Groundcoupled

Groundcoupled refers to a type of heat pump system that uses the ground as a heat source and sink by circulating a fluid through buried pipes connected to a heat pump indoors. The ground acts as a stable thermal reservoir, providing heating in winter and cooling in summer with high overall efficiency.

How it works: A loop of pipe is buried underground, either horizontally in shallow trenches or vertically in boreholes. In heating mode, the fluid absorbs heat from the surrounding soil or groundwater and delivers it to the heat pump, which boosts it for indoor space heating. In cooling mode, the process reverses and excess indoor heat is rejected into the cooler ground. Some systems also support seasonal thermal energy storage by exploiting ground temperature stability over the year.

Configurations and installation: The main configurations are vertical borefields and horizontal loops. Vertical systems typically use boreholes 60 to 200 meters deep, while horizontal loops require substantial land area and are buried a few meters below the surface. Other designs include slinky coils or groundwater-pond loops. System design depends on geology, groundwater conditions, available space, and local regulations.

Performance and economics: Groundcoupled systems offer high efficiency, with performance described by coefficients such as COP (and SPF for cooling) that can exceed air-source alternatives in suitable conditions. They usually entail higher upfront costs due to drilling or trenching but offer lower operating costs and lower greenhouse gas emissions over time. Maintenance is relatively modest but requires professional handling of the loop and any antifreeze fluids.

Considerations and applications: Viability depends on soil thermal conductivity, moisture, and space. They are used in residential, commercial, and some district-scale applications, with environmental and permitting considerations addressing groundwater safety and site impact.