Compressed air storage to replace lead-acid batteries
One of the main difficulties encountered by solar and wind energy is the problem of storing surplus electricity. Indeed, the production of energy is rarely in perfect adequacy with the need (too much or too little wind, no solar at night ...) and it is therefore necessary to be able to store the produced electrical surplus. Usually lead acid batteries are used to accomplish this task.
A young Lausanne-based company, Enairys, is betting on another system: compressed air storage. Ecological (no heavy metals) and economical (longer service life), the process is not new, but has so far been little used because its yield is low. In fact, the compression of the air causes it to heat up and consequently heat losses, resulting in a yield of the order of only 25%. (Christophe's note: this is ONLY the compression yield and not the overall yield of this storage!)
With the support of the Industrial Electronics Laboratory and the Industrial Energy Laboratory located at EPFL, Enayris offers a system based no longer on mechanical piston but on liquid piston. The water used makes it possible to regulate the heat flows and clearly improves the efficiency of the batteries, now reaching 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 there is a need for electricity, the air is extracted to supply the same machine, which this time works 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 intends for the moment to use this type of installation in isolated regions or in emergency power supplies for sensitive systems subjected to unstable electrical networks.
Source: "Energy storage by compressed air ready to replace lead-acid batteries" - Le Temps - 24/06/08
http://www.bulletins-electroniques.com/ ... /56174.htm