As the world looks for ever more inventive ways to decarbonize, a small town in Bavaria will soon use the Earth as a giant rechargeable battery.
It doesn’t matter if it’s day or night, windy or calm, winter or summer; the city of Geretsried will receive a constant base load of electricity and eventually heat for its district grid, thanks to “closed loop” geothermal technology.
Perhaps most significantly, such a system could be launched almost anywhere, potentially marking the end of the geographic lottery of geothermal availability.
Barriers to geothermal energy
Geothermal is a renewable energy source that humans have used for thousands of years, but we are only just beginning to unlock the full commercial potential of underground heat.
Perhaps the biggest obstacle to the rise of geothermal energy has been the upfront cost of drilling. Drilling a 4 km deep well can cost several million dollars, and on average only half of the first exploratory wells are successful. Finding a hot underground aquifer and extracting the liquid from it is not easy.
Another major problem has been that the conditions necessary to harness the power of geothermal energy only appear in some places in the world, usually where there is a lot of tectonic activity.
So how can closed loop technology solve these problems and how does it work?
Closed loop systems
In Bavaria, Canadian company Eavor’s closed-loop geothermal technology adds a fluid above the ground and then sends it around a sealed system, a bit like a car radiator that circulates heat from the car’s engine. vehicle High temperatures deep underground heat the fluid, which returns to the surface where it can be used for heat or electricity generation.
The fluids are heated by the Earth and circulated in a closed network of underground wells, providing a reliable, consistent and scalable source of energy.
No groundwater extraction is required, so there is no need to locate and exploit underground aquifers. Nor does the system need to be close to tectonic activity.
No pumps are needed either: the fluid circulates naturally through a process called thermosiphoning, in which the hot fluid rises to the outlet well, while the cold fluid falls.
Power on demand
The Eavor-Loop can slow or stop heat flow altogether, allowing the fluid to remain near the heat source longer, which “charges” the fluid with heat. This heat can be sent later, when needed, as if you had a rechargeable battery underground.
The project is supported by the EU Innovation Fund and is the first commercial implementation of closed circuit geothermal technology.
But the Eavor-Loop must also connect to the technology that converts heat into electricity. For the Bavaria site, Eavor opted for an Organic Rankine Cycle (ORC) system from Mitsubishi Heavy Industries (MHI) group company Turboden.
ORC systems are versatile: they can generate electrical and thermal energy from multiple energy sources, renewables such as geothermal, traditional fuels such as natural gas and even waste heat from industrial sources.
For example, in the Italian olive oil producing region of Puglia, farmers use unwanted olive branches as biofuel with an ORC system. The process is very similar despite the different heat source.
Towards carbon neutrality
Most geothermal technologies require specific and often rare conditions to be used effectively. But combining closed-loop technology with ORC turbines can open up access to geothermal energy for electricity generation.
A constant, reliable and emission-free energy source is a valuable opportunity for any country on the path to net zero. With the combination of ORC and closed-loop systems that open up geothermal availability, Geretsried’s giant Earth battery could become a blueprint for the rest of the world.
