Increasing energy demand and environmental concerns related to climate change prompt further developments in energy conservation and efficiency, and in renewable energy sources. Energy storage is required to address intrinsic fluctuations and time mismatch between energy demand and renewable sources.
Scientists and engineers are advancing energy storage alternatives, such as chemical storage in the form of hydrocarbons synthesised using electricity surplus and efficient batteries. However, urban-scale storage and power requirements call for large systems that inherently have important geotechnical implications.
Indeed, the geotechnical community has an important role to play in this worldwide challenge. Energy geostorage requires new research into material behaviour and the development of innovative geotechnical solutions for optimal long-term operation. Issues range from geomaterial response to repetitive loading (including thermal, chemical, saturation and stress cycles), coupled processes, localization (strains as well as fluid flow), spatial variability and scale effects, and engineered geomaterials among others.
Geotechnical engineers and scientists from academia and the private sector gathered in Weimar at the Bauhaus-University Weimar, Germany (July 2013), to explore geotechnical concepts and challenges related to energy geostorage. The present themed issue gathers contributions submitted to Géotechnique Letters following the workshop, supported by the German Research Foundation – DFG.
Coupled multi-physics processes involved in heat storage in geological porous media and salt cavities are investigated in Boockmeyer and Bauer (2014), and Wuttke et al. (2014), respectively. Sanchez et al. (2014) explore hydromechanical coupling in a compressed air storage facility in sandstone as an alternative storage option where no sealed caverns can be developed (e.g., in the absence of halite formations). These contributions highlight the complexity in thermo-chemo-mechanical coupled phenomena, the opportunities of new energy geostorage systems, the need to develop proper experimental and numerical simulators to investigate the processes, and for the design of optimal engineering solutions.
Roshankha and Santamarina (2014) investigate the development of engineered sediments to improve heat transfer while sustaining mechanical loads for thermal geostorage facilities. Three other papers deal specifically with shallow geothermal energy storage. Yang et al. (2014) propose an analytical solution for the problem of heat transfer in geothermal heat-pump systems that take into consideration long operating times. Yavari et al. (2014) develop a simple methodology to account for thermal effects on the mechanical response of heat exchanger piles using finite elements. Finally, Zhang et al. (2014) explore the application of shallow ground source heat pumps at the city scale.
Altogether, papers in this themed issue identify rising questions and geotechnical challenges in these early attempts at the development of robust energy geostorage as part of the global energy challenge.
