Computation of storage power and energy to stabilize a wind-and-solar-only Australian National Electricity Market grid

Abstract

The Australian NEM grid data is a unique example worldwide. No other country supplies high frequency (5-minutes-sampling-interval) data of power generation by all the facilities connected to a grid. The NEM grid has power demands between 18 and 36 GW, on average 27 GW. Presently, wind energy nominal capacity is 6.7 GW, solar energy nominal capacity is 11.4 GW storage power and energy is negligible. Capacity factors are about 0.33 for wind, and about 0.125 for solar (0.27 facilities, 0.10 rooftop). Wind and solar capacities must be increased to 53.2 and 90.5 GW (growth factor 7.94) to cover the NEM grid demand. Minimum storage power needed is more than 45 GW net, while the net storable energy is computed as 3500 GW h. The nominal power and energy are much more than that, depending on the specific technology adopted, as storage only works at a fraction of the nominal power during charge and discharge, and only a fraction of the nominal capacity, with round-trip efficiencies everything but unity. While the trend is to move towards more solar rooftop, this not the case, as it further increases variability and needs larger storage.