Geothermal heat can be extracted directly from the surface all the way to the limits of drilling technology, kilometres below the surface. There is an economical balance between amount of heat extracted and costs of extraction, where different technologies are used to extract the heat from different depths. Moreover, in the shallow sub-surface (100s of meters) heat can also be stored for re-use, for example capturing the summer heat for use in winter, and using the cold ground to provide cooling during summer. Deep subsurface heat (1-5 km) can be used for direct heat supply, and even for electricity generation (where temperatures are over 100 ºC).
In July 2018, the Board of Delft University of Technology has made a decision-in-principle to realise a geothermal well, called DAPwell, for more information, please click here.