Here we will talk about two types of cooking. Not gas and electric either! Both these are free! We are going over solar and wood. I know the word "solar" sounds expensive but in this case it's not, and you may be thinking that wood cooking is a primary reason for deforestation so why go there? Well there are ways to cook with wood that use 75% less than traditional ways and in half the time which we will go over. So let's get to it!
Solar
For low cost solar cookers, you basically have two types; the box type and the concentrator type. There is a newer panel type which is a hybrid of the two, but I don't have much information on it at this time.
Box Cookers
Box type cookers are basically insulated boxes with a cover made of glass or plastic where the sunlight enters through that and the light is absorbed by the interior of the box. The heat rays or "infra-red" rays can not escape through the glass. So the box becomes a heat trap like a green house but hotter!
As a result, the temperature of the interior of the box will gradually increase. Your food is kept in pots or kettles and put inside the box. The box will lose heat to the surrounding; so it is important to insulate the box well, with at least 25mm [1 inch] of good insulation. Typically the box temperature could go up to 120 deg centigrade or higher on a very hot day. And anyone who has walked around in the sun here, you know these will cook pretty fast. Most of cooking is done slowly at around 80 to 100 deg C. Except in very hot regions like desert conditions, box cookers would require 1 to 3 hours to cook well. The time, of course, would depend on the item cooked and the quantity. Since cooking is done at lower temperatures, the food retains much nutritional value and also flavors. This is a big advantage in using box-type solar cookers. The chance of burning food is very low.
Concentrating type cookers
You can buy beautiful parabolic reflectors with stands which will be costly, but they can also be made out of foil and cardboard just as effectively. I will post plans as I get time, but for now there are many to be found on the net, just Google them.
In theory this type cooker is like a satellite antenna dish and the rays falling in the area of the dish and focusing at the focal point which could be over a small area. The concentrators, due to focusing action, result in higher temperatures, can be as high as 250 deg C.. This results in rapid heating of the food kept at the focal plane. The cooking pot is a blackened pot kept on a stand near the focal plane. This type of cooker requires frequent focusing by tilting the mirror which should be done manually or by a tracking mechanism. The tracking mechanism are quite expensive and hard to get in third world countries. Therefore simple ones are kept by tilting by hand. The user must stand in the hot sun and keep adjusting the position of the reflector. For me, I don't even like going into town when it gets hot, let alone sit in the sun! It is also likely that food items may be scorched by intense heat. Not only that, the user should not keep looking at the focal area as this may damage one's eyes. These limitations make this type of cookers less usable in many communities.
Rocket Stoves
So what is a Rocket Stove? A rocket stove/Rocket mass heater is a type of stove combining the air-intake with a fuel-feed slot in an opening ending in a combustion chamber, further leading to a chimney and heat exchanger. There are several advantages to using this type of stove, they reduce air pollution as well as the amount of firewood needed to cook and keep the food warm by about 75%. It also improves cleanliness reducing soot so respiratory problems are reduced drastically.
A rocket stove is signified by ease of construction and simplicity of building materials while accepting small-diameter fuel such as twigs or small branches, yielding high combustion efficiency and directing the resultant heat onto a small area. These can be made into portable and stationary brick models that incorporate both stove and oven if you choose. (see also http://en.wikipedia.org/wiki/Rocket_stove and the references at the bottom)
Dr. Larry Winiarski, now Technical Director of Aprovecho, began developing the Rocket Stove in 1980 and invented the principles of the Rocket stove in 1982. TWP and AHDESA were winners at the Ashden Awards for Sustainable Energy in 2005 in the 'Health and Welfare' category for their work in Honduras with the 'Justa Stove' which is based on principles of the rocket stove. Aprovecho were winners of the Special Africa Award at the Ashden Awards in 2006 for their work with rocket stoves for institutional cooking in Lesotho, Malawi, Uganda, Mozambique, Tanzania and Zambia.
Box type cookers are basically insulated boxes with a cover made of glass or plastic where the sunlight enters through that and the light is absorbed by the interior of the box. The heat rays or "infra-red" rays can not escape through the glass. So the box becomes a heat trap like a green house but hotter!
You can buy beautiful parabolic reflectors with stands which will be costly, but they can also be made out of foil and cardboard just as effectively. I will post plans as I get time, but for now there are many to be found on the net, just Google them.
So what is a Rocket Stove? A rocket stove/Rocket mass heater is a type of stove combining the air-intake with a fuel-feed slot in an opening ending in a combustion chamber, further leading to a chimney and heat exchanger. There are several advantages to using this type of stove, they reduce air pollution as well as the amount of firewood needed to cook and keep the food warm by about 75%. It also improves cleanliness reducing soot so respiratory problems are reduced drastically.
