Electrical energy storage systems

Electricity is a particularly attractive energy carrier, as demonstrated by its ever-increasing penetration rate [D 3 900v2] . However, its production today consumes almost 40% of the world's primary energy, whereas in 2009 it only contributed 17.3% of final energy (in France, this proportion was 22%). What's more, the importance of electricity in final energy demand is growing all the time: less than 3% in 1940, 9.4% in 1973, 17.3% in 2009 and forecasts of 25-30% by 2030.

At present, over 80% of electricity is of non-renewable origin, and contributes significantly to the depletion of non-renewable fossil and fissile resources, as well as to environmental degradation (from mining to the waste associated with its production). However, the proportion of its use that is renewable is growing, and it appears that electricity is one of the leading energy vectors for ensuring sustainable development for mankind . Among its advantages, we would highlight the fact that it can be easily produced from all primary resources, especially renewable ones, and converted with unrivalled qualities such as high efficiency, great flexibility and very low local pollution, in almost all energy services (e.g. lighting, ventilation, information processing, transport...).

However, it suffers from a serious handicap linked to the "modest" performance of its storage resources. This applies both to their specific energy (kWh/kg or kWh/dm ³ ), which is much lower than that of oil, even though this is an essential characteristic for on-board applications, and to their cost. It should be noted, however, that our current energy storage performance requirements are essentially dictated by our habits of exploiting oil and other non-renewable primary resources, which are abundant and already stored (free of charge)... This performance is undoubtedly behind the absurd statement, so often heard in the context of electrical production-distribution networks, that "electricity can't be stored...".

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