can your lawn keep your home warm?

The Guardian has an article about how "[a]n environmentally friendly and low-cost heating system could drastically reduce the nation's reliance on fossil fuels." The idea is to use domestic heat pumps to absorb heat out of the ground (obtained during the day from the sunlight) and pump it into one's home for household use. Sound futuristic and wacky to you? Apparently in Sweden, 97% of all new buildings are powered these pumps.