Joint project "Hydropower and geo-energy"
The transition towards a CO2-free energy system requires the growth of established technologies such as hydropower and the development of new sources such as geothermal heat or electricity. This project makes important contributions to this goal by showing the potential for new hydropower plants, and by advancing our understanding of the subsurface and the processes related to its exploitation.
Project description (completed research project)
The objective of the Energy Strategy 2050 is to substantially reduce energy-related CO2 emissions while at the same time phasing out nuclear power. This calls for the development of new sources such as geothermal electricity and heat, the adaptation and extension of existing sources such as hydropower, and additional options such as geological CO2 storage.
The challenge for geoenergy and geological CO2 storage is an inadequate understanding of the subsurface. New geophysical exploration techniques and numerical simulation tools were developed to remedy this problem. The future challenge for hydropower will be to increase production while adapting infrastructure and operation strategies to drivers such as climate change and aquatic ecology requirements. Subprojects were aimed at understanding the potential (and challenges) for new hydropower plants (HPPs) in the periglacial environment, an improved treatment of sediments in desanding facilities, and improved forecasts and operating schemes that consider the economy and aquatic ecology.
Enhanced geothermal systems (EGS, also termed petrothermal) do not require natural permeability, they instead rely on hydraulic stimulation. A number of prediction codes were developed for this purpose, which will aid the development of EGS. Conversely, it was found that the Upper Muschelkalk formation below the Swiss Plateau is generally not suitable for hydrothermal electricity production. The Upper Muschelkalk represents a CO2 storage capacity of ~50 million tons, one order of magnitude below the theoretical potential assessed in the CARMA project (Carbon Dioxide Management in Power Generation).
Suitable reservoir sites for new potential HPPs in the Swiss periglacial environment were selected with a potential of an additional 1.1 TWh/yr. Novel design guidelines for longer desanding facilities were developed targeting application by design engineers. For some catchments, an improvement of meteorological and hydrological forecasts can lead to an annual average production gain of between 4% and 6%. The understanding and mitigation of risks related to geo- and hydropower were advanced using various approaches.
Implications for research
New software tools provide a virtual testbed for the development of protocols for seismically safe and efficient hydraulic stimulation. Novel geophysical techniques allow detailed characterisation of hydraulically active fractures around boreholes. New experimental approaches reveal the behaviour of fractures during hydroshearing stimulation at reservoir conditions.
The subglacial sediment transport model developed in this work is the first of its kind to be calibrated with data. This represents a major step forward in the ability to understand the response of sediment discharge to glacier retreat. The comparative parameter study with another numerical model made it possible to relate the trapping efficiency to various geometrical and structural design properties of desanding facilities. The project also demonstrated the potential of hydro-meteorological prediction systems for hydropower optimisation in the Alpine area.
Implications for practice
The newly developed software tools will be used to perform R&D needed to advance geothermal hydraulic stimulation from trial and error to true engineering. New borehole geophysical techniques aid the planning and implementation of hydraulic stimulation and reservoir exploitation. Any exploration for CO2-storage in the Upper Muschelkalk should focus on the Olten–Schaffhausen area.
The evaluation framework for new HPPs in a periglacial environment allows for the selection of potential new schemes to meet the goals of the Energy Strategy 2050. The new design guidelines for desanding facilities could potentially be widely used in the hydraulic engineering community, which would contribute to the sustainability of hydropower by reducing abrasion and wear and increasing scheme efficiency. Operational use of meteorological/hydrological prediction systems could increase the revenues for existing hydropower systems at relatively low cost.
New methods can support the risk-informed decision-making of practitioners in different fields, such as the detection of induced seismicity in geothermal project, the risks of dam break or landslides, or even the optimum ratio of wind vs PV to alleviate seasonal power deficits. Furthermore, risk communication analysis provides clues on how to interact with the public regarding, for instance, the acceptance of new geothermal projects.
Supply of electricity for 2050: hydropower and geo-energies
The joint project consists of seven research projects
- Prof. Larryn W. Diamond, Institut für Geologie, Universität Bern; Prof. Jean-Pierre Burg, Prof. Marco Herwegh-Züger, Prof. Klaus Holliger
- Dr. Massimiliano Zappa, Eidg., Forschungsanstalt für Wald, Schnee und Landschaft WSL, Birmensdorf ZH; Dr. Christoph Spirig, Dr. Mark Liniger, Herr Frédéric Jordan
- Prof. Robert Michael Boes, Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie, ETH Zürich; Prof. Martin Funk, Dr. Ismail Albayrak, Dr. David Vetsch
- Prof. Robert Michael Boes, Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie, ETH Zürich; Dr. Ismail Albayrak, Dr. David Vetsch
- Dr. Thomas Driesner, Institut für Geochemie und Petrologie, ETH Zürich;Prof. Stephan Konrad Matthai, Prof. Rolf Krause, Prof. Stephen Miller
- Prof. Paolo Burlando, Institut für Umweltingenieurwissenschaften, ETH Zürich; Prof. Peter Molnar, Dr. Christopher Robinson, Prof. Tom Battin, Prof. Stuart Lane
- Prof. Stefan Wiemer, Schweizerischer Erdbebendienst, ETH Zürich; Prof. Peter Burgherr, Dr. Michael Stauffacher, Prof. Bozidar Stojadinovic, Prof. Michael Lehning, Prof. Domenico Giardini
Cooperation with other projects from NRP 70
Joint project "The Future of Swiss Hydropower: An Integrated Economic Assessment of Chances, Threats and Solutions"
- Prof. Hannes Weigt, Wirtschaftswissenschaftliche Fakultät, Universität Basel