How is Geothermal Different than Other Heating Systems? A Question from Brookhaven

There are many methods to heating a building in Brookhaven. Early methods included burning coal and wood. Today, sophisticated building controls call for more efficient means of heat – and a method gaining in popularity is geothermal heating.

Many use air handling units to deliver heat – and that method has remained constant over the years. But air handling units are only designed to move air from one space to another. How that air is heated from the source is what differentiates geothermal from other energy sources.

To understand some of the differences, let’s look at the definition of geothermal heat. By definition, geothermal heating comes from its direct use of geothermal energy, which comes from below the Earth’s surface. And the Earth is known as the greatest conductor of heat. The constant, renewable temperature of the Earth (56-58 degrees on average below 10 feet) provides a heat source requiring no energy conversion, which adds to heating efficiency and ultimately, the cost to heat a building.

In order to heat a building, natural heat from the ground absorbs a colder refrigerant, which is circulated throughout the ground by a series of polyethelene tubing, which is generally positioned five to ten feet below the surface. This heat is transported via the refrigerant to a compressor inside a heat pump, where it is compressed and the lower temperatures are transformed from around 50 degrees to temperatures much higher, as high as 100 degrees of more. This hotter refrigerant is circulated through the tubing within an air handling unit, where colder return interior air absorbs the heat. The heated air is then carried to a building’s interior via fans. The refrigerant, with the heat removed, now becomes colder as is re-circulated into the ground to absorb the natural, renewable heat. In essence, the ground provides free heat.

Other methods of heating include forced air natural gas, oil, solar, propane, electric, radiant, and steam. Each heat source requires mechanical means to heat up the supply air. For example, natural gas – which is used to heat about half of all U.S. homes – is heated via a heat exchanger in a mechanical furnace, which runs on electricity. Radiant or steam heat is generated by mechanically raising the temperature of water or refrigerant via electricity. These methods differ from geothermal because the natural heat of the Earth provides the means for raising the temperature of the refrigerant used to transport heat to the air handling unit.

One drawback to using geothermal heat compared to other energy sources is the cost to bring this natural heating method into a building. The initial installation of a geothermal heating system is much higher than conventional natural gas heating – for example – because of the cost to install the tubing called a ground loop beneath the Earth’s surface. No other heat source, other than radiant heat, requires a series of tubing to deliver heat. But then again, radiant heat does not require a ductwork system to transport heated air or remove colder air. Geothermal requires a series of metals tubes to heat the refrigerant and the ductwork to move the heated air throughout the building.

On the flip side, its energy efficiency – using the Earth’s natural heat – is much greater than other heating sources resulting in lower utility costs, often fractions of the cost to use other heat sources. Energy savings could pay for the cost of installing the geothermal system over several years – another characteristic of geothermal heating.