Solar Thermal Ochollage
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Transcript of Solar Thermal Ochollage
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[email protected]/09/2011
Solar thermal energy utilizingDevices
By
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Half the world’s people must burn wood or drieddung to cook their food.
Nearly 1.2 billion people, a fifth of the world’s
population, do not have access to clean drinking
water.
Over 1 million children die yearly because of un-
boiled drinking water.
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Wood cut for cooking purposes contributes to the16 million hectares of forest destroyed annually.
Half the world’s population is exposed to indoor
air pollution, mainly the result of burning solid
fuels for cooking and heating.
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Overview
Types of cookers
Principles of solar cooker design
Retained heat cooking
Cooking guidelines
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Types of thermal devices
Box CookerPanel Cooker
Parabolic Cooker
Water Heaters
Food driers
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Solar thermal energy utilization
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
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A solar box cooker traps the sun's energy in aninsulated box.
Such boxes have been successfully used forcooking, pasteurization and fruit canning.
Solar cooking is helpful in many developingcountries, both reducing demand for local
firewood and maintaining a cleaner breathingenvironment for the cooks.
Parabolic type cookers focus the sun’s rays at thebase of the cooking vessel to simulateconventional cooking devices.
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Box cookers
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Solar Box cooker
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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Panel cooker/ Cookit
Sunlight is reflected off of multiple panels onto apot under a glass lid or in a bag
Can be built quickly and at low cost
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Parabola
Highly focused light and high temperatures
Cooks nearly as fast as a conventional oven
Costly and complicated to make and use – have to
turn frequently to follow the sun
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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, allowscooker 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 Water Heaters: Types of Systems
Active vs. Passive
Terms refers to whether the systems rely on pumps or onlythermodynamics to circulate water
Active = uses an electric pump to circulate the heat-transferfluid between the collector and storage tank
Passive = relies on gravity and the tendency for water tonaturally 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 solarcollector
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Passive direct solar water heater
Passive = does not use pump Direct = Circulates water through the collectors
Most common type used in Africa
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Active – uses pump
Open loop = direct system
Direct = Circulates water through the collectors
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Solar Water Heaters: Benefits &
Barriers
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 Driers: Benefits & Barriers
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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Solar for lighting
Light energy from the sun isconverted to electrical energy
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Simple Solarlamps
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Solar for domestic lighting
Parts of the Lamp Product Information
12 LED Lights Lamp is 10 times brighter than the kerosene
lamp
1.5 W Solar Panel Lifetime of the LED and battery (900
mAh) as being for 12-18 months
Wire Lamp charges in 4 Hours
Battery When fully charged the lamp will last:
4 hours on a high setting
7 hours on medium
50 hours on a low setting
Circuit Warranty of 6 for the lamps and 1 year
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HAVE ASOLASTIC DAY