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

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.



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




Pico SPV system.

Solar home system.

TECHNOLOGY OVERVIEW1. SPV home-based Systems



SPV community-based systems

TECHNOLOGY OVERVIEW2. SPV community-based systems


TECHNOLOGY OVERVIEW3. 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 &

MaintenanceTraining 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


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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


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 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


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


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.


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


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.


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.


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


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.


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


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).


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

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

Documents

solar http

solar panel

solar energy resource

conductor solar energy

minigrid systems

solar pv array

number of solar cells

technologies overview