By Brian Indre
As the City of Falls Church takes steps towards its future environmental sustainability goals, geothermal technology is being used in some homes and development projects in the area, including the new George Mason High School currently under construction.
Using geothermal for the project at Mason will ultimately be the best return on investment for the long-term cost for heating and cooling it. Besides its environmental benefit, another advantage of geothermal is that traditional heating and cooling units have a shorter lifespan resulting from their outdoor location and their exposure to the elements, leading to significant repair and replacement costs.
Kate Walker, the environmental programs coordinator for the City of Falls Church, said that the decision to use geothermal for the new high school took lots of planning and expertise to make sure that the ground is suitable for digging the deep wells needed to make the system work. The project will consist of just shy of 200 wells that reach down to more than 500 feet deep.
The City collaborated with the U.S. Department of Energy Climate Action Champions Program, Oak Ridge National Laboratory and the Metropolitan Washington Council of Governments on a feasibility study to make sure that the project was possible within the space of the site that the city had available.
To ensure that holes could be drilled down the required depth without collapsing, thorough research on the ground stability and soil and rock properties was needed. Calculations on the thermal conductivity of the local ground conditions determined how many wells would have to be drilled.
Once approved, the city has been waiting on drilling permits. Allied Well Drilling company will be in charge of digging the wells, while Pro-Air Inc., a mechanical contracting company, will be taking care of the heat pump and other mechanical installations.
Geothermal HVAC (heating, ventilating and air conditioning) systems are a more efficient way to heat and cool buildings like homes, office buildings and schools than traditional gas and electric units that rely on fossil fuels. By using the ground below, geothermal units can harness the natural stable ground temperature as a more moderate starting point for heating and cooling.
“Geothermal is a workable technology in this area because of the moderate belowground temperature, so it works well in both the winter and the summer as a heat exchange medium,” said Walker.
At about four-to-six feet below the ground, the temperature stays at a consistent 56 degrees in the F.C. area, and is not affected much by the seasons. The pipes for a geothermal system are placed in a loop, either horizontally or vertically in the ground, that contains a mixture of water and antifreeze liquid that absorb the stable ground temperature from below and transport it back inside.
During the winter, the warmer ground temperature is absorbed and brought indoors to the pump. In the summer, the system runs in reverse by absorbing the heat from indoors and sending it underground to cool it and then circulate it.
Geothermal HVAC systems are more energy efficient than traditional HVAC systems and can reduce the load on the electric grid, especially during peak times, which makes it ideal for saving money and lowering greenhouse gas emissions in homes and buildings. That’s part of the reason why the Railroad Cottages completed this past spring opted for geothermal technology.
“Minimizing the noise was also a decision factor for Railroad Cottages. When you’re using the ground to preheat or precool the air, then you don’t have to have the loud and forceful outdoor AC units, especially since the cottages are so close together,” Walker said.
The cost effectiveness of geothermal depends largely on federal tax incentives that help influence developers and homebuilders to implement green energy. Geothermal tax credits are slated to go away in about two years, unless Congress acts to extend them.
“You can’t discuss this issue without stepping into national politics,” said Dan Sze, a Falls Church City Councilmember and the liaison to F.C.’s Environmental Sustainability Council. “This is why we need someone who recognizes the value of being a part of the Paris Agreement,” Sze added.
A groundbreaking ceremony for the geothermal well drilling is scheduled at the site of the new George Mason High School this Monday, Dec. 16.