How solar-thermal panels work

In the simplest panels, Sun heats water flowing in a circuit through the collector .The water leaving the collector is hotter than the water entering it and carries its heat toward your hot water tank.The water doesn’t actually enter your tank and fill it up. Instead, it flows into a pipe on one side of the tank and out of another pipe on the other side, passing through a coil of copper pipes inside the tank and giving up its heat on the way through. You can run off hot water from the tank at any time without affecting the panel’s operation. Since the panel won’t make heat all the time, your tank will need another source of heating as well—usually either a gas boiler or an electric immersion heater. The cold water from the heat exchanger returns to the panel to pick up more heat.An electric pump (powered by your ordinary electricity supply or by a solar-electric  cell on the roof keeps the water moving through the circuit between the collector and the water tank.