Solar Cooker Design Requirements
BLACK MAGIC :- The colour BLACK is the ‘Magic Wand’ when converting sunlight into heat. ‘Sunlight’ only needs to make contact with a black surface and ‘HEY PRESTO’ we have HEAT, with not a grain of harmful byproduct to dispose of, unlike ‘coal’ which needs to be burnt (combustion), leaving all kinds of residue and poisons behind in the air, on land and waterways. That is the one and only process required. – Simple isn’t it? ( maybe this principal is still too complex for our learned leaders to comprehend ).
Once we have produced heat we need to capture and magnify it to a temperature suitable for cooking, remembering that MORE SUN = MORE HEAT. This can be done with any one of our cookers which must incorporate certain fundamental inclusions for them to function efficiently. Because the low wattage we are trying to harness, (750 watts from a ‘parabolic dish’ to about 200watts from a simple ‘panel cooker’), we must maximise every aspect, convert every available ray into heat and once produced, capture and use it without losing it otherwise cooking will take forever and frustrate the user.
A – SUNLIGHT– The location for cooker should be in a place where sunlight can be assured for long periods during the day, free of any overhanging tree branches or structures, etc. Constantly relocating a cooker in search of a sunny spot can be frustrating.
B – BLACKENED SURFACE – Since ‘Black’ is a requirement for sunlight to heat conversion, certain things must be Black (preferably matt finish) i.e. the interior of a ‘Box Cooker’ and the cooking pots.
C – ENERGY MAGNIFYERS – The heating capacity of any solar device is relative to the amount of sunlight directed at it and can be measured in ‘Number of Suns’. To give an example, a black pot left in the sun is heated with the power of One Sun however if a mirrored reflection is used also on top of the original exposure we can say the pot is heated with the power of Two Suns and so on. It can get a little complex to calculate when, in a Panel Cooker, a number of horizontal and vertical reflectors are incorporated, the number of suns can be more than the number of reflectors (e.g. a 5 reflector device can generate 10 sun capacity). In general “the more reflectors – the more suns – the greater heating potential”
D – HEAT TRAP – Imagine baking something in your home oven with the oven door left open. Good for warming the house but impossible to bake in. The oven compartment is the ‘Heat Trap’. The same conditions apply to a ‘solar cooker’. when a hot pot is exposed to the air and breezes, it can rapidly cool down extending the cooking time, and if coupled with a little cloud cover and slight cooker misalignment to the sun the cooking process can be compromised greatly. This can be solved by placing the pot into an ‘OVEN BAG or a heat trap’ to prevent heat escape. This procedure is only required with the panel cookers, the ‘Box Cookers’ are a heat trap in themselves while the ‘parabolic’ is powerful enough not to require any trap.
E – POT STAND (Trivet) – This is a most undervalued component of the solar cooking assembly, especially when using a ‘Panel Cooker’. By raising the pot off the floor (app. 3cm to 5cm) it exposes the base surface of the pot to reflected sunlight allowing for extra heating. It should be made of thin wire mesh to allow as much sunlight through as possible.