Solar Thermal Ochollage

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[email protected]/09/2011

Solar thermal energy utilizingDevices

By

[email protected]



11/09/2011 [email protected] 2

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.




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.




Overview

Types of cookers

Principles of solar cooker design

Retained heat cooking

Cooking guidelines




Types of thermal devices

Box CookerPanel Cooker

Parabolic Cooker

Water Heaters

Food driers




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




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.




Box cookers







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



11/09/2011 [email protected] 11Panel cooker




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







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




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







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







Passive direct solar water heater

Passive = does not use pump Direct = Circulates water through the collectors

Most common type used in Africa







Active – uses pump

Open loop = direct system

Direct = Circulates water through the collectors




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










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




Solar for lighting

Light energy from the sun isconverted to electrical energy







Simple Solarlamps




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







HAVE ASOLASTIC DAY

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