Super-capacitor/lead acid battery hybrid energy storage suitable for remote area power supply (raps) systems.

Abstract This paper presents the results of simulations based on real load data collected from a RAPS system in the south west of Western Australia. The load data was collected at a rate of one sample per second to capture the transient changes. The data had features of a base load suited to lead-acid batteries and transient spikes in load suited to super-capacitors. A model of a RAPS energy storage system including batteries and super-capacitors was built in Simulink. This model was designed to capture the major influences on battery life and performance: battery current, state of charge and battery temperature. Simulations were run under standard conditions of no diesel generation (solar generation only), fixed ambient temperature (25°C), fixed total energy storage of 875Ah and equal hours of daylight and darkness. An optimum super-capacitor size of 65Ah capacity was identified for the conditions of the simulation. Battery temperature was found to be dominated by ambient temperature and little improvement was achieved by including super-capacitors. Battery life was improved by seven months from nine years and fourteen weeks to nine years and forty one weeks. With the use of a 65Ah super-capacitor equivalent performance to the battery only base case can be achieved with a battery of 460Ah, approximately half the capacity of the existing batteries. A 450Ah battery bank costs by $3520 less than the 875Ah battery bank used in the RAPS system that was monitored. A 65Ah super-capacitor costs between $115 500 and $147 500 indicating that a reduction in price in the order of forty times is necessary before super-capacitors could be justified in a battery super-capacitor hybrid energy store