ABSTRACT
Half of humanity is yet awaiting electricity, economical development and improvement of its quality of life. Renewable energy systems may be used for supplying electricity to isolated sites. It is then necessary to store energy in batteries. Vented lead acid batteries, which are generally used, are particularly subjected to two kinds of problems in such autonomous systems: stratification of electrolyte concentration and irreversible sulphate formation. Stratification of electrolyte concentration is provoked by incomplete charges; it leads to heterogeneous discharge of the plates of the lead acid batteries and accelerated ageing of the lower parts of these plates. Irreversible sulphate is produced when lead acid battery remains partially or totally discharged for a prolonged period. This process may lead to sensible reductions of battery capacity. EDF has developed an innovative concept of PV plant architecture and energy management. This concept, based on individual management of several batteries, is aimed at solving electrolyte stratification and irreversible sulphate formation.
