reasons why concentration of the sun might be effective.
the exposed area could be smaller, reducing loss back to the environment.
you could achieve steam , that you could not possibly with non-concentrated sun, steam could be created that would form a steam bubble that would motivate the water.
these 2 things might offset the disadvantages of having to aim the lens somehow.
them coffee heaters are lotsa watts (as stated above) and you would have to have one big arse lens , or many lenses combined to collect the sun to concentrate it.
but the logic of the IDEA is what i like, to think of ways to motivate the fluid without pumps.
this trick works in the coffee heater to move the water quite a few inches without a pump, WHILE heating the water, 2 stones one boyrd.
so much of todays thought processes revolve around what we have seen, what we do, and old archaic ideas that were thought up when power was 2.5c , and death by CO2 was because you TRIED to kill yourself :-)
If we can take all Waste by products of things and utalize them, where then would we be?
will your CPU heat all your hot water? no but the waste heat from your whole house will.
just how much steam power could be made of the waste heat of an automobile engine? enough to run 2 more cylinders for free?
so i like the IDEA, even if it is not practical as presented.