Solar Thermal vs. Solar Photovoltaic: Sensible vs. Sexy?

Can you post any pictures, pretty please?

a 15 watt panel will generate 15 watts at high noon, with the collector at exactly 90 degrees to the sun. Well in a fixed position, the best you can expect is 6 hours at 100%, but you need to live at a low lattitude. so in general, you will get about 75 watt-hrs/day. thats worth oh, $.008 per day or 3 per year. so $210 in materials is a 70 year pay out.

your cooker is making 200 watts per hour? so it'll make 1 Kw-hr or $40 per year. looks like a payout if you use it 1 time per week to cook with.

200W doesn't sound much but it isn't bad for a less <1m2 surface (if I understood you correctly or is it 1m in diameter?). What did you make the reflector material from?

Years ago I saw a similar arrangement to yours, a 3m dia collapsable parabolic reflector made from a flimsy reflector material, like the ceiling fluorescent light-boxes have, and used to boil about 5liter of water in a vat that was coated black on the out side, on a nice sunny day.

According to the designers they ment to use it in some poor parts of africa, where they used to work themselves for a while, and they said it also had an oven made for it.

So you're on the right track just try to use a good reflector material that is also light.

Ofcourse the electrical solar is better because you can store the energy in a deep-cycle battery but as you put it it is a more expensive setup.

You said the electric is better because the energy can be stored in an expensive battery. But another poster pointed out the 70 year payout on the electric system. I am not sure what an economist would say about a 70 year payout compared to a 1 year payout. And an optimistic lifetime for the panel is 20 years with the battery life less than 10. People laugh at people who are using solar cookers. Yet solar cooks are using sound economics and reducing CO2 emissions. Perhaps it would be sensible to spend some money on solar cooking research as well as solar panel research? Brian

Of course, electric energy can be stored conveniently in batteries as opposed to heat. The 70 year payout on the electric system is not a good option if you can find something better go for it. This is more of a financial thing that you must work out what's best for you.

When it comes to using renewable energy, in my view, being dependent on a grid is a little beyond comprehension. You are still at the mercy of the energy provider. This is something that should be more Tailor made for the individual user and leave it up to them if they wanna join the grid or not.

Do not look for expensive reflector materials either, like a guy tried from SA once! The efficiency you would get as opposed to a reflector in a fluorescent light-box is minimal. And I guess it must be pretty cheap as well having been so widely used for such a long time.

Do not give a fat rats...what people think either just do what you think is good for you as well as affordable. The solar cooker, I told you about, was setup in a square in Munich back in 2002. If it was good for those Bavarian designers, who demonstrated it, then I cannot see any reason why it should not be good for the rest of the world even. I recently posted a question here to find out if anyone would know how that reflector material is made in those fluorescent lights and nobody could seem to give a proper answer. Therefore, you cannot trust this blog too much either because a lot of people have nothing but bad ideas.

So, you better keep on searching until you'll get the desired result and screw those who criticise or laugh at you. They are the hopeless ones or at best the sales type of people who could later sale your product.

good luck!

A large number of the large-scale solar projects are solar thermal. They use mirrors to focus energy on a central target to create a hot fluid for use in a turbine or other form of generator.

A reflective solar heater is more cost-efficient. To keep the technology simple and lower costs is the challenge. Figure out the watts you need and build your reflector the size you need with a power driven sun tracker to keep it aimed at the sun. At the focus use a helical tube of water to create steam. Use the steam to power a steam engine of the right size to drive a generator which will produce the electrical power you need. Check Mike Brown's Steam Engines, Green Steam Engines, Lysholm expanders and Tesla Turbines and decide which type is most suitable for your purposes.

Now this will work for daytime power. For nighttime you have two choices, spend a lot of money on a battery bank or use a fuel-fired boiler to run the steam engine/generator at night. For this you have to decide on how much power you will use at night. If all you do is keep the refrigerator/freezer operating you can get by with fewer batteries, but if you want lights, TV, computer, AC and other electrical appliances you may need a larger and more expensive battery bank than the alternative.

The alternative is a fuel-fired boiler using a forced draft open flame which is very clean. You can use any liquid or gaseous fuel very easily. A solid fuel would take some extra machinery to feed the fuel in mechanically. Your choice of fuel depends only on what is available and what you decide to use. [Biofuels like ethanol, methanol or vegetable oil, compressed dried vegetation, wood pellets, charcoal would work. Could also use furnace oil, kerosene, pea coal if needed.]

Whatever configuration you use you will be taking a step in the right direction, energy independence. I have two left thumbs and no money or workshop, but I would love to build one. Please post photos of your project and inspire all of us.