International legal status of the use of shallow geothermal energy

Shallow geothermal energy (<400 m depth) is used in many countries worldwide, with a rising number of installations over the last decades. The use of ground source heat pump (GSHP) and groundwater heat pump (GWHP) systems results in local temperature anomalies (cold or heat plumes). Since groundwater is used in many countries as source for drinking water a balance between its use and protection has to be found. Therefore, to avoid detrimental environmental impacts it is necessary to define groundwater temperature limits for heating and cooling and minimum distances between such geothermal systems. The aim of the present study is to provide a comprehensive overview of the current international legal status for the use of shallow geothermal energy. Therefore, an international survey was performed using a questionnaire, which was sent to more than 60 countries worldwide. The questionnaire requested information on the corresponding national legislation, temperature limits and minimum distances for GSHP and GWHP systems. The answers to the inquiry showed an extremely heterogeneous outcome. Until now national and legally binding regulations only exist in few countries such as Denmark or Sweden. However, all existing regulations show a wide range for minimum distances (5–300 m) and temperature limits for groundwater. The highest inconsistency was observed for the acceptable temperature change with 3 K in Switzerland to 11 K in France. However, most countries have no legally binding regulations or even guidelines, which highlight the urgent need for further research on the environmental impact and legal management of shallow geothermal installations.