The history of solar energy started in 1921, when the photovoltaic effect was discovered. In the 1950s PV power satellites were sent into orbit. The oil embargo in the 1980s led to a reorganization of energy politics and heralded the Green Revolution.
Factors like climate, site, design, and heating needs of a house determine what kind of hot water solar system is best for your home. Active systems require an electrical pump, whereas passive systems work without electricity and rely on gravity.