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General Compression and ConocoPhillips to Develop Compressed Air Energy Storage Projects

General Compression, Inc., a Massachusetts company developing an innovative compressed air energy storage system, has signed an agreement with ConocoPhillips to develop compressed air energy storage (CAES) projects, beginning with a pilot project in Texas, using General Compression’s Advanced Energy Storage (GCAES) technology.

The GCAES system. Click to enlarge.

GCAES is a modular compressor/expander unit that has a nominal size of 2 MW and features a roundtrip electrical efficiency in excess of 70%. Unlike conventional turbomachinery-based compressed air energy storage, GCAES consumes no fuel and emits no carbon. GCAES technology can increase utility reliance on renewables, eliminate wind power curtailment, enhance transmission utilization, and make dispatchable renewable power available to customers.

Founded in 2006, General Compression, Inc. has made patent-pending advancements in the fields of isothermal compression and expansion to provide utility-scale storage for clean electricity sources such as wind and solar. General Compression raised more than $17 million in Series A financing in 2010.



Interesting, although it seems silly to put renewable energy through a 75% round trip efficiency.

A better option might be just to have a flywheel or two in the base of each turbine to cope with changes in output, although improvements in forcasting including forward facing LIDAR systems can give an accurate forcast of likely production over the next 10 minutes / hours / days.

Compressed air storage might be able to share equipment with a CSP plant with thermal storage, although finding a good site could be tricky!


How do they get 75%?

Is this the goal?

I don't follow how LIDAR could be involved, but this is not new and could provide some smoothing for any kind of intermittant power.



70% roundtrip efficiency is excellent compared to the 0% efficiency that you get if you have to dump the power. Renewables like wind or PV are a use-it-or-loose-it proposition.

Furthermore, not all renewable energy is put through this storage, only the excess.

Flywheels can only store a very small amount of energy at a high cost and are therefore in a different category than comporessed air storage.

Forecasting does help to anticipate, but sometimes with high winds during periods of low demand, you can run out of options with respect of what to do with the energy.


Eventually, lower cost, long lasting very large battery banks will do the job best. Meanwhile, other means such air compressed air could do it.

In our area, Wind power coupled with Hydro power works best because Hydro power can quickly and easily be adjusted to meet variable demand and/or wind power production variations. No energy is lost because unused water is stored in the huge reservoirs and is available whenever required. Keeping the water reservoirs full (or fuller) increases the water pressure and hydro power production potential. No water pumps are required. The large power grid currently used interconnects up to 100+ hydro power plants and 1000+ (soon to be 2000+) Wind power turbines for a total of over 40 000 MW (soon to be about 48 000 MW). By using Wind turbines for base load, you can effectively use 100% of the power produced by wind, increasing the power factor.

Henry Gibson

It is well known in the electric industry that it is cheaper to not store electrical energy. Coal burning steam power plants have ignored a possible option for many years just to make their turbines as efficient as possible. Much smaller but cheaper, lower efficiency turbines can be built that will allow a rapid start up within a few seconds and massive amounts of high pressure hot water can be stored in tanks to have immediate steam available. High temperature molten salts can also be used to store the immediatly need heat energy. Later needed energy can be kept in the low cost coal until it is burned. The lower efficiency turbines are compensated for by the low cost of the coal and the immediate response of the small turbines and the redundant use of many small turbines for peak power.

A generating station with more than 16 large natural gas powered engines earns its money mostly by not operating but by being ready to operate one or all of the engine generators on a few moments notice. A nearly identical power station operates much of the time to send cheaper power to its owners at a distant mine.

Each windturbine should be required to have an associated engine or gas turbine that can substitute for the failure of the wind to blow. This engine should be located in large buildings in places near the turbine, so that it can be also used for combined heat power and cooling. On a hot summer afternoon every wind turbine that is not generating full power has a substitute fossil powered generator running somewhere and generating CO2 that should be atributed to the windturbine and its owners. ..HG..


General Compression's site says nothing much about their technology, but "isothermal" is suggestive. Near-isothermal compression of air means it's probably mixed with an incompressible heat-storage medium during the compression process. The likeliest candidate is water. Extracting hot liquid before the air goes to storage, and spraying it back into the stream of air on expansion, is a fairly obvious way to deal with the heat-cycling issues of CAES.

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