Posts Tagged ‘Fresnel lens’

13 March

Solar Scorcher In Action


Dear Friends, Visitors/Viewers/Readers,

(Please click on red links below)

Ever tried to melt a stack of pennies, burst a glass bottle, or incinerate wood using the power of Sun?!

Periodically I ‘d like to remind us the power of our Sun in a great variety of places. For a change of pace, I’d like to share this interesting video of Grant Thompson, who created his sun-scorcher from a part he found inside a 13-year old Toshiba 50-inch flat screen TV (picked it up for free, hacked it open, and used only the large and flexible plastic sheet that is effectively a giant Fresnel lens.  When placed under the sunshine,  take a look how quickly and hot this Fresnel lens or Solar Corcher focuses the sunshine on one spot (boiled water in less than a minute, welded a nickel to concrete, and instantly torched any piece of wood in its way).

Warning: Do not try this without adult supervision and adequate training. Misuse, careless use, of tools or projects may result in serious injury property damage or death. Concentrated solar energy can start fires and cause personal and property damage. Extreme caution is always advised.  Now, you should be ready to view this video, below:

Legalities: As for treating pennies, the federal law states that there are exceptions made for use as “educational, amusement, novelty, jewelry, and similar purposes as long as the volumes treated and the nature of the treatment make it clear that such treatment is not intended as a means by which to profit solely form the value of the metal content of the coins.” For more information, please visit:

Grant Thompson also shared the steps how he obtained his Solar Scorcher  by hacking it out of an old TV:

Hope you’ve enjoyed this slight diversion and had just been reminded of the power of the Sun.

~have a bright and sunny day~

gathered, written, and posted by sunisthefuture-Susan Sun Nunamaker

any comments or suggestions will be welcomed at


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5 January

Cooking With Fresnel Lens-Using Solar Energy


Dear Readers,

If you are in favor of renewable,  clean, or solar energy, please sign this petition for FIT/CLEAN Program, accessible at Thank you very much.

Dear Friends & Readers,

In light of my Jan. 1, 2012, post on Kiva (microfunds for small businesses throughout the planet), I started to search for more ideas and applications (for consumers and/or entrepreneurs) that would be useful for people every where, be it for developed and/or developing countries.  I came across the idea/application of Cooking with Fresnel Lens.  Fresnel lenses, originally created for lighthouses, are glass structures used to magnify and increase the power of light.

How a Fresnel lens focuses light. Wikimedia Commons

Cross Section Comparison of Fresnel lens 1 vs plano-convex lens 2 (wikimedia)



Due to its ease of use and low costly nature, there are many different possibilities for its usage.  Cooking with a Fresnel lens has become popular and is a viable alternative for green cooking or in areas with little electrical or gas power.
Fresnel lens (play /frˈnɛl/ fray-nel)

Lighthouse Fresnel Lens, on display at the Musee National de la Marine, wikimedia

is a type of lens originally developed by French physicist Augustin-Jean Fresnel for lighthouses. The design allows the construction of lenses of large aperture and short focal length without the mass and volume of material that would be required by a lens of conventional design. Compared to conventional bulky lenses, the Fresnel lens is much thinner, larger, and flatter, and captures more oblique light from a light source, thus allowing lighthouses to be visible over much greater distances.

Very few tools are needed in cooking with a Fresnel lens: a lens capable of heating a large area with a spot focus (about one meter square): For a single square meter Fresnel lens, you will want to keep the focus of the light about 10 centimeters (four inches) wide on the cooking pot. This will ensure optimal heat distribution.  It is also helpful to have a stand that allows raising and lowering of the lens so to be able to keep an ideal distance from the cooking area.  Usually, a cast iron cooking pots or pans is ideal for its even heat distribution and its speedy  energy absorption.  Keep in mind that cast iron can be incredibly hot and takes some time to cool off, so be sure to handle with care.  Using a pan that is 15 to 18 cm or a pot with a bottom of the same dimensions will allow good heat distribution with minimal burning. It is best to use only water (not oil) as the cooking medium since adjusting the lens may ignite the medium and cause severe burns. This setup can easily boil water for pasta, vegetables, and meat.  Preheating the pots or pans before adding the food would help to insure even heat distribution and prevent burns or scorching.  Last but not least, be sure to never allow a spot focus to concentrate on one area or become too small.  Even though cast iron is hard to damage with this method, enough solar energy can work as a forge and actually melt through all but the sturdiest of metals. In the video clip below, our chef Denise Rojas is using olive oil (rather than just water) and is therefore needing more protection such as her goggle from potential burns.

Cooking with Fresnel lens also has the added advantage of outdoor cooking: keeping the fumes outdoor so to keep inside of the house free from air/aroma pollution.

Happy Cooking!  Please feel free to write me with your comments (esp. if you’ve tried to cook with Fresnel lens) and suggestions (care to share your recipes for Fresnel lens?!).

~have a bright and sunny day~

sunisthefuture-Susan Sun Nunamaker,


Any comments and suggestions are welcomed at

Please also get into the habit of checking at these sites below for more on solar energy topics:

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