One of renewable energy sources’ biggest challenges is the intermittency of power generation. Finding a way to store power for later use helps make renewables more practical for tying into the grid where demand does not always coincide with the wind or the rising sun.

A group of utilities in Washington may have found a way to overcome that challenge. Kennewick, Wash.-based Benton PUD recently announced that it will begin testing a new device that stores electricity when prices are low and then releases it back to the grid when it is needed most. Testing on the device will begin in September and last for two years.

The 10-kilowatt energy storage device referred to as the “Demand Shifter” was recently branded as the Grid.Balancer, manufactured by Demand Energy of Liberty Lake, Wash. It extracts energy from the grid during off-peak hours, when electricity is most abundant and least expensive for utilities. The device has the potential to store and provide up to four hours of energy, which it releases it back to the grid during times of peak demand.

It communicates information about price and current demand for power back to a master controller located at the utility. Using wireless technology, the master controller then signals the device to “charge” or “discharge” energy.

Franklin PUD joined Benton in testing the device. Grid.Balancers are now installed at facilities for three utilities. The testing is part of the Pacific Northwest Smart Grid Demonstration Project, a massive project involving 11 utilities and five technology partners in Idaho, Montana, Oregon, Washington and Wyoming.

With partial funding of $178 million from the Department of Energy, it is designed to quantify smart costs and benefits, facilitate the integration of renewable resources, validate new smart grid technologies, advance standards, and provide communications between distributed generation and the existing grid.