Solar Thermal

Sunlight contains an incredible amount of energy. When sunlight falls on a dark surface, that surface heats up. Trapping sunlight, heating something up, and storing that heat are what solar thermal is all about. Super insulated buildings can be heated by solar energy (as long as there is sunlight). Solar thermal systems can be divided into “passive” and “active”. Passive systems have no moving parts. A black painted tank filled with water and exposed to sunlight is an example of a passive system. An active system has moving parts (blowers, pumps, valves, etc.). An example of an active system might be a rooftop mounted solar thermal panel filled with antifreeze (so that it does not freeze during the winter) that is connected to an indoor insulated water heater. There is a pump which pushes the antifreeze through a heat exchanger coil in the water heater (where the trapped solar heat is given over to the water) and back again to the rooftop solar thermal panel where it picks up more heat from the sun. Active systems tend to break down and should not be used where a passive system will suffice. Both active and passive systems can heat air, water, and even rock. Passively and actively heated solar building both use some sort of thermal storage system (water or rock) to trap excess solar heat and release it gradually over time, maintaining an even temperature indoors. Some people have even constructed solar thermal “heat engines” which turn sunlight into mechanical power to spin generators, pump water, and run drills, lathes, and fans.