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Geothermal / Ground-Source — The Earth as Heat Sink

Geothermal / Ground-Source — The Earth as Heat Sink

Geothermal / Ground-Source — The Earth as Heat Sink

Geothermal (ground-source) HVAC uses the stable temperature of the earth a few meters down — roughly the local annual-average air temperature, far cooler than summer ambient — as the heat-rejection sink (and winter heat source) for a heat pump. In cooling, that means dumping the building’s heat into ground that’s ~20 °C instead of into 38 °C August air, which raises the heat pump’s efficiency exactly when cooling demand and electricity prices peak. It’s not a separate refrigeration cycle so much as a better sink for one.

The collection is the design-and-practice canon — Geothermal HVAC, Modern Geothermal HVAC, Geo Power, and Geothermal Heating and Cooling: Design of Ground-Source Heat Pump Systems — covering closed-loop ground, open-loop groundwater, and surface-water systems, residential through nonresidential, and notably the integration of geothermal with hydronic distribution (the same chilled/hot-water loops the sorption and conventional systems use).

Why it matters in a heat-driven strategy

Geothermal and adsorption attack cooling cost from two different angles that stack:

  • Adsorption removes electricity from the driving side (heat instead of compressor work).
  • Geothermal removes electricity from the rejection side (cool ground instead of hot-air condenser) for whatever compressor work remains.

A site can do both: an adsorption chiller still needs to reject condenser heat, and a ground loop is a superior place to put it versus a cooling tower (no water consumption, lower approach temperature). So geothermal is also the natural heat-rejection partner for adsorption, not just an alternative to vapor compression.

Cost/feasibility caveat

The economics are dominated by ground-loop installation (drilling/excavation) and by available land and geology. Geo Power foregrounds payback and installation issues; the nonresidential design texts foreground sizing the loop field correctly. Whether it pencils is highly site-specific — soil thermal conductivity, water table, and how much land or borehole depth is available.

See also