Clean Energy Systems in the Subsurface: Production

Book Preface

The worldwide consumption of energy is still largely dependent on conventional fossil resources – the main reason for global warming and climate change. The new energy policy paradigm in Germany (Energiewende: from fossil fuels to renewable energy) foresees the utilization of renewable resources to produce 50% of the German electrical power demand by 2030 and 80% by 2050. On one hand Germany has taken a lead in the extensive research for increased production and usage of renewable energies to promote its energy policy, the “Energiewende”. However, the country still has a rather modest contribution of 3% to the global greenhouse gas emissions. On the other hand 68% of China’s primary energy consumption is provided from coal alone, contributing about 20% of the global greenhouse gas emissions. Like Germany, China intends to reduce its emission intensity by 40–45% by 2020, based on the 2005 levels. In order to face this huge challenge, clean energy resources in the underground have to be considered in the near future for producing geothermal energy and unconventional gas. In this regard, geo-reservoirs are going to serve as large storage systems for the fluctuating renewable energy converted into e.g. compressed air, synthetic methane, hydrogen or heat. In addition, through the use of new technologies, geo-reservoirs will help to dampen the detrimental effects that result from the excessive use of fossil energy. These new technologies allow a switch from carbon intensive fossil fuels to low carbon energy carriers (e.g. natural gas) via CO2 capture and utilization (CCU) or CO2 capture, utilization and storage (CCUS) or as biochemical reactors to convert hydrogen and carbon dioxide into methane under favorable high pressure and high temperature conditions deep underground. Geo-reservoirs may thus be used for production, storage and conversion purposes in the context of the “Energiewende”