Groundwater Use for Thermal Energy

Abstract

The temperatures of the ground and groundwater a few metres beneath the earth's surface remain relatively constant throughout the year, even though the outdoor air temperature may fluctuate greatly every season. The ground temperature is almost the same as the annual average of the air temperature in each city. At a depth of approximately two meters, for example, the temperature of the soil in most of the world's regions is stable between 10C and 20C. This is why groundwater tastes cool even on a hot summer day. This temperature difference between groundwater and ambient air is often utilized as ``temperature difference energy.''