In most of the remote areas of Australia and in many other parts of the world, diesel generators are used to provide electrical power. Such systems are often characterised by either poor efficiency and high maintenance costs because of prolonged operation at low load levels, or intermittent power because the unit is only run during period of significant load. The addition of a battery bank and a power conditioner to produce a diesel-battery-inverter hybrid system has been identified as producing a number of benefits. Such systems can be broadly classified according to their configuration as series, switched, or parallel hybrid systems. A new parallel hybrid energy system developed in Western Australia is described in this article. The heart of the system is a high quality sinewave inverter which can also be operated in reverse as a battery charger. The system can cope with loads ranging from zero (inverter only operation) to approximately three times the generator capacity (inverter and diesel operating in parallel) with excellent efficiency. The system is fully automatic, provides continuous power, and can readily incorporate input from wind or photovoltaic systems. This article also includes a description of a 5 kW wind generator charging a battery bank as part of the hybrid system, and an economic analysis indicates a favourable result for this hybrid system with payback period estimated to be the order of three years.
