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Geothermal Pond Loop

Posted by Taylor Hendricksen on Jan 16, 2012 in Ground Loops | 0 comments

A Geothermal Pond Loop can be open or closed loop.

On closed loop systems they can be constructed by sinking loops of poly pipe to the bond bottom or they can use purpose built heat exchangers. The primary advantage of a pond loop is that significant excavation is not required. The disadvantage is that most homes are not near ponds.

Like all ground loops a pond loop must be appropriately sized for the system it serves. The pond must be large enough and deep enough to meet the system demands year round. The temperature in the pond will be made colder in the winter as heat is removed from it and made colder in the summer as the homes heat is rejected into it. If fish or other aquatic life exists in the pond considerations should be made as to how it will affect them. Excessive thermal alteration could kill fish or cause algae blooms. The more the water is circulated or exchanged in the pond the better the heat exchanger will work.

Open loop systems that involve ponds often pull water from a well and then discharge into a pond below the surface. This allows the pond to get lots of fresh water flowing through it and greatly limits the thermal alteration. Each system should be constructed based on the combined attributes of the site.

A geothermal pond loop does not have to be a pond. It could be any body of water that is near the structure.

Here in Montana, I was involved in bidding a project where a sewage settling pond was used as the earth loop for a 10,000 sq. ft commercial building. (It was basically clean water in this pond as it was the last stage of treatment and was pumped out to water a golf course.) It is not recommended that geothermal loop fields be built into active septic drain fields as the thermal alteration could slow or stop the necessary bacterial break down of he sewage.

I did not get the bid but a competitor did and the system has been running great for two years. The point is that an earth loop can be anything that is of sufficient capacity (thermal mass) to serve the load.