Solar cooker

A solar cooker is a device to generate heat from the energy of the solar radiation. The radiation is focused at the focal point of a concave mirror.

Construction

The parabolic mirror focuses the sun's rays on a mostly matte black container in the focal region. The container absorbs the sun's rays, so that its contents will be very hot. The solar cooker is suitable for example for boiling water, for heating food, for cooking, frying, baking, grilling or frying, for commercial use in dyeing, for soap production, juice production, processing of natural fibers for weaving or as little food stalls in the open.

There are different types of solar cookers. A solar cooker can consist of one or more usually curved mirrors. The mirror can be made ​​from polished aluminum sheet, foil or mirrored, for example, metallkaschiertem box. The focus there is often a holder for a pot. In order to follow the sun, and the mirror holder are usually pivotally mounted in two axes.

Since solar cookers with relatively little material can be produced and consume no fuel, they are seen as a solution to many problems, especially in poorer regions of the world. In areas with little clean water, a solar cooker can be used for disinfection.

  • Solar Cooker

Scheffler

Sun Oven

Solar cooking box

Solar cookers Alsol

Global Sun Oven

Social impacts

Solar cookers can have a significant social impact in poorer regions. This eliminates in societies that traditionally cook their food with collected wood, the time required for the fuel procurement. The time saved can be put to good use for other tasks.

In the diffusion of solar cookers must be given to how they fit in with cultural conditions ( meal times, special symbolic power of fire), otherwise they will not be accepted by the target group.

Benefits

  • The trees will be obtained. Afforestation have been more successful, and fertilizer - for example, cow dung, which is dried as a fuel in many areas of the world - no longer needs to be burned, but is used in agriculture.
  • Women and children in countries with lack of fuel to be relieved from the daily gathering wood.
  • It arises when cooking no harmful smoke.
  • Avoid burns on an open fire.
  • Independence from traditional fuels such as gas, kerosene and firewood.
  • The overall temperature of the atmosphere is increased, unlike the combustion of fuels, does not.
  • Compared with the kindling of a conventional oven fire up times for the commissioning of solar cookers are low. This work can be used for other purposes.
  • Can be made ​​in self-help groups of works on site or easily assembled. This improves the level of training, creates jobs and makes the solar cooker for local affordable. (Promotion mostly in the context of development aid )
  • Food may be preserved by heating and air.
  • ( Widely used eg in Africa) Even in the habit until the evening hot to eat, an application is useful, for example, to pre-cook food already (which must be in the evening only boiled or heated finished), as well as hot water for coffee, tea, etc., which is independent of other eating habits worldwide also midday and afternoon practice.
  • Also for washing clothes (which in many regions of the world, especially in Africa, still by hand ( without washing ) is performed ). For other purposes so that water can be heated to any desired temperature.
  • It can be improved in small villages in the countryside living conditions. The rural exodus, with its devastating consequences, is prevented.
  • It is significantly lighter than a conventional oven recyclable.

Disadvantages

  • Application hardly worth too little sunshine, or is less sunshine a more extended period of time or even larger mirror surfaces, or both necessary. Seems not the sun, cooking is impossible.
  • In some cases, cooking habits must be changed, which may limit the acceptance of solar cookers.
  • Cooking with solar cookers usually takes longer than with gas or electric stoves. Only the parabolic ( 1.4 m reflector diameter) similar cooking times can be achieved.
  • The cost for solar cookers (especially mirror cookers ) are also at local manufacturing usually so high that they are unaffordable for the poor and represent energy- efficient stoves usually the better alternative.

Studies have shown that solar cookers can save only about 30 to 40% of firewood in the rule. This is less, do as improved cooking stoves that save 50 % or more. However, they could possibly be used as an additional energy-saving technology. Meanwhile, budget solar cookers are available, but the other drawbacks remain.

Instructions on using and cook duration

A solar cooker with a diameter of 140 cm readily achieved a power output of around 750 watts. With good sunlight boil three liters of water in 25 minutes. Matte black container and absorb the sun at best and thus speed up the cooking process additionally. A cover in the same color can also speed up the heating.

A stove up to 20 people can be supplied when it is operated using a 12-liter pot.

The cooker works from one hour after sunrise to one hour before sunset. Due to its high performance it is effective even for a relatively short direct sunlight.

Once parboiled food can continue to cook in a holding cage also. This goes for example with rice, which is why the solar cooker is often colloquially called rice cooker.

With a focal length less than 30 cm, the mirror must be aligned every 15 to 25 minutes on the new sun. The tracking is done using simple hand movements. The focal range is within the mirror, thus burning and aperture is largely avoided. To be edited ( stir, fill, etc.) However, the reflector should always be pivoted so that the container (pot ) is on the shady side.

Solar cooking box

A special form of the solar cooker is the solar cooking box. It is an internally insulated sheet metal lined wooden box with a glazed windows as inner cover and an outer cover with sun mounted above the mirror. This is a -covered on the bottom with aluminum foil lid for reflecting the sun's rays into the interior of the box. It is attached to one of the upper longitudinal sides of the cooking box with hinges to be pivotable, and thus each position of the sun adjustable. The sheet to which the box is knocked out, it should be black in color with a non-toxic, tasteless color to reduce reflection of the sun's rays and thus to have a very high proportion of heat energy for cooking are available. The inner insulating lid of the cooking box lets in the heat radiation, but no heated air back out. This makes the solar cooking box to one ( apart from its manufacture, or its components) extremely affordable, ecologically meaningful stove, might be interesting for wood anyway poor developing countries. The solar cooking box was invented in 1767 by Horace Bénédict de Saussure.

A solar furnace is an apparatus for generating heat by means of sunlight using different mirror designs. Solar ovens exist in different forms, but mostly in the form box.

Use

The solar oven is a usually portable device for heating, baking or cooking food and drinks. The smaller models are mainly used for the preparation of Proviants while hiking, trekking tours, expeditions and longer stays in the wild. The larger solar ovens are used in sun-rich countries to earn income by bread and cake is baked or peanuts are roasted and sold as a success projects today are mainly solar-heated commercial kitchens. For example, in the largest solar kitchen in the world in Abu Road, Rajasthan (India), boiled solar for up to 18,000 visitors a yoga center. Solar cookers are also well suited to illustrate children, how much is the radiant power of the sun.

Performance

All data refer to an irradiation of 1 kW / m² under a clear sky and optimal positioning of the reflectors.

Since on glass plate and reflector, the sun radiates directly (for example, 665 watts), the calculated efficiency is around 37 %, the remaining 63 % is lost by partial shading of the cooking chamber, convection, evaporative cooling, absorption and reflection. The use of high-quality mirrors ( for example, anodized aluminum sheet ), 95 % of the radiation is reflected, with the use of aluminum foil on the other hand only 50%. The boiler space exceeds idling, i.e. without cooking contents, within 2 to 3 minutes, the 100 ° -C brand.

Hazards

  • The solar furnace has reached idle temperatures 140-205 ° C.
  • It is important to ensure that potholder or insulated gloves are used to prevent burns.
  • The eyes must not fall into the path of reflection or the focusing range to exclude the risk of glare.
  • When you open it must be expected that the cooking chamber, hot steam escapes. The used containers should not be closed tightly so that steam can escape.

Similar devices

  • Solar furnace - working on the same principle furnace
  • Solar dehydrator - solar-powered oven dried
Insolation Foil (metal) Drinking water
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