Shallow subsurface thermal structure onshore Denmark: temperature, thermal conductivity and heat flow

Shallow subsurface thermal structure onshore Denmark Subsurface temperatures and thermal properties are important factors in controlling the amount of thermal energy that can be extracted or stored in the ground. Local and regional variations in the thermal conditions affect the design and efficiency of shallow geothermal installations, especially when heat pumps are applied (Rasmussen et al. 2016; Sanner 2016). Thus, knowledge about temperature, subsurface thermal properties as well as heat flow are required for estimating geothermal resources and in evaluating methodologies for heat extraction. In contrast to deep geothermal conditions (cf. Balling et al. 1992, 2002; Mathiesen et al. 2009, 2010), until the present study, the shallow subsurface thermal conditions in Denmark have not been analysed on a national scale. The first borehole temperatures were measured around 1900 as accurate bottom hole temperatures (Bonnesen et al. 1913) while the, at the time, deepest Shallow subsurface thermal structure onshore Denmark: temperature, thermal conductivity and heat flow