Optimierung des Einsatzes von Blei-Säure-Akkumulatoren in Photovoltaik-Hybrid-Systemen unter spezieller Berücksichtigung der Batteriealterung

Sauer, Dirk Uwe (Corresponding author)


Dissertation, Universität Ulm, 2003


Lead-acid batteries are widely used in off-grid and stand-alone power supply systems. In many cases these systems are powered by photovoltaics and wind turbines. The battery is necessary for levelling energy supply and demand at any times. Based on a lifetime cost calculation it becomes obvious that the battery has the highest share of the lifetime costs. This thesis analysis in detail the operating conditions of batteries in stand-alone PV-battery and PV-hybrid systems. Furthermore an overview on typical ageing processes is given. The main part of the thesis deals with the development of a mathematical model for the lead-acid battery as a basis for lifetime simulations. This includes models for acid stratification, growth of sulphate crystals and a simulation of the spatial distribution of currents, potentials, temperature and acid concentrations in the battery. Finally a simplified battery ageing model is developed and used for lifetime predictions in system simulations over periods of up to 20 years. This includes detailed models of all components in such systems including the energy management strategy. The optimisation is based on genetic algorithms, which have been optimised for the specific application.