Solar hot water heaters

I'm sold. Okay, the weather is quite conducive to solar anything, whether you like it or not. But last night at 9:30 pm, a full 3 hours after sunset, I had a super warm shower. HAd to even mix some cold water to get the temperature right. So much better than the feeble solar powered showers I had over a decade ago in Greece.

M has explained to me how they work- they're passive- no pumps, no moving parts, no fancy working fluid like glycol (was looking at a Popular Mechanics article on this, oy, so complicated). It consists of a reservoir (silver horizontal tank at top), the collectors (multiple black tubes coming down at an angle to be most exposed to the sun), and a box on top that has the equivalent of a toilet tank control.

Here's a photo.

No moving parts. The way it works is that the collector tubes fill with cool water- colder water drops into them. They heat up, and any other cooler water in the reservoir falls into them, displacing the hot water, which stays in the reservoir. A pipe from the reservoir supplies the hot water to the shower. When the reservoir gets too low, the toilet tank-like float valve admits more supply water into the the bottom of the reservoir. Then it falls into the collectors, and the water continues to be heated.

All for US$195, according to this article (US$400 shipped to Laos).
http://www.worldwatch.org/node/5060

This is pretty amazing:
http://www.environmentalgraffiti.com/sciencetech/china-solar-hot-water-capacity-soon-to-be-equivalent-to-40-nuclear-plants/822

Apparently all the solar collectors in China will produce an amount of hotwater equivalent to 40 nuclear plants.

It's got me thikning that I should try this at home, to knock down my natural gas usage. I was told earlier that my tankless gas powered water heater isn't solar hot water friendly (e.g., I can't use it as a pre-heater to the gas heater, which theoretically would reduce the amount of gas used to heat it to where I want it). But maybe it can be run in parallel. When the solar heater gets low (cool), maybe a thermally controlled valve can call upon the gas heater. One has to wait for the gas heater to fully kick in; that water should be used to replenish the solar heater in order not to waste it.

Some sources:

http://www.made-in-china.com/products-search/hot-china-products/Solar_Hot_Water_Heater.html

http://www.china-solarwaterheater.com/

How about some Detroit or Wall Street bailout money for a US solar industry?