Abstract
Clean energy is nowadays cost-competitive with fossil fuels. Both photo-voltaic and wind can provide clean power for most of the world’s population, because people tend to live on windy coasts or sunny regions. Clean energy storage is needed to match production with demand, and to allow large scale deployment of renewables. Specifically, underground pumped hydro and compressed air energy storage (CAES), can accumulate massive amounts of energy in suitable caverns. Modern underground mining technology allows efficient construction of these projects, putting to use existing mining and transmission infrastructure, waste heaps and tailings ponds and, above all, specialist mining skills.
In the case of existing and future mines, it is probably a good idea to study the viability of an associated energy storage project, which can supply firm power for the mine operations, and/or store energy for the power grid. This can help with project cash receivables and also extend the project life into a sustainable green storage facility. The technology is suitable for deployment in operating and decommissioned mines. With the lessons learned, it will become possible to build caverns solely or mostly for energy storage purposes. We have built coal and uranium mines for energy, now the challenge is to store energy, and we can safely build energy storage mines for that.
We have developed high density fluids from inert mine waste, which are held in a top reservoir or tank. To generate power, they are let into the cavern through a lower port at the bottom. The pressure from the dense fluid column is then transferred to the water in the upper part of the cavern, forcing it upwards into a turbine on the surface. To recharge the system, water from the lower reservoir is pumped into the cavern from the port at the top, transferring the pressure to the dense fluid, which is then forced down to the lower port, and then up into the top reservoir. This gives significant improvements compared to models without our high density fluid.
As well as a technical and economic overview of the system, we describe various implementation methodologies and models.