polysilicon ingots
wafers
photovoltaic
photovoltaic cell
module
EDISON’S SOLAR PLANTS
1. ALTOMONTE
Altomonte (Italy) Solar Facility
In 2009, Edison made its debut in the Italian photovoltaic market, completing construction of a
facility with a peak capacity of 3.3 MW and panels covering a surface area of more than one million
square feet. Located in Altomonte, this facility is adjacent to a combined-cycle power plant fired
with natural gas. The system is comprised of about 16,500 crystalline silicone panels for an
average production of 4.4 GWh a year. This facility will help save about 2,000 tons of CO2
emissions a year.
2. EDISON’S HEADQUARTERS
Solar Facility at Edison’s Milan Headquarters
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8. In addition, a photovoltaic unit installed on the roof of Edison’s Foro Buonaparte headquarters, in
Milan, was commissioned in January 2009. This system, which has a capacity of 20 kW, was
designed using the most modern technologies available. Its crystal silicone panels deliver an
efficiency of 17%. This facility will help save about 10.3 tons of CO2 emissions a year.
ENERGY FROM BIOMASSES
This type of energy is obtained by the combustion of various types of organic materials that are
used as fuel either directly or after treatment.
These materials consist mainly of logging waste, industrial scrap, solid urban waste, effluents form
livestock farms and certain vegetable species that are farmed for energy production purposes
(mainly sugar cane, beets, corn, soy, poplar, etc.).
Biomasses can be used in different systems, including, by way of example, the following:
small home systems for the production of thermal energy (system widely used in the
mountain regions with mini-boilers);
large facilities for the production of electric power using internal combustion engines,
originally designed for marine applications, that are fueled with liquid vegetable oil;
larger facilities that use solid biomasses (e.g., wood chips) to produce both electric power
and heat and serve multiple users and/or district heating systems;
farming operations that generate effluents from livestock breeding and use them to produce
biogas from anaerobic fermentation suitable for electric power generation;
automobiles (with biofuel used as a percentage of conventional fuel).
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