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

Thursday, February 5, 2015
By Paul Martin

by: Daniel Barker
Thursday, February 05, 2015

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.

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