 During the 2003 expansion a vanadium redox flow battery was installed at a cost of $4M (or $20,000 per kW), containing 55,000 litres of vanadium based electrolyte—one of the first such installations on a wind farm.This allowed up to 800 kWh of surplus electricity to be stored.The battery has an output power of 200 kW, making up around 3% of total capacity, and could be used to smooth the substantial variability in wind output over minutes to hours.