Demand and energy avoidance by a 2 MWh energy storage system in a 10 MW wind farm

Abstract All power generators require power for their auxiliary loads. Unlike conventional generators, intermittent renewable generators such as wind turbines depend on the wind for their fuel. During periods of low wind speeds, they consume power from the public grid to supply their auxiliary load demand. As the wind is intermittent, periods of low wind speed may coincide with periods of peak energy rates on the grid resulting in a significant energy charge. In addition, the peak power demand results in a demand charge. The energy and demand charge represent a net cost to the owner. A battery storage system can be used to minimize the energy drawn from the public grid to supply these loads. The Wind Energy Institute of Canada operated its 1 MW/ 2 MWh storage system, utilizing a wind forecast prediction, to reduce the energy consumption of their 10 MW Wind R&D Park during periods of low wind. The storage system was charged from the Institute’s wind turbines and the energy stored was discharged to the wind park internal network when the wind park power dropped below 0 kW. The discharge rate was determined based on the wind forecast so that the energy would last for as much of the forecasted low wind period as possible. The use of the forecast reduced the number of occurrences of the battery reaching its minimum state of charge, but it was not able to reduce the demand charge. The storage system was able to offset 17.2 MWh, resulting in a cost avoidance of $2804 in the 2 month trial. This financial gain was insufficient to offset the net energy losses in the storage system.