Solar Cooker & Solar Distillation Plants

8/6/2019 Solar Cooker & Solar Distillation Plants

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107107001 Somatai Kashung

107107007 R .Prashanth


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Solar cookeryAsolar cooker or solar oven is a device which uses

sunlight as its energy source to cook food.

y They are a form outdoor cooking and are often used insituations where minimal fuel consumption isimportant, or the danger of accidental fires is high.


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Principlesy Concentrating sunlight: Device like mirror or

some type of reflective metal, is used to concentrate

light and heat from the sun into a small cooking area.y Converting light to heat: Sunlight is converted

into heat by using black pan which absorb almost allof the sun's light and turn it into heat.


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y Trapping heat: Air inside the cooker is isolatedfrom the air outside the cooker. Using plastic bag or a

glass cover allows light to enter, but once the light isabsorbed and converted to heat, plastic bag or glasscover trap the heat inside.

y Plastic Sheet: Plastic sheets are used to assure

that liquids do not seep into the oven. It also preventsstaining of the underlying sheet in the oven.


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Types of solar cookersy Box cookers

y Panel cookers

y Solar kettlesy Cookers with parabolic reflectors

y Cookers with spherical reflectors

y Hybrid cookers


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Box cookers


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Box cookersy Insulator for the solar box cooker has to be able to

withstand temperatures up to 150.

y Most of the heat escapes through the top glass orplastic, very little insulation in the walls is necessary.

y Crumpled newspapers, wool, rags, dry grass, sheets ofcardboard are used as wall insulation.

y The transparent top is either glass, which is durablebut hard to work with, or an oven cooking bag, whichis lighter, cheaper and easier to work with but lessdurable.


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Panel cookers


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Panel cookers

y They use reflective panels to direct sunlight to acooking pot that is enclosed in a clear plastic bag.

y They are expensive.y It is considered a low-to-moderate temperature solar

cooker.


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Solar kettles


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Solar kettles

y Solar kettles are solar thermal devices that can heatwater to boiling point through the reliance on solarenergy alone.

y Some of them use evacuated solar glass tubetechnology to capture, accumulate and store solarenergy needed to power the kettle.

y It can reach as high as 220 C.

y Solar vacuum glass tubes work on accumulated ratherthan concentrated solar thermal energy, so solarkettles only need diffused sunlight to work and needsno sun tracking at all.


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Cookers with parabolic reflectors


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Cookers with parabolic reflectors

y Parabolic cookers reach high temperatures and cookquickly, but require frequent adjustment and

supervision for safe operation.y Parabolic reflectors that have their centres of mass

coincident with their focal points are useful.

y They can be easily turned, to follow the sun's motions

in the sky, rotating about an axis that passes throughthe focus, so the cooking pot stays stationary.


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Cookers with spherical reflectors

ZipUtility.jar


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Cookers with spherical reflectors

y The Solar Bowl is a unique concentrating technology

that uses a stationary spherical reflector unlikeconcentrating technologies that use tracking reflectorsystems.

y The reflector focuses light along a line perpendicular

to the sphere's surface and a computer control systemmoves the receiver to intersect this line.

y Steam is produced in the solar bowl's receiver attemperatures reaching 150 C


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Hybrid cookers


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Hybrid cookers

yA hybrid solar oven is a solar box cooker equipped witha conventional electrical heating element for cloudy

days or nighttime cooking.yA hybrid solar grill consists of an adjustable parabolic

reflector suspended in a tripod with a movable grillsurface.

yThey are more independent.

y They are expensive.


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Using of solar cookersy The different kinds of solar cookers have somewhat

different methods for use, but most follow the same basicprinciples.

y The container of food is placed inside the solar cooker,perhaps elevated on a brick, rocks, metal trivet, or otherheat sink, and the solar cooker is placed in direct sunlight

y foods are cooked in smaller pieces as it cooks faster.

y

Not much supervision is required.y The cooking time depends on the equipment being used,

the amount of sunlight at the time, and the quantity offood that needs to be cooked, air temperature, wind andlatitude.


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Advantages/why solar ooking?y Solar energy is free of cost.

y Solar cookers do not produce any smoke, ashes etc.

y Unlike cooking over an open fire, children cannot beburned by touching solar cookers.

y Unlike all fuel-based cooking arrangements, solarcookers are not fire hazards.

y They can be used to prepare anything that can bemade in a conventional oven or stove.


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Disa vantages

y Solar cookers take longer time to cook food.

y Cooks may need to learn special cooking techniques to

cook common foods, such as frying eggs or flatbreadslike chapatis and tortillas.

y It may not be possible to safely or completely cooksome thick foods, such as large roasts, loaves of bread.

y Solar cookers are less usable in cloudy or rainy weather.y Solar cooking is affected by strong winds, which can

slow the cooking process, cool the food, and disturbthe reflector.


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Where is solar cooking possible?

The darker regions on the map have longercooking seasons.


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Solar distillation plantsy Solar distiller is a device that is used to clean water

using solar energy.


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y Solar Stills operate on the same principles thatproduce rainfall.

y The sunlight is allowed into and trapped in the Still.

y The high temperatures produced destroy allpathogens.

y The water evaporates, and in this process, only purewater vapor rises in the Still and condense on the

glass.y The glass is sloped to the south, and the condensed

water runs down the glass and is collected in a trough.The water is allowed out of the collector throughsilicone tubing, and is collected.


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Workingy Put dirty or salt water on top of it as seen in the above

picture. There is a black pan that sits underneath. The

water evaporates inside and condenses on the insidewall. It then drips down to the curved side tray area.We can then lift it out of the water carefully and openthe top and pour out the fresh condensed water.


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y Solar stills use no external power source to remove the saltfrom water and hence they can be used in remote places.

y Because of the simplicity of their design, solar stills can be

made small enough to be portable.y . Because of their simplicity, portability and energy-

efficient design, they can be transported and put to usequickly at little expense.

y It is mostly used for distilling sea water and hence we getsalt as by-product.


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Disadvantagesy Solar water distiller do not boil the water.y It does not killing bacteria that may and will be present.y Solar distillers are more of an evaporator, not a distiller.

y Most of these solar water distillers do not have volatileescape vents.

y Because of the large surface area of the glass solar distillers,this leaves a LARGE moist body of water that you have totry to keep sealed to keep BUGS and bacteria out.


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Solar Cooker & Solar Distillation Plants