State of the Art in Deep Geothermal Energy in Europe : With Focus on Direct Heating

Since nearly 50 % of Europe's energy demand is in the heating and cooling sector, it is expected that geothermal energy will play an important role in the transition to a decarbonized energy system. However, deep geothermal energy is currently harvested mainly from areas with very favorable geothermal conditions. As these areas are geographically limited, the use of geothermal energy in less favorable regions is essential for unleashing the full potential of geothermal energy, since they make up the majority of the total geothermal potential in Central Europe. Motivated by the growing interest in deep geothermal energy among, e.g., energy companies and communities, this text reviews the state of the art in deep geothermal energy with focus on direct heating in geothermally less favorable regions. It provides an overview of technologies used to generate heat from the deep underground and discusses main technical and non-technical risks associated with deep geothermal projects. The text addresses readers with an interest in geothermal energy but does not require a background in geoscience or engineering sciences. It is suitable as textbook for Geothermal Energy courses for undergraduate students from different disciplines. Preface 6 References 7 Contents 8 1 Introduction to Geothermal Systems 10 1.1 Introduction 10 1.2 Earth's Heat 11 1.3 Rock Types and Their Properties 12 1.4 Stress Field and Seismicity 13 1.5 Classification of Geothermal Systems 15 1.5.1 Geothermal Play Types 15 1.5.2 Geothermal Reservoir Types 17 References 18 2 Geothermal Potential Across Europe 20 2.1 Geothermal Conditions Across Europe 20 2.2 South Sweden 22 2.3 Poland 26 2.4 Hungary 30 References 34 3 Technologies for Deep Geothermal Energy 37 3.1 Introduction 37 3.2 Prediction and Assessment of Geothermal Resources 39 3.3 Resource Access and Development 43 3.3.1 Geothermal Drilling 44 3.4 Enhanced Geothermal Systems (EGS) 49 3.4.1 Stimulation Techniques 50 3.4.2 EGS Demonstration Projects 53 3.5 Reservoir Operation 54 References 73 4 Risks and Barriers 82 4.1 Introduction 82 4.2 Non-technical Risks 83 4.3 Technical Risks 84 4.4 Environmental Risks 88 References 89 5 Summary and Conclusions 93 References 95 Index 96