Solar heating is a more efficient way to utilise the sun’s power than photovoltaics, but somewhat more limited in applications. It is also much cheaper. In fact the team at The Seitch built a solar thermal panel for $5. They used the heat dispersal tubing from the back of a fridge (which had been purged of CFCs at the local dump) mounted behind a sheet of glass.
If you watyched It’s Not Easy Being Green (we finally caught it on DVD-RWs from my parents) you might have seen the clever heat trap built into the Strawbridge’s greenhouse. Perhaps a solar thermal panel such as this could make a near tropical greenhouse for exotic gardening.