In late January, FERC issued an order in response to a filing by Western Grid Development LLC that asked FERC to declare that Western Grid's proposed battery storage devices are transmission facilities eligible for certain rate incentives. Western Grid described its battery technology as 10 to 50 MW sodium sulfur batteries that would be installed at strategic places on the California ISO transmission grid in order to provide voltage support and protect against transmission overloads. In a description that seemed significant to FERC, Western Grid stated that its batteries would only enhance transmission reliability at the California ISO's direction, and that the batteries would not operate or participate in energy markets or provide electricity for commercial sale.
FERC examines energy storage devices on a case-by-case basis because storage devices don't fit squarely within the traditional transmission, distribution, or generation categories of assets. In this case, FERC gravitated to the notion that the battery devices would not provide capacity or energy to be sold in the energy market, and that Western Grid would not retain any revenues outside of the transmission access charge (unlike generators). For these and other reasons, FERC distinguished Western Grid from similar filings (see Nevada Hydro II--pumped storage), and determined that Western Grid's technology will act enough like transmission assets to warrant eligibility for transmission rate incentives. FERC's approval of rate incentives, however, was conditional upon the California ISO approving Western Grid's projects in the transmission planning process.
Although FERC repeated numerous times that its decision was based on the "specific circumstances and characteristics" of Western Grid's projects, the order shows potential for energy storage devices. If such devices can show that they act sufficiently like traditional transmission assets (like capacitors), they may be able to obtain very valuable transmission rate incentives. Whether this opens the door for compressed air energy storage and pumped hydro (but see Nevada Hydro II) is still up in the air, but rest assured that these questions will be at FERC before too long.