Swiss agency to explore closed-loop Advanced Geothermal Systems
A project under Swiss agency Innosuisse will explore the potential of advanced geothermal systems (AGS), essentially closed-loop systems with CO2 as circulating fluid.
Innosuisse, the Swiss Agency for the Promotion of Innovation, has selected 15 projects as part of its new Flagship initiative. One project, called “AEGIS-CH,” will do a comprehensive analysis of Advanced Geothermal Systems (AGS) – closed-loop systems that use CO2 as carrier fluid.
The Flagship is headed by Prof. Dr. Martin O. Saar, Founder and Head of the Geothermal Energy and Geofluids (GEG) at ETH Zurich. Saar describes AGS as consisting of two boreholes drilled to a depth of around 10 kilometers and connected at the subsurface by several cross-connections up to 5 to 10 kilometers wide. Although the concept is not new, more recent innovations can now make such systems more economically viable.
The use of CO2 as fluid for the closed circuit is a crucial element of the project. Since CO2 transports heat better than conventionally used groundwater, the system can be up to 50% more efficient. Drilling costs can also made much lower with recent technological advancement, notably the Plasma Pulse Geo Drilling (PPGD) technology which also been investigated by Saar and his team. This technology uses high voltage pulses to fracture the rock without mechanical abrasion by the formation of plasma.
AGS projects can be implemented virtually anywhere, independent of geology. They can be flexibly integrated into existing heat or power networks and can be used to complement solar or wind farms. They can be drilled without stimulation and would require little maintenance. The smallest envisioned size of an AGS project would have a capacity of 1 MW electrical power or 10 MW thermal power.
Saar is convinced that the potential of AGS to contribute to a stable and secure energy supply will help in the social acceptance of such facilities, even if initial costs are high.
Source: Geothermie Schweiz