Solar Thermal (ST) water heating is a great way to take advantage of free energy from the Sun. Before we go in-depth on how solar thermal water heating works, let's go over the bare essentials.
1) Solar Thermal water heating is different from Solar PV (electricity)
2) Solar Thermal water heating is different than Solar Thermal power generation.
3) Put simply, solar thermal water heating is water running through a copper pipe that is sitting in the sun. The sun heats the pipe, the pipe heats the water running through it.
4) In most cases ST is only meant to replace a percentage (up to 70% for residential users) of your water heating needs. It does not usually get rid of the need for natural gas or electric heating.
So these are the basics. Keep reading for much more information on ST water heating!
-check out this wikipedia image, that was also taken in Santorini like the one I took below.