Inflatable Solar Concentrator
This is a concentrator to concentrate the sun's energy to a point for cooking food or focusing it on a small solar battery recharger. I got the idea for this from Cool Earth's solar concentrators (see http://www.coolearthsolar.com/technology). In addition to saving energy, reducing pollution and speeding up the recharging of batteries (especially on cloudy days), food cooked in these concentrators would form fewer, if any, carcinogenic compounds during cooking compared to food cooked on a grill, depending on the food being cooked. Animal products are the most carcinogenic and not very eco-friendly either according to the UN and many other authorities.
The concentrator would be made of two sheets of PET (polyethylene terephthalate) polyester film (see http://www.coolearthsolar.com/materials), one aluminized and one clear. You can get mylar sheets from make-your-own-balloons sites online. Each sheet would be cut to the shape of a disk and fused together at the edges except at one point where a small channel for inflation would be created. For larger concentrators they could be cut into contoured wedges that could be fused together to form a more parabolic curve. Be careful though as the larger the concentrator gets, the more heat it produces, and it may get hotter than the materials or your food or charger can withstand.
To use, the concentrator would be filled with food or the small solar charger, inflated, sealed with a clip and angled to face the sun. Containers for food would need to be matte black and very heat conductive to absorb the concentrated solar energy. Food or the solar charger would be put into the concentrator in one of the following ways:
Integrated Container: A container permanently sits inside the reinforced opening in the center of the clear plastic. A lid is secured onto the container by some means. I don't recommend this for a reusable design as the container couldn't be separated from the concentrator for washing. However, it could work in a disposable design for heating packaged food in a black metal container covered with heat-sealed plastic film.
Separate Container: A container is held in place with its rim under the reinforced opening in the center of the clear plastic and its mouth secured by a screw-top lid above the plastic. Other methods of securing the container, such as clips, are also possible and the container and lid could be secured between the reinforced opening of the plastic and something else as well.
Integrated Pocket: A black pocket (for food) or clear pocket (for a solar charger) is sealed into the clear plastic with a slide lock seal on the outside. This could be included with packaged food products. The clear pocket design would be ideal for solar chargers.
Integrated Receptacle/Separate Container: Features a receptacle of the same configuration as "Integrated Container" above. A glass receptacle would trap some heat next to the container.
Separated Receptacle/Separate Container: Features a receptacle of the same configuration as "Separate Container" above. I think that this method, with a glass jar would be the most effective cooker and easiest to make a prototype of.
Reward: A free one for cooking.