Geothermal energy, whether as a source of electricity or to heat or cool buildings, has an enormous potential as a renewable energy source. This paper presents a broad overview of geothermal energy, with a focus on the emerging technologies of Enhanced Geothermal Systems (EGS) and Ground Source Heat Pumps (GSHPs). EGS and GSHP systems are important because of their potential for widespread use, as opposed to traditional geothermal energy systems which are generally limited to tectonically active regions. Commercial application of EGS technology is some years off but its enormous potential demands investment for further research. GSHP heat pump technology is available now — policy makers need to be educated and the potential of GSHPs demonstrated. Research should focus on optimising the design of the in-ground component of GSHP systems to maximise their economic, as well as environmental, benefits.

Summary. The hydraulic conductivity can control geotechnical design, resource recovery and waste disposal. We investigate the effect of pore-scale spatial vari