We have great results in the winter time with solar energy, sometimes even when it is 20 below zero.
In the morning, right around daybreak, we open the curtains and shades on the south windows to get passive solar radiation. About the time the sun goes down, we draw the shades and curtains tight again. Seems to work really good, and has a few thousand year history of working!
We also have had great luck using stored solar energy for powering cars, trucks, mowers, and even our house furnace!
