Av Henrik Holmberg, stipendiat ved Fakultet for ingeniørvitenskap og teknologi, Institutt for energi- og prosessteknikk, NTNU
The research on EGS or, hot dry rock (HDR) systems as it was first named started in the seventies. Primarily sedimentary basins and the periphery of the active regions were of interest in the subsequent projects aiming to extract heat from 4-5 kilometers depth through artificially created or stimulated fractures. A milestone was reached in 2006 when electricity production could be started from a research project in Soultz, France. Since then, commercial companies have been joining the field, and amongst others, USA and Australia have invested significant amounts into the research and support of geothermal energy. 3rd of may this year, electricity production started at the commercial EGS power plant in Habanero, Australia , where heat is extracted from a sedimentary basin. Although these pilot-plants have a relatively low power output in the range of 1 MWe, they are important proofs to the validity of the concept with artificially created geothermal systems.
Geothermal energy is ideal as a base load resource for direct usage of heat. Through history, geothermal energy has been used to cover direct heating purposes such as space heating, bathing and agricultural demands. In the development of EGS it is electricity production that has been in focus and thus areas with the highest geothermal potential have been sought. While low temperature resources that can be exploited for direct heat-purpose have been neglected for some time. This was recently pointed out in the IEA- roadmap for geothermal energy , which urges countries to also asses their potential for low temperature applications.