Solar Thermal and Geo Thermal
Solar Heating and Geothermal are both very similar in nature. They both harness the heats energy from Sun. In most of North America we heating from the earth Geothermal heating. However in reality this is not correct as this is properly defined as a ground source heat pump. A proper geo thermal as found in Iceland, New Zealand, and other parts of the world uses the earth’s core temperature to heat up water and turn it to usable space heat.
In ground source heat pumps the pump pull the energy that is stored in the surface of the earth created by direct radiant heat from the sun during the summer months. In fact the earth is the same as a hot water storage tank that is used in our solar thermal systems, only it is much larger and capable of storing a year's worth of electricity at a time!
Using these two similar technologies together is becoming more popular as both work to help each other.