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ADB FINESSE Training Course on Renewable Energy & Energy Efficiency for Poverty Reduction. 19 th – 23 rd June 2006 Nairobi, Kenya. Module 8: Solar Thermal. Jennifer Wangeci. Overview. Solar Water Heaters Fundamentals and Principles of Operation Types of solar water heating systems

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Adb finesse training course on renewable energy energy efficiency for poverty reduction l.jpg

ADB FINESSE Training Course on Renewable Energy & Energy Efficiency for Poverty Reduction

19th – 23rd June 2006

Nairobi, Kenya


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Module 8: Efficiency for Poverty ReductionSolar Thermal

Jennifer Wangeci


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Overview Efficiency for Poverty Reduction

  • Solar Water Heaters

    • Fundamentals and Principles of Operation

    • Types of solar water heating systems

    • Dissemination levels

    • Estimated costs

    • Project considerations

    • Case studies

  • Solar Driers

    • Fundamentals

    • Case studies

  • Solar Cookers

    • Fundamentals

    • Case studies


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Solar Thermal Efficiency for Poverty Reduction

  • Solar thermal energy = solar heat energy (heat application of solar energy)

  • Solar thermal technologies disseminated in African countries:

    • Solar water heaters – water heating in residential and commercial buildings

    • Solar cookers/ovens – cooking in households and institutions

    • Solar driers – drying agricultural produce such as fruits, fish and vegetables

  • Other solar thermal applications = water purification, space heating, space cooling,


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Solar Water Heaters: Fundamentals and Principles of Operation

  • Components

    • Collectors

    • Storage tanks

    • Electric pumps (depending on the system)

  • Principles of Operation

    • Sun heats a heat transfer fluid in the collector

    • Heated fluid heats water

    • Hot water held in the storage tank ready for use

  • Amount of water heated depends on

    • Type and size of system

    • Solar radiation and insolation at the site

    • Proper installation

    • Tilt angle and orientation of collectors


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Solar Water Heaters Operation

  • Fundamentals and Principles of Operation

Photo credit: RETSCREEN® International, 2004


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Solar Water Heaters: Types of Systems Operation

  • Active vs. Passive

    • Terms refers to whether the systems rely on pumps or only thermodynamics to circulate water

    • Active = uses an electric pump to circulate the heat-transfer fluid between the collector and storage tank

    • Passive = relies on gravity and the tendency for water to naturally circulate as it is heated

  • Direct vs. Indirect

    • Terms refer to whether water or heat transfer fluid (e.g. antifreeze) is pumped through the solar collector

    • Direct = water is pumped through the solar collector

    • Indirect = heat transfer fluid is pumped through the solar collector


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Photo credit: Kenital, 2006


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  • Active Operation – uses pump

  • Open loop = direct system

  • Direct = Circulates water through the collectors

Photo credit: www.southface.org


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Active Operation = uses pump

Indirect = Circulates heat transfer fluid (glycol) through the collectors

Photo credit: www.southface.org


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  • Closed loop = Operationindirect system

  • Indirect = Circulates heat transfer fluid (water or diluted antifreeze solution) through the collectors

  • Uses a heat exchanger to transfer the heat to water

Photo credit: www.southface.org


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Solar Water Heaters Operation

Solar water heaters dissemination levels

Photo credit: RETSCREEN® International, 2004

Source: Karekezi and Kithyoma, 2005; World Energy Council, 2005; GEF, 2001, 2004


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Solar Water Heaters: OperationEstimated Costs

Cost of 100-litre Solar Water Heating System in Selected African Countries (2001)

Source: AFREPREN, 2004

Photo credit: RETSCREEN® International, 2004


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Solar Water Heaters: Benefits & Barriers Operation

  • Benefits

    • Solar water heaters offer large potential savings

      • Owners saving as much as 50% to 85% annually on their utility bills over the cost of electric water heating

    • Reduced need for gas or electricity to heat water

      • Cushioned from fuel/electricity shortages

      • Reduced petroleum import bill

      • Environmental benefits

  • Barriers

    • Cost – beyond the reach of most people

    • Attitude – solar water heaters are for the rich


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Solar Water Heaters: Project Considerations Operation

  • Factors for successful projects:

    • Large demand for hot water to reduce importance of fixed costs

    • High energy costs (e.g. natural gas not available)

    • No reliable conventional energy supply

    • Strong environmental interest by building owner/operator

    • Utility-based dissemination of solar water heaters can be very effective

  • Daytime hot water loads require less storage

  • Lower cost, seasonal systems can be financially preferable to higher-cost year-round systems

  • Maintenance similar to any plumbing system, but operator must be committed to timely maintenance and repairs

  • Domestic vs. commercial (hospital, schools, hotels) application


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Solar Water Heaters: Ethiopia Case Study Operation

  • Solar water heaters increasingly economically feasible due to:

    • Increase in oil prices and electricity tariffs

    • Removal of end-use supply subsidy of oil

  • Since 2000, 10 private companies have entered the SWH market and installed more than 880 units

  • With current electricity prices, SWH investment cost can be paid back within 6 months

  • Advantages of SWH compared to electric boilers:

    • Better durability

    • Lower bills

    • Now running costs

    • Low maintenance costs


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Solar Water Heaters: Ethiopia Case Study Operation

  • Disadvantages of SWH compared to electric boilers:

    • Not being able to get hot water especially at night (for those without a storage tank)

    • Technical problems associated with locally manufactured SWHs (before improved standards). Initial installers were poorly trained plumbers who adversely affected public reputation of technology

  • Challenges faced in SWH dissemination:

    • Prices – beyond the cost of most individuals

    • Low Government and NGO intervention/involvement

    • Involving utilities – requires good data on contribution of electric heating to peak loads.


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Solar Driers Operation

  • Developed as an alternative to open-air sun drying and other conventional drying methods

  • Mainly used for drying agricultural produce such as fruits, vegetables and fish

  • There are two common types of solar driers:

    • Direct solar drier:

      • Closed insulated box in which both solar collection & drying takes place

      • Solar radiation passes through transparent glass/plastic into drying compartment

      • Moisture exits through vents at the top of compartment

    • Indirect solar drier

      • Flat plate collector and separate drying chamber

      • Air pre-heated in flat plate collector and rises to drying chamber to dry


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Solar Driers: Benefits & Barriers Operation

  • Benefits:

    • Reduce post harvest losses

    • Increase quality of product

    • Time marketing of product enabling one to fetch the best price possible

    • Help reduce environmental degradation caused by use of fuel wood and fossil fuels

    • Reduce cost associated with using fuel wood and fossil fuels -> reduces the cost of the product

  • Barriers:

    • Cost – beyond the reach of most individuals

    • Longer drying times – compared to fuel wood and fossil fuel


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Photo credit Operation: www.igadrhep.energyprojects.net

  • Solar Drier from Jinja

  • Solar Mango Driers

Photo credit: www.onecountry.org


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Photo credit: www.solarengineering.co.za


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Solar Driers: Case Studies Operation

  • Uganda

    • Solar driers introduced household storage of fruits & vegetables

    • Rural groups preferred them for income generation

    • Used by women groups for fruits and vegetables drying for export (40 tonnes of dried fruit exported in 2000)

    • Within 3 years, more than 50 groups had taken up the technology

    • Impact: Increased incomes, productivity and employment creation

  • Kenya

    • Solar driers used by women’s group to dry mangoes for export

    • In 13 weeks, each woman in the group earned Ksh. 6,000 (US$ 80)

    • Impact: Increased incomes and productivity


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Solar Driers: Case Studies Operation

  • Burkina Faso

    • Solar driers used by women’s groups and cooperatives to dry fruit for export

    • To maximise benefits from solar drying, the groups and cooperatives formed the Circle of Driers (CDS)

    • In 2003, CDS exported 68 tonnes of dried mango, 10 tonnes of juice and 8 tonnes of syrup

    • Impact: increased incomes, and employment creation

  • Nigeria

    • Solar drying of fish introduced to replace traditional method of open-air sun drying

    • Impact: increased quality of fish thus increased incomes and profit, reduced demand for firewood for smoking fish


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Solar Cookers Operation

  • Parabolic cooker

  • Consists of 3 main parts

    • Parabolic reflector – concentrates the sun onto en small area

    • Control arm – allows the reflector to be set facing the sun, holds the pot at a focal point

    • Stand – holds the reflector + control arm together, allows cooker to be rotated to follow the sun

  • Under strong sunlight, a litre of water can be brought to a boil in about 10 minutes


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  • Solar Box cooker Operation

  • Consists of:

    • Insulated box

    • Transparent top

    • Reflective lid

  • Use plane reflectors to reflect radiation through a glass window into an insulated cooking box

  • Make use of the greenhouse effect to trap the heat behind the glass window inside the box

  • Solar cookers are completely sealed to prevent heat from escaping

  • They are thickly insulated with suitable material which allows them to retain the heat energy


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Solar Cookers Operation

  • Solar cookers good for institutions (schools, refugee camps)

  • Dissemination levels still low

  • Key barriers include:

    • Slow cooking time compared to biomass stoves

    • inconvenience of use (cooking in the sun)

    • socio-cultural constraints (cooking in the open)

    • Cost

    • Only effective during hours of strong sunlight – another stove is required for cloudy periods or during morning and evening hours


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Solar Cookers Operation

  • But technology useful for pre-heating water to be used for cooking

  • Can also be a useful for purifying water for potable applications (up to 70 Degrees centigrade can eliminate up to 90% of water borne pathogens)

  • Solar distillers which operate on similar principle as solar cookers can produce distilled water for use at household, dispensaries and batteries.


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Solar Cookers: Case Study – Kakuma Refugee Camp Operation

  • Location:

    • North Western Kenya

  • Background:

    • Home to 100,000 refugees

    • Extremely dry and wood is very scarce

    • Majority of families cook on wood and charcoal fires

    • Wood cannot be sourced locally

    • Refugees not allowed to collect firewood from outside the camp - have to rely on monthly rations of wood for cooking

    • The 8-10 kg they are given is barely enough to last a month.

  • Solar Cookers International (SCI) started a pilot project in Kakuma in 1995 that provided refugees with portable, lightweight solar cookers called 'CooKits'


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Solar Cookers: Case Study – Kakuma Refugee Camp Operation

  • The project distributed the CooKits and taught people how to use them effectively

  • The CooKit is cheap, lightweight, simple and very easy to use

  • Requirements - blackened pot with a lid and a clear plastic bag

  • How it works:

    • Food is put into the pot, covered with the lid and then put inside a plastic bag

    • The whole lot is then placed in the centre of the cooker and left in the sun

  • Kakuma’s climate has made it ideal for using the CooKits

  • Impact - reduced the need for using firewood in the camp


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Solar Cookers: Case Study – ITDG Kenya Review Survey Operation

  • Major factor in adoption of solar cookers in Kenya is degree to which the technology can be used to undertake existing traditional cooking activities

  • Of people reviewed:

    • 90% found the cooker to be too slow

    • 54% complained that it could not cook their preferred dishes, and in many cases could not cook enough for all family members

    • 67% has misgivings about leaving their food or cooker unattended and so only used them when they were present to watch over them

    • 53% see the cooker as an expensive item

    • In 7 out of 10 project areas visited firewood is freely available and there is little incentive for people to buy or use solar cookers

  • Socio-economic factors appear to influence adoption more than technical features

  • Wrong area or target group affected adoption and dissemination


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