Probably, almost everyone in childhood burned inscriptions and drawings on a tablet or tried to start a fire with a magnifying glass. As you know, this is possible due to the fact that a magnifying glass focuses the sun's rays at one small point. Remembering this, the author came up with the idea of creating a solar oven for cooking based on a large magnifying glass.
Materials and tools that the author used to create a solar furnace based on the Fresnel lens:
1) old projection tv
2) aluminum profile
3) bolts and nuts with clamps
4) wooden bars and slats
5) drill
Let us consider in more detail the creation of this design of a solar furnace and the main points regarding its operation.
Naturally, the temperature at the focal point depends not only on the intensity of solar radiation, but also on the size of the magnifying glass itself. Cooking and creating a solar oven will require a rather large magnifying glass, so the natural question is: where to get it?
In addition, the lenses that you used as a child were made of glass and were quite thick, and therefore the glass of the required size for the solar furnace will be even thicker. In addition, a large magnifying glass is not so easy to find. because they are not particularly popular. And even if you get such a glass, it will cost a lot of money, and it will also be heavy, which means inconvenient in practical use.
While searching for answers to these questions on the Internet, the author came across a so-called Fresnel lens. They are much more popular for several reasons. Firstly, they can be large and at the same time only a few millimeters thick. Secondly, they can be made not only of glass, but also of plastic, which greatly affects the price of such lenses in the direction of their cheapness.
Such lenses can be ordered through foreign online stores such as Taobao, Aliexpress, Ebay.The author also learned that such lenses are used in models of projection televisions.
Below is a diagram of the structure of one of these TVs:
Therefore, the author chose to use a lens from an old projection TV that was no longer working; by the way, these can also be found on flea markets of radio markets.
As a result, a Fresnel lens of the same size was dismantled from the projection TV screen.
Since the lens itself is quite thin and plastic, for its practical use it is necessary to create a frame in which it will be mounted.
Based on the aluminum profile and wooden blocks, the author built a rigid frame to fit the size of the lens. In order to install the lens in one position, the author also made a tripod from wooden blocks, and drilled several holes for fastening the clips in its vertical guides. On the lens frame, special shelves were also made into which the bolts are inserted, fixing these bolts in the appropriate divisions on the scabbard of the stand, you can adjust the height of the lens and the tilt of the lens.
After the lens was on the stand, it remains only to take it out to the sun, determine the point of focus of the rays and put in it a pan or frying pan where the food will be prepared. Be extremely careful when installing utensils for cooking under the focus point of sunlight, since the temperature at this point can reach 1000 degrees. In order to adjust the cooking temperature, place the pan a little higher or lower than the focus point.
Once again I remind you that you must adhere to safety precautions when working with such lenses so as not to harm yourself and others. Below is a video clip in which you can see all the power that this design of a solar furnace is capable of: