Off-grid cooking: How to make a Fresnel solar cooker

(NaturalNews) For those interested in living off-grid, solar energy offers one of the best and most readily-available sources of energy. There are many ways to harness the sun's power for performing a number of tasks, such as creating electricity and heating a home.

The sun's rays can also be used to cook meals. Building a simple cooker using a Fresnel lens to focus sunlight on a cooking apparatus is easier, cheaper and more effective than you might have imagined.

Fresnel lenses are devices you've seen used in many ways, perhaps without realizing what they are or how they work. Essentially a Fresnel lens accomplishes the same thing as a convex lens -- it concentrates light by bending the rays towards a focal point, creating a powerful beam that can be projected for long distances, or aimed at something nearby, such as a cooking pot!

The difference between a convex lens and a Fresnel lens is that the latter performs the same function, but with a much smaller thickness. Its design incorporates "steps" comprised of ridges arranged in concentric rings which are progressively angled to focus light towards a central point, thereby eliminating the need for a thick convex lens.

Fresnel lenses are the ones used in lighthouse beacons, but they are also found in the plastic covers of car headlights, taillights and other common devices. The solar cookers I will be discussing here are made from the Fresnel lenses found in old rear-projection wide-screen television sets.

They are easy to find on eBay, where you can purchase one very cheaply, or on Craigslist, where you will often find them being given away. You may also see one of these old TV screens discarded on the side of the road, waiting to be picked up by the trash disposal trucks. You may already have one laying around your garage or storeroom.

Once you've found or purchased your own Fresnel lens, making a frame for the lens and a stand for holding the cooking apparatus (frying pan, dutch oven, etc.) is a relatively simple undertaking and you may already have all the materials you need just lying around the house.

There are many designs to be found on the Internet, some with detailed plans and others that just give a general idea of how they work. There are lots of YouTube videos on the subject, as well.

But the basics are pretty much the same with all these designs. You'll need to fashion a free-standing frame to hold the lens, which can be adjusted according to the angle of the sun's rays. The cooking stand needs to be high enough and strong enough to hold the cooking apparatus at the focal point of the lens -- roughly two or three feet from the surface of the lens.

The focal point can be adjusted by moving the frame in relationship to the cooking stand while also adjusting to the angle of the sun's rays -- it takes a bit of practice along with some trial and error, but it's relatively easy to find the right position for cooking.

One of the advantages and disadvantages of this type of solar cooker is that the Fresnel lens is so powerful that it can burn food easily, but it can also cook food very quickly. It takes some time to get the hang of it and to find out the best techniques for different pots or pans and the types of food you wish to cook.

It's important to be very careful handling Fresnel lenses as well, because they can create flames very quickly (within a matter of seconds) and can also burn the skin. Particular care must be taken to not cause damage to the eyes.

For a clear and simple design for a Fresnel lens solar cooker, click on the GraywolfSurvival.com link found below. I have also included a couple of other links presenting variations on the basic theme as well as one explaining in detail how Fresnel lenses work.

Sources:

http://graywolfsurvival.com

http://www.offgridworld.com

http://rimstar.org

http://www.explainthatstuff.com