Abstract
Geothermal heat pump systems (GHP) are the spearhead of geothermal achievement and development, and one of the fastest growing applications of renewable energy technologies worldwide. When Swiss GHP activities started in the late 1970s, market introduction and penetration needed science-based proof of reliable, stable, long-term GHP operation. A special, extended project, realized in a field-laboratory setting, provided this proof. Detailed measurements, as well as numerical model simulations, proved the sustainable operation of the installed GHP system. The measurement setup, the recording of the various time series, and their interpretation are presented. Furthermore, basic perceptions were elaborated concerning geothermal resources behavior in production and regeneration. The Swiss GHP was developed from nothing. Early GHP installation costs halved within 20 years; GHP growth was nearly exponential from 1980 to 2020 (8.5% annually). Drilled borehole heat exchanger (BHE) meters are today around 300,000 m per year; heat delivery of GHPs in Switzerland amounted to 3280 GWh 2020—over 85% of Swiss geothermal direct uses (among others like thermal spas, district heating). Large installations with hundreds of BHEs are now common, and are also used for heating and cooling. The international ranking of Swiss GHP realizations is excellent in terms of annual energy use (TJ/yr/area), and is number one worldwide. Switzerland is a global GHP leader, and the Swiss success story is well documented.