Optical Testing for Solar Reflectors Before You Make Them

I await the video with interest...I'll have a lokk at the links later (when I'm at home)
I never got around to making my solar kettle this year (I did most of the other stuff on my 'to do' list)

Del

http://www.youtube.com/watch?v=9eY0xh23Anc is the making of the dome and making of 1 dish. I have done 2 tests. With a few ounces of water in a 7 liter alu pot (painted black with an oven bag round it) the air inside went to 100c in 10 minutes. I will weigh the pot later). Today with the same pot, with 7 liters of water inside, it has gone from 17C to 48C in 1 hr 15 minutes. It is a clear day with little wind too. I can do the math later! With solar cooking, I think a pot can be used as an oven, with the air transporting the heat from the sides to the food. Or perhaps, you could have a little water in the bottom and toweling round the outside of the inside to wick up the water. That way you could steam cook your food. (If it wicks up and steams off). Anyway, it is just the first couple of tests with this cooker. I hope others try it or make their own variations. Of course test with the laser test models first! (I didn't, instead I drew hundreds of lines on tracing paper which was bluddy tedious) and then I still needed to show fairly clearly what I was doing). Wish I had thought of the laser thing first! I also have high hopes that people will try half dishes and maybe half dish cusp collectors too. In that way, you could perhaps concentrate the light on a smaller area lower on the pot, insulate the rest and get faster cooking. Perhaps panel cookers could be made with a mold too? Either a dome or a dish mold made larger and put in the cardboard and cut and bend as necessary to fit fairly snugly to the mould Brian

I am not sure i understand. You built a pilot scale model? You built this model to explain why your latest solar dish is a a compound parabolic shape rather than doing the math to understand the mechanics? It seems solving the math to understand the mechanics of an optical system would: a. be cheaper, b. provide a simple way to analyze modifications and expected performance, c. Require less time, d. provide a means to estimate performance over a multitude of conditions without having to reproduce all those conditions. It seems more like you now know that something happens because of the system, but you will figure out how it works later.

I built the laser level model so that people who have not gone to school for decades could use 20 dollars worth of equipment to design their own compound parabolic dishes to suit their cookware and local conditions. Thousands of home diy people are building parabolic dishes for solar cooking. I am gently explaining that perhaps compound parabolics is a better way to go. The math was done by the laser bouncing off the mylar strip, this was done and can be adjusted faster than any computer program. Adjustments to the mylar strip can be done in real time to improve the optical configeration in a couple of minutes. The math gets even more complicated as the sun moves across the sky. It is easier with the laser level and it has to be explained to average joes. Nobody has ever bothered to explain what happens to a parabolic dish focal point when it is not exactly aimed at the sun. I have explained it with extremely modest equipment. And I have explained it pretty well too. Brian

This raises the question ..

Does the mathematical or empirical approach give better understanding?

I have a preference for the latter, but that's just my personal bias and flakey maths.
I feel that understanding is the key, once I understand I then know where to apply the maths.

Maths, like the cardboard, scissors and lightsource is just another tool.

Del

Well, bless your initiative-taking little heart! Good on you, here's a reward...

what is the power output in this??? how much KwH can be obtained????

I just made a solar cooker so far! It has a bit less than 1m2 of surface to face the sun. In my particular setup, at my location, that size has dilivered just over 200 watts to the food (or whatever you are cooking in the pot) for about 3 hours. The pot is a 7 liter pot painted flat black. Also, I made the solar cooker before I thought up the the optical experiment, and I didn't resolve the curve right behind the cooking pot (or behind the focus of the compound parabola) so there is leakage of light there. You can find info about compound parabolics at http://www.fossilfreedom.com/increase-output.html and at http://www.appropedia.org/Understanding_Solar_Concentrators I didn't find the fossilfreedom stuff until after I had made the dome. I think it is definitely worth a read and a look at the diagrams. If I had thought of the optical experiment first, then seen fossilfreedom, I think my dish might have been quite different! I notice that the fossil freedom stuff is all trough stuff. It would certainly be easier to fold the material! Dishes give more concentration and my aim is to stimulate basic homegrown research in solar cooking and that is why I did a dish. Hope that helps, Brian

Yes Dear,

You seem to have done a lot of home work and physical efforts to make a simple device to replace a Solar reflector.

I am Dr N P Singh, after having done my Ph.D. in the field of Energy XConservation from IIT Delhi I am working for a Govt of India Company (ONGC).

I tried to folllow the link to see the video but it did not work it will be appriciated if you can send the video on my e-mail; npsdhillon@gmail.com

-NPSingh

try search utube user gaiatechnician and I think it is the second video. I cannot send it by email as it is way too big.

Brian