Green Design: Geothermal Heat Pumps

Click on the images above to learn about the green design features of 14 Maple Avenue.

 

What is geothermal energy?
In Greek, “geo” means “earth” and “thermal” means “heat,” so geothermal energy is literally “earth-heat.” The deeper you go into the earth’s crust and eventually to its core, the hotter it gets. However, almost everywhere across the entire planet, the upper 10 feet below ground level stays the same temperature: between 50 and 60 degrees Fahrenheit.

What is a geothermal heat pump?
A geothermal heat pump takes advantage of that constant temperature to heat or cool a building. Pipes are buried in the ground near the building, and inside these pipes a fluid is circulated (much like antifreeze in a car’s radiator); it is a closed loop system so that the fluid flows down one side of the tube (cooled or heated, depending on the season) and flows back up the other side of the loop.

In winter, heat from the ground goes through the heat exchanger of a heat pump, which sends warm air into the building. During hot weather, the process is reversed: hot air from inside the building goes through the heat exchanger and the heat is passed into the ground. Heat removed during the summer can also be used to heat the building’s water.

What are the challenges to having a geothermal system?
Constructing geothermal systems in urban areas can be challenging. Typically there isn’t enough accessible land to drill the optimum number of wells for a building project; wells must be 27 feet apart or they interfere with another. In this project, because the building and garage were planned together, we were fortunate to have a lot big enough to drill 22 wells and, better yet, to space them 33 feet apart to maximize their productivity. Additionally, there was enough room to drill two extra wells as backup.

Why use geothermal heat pumps?
Geothermal energy is a clean, renewable resource which emits no greenhouse gases. Geothermal heat pumps use 25 to 50 percent less electricity than conventional heating or cooling systems, and can reduce energy consumption and corresponding emissions anywhere from 44 percent to 72 percent.  They also have relatively few moving parts, making them durable and reliable.  You may have heard that installation costs are higher than more traditional systems, but the energy savings usually provides returns within 3 to 10 years. As demand for cleaner energy sources increases, the cost of producing geothermal energy will become more affordable.

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