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.
The solar thermal can be used to with a heat exchanger to transfer its heat energy to the geothermal heating loop. This increases the temperature before it goes into the heat pump. Since a heat pump has a Co-efficiency of Performance that is greater than one (3-4 COP is average), this means that for 1 degree of heat energy added you will get more on your heating side. With a COP of 3 you will see 3 degrees of home heat energy added for every 1 degree of solar energy that you can provide.
The geo thermal is a perfect place to dump heat in the summer. This is often a problem with larger solar space heating system. They have good heat fro the winter but too much for the summer. Unless you are a lucky pool owner you will need a place to dump the heat or else cover you solar collector array. A geo thermal loop is perfect for dumping the heat.
Load up you geo loop in the summer for more heat energy in the winter. Some geo thermal loops are weak because of poor design or poor soil conditions. This means over time the geothermal unit can draw off more heat energy than the sun is capable of supplying. By adding a geothermal system you can use the energy to re-charge the ground loop and increase the overall performance.