How to Build a Parabolic Solar Heater
I am a fan of solar energy, especially when its limitations are accounted for. Through research, I have decided that the heating aspects of solar is easier to utilize than converting it to electricity. Its also much cheaper.
A man that has done quite a bit of work in this area is Dan Rojas of Green Power Science. He has done quite a few projects that I admire and plan on emulating. He also sells some supplies for these projects and that where I bought the solar film I used in this project
Re-purposing a Direct TV Dish
What I did was dismantle the Direct TV dish and sand it smooth, I then painted it with black paint (and should have sanded that smooth also).
I cut strips of the mirror film and attached them to the dish. Its easiest to just cut straight strips and overlap them slightly. Early cartographers learned that it is impossible to draw a round earth accurately on a flat sheet of paper, its the same with the film and a parabolic dish. You cannot just slap the film to the dish, it will bubble up and refuse to form to the shape. Some try to calculate the curve and cut out “pie” slices, but this works best in theory, the math works, but it does not translate well to the real world. Strips that are allowed to slightly overlap each other works the easiest.
You will find its impossible to separate the thin strip of film from its backing by hand. Mr. Rojas suggested to use slap a piece of tape to both sides of the film (at the end of the strip, and don’t let your tape strips touch). When you do this the film and the backer adhere to the tape so when you pull the tape in opposite directions the film will peel away.
Its a lot like Window Tint
Very carefully install the film on your dish, if you have ever installed window tint, its the exact same process. I started in the center and worked outward, as this was easiest for me. I imagine it does not make a big difference. Just try not to overlap the strips too much, don’t allow bubbles to form, and don’t get two worried about the holes for the mounting bracket.
After the strips filled the dish, I took a very sharp razor knife and cut a cross into the area of the mounting bracket holes. This allows the screws to be inserted back into the dish. I also trimmed around the edges of the dish.
For some reason (dust and a bad paint job most likely) the film did not want to stick at the edges. I had planned on running around the center of the dish with tape for decorative purposes, but I ended up doing it to help hold the film down.
Reinstall the Dish and Focus the sun on the Jar
I then reinstalled the dish on the post (don’t just leave it there, the focused sunlight can be dangerous – so don’t leave it unattended for long periods). Pointed it a the sun, and rigged a empty glass jar at the focal point.
The sunlight then heats whatever is in the jar. You can use this to cook. I have seen this on a large scale to boil water, and even make steam. In California, Rojas’s dish actually burned a wood board. I was not patient enough for that, but it did heat the jar uncomfortably hot. (it was about 4pm in the afternoon, and there are a lot of trees in my neighbor’s yard, so that contributed to the heat difference.)
I plan on working with this a little more, and seeing how effective this can be to cook. Who knows, I may even come up with some recipes.
