PV Peak Lopping – using photovoltaics to offset a proportion of peak power requirements either to avoid or defer network investment costs, or as a demand-side tool to reduce peak tariff charges – is emerging as a viable opportunity for grid-connected PV systems in many parts of the world. In Australia’s Northern Territory the same concept is being developed to significantly reduce diesel fuel consumption and part-load operation of generators on isolated grids.

The Northern Territory (NT) has numerous remote communities, including aboriginal outstations and mining sites which rely on diesel mini-grids for power. The peak profile amongst these communities typically demonstrates a power demand 40-50 % greater than the base load during ‘work’ hours, with maximum demand occurring early in the afternoon. The peak pattern closely matches the solar resource availability, such that a solar array sized to meet roughly 30 % of the peak demand can effectively allow the diesel engine(s) to serve as the base-load generator, the peak being met virtually exclusively by PV. This extends the period required between refuelling, which can be critical for isolated communities. It also allows a smaller diesel set to be operated at optimal load rather than a larger unit operating inefficiently at part load, which reduces operation and maintenance costs and further assists overall system reliability.

Following a successful small-scale demonstration project which confirmed the diesel-fuel and emissions abatement potential of what has been termed the ‘1/3rd peak lopping’ concept, the NT Power and Water Corporation recently completed two larger systems, assisted by the NT Centre for Energy Research. The project received financial support from the Australian Green-house Office and NT Department of Mines and Energy. Together they are expected to save 130 000 liters of diesel and reduce CO2 emissions by over 400 tonnes each year. The first of these systems, a 56 kW plant at Bulman, an Aboriginal community located in the tropical zone 350 km southeast of Darwin, has been operating since November 2002. The 2,9 million AUD (2,2 million USD) second phase of the project saw a further 241 kW commissioned in the Kings Canyon national park in Australia’s arid ‘red-centre’, 480 km west of Alice Springs in November 2003. The different climatic conditions and load profiles of the two installations will further help to confirm the viability of the concept for future commercial projects.

Power and Water Corp are expected to replicate the concept in other locations in the Northern Territory, but there is also good potential for transferring the same principle to other remote village communities, particularly in South East Asia and Latin America.

Contact: Wolfgang Meike, NTCER, Fax: +61 (0)8 8946 6885

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