Characterisation and mitigation of renewable droughts in the Australian National Electricity Market

In a decarbonising world, the electricity generation mix in Australia’s National Electricity Market (NEM) is likely to be heavily dependent on wind and solar. Designing an electricity system dominated by variable renewable energy generation requires careful examination of periods of low renewable output to ensure storage or other back up generation is sufficient to avoid loss of load. This study uses 15 years of climate and electricity demand data to examine the frequency and nature of the occurrence of low renewable periods. It examines strategies for their mitigation so that unserved energy standards are not breached. We have found that the winter period, May to August, is the time where the NEM is at greatest risk of loss of load. This winter period is when the demand in southern Australian states is higher, solar generation is lower and a series of low wind periods can drain storage. It has been demonstrated that any proposed generation mix reliant on renewable energy generation should be stress tested across a low wind winter, like the complex winter of 2010, not just a single isolated low wind period. Storage was found to be ideal to provide energy for a few hours overnight, but firm dispatchable thermal generation is likely to be a lower cost option than long term storage for extended low wind periods. Diversifying generation with the addition of offshore wind may reduce the need for storage, although the need for floating wind turbines may make this alternative too expensive to add any value in the Australian context.