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Page added on September 18, 2013

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Compressed Air Energy Storage Makes a Comeback

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IEEE Spectrum has an article on a new CAES technique being piloted in the US – Compressed Air Energy Storage Makes a Comeback.

The last time a compressed air energy storage (CAES) plant was commissioned was in 1991. This week, SustainX is bringing the technology back to the U.S. electricity grid, albeit in a vastly different form.The startup, based in Seabrook, New Hampshire, began operating a full-scale demonstration system that stores energy as compressed air in pipes and supplies 1.65 megawatts of power. The company will use the machine to gather data on performance and and to show off the technology to potential investors and customers. The project was funded by $5.4 million from the Department of Energy and at least that much from SustainX, according to a representative.

Conventional compressed-air energy storage uses a compressor to pressurize air and pump it into underground geological formations. The two plants of this type currently in operation—one in McIntosh, Alabama, and the other in Huntorf, Germany—use salt caverns as storage tanks, pumping compressed air in at night, when energy demand is lowest. During the day, the air is released, heated with natural gas, and forced through a turbine to generate power. The appeal of this technology is that it’s relatively low cost and can store many kilowatt-hours of energy.

SustainX takes a different tack: it uses compressed air as the energy storage medium, but holds the air in large pipes, the same used in natural gas pipelines. That means utilities or even commercial customers could place a storage device in a range of industrial locations, rather than only where there’s an underground formation available.

At the base of SustainX’s machine, called the S165, is the bottom half of a diesel engine normally used to propel ships. To store energy, a permanent magnet motor-generator turns the engine’s crankshaft, driving six pistons located above it. The pistons, each of which is taller than a full-grown man, compress a combination of air and foamy water, which is then pumped into storage tanks. When power is needed, the air is released, driving the pistons and turning the generator to create a current.

A key difference between SustainX’s technique and conventional CAES technology is that the compression and expansion of air are done at near-constant temperature and the process doesn’t require natural gas. And unlike conventional batteries, this system can vary the amount of energy independent of the power output. In other words, you can expand the amount of energy it stores simply by installing bigger pipes. That’s different from a battery designed to deliver, say, 1 megawatt for 2 hours. If you wanted four hours of storage, you’d have to buy another battery–a more expensive approach, the company says.

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4 Comments on "Compressed Air Energy Storage Makes a Comeback"

  1. PrestonSturges on Wed, 18th Sep 2013 5:10 pm 

    The soapy water thing is interesting because there is a lot of heat released when the gas is compressed and then it get’s very very cold when the gas is released again (CO2 fire extinguisher. The soap would be to prevent ice during decompression.

    Anyway, consensation is a big problem in compressed gasses, so this just makes water part of the system. The ships engine/compressor is clever since the machinery to make is nothing high tech, just large.

  2. rollin on Wed, 18th Sep 2013 7:00 pm 

    Interesting concept, no statement on efficiency but it should be reasonable with the reuse of heat energy.

  3. BillT on Thu, 19th Sep 2013 1:16 am 

    Question #1: Can this form of energy storage actual net enough energy to reproduce itself?

    Look at that picture. There are many tons of steel in that blue machine. Look at the gret personnel lockers to the left of the machine for scale.

    Question @2: How many machines did it require in it’s manufacture from mines to the ship? I can tell you it took a big crane just to set it in place here.

    Question#3: What did it cost? $5,400,000.00? Taxpayer’s money? If it was a viable (profitable) answer, why did it need taxpayer money to exist?

    So many questions, so few answers…

  4. blacknail on Thu, 19th Sep 2013 1:20 am 

    Quick question, let’s say that we can develop 5000 psi tanks that store enough energy for a car to drive 500 miles or something. Any chance on a global scale that we will compress enough of the atmosphere into tanks that the atmosphere becomes to thin to breathe?

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