I've been wracking my brain for a simple way to implement a Sterling Engine as a water pump, rather than an engine, and using solar power as a heat source, rather than a flame. The attached diagram is the simplest implementation I could come up with: Rather than pushing/pulling a piston, like in a Sterling engine, the gas in the outer cylinder pushes/pulls a column of water. Rising water column should suck in water through the bottom valve; descending water column should push the water out the top valve. (Alternate design: Rather than an inner and outer cylinder, it could be configured as two separate cylinders, one for water (with the valves), and one to heat gas in. These two cylinders would be connected by a tube at the bottom.) If someone already came up with this, which I suspect is the case, please ignore the rest, and just let me know what term/name I should look-up. I don't have the physics knowledge to figure out if this design will actually work like a sterling engine, and pump the column of water up and down. Will it? Or, will the dynamics of water somehow mess up the cyclic nature of the expanding/contracting gas? If it WOULD work, would it self-prime? (i.e. Starting from reservoir water level, would it fill the inner cylinder with water?) Any other things you think I should consider?