By spending years in the flywheel industry, Jim Fiske learned a great deal about grid-scale energy storage and its true requirements. After determining that flywheels were not the best option, he and the investor of his flywheel company founded Gravity Power. Gravity Power’s technology has the potential to change energy storage worldwide.
Presently, pumped hydro provides nearly all grid-scale energy storage, but requires vast quantities of water, two very large reservoirs, and extreme differences in land elevation. It can be difficult to fulfill all three necessary parameters, and a big plant can cost over a billion dollars with delayed financial returns.
Gravity Power’s technology is similar to the concept behind pumped hydro, but overcomes many of pumped hydro’s limitations. Each Gravity Power Module is a closed system that operates underground. Thus, once the device is initially filled with water, no additional water is needed. A 40MW unit is 30 meters in diameter and 500 meters deep, while a 250 MW unit is 80 meters in diameter and 500 meters deep.
To generate energy, the piston drops, and forces the water through a Francis-style pump-turbine that drives a motor/generator. To store energy, energy from the grid causes the pump to force water down the pipe and lift the piston. The following figure from Gravity Power’s website illustrates the process:
According to Fiske, Chief Technology Officer and Founder of Gravity Power, the company is currently doing a deep cost-analysis of the technology. The bigger the unit, the more cost-effective it becomes. Mr. Fiske anticipates that a 250 MW storage device would cost approximately 250 million dollars.
The company is currently seeking additional investors, and countries including Germany, South Africa, China, and India are interested in utilizing the technology. Utilization of this type of energy storage could help compensate for the variability of wind power and other renewable energy generation techniques.
The company currently has patent applications for its technology all over the world. According to Cleantech PatentEdge™, LaunchPoint Technologies, from which Gravity Power was spun out, owns seven U.S., International, and European patents and applications.
U.S. Patent Application Publication No. 2009/0193808 (’808 Application) lists LaunchPoint as the owner of record. Entitled “System and method for storing energy,” the ’808 Application relates to an energy storage system in which electricity can be generated by gravitational movement of a slidable piston. The claims of the ’808 Application were recently allowed, and the company anticipates that a patent will issue in the next few weeks, with several others in the works.
The company’s goal is to complete a small-scale demonstration module first to verify the technology. According to Mr. Fiske, one of the great benefits is that the units can be easily built by civil engineering companies all over the world because no exotic materials are needed – just concrete and steel. The technology is based on existing technologies, but this will be the first time the pieces will be combined in this particular way.
“A big advantage of our technology is its level of efficiency. Efficiency is expected to exceed that of pumped hydro, and be as high as 83%. In addition, it is quite feasible to build many gigawatts of storage per year due to the ease of construction of the Gravity Power Modules,” stated Mr. Fiske. Sounds like an energy storage device with great potential.
Article by Rosemary Ostfeld, appearing courtesy Green Patent Blog.
1 comment
Sounds like a hyped-up system that hasn’t really been designed, built, or prototyped yet. It is obvious that the seals of the piston, and possible leaks, are the weak point of the system. You have to build it to show that it can work.
What about my ‘simpler’ alternative: hang the weight up on cables that you can wind over an electric winch/generator. Why would a hydrolic system be more efficient? Why would a whole bunch of old-fashioned steel cables be less reliable than an enormous seal, much larger than the famous O-rings of the shuttle? ‘My’ system would be like old clocks running on a weight. A small version of it could be installed as an add-on in the elevator shaft of every talll building.
.. this patent is clearly just an idea, not past the stage of testing it by talking with a few engineers over coffee. Not at very useful before it has been tried out, and made to work in practice. Does giving out such a patent help to finance the design process .. or does it just stop others from doing what is necessary?
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