This idea is *mainly* to produce heat for hot water, but also to produce a little bit of mechanical power to generate electricity.
We have a couple of not-unusual components, and some slightly odd components :).
Firstly, our working fluid: mostly water, but with some corrosion inhibitors and perhaps
some antifreeze. The pressure of this liquid, when the system is cool, will be significantly sub-atmospheric... about .25 in Hg, so that it's boiling point will be about 40F.
Naturally, all of the components need to be strong enough that they aren't crushed by the atmosphere when the working fluid is cold.
The first not-unusual component is a solar collector, mounted on the roof. It should be efficient (able to produce high temperatures even when the air is cold), big enough to collect enough heat for our regular domestic hot water needs.
The second not-unusual component is the heat exchanger. It should be efficient, and should be big enough to store at least one day's with of hot water. It can be located almost anywhere, though the basement is probably best (due to it's weight).
The *unusual* components are a gas/liquid separator, a condenser, and a water turbine.
The separator is mounted as high as possible, possibly on a tower.
The condenser is a direct contact heat exchanger, bringing cool liquid into contact with steam, resulting the steam condensing and mixing into the steam. The best design is probably to have the cold liquid enter the condensing chamber through a shower-head type device near the top, the steam enter through an airstone just above the bottom, and a drain at the bottom.
The device works as follows:
Cool liquid enters the bottom of the solar collector, and *some* of it (but not all of it) boils as it passes through. Bubbles of steam alternate with slugs of liquid.
The bubble of steam provide the bouancy to push the water up the pipe to the gas/liquid separator.
The liquid from the separator flows down another pipe, through the heat exchanger, then through the water turbine, then up to the condenser.
Steam from the gas/liquid separator is also piped into the condenser.
The condenser is located at the highest point on the roof; above the solar collector, and below the separator. Liquid draining from the condenser goes into the bottom of the solar collector.