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Chapter 11: Solar Electric Power Supply with Batteries

Solar electric plants shall be understood to be photovoltaic energy converters that are able to self-sufficiently satisfy a mean energy demand over a significant period of time, be it an appliance that is permanently hooked up or just for sporadic power supply of appliances. Such plants have in common that their input and output quantities fluctuate widely. They can therefore only be dimensioned on the basis of a mean value and are not able to satisfy this demand without the possibility to store energy. . | 11 Solar Electric Power Supply with Batteries H. K. KÖTHE 11.1 INTRODUCTION Solar electric plants shall be understood to be photovoltaic energy converters that are able to self-sufficiently satisfy a mean energy demand over a significant period of time be it an appliance that is permanently hooked up or just for sporadic power supply of appliances. Such plants have in common that their input and output quantities fluctuate widely. They can therefore only be dimensioned on the basis of a mean value and are not able to satisfy this demand without the possibility to store energy. The solar generator is to be dimensioned dependent on solar radiation and the demand to be encountered the same goes for the battery. This difficult problem shall be treated first as it makes the problem definition for the energy storing device and the system on the whole clearer. Afterward the construction of the system as whole and the most important components shall be discussed. The demands for the energy storing devices and which system is best supplied with which battery shall be discussed with the help of some typical examples for design of such systems. Deceased. Copyright 2003 by Expert Verlag. All Rights Reserved. 11.2 DIMENSIONING A SOLAR ELECTRIC SYSTEM 11.2.1 Preconditions The basic precondition is that the mean solar electric power supply must be at least equal to the mean power demand. Whenever demand and supply are exactly of the same size the system is termed as being critical whereas systems that have a certain reserve that can be called upon anytime are termed well dimensioned . Whenever this reserve is unnecessarily high the reason for this can be only of economic nature paradoxical but most often the case the system is termed economically matched . 11.2.2 Calculation of the Mean Consumption Figures 11.1 11.2 and 11.3 explain how the mean demand is ascertained. The load demand currents throughout a day are shown for example by Figure 11.1 for a given system-dependent .