The heat does not have to be converted to electricity, 60% of a home's energy usage is in the form of heat. 42% for space heating and 18% for water heating.
I am deriving 33% of the energy used for heating our startup headquarters with a solar thermal system we rigged up out of cardboard and black aluminum foil. We are bootstrapping and the electric heat the building has is much more expensive per BTU than oil/gas.
Black aluminum foil will reach 156F in direct sunlight in December in Southeast Connecticut. I have read that black aluminum foil will convert 88% of light to heat. We have 50 square feet of these panels that spend every clear or partly cloudy day between 130-156F, warming the building through convection. On a clear day with an outside temperature of 27F our rig heats two floors to 61F. We are going to add another 50 sq. ft. of panels to attempt to reach 70F+
And the heat mass of the building keeps it warm for four hours after the sun sets. We have some large floor to ceiling windows and we installed the panels so they stand behind the bottom three feet of some of the south-southeast facing windows.
The total cost of our system was $94 and a couple hours of time.
If we owned the building I would install solar hot air panels (basically an insulated rectangular box with a plexiglass top and black aluminum foil tacked into the inside with an intake and exhaust) and run a couple air ducts into the building.
This building already had a solar hot water heating system, with two 4' x 8' water heating panels on the roof. This gives us much of our hot water.
We are awash in solar energy, and heating air with the sun is the cheapest and most efficient way of capturing it. Solar hot air is THE low hanging fruit of solar power.
The only downside with our system is that there is no energy storage. But that could be engineered easily. A concentrated solar trough connected to a buried large cement block or other heat sink could easily store a day or two worth of heat for night time and cloudy days.
55% of the days here are clear or partly cloudy and great for solar heating.
Update:
If you were wondering what we are doing in Southeast CT, we are participating in the first of what we are calling The Winter Startup Challenge, our own laid back, low burn rate version of Y Combinator.
My team rented a waterfront three bedroom house in a beach community for the offseason, October-May. Being the off season we got a great deal.
We have to leave May 31st. We have 8 months to develop the product and reach ramen profitability or get funding. The product challenges have been overcome, the prototype is being built, we have committed buyers waiting for the first production run. Five months left.