Here’s How We’ll Store Energy Underground

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Storing the energy that we produce one way or another is one of those things that we are still unable to solve. Massive batteries are out of the question for obvious reasons, massive capacitors have a number of practical drawbacks, and hydro-power reservoirs have a very limited scope of application as they can only be built on high mountains. This is about to change, as the European Union and the Austrian government has funded a research program named “RICAS 2020” that has been working on ways to realize compressed air storage systems since June 2015. With more than a year of research time remaining, the team of engineers working on the RICAS program have recently announced their most promising concept yet, which actually looks like it’s gonna work well, or at least it looks like it in theory.

So, the energy storage system proposed by RICAS will take the excess power produced by a wind turbine or other means of renewable energy harvesting systems to power up an electric motor. The motor will, in turn, pass the energy of motion to an air compressor which will take the regular atmospheric air and pump it into a large underground reservoir. On its way down there, the hot pumped air will pass through a section filled with crushed rocks which are an excellent heat conductor, cooling the air thus allowing more air molecules to fit into the reservoir at a lower pressure. When energy is needed on a different point of time, air from the underground reservoir is released upwards through a second pipe, passing through the crushed stone compartment again, receiving heat from the hot rocks and thus increasing its pressure/flow velocity. The released air is then passed through a turbine which is connected to a generator, so there we have it, an energy storage system of great potential.

RICAS claims that their system can hold pressures of up to 50 bar and temperatures of up to 800 degrees Celsius without using expensive materials. In fact, there are already countless of abandoned underground tunnels, mine-shafts, and reservoirs that can be re-purposed to serve as air storage batteries. According to the numerical simulations run by the RICAS team, the expected efficiency of this system can reach to up to 80% which is amazing compared to the efficiency achieved by previous attempts of other teams of scientists. Moreover, these air storage reservoirs can go beyond the purpose of energy storage and also provide compressed air to industrial units that need it. Right now, and thanks to the addition of the “crushed rocks” heat exchanger step into the system, the data look promising enough to allow an actual pilot site construction.

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