Anthropogenic greenhouse gas emissions, energy security and sustainability are three of the greatest contemporary global challenges today. This year the Sino-German Cooperation Group “Underground Storage of CO2 and Energy”, is meeting on the 21-23 May 2013 for the second time in Goslar, Germany, to convene its 3rd Sino-German conference on the theme “Clean Energy Systems in the Subsurface: Production, Storage and Conversion”.  This volume is a collection of diverse quality scientific works from different perspectives elucidating on the current developments in CO2 geologic sequestration research to reduce greenhouse emissions including measures to monitor surface leakage, groundwater quality and the integrity of caprock, while ensuring a sufficient supply of clean energy. The contributions herein have been structured into 6 major thematic research themes: Integrated Energy and Environmental Utilization of Geo-reservoirs: Law, Risk Management & MonitoringCO2 for Enhanced Gas and Oil Recovery, Coal Bedded Methane and Geothermal SystemsTrapping Mechanisms and Multi-Barrier Sealing Systems for Long-Term CO2 StorageCoupled THMC-Processes and Numerical ModellingRock Mechanical Behaviour Considering  Cyclic Loading, Dilatancy, Damage, Self-sealing and HealingUnderground Storage and Supply of Energy“Clean energy systems in the subsurface” will beinvaluable to researchers, scientists and experts in both academia and industry trying to find a long lasting solution to the problems of global climate change, energy security and sustainability.