5.5 off main-grid technologies for power generation in rural contexts

Off-main-grid technologies for power
generation in rural contexts
Stefano Mandelli stefano.mandelli@polimi.it
Lorenzo Mattarolo lorenzo.mattarolo@polimi.it
UNESCO Chair in Energy for Sustainable Development
Department of Energy

Step 1: Deep analysis of current and forecast local needs
Step 2: Accurate assessment of local resources
Step 3: Optimize the cost/efficiency of the match need – resources
Step 4: Choice of the technologies
An integrated
system of
appropriate
technologies
Needs
Resources
Electric Energy
Other Supply
End Use
/Services
Ex post evaluation
GasEx ante evaluation
Strategies for access to energy

3
Loads profile
When defining the electric demand, it is necessary to know the type of
appliance and the modaility of utilization. Through these information it is
possible to define a load profile variable with the time.
Lack of available data ASSUMPTIONS
Example:
load profile of two lamps in a household
P fluorescent lamps 8 W
t utilization 6 h + 3 h
Electric energy demand: 8 W · 6 h + 8 W · 3 h = 72 Wh
Needs assessment

Needs assessment
Loads profile
Peri-urban area in Kampala (Uganda):
 about 100 households, about 30 economic activities, about 1.000 people involved
 16 consumer-classes (114 appliances)

5
Solar
 http://www.nrel.gov/gis/mapsearch/
 http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php
 http://en.openei.org/apps/SWERA/
 http://eosweb.larc.nasa.gov/sse/
Wind
 http://www.geni.org/index.html
 http://eosweb.larc.nasa.gov/sse/
 http://publications.jrc.ec.europa.eu/repository/
«Renewable energies in Africa»
 http://www.iwindsurf.com
Resources assessment

Generation technologies can be identified as follows
Off-main-grid systems generation technologies

8
The solar resource
Technology trends: PV
Technology trends: Thermal Solar
Technology trends: Thermodynamic Solar
Solar Energy

9
The dominant material for creating PV panels is the silicon wafer, which can be
manufactured in three forms:
• Monocrystalline (silicon based)
• Multicrystalline (silicon based)
• Amorphous (new semi-conductor)
Solar Energy: PV
PVGIS (Photovoltaic Geographical Information
System) is a research, demonstration and policy-
support instrument for geographical assessment of
the solar energy resource in the context of
integrated management of distributed energy
generation.
http://re.jrc.ec.europa.eu/pvgis

Solar energy is the most abundant of REs resources.
Solar photovoltaic (SPV) generators
• Semiconductor solar cells to convert solar radiation into electricity
Off-main-grid technologies
ASSESSMENT: Solar radiation is available at any location,
The value at the ground level varies due to geographic conditions
• higher values closer to the Equator,
SPV generation is also influenced by seasonal climatic variations
• Higher during warmer than in cold months.
• Higher during the dry season then rainy season.
Databases are available to obtain an estimation of annual plant productivity
• Photovoltaic Geographical Information System (PVGIS)
• IRENA's Global Atlas
No Data
• Weather Modeling and Forecasting of PV Systems Operation (radiometers)
Solar photovoltaic systems

TECHNOLOGY OVERVIEW
SPV generators convert energy from the sun with solar cells
• Solar cells semiconductor materials: monocrystalline/polycrystalline silicon.
• A number of solar cells are gathered together to form a solar panel.
• Typical power for each solar panel is 80-200W,
• The conversion efficiency of each panel is 15-18%.
• More panels can be combined, high degree of modularity and scalability:
SPV systems consist of different components other then the cell
• Batteries and Charge controller for energy storage;
• Inverter
• Wires/cables and other hardware for electric connections
The technology is suitable for different applications,
• from small lanterns up to mini-grid systems.

TECHNOLOGY OVERVIEW
SPV systems are classified as follows:
1. SPV home-based systems
- Pico SPV systems
- Classical solar home systems
2. SPV community-based systems
3. Micro-grid SPV systems
SPV systems have higher performance in most developing countries
• Values of solar radiation :
• 1400 to 2300 kWh/m2 in Europe and US:
• around of 2500 kWh/m2 in Tanzania , East Africa
• Advantages
• High reliability, long lifetime, absence of moving parts, free fueled

Pico SPV system.
Solar home system.
TECHNOLOGY OVERVIEW
1. SPV home-based Systems

SPV community-based systems
TECHNOLOGY OVERVIEW
2. SPV community-based systems

TECHNOLOGY OVERVIEW
3. Micro-grid SPV systems
Micro-grid SPV systems

ECONOMICS and ENVIRONMENTAL IMPACT in a glance
Prices of SPV generation are
• in developed market around 2.5 $/Wp, in emerging markets below 1 $/Wp.
• For Micro-grid:
• about 50-60% is due to the solar PV array,
• About 10-15% to battery bank and 25-25% to power conditioning unit
Greenhouse gas (GHG) emissions range in 23-45 g CO2-eq./kWh,
• an order of magnitude smaller than that of fossil-based electricity
• emissions from a diesel generator are > than 700 g CO2-eq./kWh

Lorenzo Mattarolo – POLIMI – UNESCO Chair
Innovative Supply Chain for PV
Importation of panels,
charge controller,
battery, inverter
Distributor / SalesInstallation Maintenance & Service
Current supply chain for solar energy in DCs
Importation of
cells and
components
Training in
Distributors / SalesLocal assembly
Installation &
Maintenance
Training in design
of solar system
Innovative supply chain for solar energy in DCs

Innovative Supply Chain for PV
Solar panel component works Locally assembled solar panels
Production of charge controllers Assembling of solar street light Installation

19
With the wind impacting the blades a slow down of the velocity occurs: kinetic energy is
transformed in energy over the rotor, then (possibly) in the generator converted into electricity
Wind Energy
Two categories of aerogenerator:
• horizontal axis wind turbines (HAWT, Horizontal Axis
Wind Turbines)
• vertical axis wind turbines (VAWT Vertical Axis Wind
Turbines)

Wind energy is site specific
A wind power generator (WPG) converts kinetic energy of wind into
electric power through rotor blades connected to a generator.
• Stand-alone applications, small wind (SW) turbines,
• Are around 50-100 kW , with efficiency around 35%
• There is a variety of technologies for rural communities in DCs:
• rely only on well proven and mature technologies
• use artisanal turbines (lower costs and participative)
Wind Generators

ASSESSMENT: Wind power is site specific
Energy produced depends on wind speed at the site:
• Wind speed is highly influenced by topography and obstacles:
Wind power changes during the day, and the seasons.
• Wind speeds of 4-5 m/s are required to achieve economic sustainability
Data all along the year are required.
• Direct measure can be taken with meteorological towers with
anemometers and wind vanes to have speed and directions
• Secondary data can be taken from other measuring meteorological or
airport installations, together with appropriate calculation models (model
selection is done according to available information and site characteristics)
Wind Generators

TECHNOLOGY OVERVIEW
SW systems are classified as follows
1. SW home-based systems
2. SW community-based systems
3. Micro-grid SW systems
Main General features are
• The three-blades design is prevalent, it minimizes vibrations and noise
• Have a direct drive, permanent magnet rotor generator
• simplest configuration, without gearbox: produces alternate current
• Turbines are placed higher than 15 m on a pole out of ground turbulence
• Tilt-up poles/towers are ok up to some kW: easy to install/maintain
Wind Generators

• The price depends on the size, material and construction process.
Costs of SW systems include
• turbine and components: tower or pale, battery storage, power
conditioning unit, wiring, and installation.
• overall costs are in the range 3000 - 6000 $/kW.
• Maintenance: turbine requires cleaning and lubrication, while
batteries, guy wires, nuts and bolts, etc. require periodic inspection.
Costs depend on the cost of local spares and service.
• GHG emissions values in the range 4.6-55.4 g CO2-eq./kWh.
Wind Generators

Distributed Generation – Small Wind
MECHANICAL POWER FOR WATER PUMPING (Wind pumps)
Water
supply
Head [m]
[m3/day]
Typical rotor
diameter [m]< 3 3-10 10-30 >30
Domestic X X 1-3 (small farm) 1.5 to 2.5
Cattle X X 20 (500 head) 1.5 to 4.5
Irrigation X X 40-100 (1 ha) 2.5 to 5.5
Diameter [m] Power [kW] cP [$/W] MWh/year
Average 4,09 3.32 2,5 5,8
Minimum 1,95 1.30 1,0 0,4
Maximum 5,8 6.00 5,5 16
Self-constructed wind generator:
 Three wood blades 2,4m / 1,2m wind-rotor with tail vane
 Permanent magnet alternator (12 or 24 or 48V)
 Built in AC-DC converter
 Max power output 0,5kW
 Furling tail system for preventing overload
ELECTRICAL APPLIANCES
Small wind
Smulders 1996, Harries 2002
Simic 2012, Piggot 2007

SHP plants transform kinetic into mechanical energy with a hydraulic turbine
• Mechanic energy drives devices or is converted in EE via an electricity generator
• No unique definition of small hydropower (SHP), but it generally includes pico-,
micro- and mini-hydro, with generating capacities up to about 5 MW.
• Electricity production is continuous, as long as the water is flowing
Small Hydropower Systems
ASSESSMENT: Hydro resources are site specific
• the right combination of flow and fall is required to meet a load.
• A river flow can vary greatly during the seasons,
• a single measurement of instantaneous flow in a watercourse is of little use
• detailed information is required to estimate production potential
• also the evaluation of the best site is required.

• SHP is the most mature REs technology and has conversion efficiency up to 90%
• Best geographical areas: presence of perennial rivers, hills or mountains.
• SHP generally require some infrastructures:
• a canalization system is necessary to send the flow to the turbine,
• the construction of a building to protect the generator
• SHP require low maintenance.
A typical SHP includes the following elements :
Weir, intake and channel
Forebay tank
Penstock
Turbine
Generator
Small hydro plant
scheme. Source

• Data about water resources assessment can be obtained by databases
• Infohydro, a database provided by the World Meteorological Organisation
• FAO provides database of rainfall patterns to compute approx. hydrograph
• Smallhydroworld by UNIDO and the International Centre on Small Hydro
Power (ICSHP)
• A direct evaluation may be required, several methods exist:
• Velocity-area method
• Weir method
• Data can be organized in a Flow Duration Curve, a curve showing the proportion
of time during which the discharge equals/exceeds a value: to size the turbine
• Estimation of waterfall is required. Field measurements of gross head are usually
carried out using instruments such as theodolites, laser level or GPS.

SHP can be classified as follows:
1. SHP home based systems
2. SHP community based systems
3. Micro-grid SHP systems
The turbine is the core element, type depending on the flow and head:
• High-head:
• Pelton, Turgo and Banki
• medium-head, and low-head:
• Kaplan or Francis,
• but also pumps as turbines: advantages - lower cost and a greater
availability of equipment – disadvantages lower conversion efficiency.

• SHP costs depend
• on site characteristics, terrain and accessibility.
• For micro-systems, the distance between the power house and the loads
can have a significant influence on overall capital costs
• the use of local materials, local labor, and pumps as turbines reduces costs
• Operational costs are low due to high plant reliability , proven technology
• GHG emissions vary greatly depending on the presence of a reservoir
• run-of-river SHP emissions in the range 0.3-13 g CO2-eq./kWh,
• For reservoir SHP range is 4.2-152 g CO2-eq./kWh

Distributed Generation – MiniHydro
ELECTRICAL APPLIANCES
Pico-hydro
Lahimer et al. 2012
Plant size [W]
60-5.000
Inv. cost [US$/kW]
~ 3.000
LCOE [cUS$/kWh]
10-20
Research areas for Developing Countries:
• Improvement in electronic equipment for power quality improvement
• Integration with other RE for extending life span and reduce O&M costs
• New turbine concept for low-head site and pipe loss analysis
• Standardization

Storage Systems
Storage is a key issue when renewable energy systems are used
- a number of technologies based on different principles are available but for small
scale systems up to some MW batteries are the most common device.
- battery storage is a mature technology, owing its success to the high energy
density and modularity (number of batteries can be connected together).
Most common type of batteries is lead- acid:
Lead Acid
- good energy density at reasonable price: deep-cycle - batteries must be used,
since storage must discharge large amounts of energy in a single cycle: the valve-
regulated lead–acid (VRLA) requires lower maintenance.
- Lifetime can be up to 10 years, but adverse environmental conditions (high
temperatures), intensive charge/discharge cycles, over-charging can shorten.

Hybrid Systems
GENERAL CONSIDERATION
Hybrid systems can produce electricity even when one resources is off
A typical layout for rural areas includes the following components:
• One or more technology using unreliable renewable energy sources
• Secondary technology : typically a genset or a hydropower plant
• Storage system
• Inverter and charge controller
• Other electric material (cables, wires, etc.)
A hybrid system can be used
1. to provide electricity to single community services: health centers, schools,
water pumping systems,
2. to supply multiple loads in a micro-grid scheme, composed by 3 subsystems:
• Production subsystem, consisting of the above components
• Distribution subsystem, including all the distribution equipment
• Demand subsystem, including all the end-use equipment

Hybrid Systems
GENERAL CONSIDERATION
Typical configuration
SPV/Diesel or Wind/Diesel
SPV or small wind coupled with a diesel genset is common
- SPV or wind provides most of the electricity,
- the genset balances the production taking care of the long-term fluctuations.
- batteries meet short-term fluctuations,
SPV/Small hydro or Wind/Small hydro
- similar to the precedent
- small-size hydropower plant is used in place of the genset.
- Produced electricity is 100% from renewable sources (not frequently possible).

Evaluate the impact on local Development
Physical Capital
better use and management of resources & infrastructures
Environmental Capital
conservation of the environment
indoor quality
Economic Capital
decreasing the dependence on imported fuels
improving the balance of payment
developing green economies
Social Capital
improving the human living environment
mitigation of mass migration and creation workplaces
Human Capital
local capacity and attitude to research and innovation
Participatory approach
Strategies for access to energy

5.5 off main-grid technologies for power generation in rural contexts

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