Solar cooking for everyone
10 liters transparent plastic bottles can be fond everywhere in Africa and elsewhere as well. Lately I have found a way to heat water with these transparent plastic bottles. If you follow the pictures, I will show you how you can try it out for yourself.
The only thing you have to do is to buy a black plastic bag and find an empty transparent plastic bottle. If the plastic bag has textures on the outside you can turn it inside out.
Put the plastic bag into into the transparent (PET) plastic bottle and fill up a bucket of water.
Then tilt it backwards towards the sun and let it rest in a optimal position for about six hours. You will find that the temperature of the water will rise slowly up to 50-60 degrees Celsius. Find out how hot you can get the water and let us know how well it works in your location.
It is worth mentioning that the bottle is round (of course) and this helps the bottle to stay in focus of the sun for a long time. Just make sure the bottle is placed in a position where it will receive the the rays from the sun in an 90 degree angle all day long. You can do this if you find what track the sun is following. If you imagine an axes from the top to the bottom of the bottle, the angle between this axe and the plane of the sunpath should be 90 degrees. If you are able to pose the bottle in its optimal position you don’t have to worry about changing the position throughout the day. Just make sure there are no shadows that blocks the sun. If you dont need the hot water right away you can store it in a freezer bag.
I found this to be a very cheap and easy way to get all the hot or warm water I need for myself and my family. Especially is this helpful if the only alternative is to heat water with gas or wood fire. The cost of charcoal to heat so much water can easily be a couple of dollars wich is a lot of money for many poor people. The material needed can be found in almost any African villages and that is a great advantage.
If you also add a small reflector you can get water even hotter. In a 5 liter plastic bottle I once got the temperature to the boiling point. The plastic bottle got a little bit deformed, but it did not melt and there was no leak.
To prevent the bottle from deforming you should normally not heat water in a plastic bottle to more than 80 degrees Celsius and the focus area should be evenly distributed around the bottle.
Have a nice sunny day! :)