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Geothermal Heating v/s Solar Thermal Heating

Geothermal heating and solar heating are very similar in nature. Both take advantage of the sun’s energy. Solar thermal uses the energy directly by capturing it using heat tubes and heat pipes, and then moving the heat into a storage tank for future use. Geothermal takes the heat energy already stored in the earths mass and moves this energy into a heat pump to be extracted. The both use pump systems and glycol heat transfer fluid.

The question often gets asked, which is better? This is a question that has many variables to consider when looking at one compared to the other. Once of the deciding factors is the land and size of the land available to the homeowner. If you live on a good-sized rural lot then it will be easy to build a geothermal horizontal ground loop to harvest the solar energy in the ground. However, in some locations this might not be an option and a solar thermal system might be a better choice.

Solar thermal requires clear access to a southern facing exposure. In a small yard with tall surrounding trees this many not be and option even on the roof of a building. Solar thermal requires a good clean southern exposure.

Costs may also be a deciding factor. If a customer requires multiple vertical loops for a geothermal system, the cost can increase quickly. If they are on hard rock, then geothermal many not be an option at all as it would simply be too costly to drill multiple ground loops 300 feet each through hard rock. In this case solar may be the best option.

Payback - Both systems have great paybacks for green energy investment. A properly sized geothermal loop can save the homeowner 75% of their heating bill. On the other hand an average solar thermal heating system will save about 60% but can also supply the home owner with nearly all their domestic hot water supply as well as a summer heat source for pools or hot tubs. So both have a similar payback.

Installation costs - Generally a solar thermal heating system will cost less to install as the homeowner will not need to hire an excavation operator. Typically, this can cost $2000-$3000 for trenching and back filling of a geothermal field. Not to mention there will be the need for re-landscaping after wards as the grass will require seeding or new sod.

Storage tanks - The more solar thermal collectors you use the more storage capacity you should have. This means you need internal space to store the tank. A large 5 collector system should have about 250 gallons of water storage or more to maximize the performance and storage.

Solar radiation - Different parts of the country receive different amounts of solar radiation. This will be important if you are looking to heat in the winter using solar thermal. You will need to have a steady supply. The Prairies are great for Solar in the winter however areas of Vancouver Island receive large amounts of rain and as such might not be ideal.

solar radiation

Hybrid Systems

Using both Geothermal and a solar thermal can provide huge benefits especially in Northern Climates. When building a geothermal loop, adding an extra single run for solar thermal can give the geothermal loop and added boost. The geothermal needs to draw heat energy from the ground and often this can be depleted if there is not enough area. To avoid this you can choose to run a solar thermal loop in the same pipe trench. The solar thermal will add heat back to the ground for the geothermal loop to pick up. In the summer this is also an ideal dump zone to dissipate the excess heat energy of the solar thermal and store it in the ground warming your earth for the winter months.
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