Another well-known solar technology is rooftop solar water heating.
In active systems, water is heated by the sun in a variety of ways, depending on if the system is a direct system (better for non-freezing climates) or a closed-loop/indirect system (which can be used in freezing climates). Water is either directly heated, or a non-freezing liquid is heated then passed through a heat exchanger where it heats the water, which then transferred to a tank where the hot water is either used immediately, or stored for later use.
Solar water heating is a common form of solar technology, especially in warmer climates and equatorial regions where the energy available from the sun is most intense. However, with a little engineering and non-freezing heat-transfer fluids, solar water heating can be effectively used in any climate. South-facing and unshaded roofs are most effective for this technology.