Subsurface energy systems in China: production, storage and conversion

Abstract

The Thematic Issue is dedicated to different aspects of using the potential of the geologic subsurface as a resource for energy production (e.g., hydrothermal and petrothermal resources), energy storage as well as for safe deposition of energy waste, and energy conversion (e.g., as biochemical reactors to convert hydrogen and carbon dioxide into methane). Figure 1 shows an overview map of hydrothermal systems in China including a classification to high-, midand low-temperature reservoirs and basins (Kong et al. 2014). Current research efforts concerning hydrothermal resources focus on the sustainable development of large-scale geothermal fields. Pang et al. (2012) designed a roadmap of geothermal energy development in China and reported the recent progress in geothermal research in China (Pang et al. 2014). Recently, Pang et al. (2015) presented a new classification of geothermal resources based on the type of heat source and followed by the mechanisms of heat transfer. The present Thematic Issue is focusing on petrothermal resources and particularly enhanced geothermal systems. Some of the basins indicated in Fig. 1 are also of interest for unconventional gas resources which is discussed in a separate Thematic Issue in Environmental Earth Sciences (Hou et al. 2015a). Geothermal energy resources are considered to provide a significant contribution to renewable energy supply from both shallow and deep systems (Arola et al. 2014; Huenges et al. 2013; Kolditz et al. 2013; Scheck-Wenderoth et al. 2013). Understanding the thermally induced coupled processes is important for reservoir operations (McDermott et al. 2006; Kolditz and Diersch 1993). Breede et al. (2014) provide a systematic review of enhanced or engineered geothermal systems (EGS). Ramos et al. (2015) provide a systematic review of projects implemented worldwide and a methodology for screening geothermal projects. Geothermal shallow surface systems based on ground source heat pumps have already proved to be a feasible option for the heating and cooling of buildings. The present work studies the concept of using abandoned mines for geothermal heat recovery in various countries such as Germany, the Netherlands, Norway, Russia, Spain, UK and United States. De Filippis et al. (2015) are discussing the geothermal potential of the Salento peninsula in southern Italy. They propose a simple methodology for the assessment of low-enthalpy geothermal energy systems based on stochastic approaches. They found that coastal areas might lower potential due to saltwater intrusion problems. Hou et al. (2015b) introduce the first & Hongwei Zhou zhw@cumtb.edu.cn