How is a geothermal system defined?

A geothermal system is defined as one that employs a heat pump which utilizes the relatively constant temperatures found below the earth's surface. This technology takes advantage of the earth's thermal mass to efficiently transfer heat. In the winter, the system extracts heat from the ground to warm the building, while in the summer, it can reverse the process and draw heat from the building to cool it, using the earth as a heat sink.

This method is distinct from other heating or cooling systems that rely on ambient air, solar energy, or fossil fuels. For example, systems that use ambient air are dependent on outside temperatures, which can fluctuate significantly. Similarly, systems that capture solar energy harness sunlight rather than the earth's internal heat, and fossil fuel systems depend on nonrenewable resources for energy which can be less efficient and more environmentally damaging. Thus, option B accurately represents the unique functional characteristics of geothermal systems.