An idea I had based on Steve's solar cooker

[Original_Intent]

I was thinking why couldn't a larger version be used to heat water for hot water usage in homes? I actually worked up some fairly detailed ideas before I thought to look online and realize I was reinventing the wheel - there are already systems out there that are almost exactly what I was envisioning.

What I did not see in existent designs was the use of a parabolic reflector to concentrate the suns rays from a larger area. There are some concerns, obviously. The lifted edges of a parabolis surface would be extremely susceptible to wind damage. Drainage to get rid of rain would be necessary to keep from having a swimming pool on your roof. Keeping it clear of snow would also be needed.

Benefits would be that during the summer, much of the heat would be utilized for hot water, rather than heating attics which cause cooling costs to rise - double benefit! - free hot water AND lower home cooling costs. Also, it's obviously very clean energy. So much easier than photovoltaic - why convert the solar energy to electricity with the expense of PV cells when you can harvest the heat energy using reflection and dark surfaces at the capture point?

Another thought I had was on fossil fuel power generating plants - wouldn't preheating the water as much as possible with solar before it entered the plant lower the amount of foosil fuel (usually coal) required to boil the water to turn the steam turbines? I am not expert on power plant design, it just seems that having some black pipes running east -west in a concave trough with decently reflective material should significatnly raise the temp of the water...is this being done anywhere, is it a good or bad idea or is there part of the equation I am missing? Any idea if the concept has merit Dr. Jones? (or anyone else that knows?)

[SmallFarm]

I know that the solar water heaters are getting pretty popular down here in Arizona, but I don't think there's really need for extra sunlight reflecting to the pipes (at least not here). Just sitting in my garden hose the water can get hot enough to burn me. The solar water heaters I've seen have black pipes running inside a glass box with the back painted black and based on how hot water can get in my lighter colored garden hose I imagine it can get pretty darned hot in a regular solar water heater.

[Jason]

Just go for gold and build a solar powered steam generator.....always sell the extra juice back to the grid....

[Original_Intent]

Just go for gold and build a solar powered steam generator.....always sell the extra juice back to the grid....

That was my thought also - if you could actually gather enough to boil the water, you could add a steam turbine and get some electricity as well as hot water.

[BroJones]

Thanks, OIntent.

Good points, lots of variations in use around the world, happily.
Here's an idea for hot water: put a dark 30 gallon drum up on a platform, and put a LARGE solar funnel around it. Faucet at the bottom allows you to extract hot water, e.g. for a warm shower. Cover and insulate at night to retain the heat.

Cold water: do the SAME thing but uncovered during night, covered fully during the day (the funnel plus a cover over-top, to keep the sun out, and some insulation during the day only) -- and you will have COOLED water, by the radiant-cooling physics I've explained before.

Thus, side-by-side hot and cooled water, both on a raised platform for gravity feed. I plan to try this out this summer.
Thanks, OIntnet.

[bobhenstra]

Thanks, OIntent.

Good points, lots of variations in use around the world, happily.
Here's an idea for hot water: put a dark 30 gallon drum up on a platform, and put a LARGE solar funnel around it. Faucet at the bottom allows you to extract hot water, e.g. for a warm shower. Cover and insulate at night to retain the heat.

Cold water: do the SAME thing but uncovered during night, covered fully during the day (the funnel plus a cover over-top, to keep the sun out, and some insulation during the day only) -- and you will have COOLED water, by the radiant-cooling physics I've explained before.

Thus, side-by-side hot and cooled water, both on a raised platform for gravity feed. I plan to try this out this summer.
Thanks, OIntnet.

We used a "passive" solar water heater for about 10 years on our cabin. Just two 40 gallon water heaters stripped of outside shells and insulation, painted flat black and plumbed into our normal water system. At first we used them without a covering of clear plastic, water was just warm, we put a frame up covered with heavy clear plastic the water was very hot. We found however that using just one tank was more efficient than two. We removed one tank and re-plumbed. Had sufficient water for summer use, but not anywhere near enough for winter use. So we drained the tanks in early winter just to be safe.

Remembering, these were "passive" solar hot water heaters. Getting by as cheap as possible. We could have plumbed pipes inside the tanks, filled the tanks with oil or anti-freeze, let the sun heat the oil or anti-freeze and circulate our water through the hot oil.
We decided against that idea because of weight and handling concerns. KISS was, is and always will be our motto!

We then put steel pipes in our wood burning stove, using "thermo" siphoning into a 50 gallon tank, we had more hot water than we could use for winter use, and there were nine of us. We had to clean the pipes inside the stove once a week, wire brush at first, then we discovered it was easier just to scrape the pipes with a hooked steel poker. But that's a small price to pay for hot water. We also had to clean the whole water system after every winter to rid the pipes of hard water deposits. But that only took an hour, we plumbed the system to more easily take care of that minor problem.

The bigger the water tank the better. My oldest son has a 200 gal water tank hooked up to his wood burning stove, he burns mostly lump coal in a very efficient Harmon stove, same stove I have in my cabin. Since his house is all solar powered, he will use a very small inline pump to keep the water circulating instead of thermo siphon. His isn't quite finished setting it up yet, looks like I'll need to go over and supervise---- He also has 5 commercial solar water heaters he hasn't hooked up, he got them free just for the hauling, he'll only need one, he'll keep the other four for back up, or for heating the water in the swimming pool he keeps talking about. He has four wind powered generators we're going to install on top 0f 20 foot light poles. But his solar panels are working very well, he's in no hurry for that project. He uses a large fork lift battery to store his power, however his wife doesn't use electricity to cook with. They have a 2000 gal propane tank, he figures a full tank of propane will last him five years. And the propane is plumbed to everything in his house for back up in case of failure of something. He's also working on building a propane generator.

That's where I'll live when AHBL! But for now my cabin is nice and quiet, perfect!

Bob