2. Systems under development

It should be pointed out that, at the beginning of 2005, it is premature to consider that redox-flow systems have reached the stage of industrial maturity. Given their potential for high-capacity storage applications, it is mainly planned to link these systems to electricity transmission networks. As we know, there are two main reasons for this potential:

• the absence of solid reagents: there is no structural evolution of electrode materials over time, which augurs well for long lifetimes;

• decoupling the dimensions associated with capacity and power: we can envisage very high-capacity systems, obtained by using large-volume reservoirs.

These two features help to lower the cost price per kWh stored, which is particularly advantageous in the case of mass storage.