5.5 off main-grid technologies for power generation in rural contexts
TRANSCRIPT
Off-main-grid technologies for power generation in rural contexts
Stefano Mandelli [email protected] Mattarolo [email protected]
UNESCO Chair in Energy for Sustainable DevelopmentDepartment of Energy
Step 1: Deep analysis of current and forecast local needs Step 2: Accurate assessment of local resourcesStep 3: Optimize the cost/efficiency of the match need – resourcesStep 4: Choice of the technologies
An integratedsystem of
appropriatetechnologies
NeedsResources
Electric Energy
Other Supply
End Use /Services
Ex post evaluation
GasEx ante evaluation
Strategies for access to energy
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Loads profileWhen 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 profilePeri-urban area in Kampala (Uganda): about 100 households, about 30 economic activities, about 1.000 people involved 16 consumer-classes (114 appliances)
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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
Technologies Overview
Generation technologies can be identified as follows
Off-main-grid systems generation technologies
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The solar resource
Technology trends: PV
Technology trends: Thermal Solar
Technology trends: Thermodynamic Solar
Solar Energy
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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 OVERVIEWSPV 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.
Solar photovoltaic systems
Off-main-grid technologies
TECHNOLOGY OVERVIEWSPV systems are classified as follows:
1. SPV home-based systems- Pico SPV systems- Classical solar home systems
2. SPV community-based systems3. 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
Solar photovoltaic systems
Off-main-grid technologies
Solar photovoltaic systems
Pico SPV system.
Solar home system.
TECHNOLOGY OVERVIEW1. SPV home-based Systems
Off-main-grid technologies
Solar photovoltaic systems
SPV community-based systems
TECHNOLOGY OVERVIEW2. SPV community-based systems
Off-main-grid technologies
TECHNOLOGY OVERVIEW3. Micro-grid SPV systems
Solar photovoltaic systems
Micro-grid SPV systems
Off-main-grid technologies
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
Solar photovoltaic systems
Off-main-grid technologies
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 &
MaintenanceTraining in design
of solar system
Innovative supply chain for solar energy in DCs
Lorenzo Mattarolo – POLIMI – UNESCO Chair
Innovative Supply Chain for PV
Solar panel component works Locally assembled solar panels
Production of charge controllers Assembling of solar street light Installation
Lorenzo Mattarolo – POLIMI – UNESCO Chair
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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 specificA 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
Off-main-grid technologies
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
Off-main-grid technologies
TECHNOLOGY OVERVIEWSW systems are classified as follows
1. SW home-based systems2. SW community-based systems3. 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
Off-main-grid technologies
ECONOMICS and ENVIRONMENTAL IMPACT in a glance• 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 $/kW.
• Maintenance: turbine requires cleaning and lubrication, while batteries, guy wires, nuts and bolts, etc. require periodic inspection. Costs depend on the cost of local spares and service.
• GHG emissions values in the range 4.6-55.4 g CO2-eq./kWh.
Wind Generators
Off-main-grid technologies
Distributed Generation – Small WindMECHANICAL POWER FOR WATER PUMPING (Wind pumps)
Water supply
Head [m]
[m3/day] Typical rotor diameter [m]< 3 3-10 10-30 >30
Domestic X X 1-3 (small farm) 1.5 to 2.5
Cattle X X 20 (500 head) 1.5 to 4.5
Irrigation X X 40-100 (1 ha) 2.5 to 5.5
Diameter [m] Power [kW] cP [$/W] MWh/yearAverage 4,09 3.32 2,5 5,8Minimum 1,95 1.30 1,0 0,4Maximum 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 APPLIANCESSmall 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.
Off-main-grid technologies
Small Hydropower SystemsASSESSMENT: Hydro resources are site specific • 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 channelForebay tankPenstockTurbineGenerator
Small hydro plant scheme. Source
Off-main-grid technologies
Small Hydropower SystemsASSESSMENT: Hydro resources are site specific • 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.
Off-main-grid technologies
Small Hydropower SystemsASSESSMENT: Hydro resources are site specific SHP can be classified as follows:1. SHP home based systems2. SHP community based systems3. 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.
Off-main-grid technologies
ECONOMICS and ENVIRONMENTAL IMPACT in a glance• 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
Small Hydropower Systems
Off-main-grid technologies
Distributed Generation – MiniHydroELECTRICAL APPLIANCESPico-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 SystemsStorage 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.
Off-main-grid technologies
Hybrid SystemsGENERAL CONSIDERATIONHybrid systems can produce electricity even when one resources is offA 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
Off-main-grid technologies
Hybrid SystemsGENERAL CONSIDERATIONTypical 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).
Off-main-grid technologies
Evaluate the impact on local Development
Physical Capitalbetter use and management of resources & infrastructures
Environmental Capitalconservation of the environmentindoor quality
Economic Capitaldecreasing the dependence on imported fuelsimproving the balance of paymentdeveloping green economies
Social Capital improving the human living environmentmitigation of mass migration and creation workplaces
Human Capitallocal capacity and attitude to research and innovationParticipatory approach
Strategies for access to energy
Thank you