Overview

Battery Arrays have two important roles to play in a renewable energy technology solution: a) to store electrical energy generated by the front-end; b) to provide a buffer between the periodically inconsistent electrical energy generation in the front-end and the AC or DC loads in the back-end. The arrays are configured to satisfy the energy needs of a renewable energy solution in the form of two attributes: a) voltage which is essentially the energy force which pushes the electrons through an electrical conductor, i.e. wire; b) capacity which is the measure of the electric charge that can be stored in the batteries. Voltage is expressed in units of volts, and capacity is expressed in units of Amp-hours (abbreviated as Ah). Therefore, the amount of electrical energy available in a battery array is the product of voltage and Ah, resulting in a number expressed in units of Watt-hours (abbreviated as Wh) as demonstrated in the following, where a 12V battery with a 200 Ah capacity, and fully charged would be:

12 V x 200 Ah = 2,400 Wh or 2.4 kilo-watt hours (kWh)

Battery arrays are configured (connected) in a number of strings (series) and two or more strings in parallel. The configuration of the array will have direct impact on the longevity of the batteries in the array. It is adviseable to keep the battery array as simple as possible, and not exceed three parallel strings as it would increase the probability of accelerated failure of one or more batteries due to loss of equalization across a large array. Batteries connected in series in a string will increment the voltage of the string. Strings connected in parallel will increment the Amp capacity of the array, while maintaining the voltage unchanged.

References

1. US Department of Energy. Renewable Energy Technology Characterizations - Energy Storage Technologies Overview (Battery Storage). Energy Efficiency and Renewable Energy. 1997.