Grid Scale Energy Storage Solutions For Future Virtualization

Examines grid scale energy storage solutions ranging from pumped hydro, compressed air, thermal storage, advanced batteries, fuel cells and purely electric storage systems.


Renewable energy sources often have a common problem of matching supply with demand, hence the need for energy storage to bridge the gap.  One major component of future VPP (Virtual Power Plants) is energy storage, in the form of battery storage, fuel cells, pumped hydro, flywheels, compressed air or other forms of existing and new technologies.

One promising form of energy storage combines gravity with water where energy is stored in raising heavy weights.  Electrical energy is converted to potential energy during periods of over-supply and then converted back to electricity when demand is greater than supply.

>”A Cutting Edge Variation of Pumped Hydro

Gravity Power, LLC, a privately-held company, based in Southern California (in Goleta, CA just north of Santa Barbara) is developing a novel grid-scale energy storage system for global commercialization called the Gravity Power Module (GPM). Like pumped hydro the working energy carrier is water that is pumped between a high pressure and a low pressure reservoir running a reversible generator/pump assembly to either produce power by drawing down the high pressure reservoir or store it up by pumping water from the low pressure store back into the high pressure store. In this sense it operates on the very same principles – and thus can also benefit from existing capital equipment, such as the reversible hydro generator/pump assemblies for example – as traditional pumped hydro.

Gravity Powers technology circumvents traditional pumped hydro difficulties related to siting, negative environmental impact, huge land demands, permitting, long-lead times and the very large investment required, by burying it all underground…. literally.

The GPM system uses a very large and very dense high mass piston that is suspended in a deep, water-filled shaft. The piston is equipped with sliding seals to prevent leakage around the piston/shaft interface and its immense mass pressurizes the supporting water column beneath it. A high pressure pipe from the bottom of this shaft enables water to be run or pumped through a generator/pump assembly of the same types now used in pumped hydro systems. The low pressure low energy potential water is returned above the piston adding somewhat to its weight and further pressuring the remaining high energy potential water column.

The massive piston moves up and down the shaft, storing and releasing power in a closed sealed cycle. It is compact with a small land footprint and the units can be clustered together into larger groups. It also is environmentally benign, no toxic chemicals or explosive dangers.

I like the scalable nature of this store that makes it suited to incremental growth of capacity. I also like how this energy storage system could be placed very near the big urban areas of greatest need for this kind of electric capacity. The fact that this energy storage system can take advantage of a lot of already existing infrastructure and technical knowhow from the existing pumped hydro sector is a definite advantage.

I would like to see more details on the costs of the boring of the immense vertical shafts; the long term performance metrics of the shaft seals (that would be an expensive repair job I would think. All in all I think this or something like it is a strong contender in the energy storage sector.”<

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