Geothermal Heating and Cooling Is Green! | Today's Green Construction

Geothermal HVAC

The other day I attended a seminar on renewable energy systems for residential and commercial buildings. One of the topics that interested me the most was Geothermal Heating and Cooling. Geothermal heating and cooling is a system that relies on the earth as a heat source and heat sink using heat pumps.

Geothermal Energy

You might ask yourself where does all this “free” energy come from? The answer is actually quite simple. The energy from the sun that hits the planet every day is absorbed into water vapor, dust, clouds and the ground. Almost 50% (46%) of the suns energy that hits the planet is absorbed and stored in the ground (crust of the earth). That’s an amazing amount of energy that’s stored in the ground just like a giant battery.

Geothermal heating and cooling just takes advantage of the stored energy in the ground and harnesses it to reduce our need for fossil fuels. By using a heat pump and some type of ground contact interface we can actually capture some of that stored energy in the ground to heat and cool our homes.

Geo Exchange System

The basic concept here is to think of the ground as our on personal power plant. In the summer time we want to capture the cool temperatures of the ground and “dump” our hot home temperatures into the ground. Basically we’re exchanging cool for hot. In the winter time we want to extract the warmer temperatures of the ground for the cooler temperatures in our homes. Again we’re going to be exchanging energy.

In order to make this exchange we need to connect our homes to the ground. This is accomplished in a variety of ways including open and closed loop systems. The systems can be created with deep wells or shallow trenches. In either case we’re trying to make contact time with the grounds constant 50 degree temperature.

Heat Pumps

Heat pumps have been around for years and the technology is fairly straight forward. Heat pumps are very similar to air conditioners in the fact that they use a refrigerant, a compressor and a condensor to transfer heat (energy) from one medium (air or water) to another. Heat pumps are great because they can work in either direction so it’s easy to use them for both heating and cooling. Check out the following two diagrams for heating and cooling.

Geothermal Heating Cycle

Geothermal CoolingCycle

Depending on where you live and the type of ground you have there are different ground loops. You might end up with and open loop well system where you pump out water back to the heat pump and they return the water to the same well. You could have a closed loop well system where the refrigerant travels in a closed loop between the well and heat pump. Or you could have a closed loop system that uses shallow trenches (8 ft deep).

Over the coming months I’ll be writing more about these geothermal heating and cooling systems. In the mean time check out the Energy Star site for more information. One of the nice things about Geothermal heating and cooling are some of the Stimulus Home Improvement Tax Credits.