A typical remote pastoral station RAPS system


System design brief

The design brief for this system was to provide a hybrid diesel RAPS system capable of supplying power to the remote cattle station, Mundbulunga. Commonly known as Munda Station the 225,000 hectare cattle station is located approximately 100 km south-west of Port Hedland. The prime activity of this station is the breeding and exporting of cattle for the south-east Asian market. Three or four fulltime staff are on site all year round, rising to twenty during periods of peak activity. Munda Station itself comprises six main buildings and several workshops and storage sheds.

System Sizing

Due to the large seasonal variation in both climate and personel levels the power demand at the station varies widely from Summer to Winter. The average daily load for the dry season is 39.8 kWh/day, increasing to 107 kWh/day during the wet season. The average load for Munda Station is 73.4 kWh/day. While the diesel generator installed at Munda Station could be used to meet this load at all times, the renewable components of the system have been sized to reduce the need to do so.

System Installation and Specifications

This system was installed in 1999 and is comprised of the following major components:

Photovoltaic Modules and Array Frame

This system has 60 BP Solar 80 Watt panels (photovoltaic modules) arranged on five array tracking frames. The peak output from the array is 4800 Watts.



Photovoltaic Regulator

The Photovoltaic arrays are controlled by three AERL 1800 BHV solar maximisers.

Diesel Generator

This is a 27 kVA, single phase Perkins diesel generator with a rated capacity of 23kW. It is switched on when the load becomes too high or the battery bank voltage become too low. The generator usage can vary from 8 kWh/day in the dry season up to 66.8 kWh/day in the wet season. Once the generator is running, it supplies the load and charges the batteries in order to operate at its optimal loading. When the load decreases, the generator will continue to operate until the battery bank reaches a specified state of charge.



The inverter changes the DC electricity from the battery bank to AC electricity for use with standard appliances like televisions, VCRs, refrigerators, electric drills, other power tools and kitchen appliances. The inverter is a 12 kilovolt-ampere (kVA) Magnum inverter, rated at 10 kW for continuous power use.


Battery Bank

This system has 30 Magnum Power 1025 Ampere-hour (Ah) 4 V lead-acid batteries. They are housed in the third room of the shed. The batteries require little maintenance, occasional checking of the terminals and levels being all that is required.

Changeover Switch

The change over switch controls whether the photovoltaic system or the diesel generator is supplying the energy to the homestead. This can be set to do it automatically when the power supplied by the PV is too low, or manually.


System Performance

The system has provided reliable power to the station. On average the PV panels at Munda supply 80 % of the required power during the dry season and 37% during the wet season, with an overall average of 48% annually. The diesel generator is mainly required in the late afternoon and early evening when the load is peaking, typically it is meeting the stations energy demand and charging the battery bank. The diesel also automatically starts to maintain the battery state of charge when required .

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