Development of a VRLA battery with improved separators, and a charge controller, for low cost photovoltaic and wind powered installations

There are many applications and uses for which it is more advantageous to u se solar installations than to extend the electrical network and connect to it. This kind of applications are numerous covering from isolated houses t o telephone repeaters and the like. These kind of applications share some c ommon characteristics like being located in remote not easy accessible area s, require relatively low power for operation, and being difficult to maint ain. Up to now the use of photovoltaic systems, no matter the impressive growth they are experimenting, suffer from some drawbacks, mainly related with the life expectations and reliability of such systems, and as a consequence of the cost of these systems, when calculated on a lifetime basis. To try to contribute to solve these problems, a project partially founded by the Euro pean Commission, has been carried out, with the main objective of increasin g the life of these systems, and consequently to make them more attractive from the point of view of cost on a lifetime basis for consumers. Presently, the life of PV systems is Limited by its weakest component, the battery. Battery failure modes in PV applications, are related with well kn own phenomena like corrosion, but also due to the special nature of this in stallations, with other factors like corrosion and growth in the upper part of the group, induced by the development of acid stratification inside the battery, with the more prone standard flooded types now in major use, and to a lesser extent the new valve regulated lead acid (VRLA) types beginning to be used. The main objectives of this project, were: to develop a new gl ass microfibre separator material, capable of minimizing acid stratificatio n inside the battery. To develop a new VRLA battery, with a life duration o f 800 cycles on cycling at 60% DOD and partial state of charge (PSOC) condi tions, To develop a new charge regulator, that takes into account the condi tion of the battery in the near term, to modify its setting charging point. The fourth objective was the design and implementation of a PV/wind demons tration system, to test all the PV components under real conditions. The pr oject has been successful, having achieved a life increase of 50%, moving a chievable life from previous 500-750 cycles for the new battery and system. (C) 2001 Elsevier Science B.V. All rights reserved.