Energy storage by liquid piston compressed air

Compressed air storage to replace lead-acid batteries according to the Adit's BEs

One of the main difficulties encountered by solar and wind energy is the problem of storing excess electricity. Indeed, energy production is rarely in perfect harmony with the need (too much or too little wind, no solar at night, etc.) and it is therefore necessary to be able to store the excess electricity produced. Usually lead acid batteries are used to accomplish this task.

A young Lausanne company, Enairys, is betting on another system: compressed air storage. Ecological (no heavy metals) and economical (longer lifespan), the process is not new but it has remained little exploited to date because its yield is low. Indeed, the compression of the air causes it to heat up and consequently thermal losses, resulting in an efficiency of the order of only 25%. (Note from this is only the compression performance and not the overall performance of this storage!)

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With the help of the Industrial Electronics Laboratory and the Industrial Energy Laboratory located at EPFL, Enayris is offering a system based no longer on a mechanical piston but on a liquid piston. The water used makes it possible to regulate thermal flows and significantly improves the efficiency of the batteries to now reach 60-65% (almost the efficiency of a lead-acid battery, which is 70%).

The air is compressed by means of an electric motor coupled to a hydropneumatic compressor and stored in cylinders connected to each other. When a need for electricity arises, the air is extracted to supply the same machine which operates this time as an alternator.

The patents have been filed by EPFL and Enairys has an exclusive license. To date, it has completed the creation of the demonstration prototype and for the moment intends this type of installation for isolated regions or for emergency power supplies for sensitive systems subjected to unstable electrical networks.

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Source: "Energy storage by compressed air ready to replace lead-acid batteries" - Le Temps - 24/06/08

- Energy storage by compressed fluid
- Comparison of energy storage methods
- Can compressed air really replace lead acid batteries?

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