Intermittent wind power brings a number of challenges to the electrical system. On the Swedish island of Gotland, Vattenfall will mitigate some of these by combining energy storage with reactive power compensation equipment.
The energy storage system consists of about 2,300 lithium-ion batteries with a total capacity of 900KWh, used for bridging short power outages. Vattenfall’s Anders Holm, who is responsible for the sub-project, says bridging is only one of the tasks for the energy storage system.
“We also want to use it to enhance the power quality, to control the voltage, to even out the output of the wind power plants and to reduce network losses,” he says. “Much of this can be achieved without batteries, but batteries improve the results.”
One of the main tasks is to test islanding in parts of the grid, specifically around the Källunge substation, an area that include 200 customers and three wind-power mills with a total of 3MW.
“Islanding implies balancing a part of the system so that it becomes self-supporting,” Holm explains. “We want to build experience on how energy storages work, to find the optimal size of the energy storage and to understand what is needed to make it profitable. Today, batteries are very expensive, but in the future lower battery prices in combination with greater price volatility will hopefully change the picture.”
The energy storage is built by ABB on Vattenfall’s functionality specification.