First Wind first broke on Kahuku, west of Kahuku town on Oahu's North Shore, Hawaii, in March 2011. The project, which consists of 12 2.5MW Clipper Liberty turbines, included a battery storage system from Xtreme Power. It was also notable as being the first utility-scale project on the island.
A year later and the fire at the project's storage facility was so fierce that firefighters could not enter the building for seven hours. It was also the third battery fire at the 30MW wind farm since its opening. In fact, Hawaiian Electric Co (Heco), the local utility, and First Wind decided against battery storage for the re-opened project. They instead selected D-VAR, or dynamic volt-amp reactive technology, from AMSC for continuous voltage regulation.
Asked about the decision, Heco's official response was: "Hawaiian Electric worked with First Wind to evaluate the use of a D-VAR [system] and determined [that] it was a cost-effective solution to regulate voltage for safe, reliable integration of energy from the Kahuku wind farm into the grid."
Battery storage was initially chosen because of the small island grid. The "chemical capacitor" storage technology digitally smoothed the output to ±1MW per minute by rapidly absorbing or releasing power as needed, said Xtreme Power, the Texas supplier of the pilot 15MW system.
Xtreme, a leading provider of wind-project batteries, filed for Chapter 11 bankruptcy this January. It had been backed by well-known venture-capital investors, including Dow Chemical Company, Fluor, BP Alternative Energy, Dominion Resources, Posco ICT, Skylake & Co, Spring Ventures, Sail Capital Partners and Bessemer Venture Partners.
A probe of the first two Kahuku fires — in April and May 2011 — blamed manufacturing defects in the capacitors made by Electronic Concepts Inc (ECI) and contained in inverters by Dynapower. This is alleged in a lawsuit against ECI and Dynapower by Certain Underwriters at Lloyd's, London, which insured First Wind. According to the November 2013 suit, the design of the Dynapower inverters was also not "sufficiently robust".
So far, cost is the main barrier to battery storage, said Fort Felker, director of the national wind technology centre at the National Renewable Energy Laboratory (NREL). An NREL study has found that storage is "very helpful" when wind penetration in a grid exceeds perhaps 50%, he said. But in most situations a larger balancing area, for example, is enough to integrate variable generation sources such as wind.
Milton Holloway, president of the Centre for the Commercialisation of Electric Technologies (CCET), said wind farms backed by storage can respond more quickly to frequency dips than gas-fired plants. Storage can also smooth out daily variations in generation, he added.
The future value of batteries "depends upon how inexpensive they become", he agreed. "It's potentially a really important resource for the grid." Holloway noted the February announcement by Tesla Motors, the electric car maker, of a $5 billion "giga-factory" for lithium-ion batteries for electric utilities as well as for cars. CCET is trialling a 1MW/1MWh lithium-ion based battery storage system with Samsung SDI, part of Samsung Group, and Xtreme at the Reese Technology Centre in Texas for a wind integration project.