Well, if you want to circulate water other than thermo-syphon and not use an electric pump, then there is a device called a pulse flow valve, see link
PULSE FLOW VALVE FOR WET BACK | Trade Me
It fires bursts or pulses of heated water to your HCW or radiators.
I cannot see the issue with using a small 20w 12volt magnetic drive pump to circulate the water, just use a small 30W PV panel, these pumps have a life of approx 15,000 hrs. If sufficient volume of water is pumped to keep the in/out delta temperatures < 10 degrees then provided the pipe work is well insulated, losses are small.
To heat a house, a box on the exterior wall directly heating the room air would be the most efficient as if designed correctly with cooler air passing between the glazing and bits that get warmed by the sun, would prevent much of the re-radation back through the glazing.
You can always make a heat pipe to move the heat from the external solar panel, except diy ones only work in an upwards direction with the condensing area at the top of the pipe and heat source at the bottom. A 20mm dia copper evacuated tube containing R22 refrigerant will move 5 KW heat along its length over 10 meters. I still think water is simpler.
Cheers
Mike in NZ