How game are you to get onto the solar energy bandwagon? Are you already solar-ed up the wazoo with solar panels, a solar water heater, solar garden lights and a solar charger or two? Or are you still waiting for the right opportunity to give solar technology a try? Perhaps the cost of solar energy products is putting you off. Residential solar energy systems are notoriously expensive, even though prices are coming down all the time. If cost is your biggest issue, then you can always try some of the more affordable solutions, like solar cooking.
Solar cooking is, rather obviously, any form of cooking that uses the power of the sun. It’s remarkably effective and very versatile (you can do anything from fry an egg to roast a chicken, and you can even pasteurise milk and water), and it has two major advantages over most other forms of cooking: it uses no electricity (so in a sense it’s free) and it requires the bare minimum of effort.
Solar cooking in use
Solar cookers are primarily used in rural or impoverished areas where electricity is scarce. They provide people with a safe and environmentally-friendly alternative to fire and gas. They’ve been used to great effect in Africa, India and South America where electricity is non-existent, gas and coal too expensive and fire wood too limited a natural resource. Not only do they provide an affordable alternative to fossil fuels, but they provide a method to safely prepare food, milk and water to prevent the spread of bacteria and disease. They also provide a smoke-free method of food preparation, which is better for a community’s overall health, not to mention the health of the environment.
Solar cookers aren’t just designed to meet the needs of impoverished communities, however. They work perfectly well in your average residential neighbourhood – provided your average residential neighbourhood gets plenty of sunshine. If you braai or barbecue regularly, solar cooking might be a nice alternative for you to try.
Let’s look at the types of cookers available, to see what suits your needs.
Types of solar cookers
There are three types of solar cookers: Box, parabolic and panel. While they look different to each other, they follow the same basic principles, which is to concentrate sunlight on a certain point using a reflective surface (mirror, glass or even tinfoil), to retain heat by cooking food in a black (or other dark coloured) container, and to trap heat by sealing or otherwise protecting the cooking container.
The box cooker is what it says on the (ahem) box. It’s a box of about 1 – 1.5m across that has a transparent lid that seals in heat while concentrating sunlight. The bottom of the box is black to retain and concentrate heat, while the interior walls can contain reflective material to concentrate the heat onto the pot. According to Julia Layton, reflectors may be placed outside of the box to direct additional concentrated sunlight through the lid and onto the cooking pot. According to Wikipedia, you should insulate the walls for further heat retention. You can use newspaper, cardboard and even rags – anything that will withstand the temperatures reached.
Box cookers are similar to ovens, so all you need to do is prepare your food as normal, place it in the pot and then place it in the box outside in the sun and leave it for a few hours. Box cookers can reach temperatures of up to 150°C.
Parabolic cookers use curved reflective surfaces to direct concentrated heat on a very specific area. Think of a satellite dish with a cooking pot hanging off the antenna. They are bigger than box cookers and are more like stoves than ovens, according to Layton. They can reach temperatures of over 200°C.
A panel cooker is like a hybrid of the two other systems; so there is a box-type oven around which parabolic reflectors are arranged. The cooking pot is placed within a plastic bag within the box, which traps the very concentrated heat directed by the reflectors. Panel cookers tend to be smaller than box cookers and parabolic cookers, so they are considered portable and ideal for camping.
Some notes on solar cooking
When it comes to food preparation, you carry on in much the same way as if you were going to use your oven or stove, but it’s recommended that you cut up the food into smaller pieces. This is because solar cooking takes longer than stove-top or oven cooking and smaller pieces cook faster.
It’s important to bear this lengthier cooking time in mind so that you can properly coordinate your menu and insert different dishes as and when required. A pot of rice, for example, could take four hours to cook properly, while a thick meat and veggie stew could take five hours. A batch of biscuits could take two hours. Remember that various factors will impact cooking time, such as wind, clouds and your latitude. You’ll have to do some research and some experimenting to get your recipes right.
The great thing about solar cookers, however, is that it is virtually impossible for your food to burn. So the worst that can happen is that your rice becomes a bit stodgy after five hours. You won’t have to deal with blackened bits that stubbornly refuse to shift from the bottom of your pot, no matter how long you soak or how hard you scrub,
You can increase the efficiency of your solar cooker by adjusting it to track the sun, but this isn’t necessary. If you are going to track the sun, you only have to adjust it every 90-odd minutes. In the interest of retaining heat, you shouldn’t check on or stir your food. Rather trust the process and leave it be.
You can buy solar cookers from anything between R250 for camper cookers to R3500 for a proper solar oven. Or you can make your own. It all depends on how much of a DIY-fundi you consider yourself.
Solar cookers are a fun way to experiment with solar energy without going to a great deal of expense. So why don’t you try it next time you go camping or invite the family over for a “braai”.
Image credit: Earthworm, CC BY-NC-SA 2.0, via Flickr