Efficient Solar Cooker

8/2/2019 Efficient Solar Cooker

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Efficient SolarCooker

Presentedby:

Viraj Trivedi

CEPT MTM-AM3411



The Problem

Half the world‟s people must burn wood or dried dung to cook their food.

Wood cut for cooking purposes

contributes to the 16 million hectares offorest destroyed annually. Half the world‟s population is exposed to

indoor air pollution, mainly the result of

burning solid fuels for cooking andheating. Conventional Solar Cooker don‟t work in

evening and cloudy weather.



“I‟d put my money on the sun and solar energy. What a

source of power! I hope we don‟t have to wait „til oil and

coal run out before we tackle that.”

Thomas Edison



Overview

Types of cookers

Principles of solar cooker design

Temperature

Cooking time

Impact

Energy storing materials



Types of solar ovens

Box Cooker

Panel Cooker

Solar Funnel Cooker

Parabolic Cooker - not

recommended



Box cooker

Among easiest and most popular to build and use

Lid of a cardboard box reflects light onto potsunder glass

Advantage of slow, even cooking of largequantities of food



Panel Cooker

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

Many different varieties



Solar Funnel Cooker

Safe, inexpensive and easy to use

Concentrates sunlight into a dark pot in a plasticbag

Combines best of parabolic and box cookers

Anyone can make one



Parabolic Cooker

Highly focused light and high temperatures

Cooks nearly as fast as a conventional oven

Costly and complicated to make and use – haveto turn frequently to follow the sun

Potentially hazardous-not recommended



The basic principles -C.A.R.E.S.

Collect the light

Absorb the light

Retain the heat

Ease and Efficiency

Safety



C: Collect the Light

Collect the sunlight using reflectors with anapproximately 400 square inch opening(20x20)

Easy way to measure: the minimum opening ofthe cooker needs to be the diameter of anadult‟s arm

Reflective surface materials include:

aluminum, Mylar, aluminized Mylar of anythickness, aluminum or chromium paint (Note:mirror like reflectors can lead to eye damage)



A: Absorb the light

Absorb the light – paint the pot matte black oranother dark color to absorb the heat

Pots can also be elevated by a wire base or

posts, allowing the bottom of the pots to collectsunlight



R: Retain the Heat

Retain the heat – hot vessels lose their heat tothe air quickly so they need to be covered

Cover with plastic, glass, Plexiglas, or

tempered glass A tight lid will trap steam and speed up

cooking Ex: Canning jars work like

inexpensive pressure cookers



R: Retain the HeatA note on plastics

Oven bags are the best way to retain heat. Theyare sold in most large U.S. grocery stores,although they may be hard to find in other places(Reynolds © bags work well)

If you can‟t find oven bags, an alternate solutionis transparent High Density Polyethylene bags(HDPE)

Prevent the HDPE bags from touching the potsor jars, as they may melt

Avoid polyethylene – it melts too easily

Good plastic may be the most difficult material tofind, and may require extra planning, possiblyincluding importing the oven bags



E: Ease and Efficiency

Ease – simplicity of everyday use

Funnel and box cookers are the easiest to use –

they don‟t have to be turned to follow the sun Efficiency - how fast the cooker heats food

Parabolic cookers focus light to a point (most

efficient) causing dangerous conditions Funnel cookers focus light across a broader area

down the center of the cooker (efficient but notdangerous)



S: Safety

Safety – Avoid highly focused light such as that

in the parabolic cooker. It can damage eyesand start fires

Always exercise caution with cookers.Sunglasses are useful when looking into acooker

Cooking pots are hot and should be treated asthough they were on a stove-top



Temperatures

Sunny Day: heats from 130-145°C (265-300°F)

Cloudy Day: heats from 95-105°C (200-220°F)

Hot enough to pasteurize water (at least 65-70°C for 20 minutes)

Hot enough to fully cook meats, breads,

grains, vegetables, etc. Kills disease-causing bacteria



Impact

Expect solar ovens to replace 60% of fuelneeds in most places

The other 40% of the time, due to rough

weather or special types of food, traditionalmethods can still be used

Doesn‟t replace fire as a way to heat homes



Approximate Cooking Times

Vegetables: 1.5 hrs

Rice/wheat: 1.5-2 hrs

Beans: 2-3 hrs

Meats: 1-3 hrs

Bread: 1-1.5 hrs



Solar Energy Storing Materials

Thermal mass system- materials withhigh specific heat capacities such as water,earth and stone.

Phase change materials- paraffinwax and Glauber's salt

Molten salts

Pumped-storage hydroelectricity Natural zeolites

Modified Carbon Nanotubes



Thank You

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Efficient Solar Cooker