EnerVault, based in Sunnyvale, California, is a designer and manufacturer of long-duration, grid-scale energy storage systems based on iron-chromium redox flow battery technology. The company is targeting its products to enable the expanded use of renewable energy, make fossil fuel power plants more efficient, reduce the costs of grid infrastructure, and increase the reliability of electric service to commercial and industrial users.
Redox flow batteries have the potential to be the workhorses of energy storage because they hold significant amounts of charge indefinitely and can deliver megawatt-hours with high reliability and at low cost. Since the bulk of the electrolyte is stored externally in tanks, it is possible to increase the energy storage capacity of a system simply by adding more electrolyte. Redox flow batteries have great potential for replacing gas-fired peaking power plants and for providing grid stabilization services.
There are a number of flow battery technologies under development including zinc-bromine and vanadium redox along with the iron-chromium technology used by EnerVault. Iron-chromium flow batteries were pioneered and studied extensively by NASA in the 1970s-1980s and by Mitsui in Japan. EnerVault was founded in 2008 to develop and subsequently patent anovel storage system called the Engineered CascadeTMarchitecture, which improves upon the stability, reliability, and cost potential of conventional redox flow battery technology as developed by NASA .
In 2010, EnerVault and New York-based Ascension Industries demonstrated the Fe-Cr battery technology under a NYSERDA-funded program in which a 2 kW prototype system was designed, fabricated, operated, tested and improved. The system demonstrated rapid response time from full discharge power to full charging power and suitability for utility storage/load shifting applications with 2.75 hours of storage. The collaboration continued in 2012 with the joint development of a 21 kW system. In 2014, EnerVault named Ascension Industries as its preferred supplier. Ascension brings expertise in manufacturing industrial-scale process systems. Ascension designedthe control system for EnerVault’s battery system that handles all pumping, flow control, process heating, and electrical charging and discharging.
In May, 2014, EnerVault put into service its first utility-scale system: a redox flow battery system that can deliver one megawatt-hour of energy from a 250 kW battery that can provide that power level for up to four hours. The system is located at an almond farm in Turlock, in California’s Central Valley. The storage system is located next to a 150 kW solar energy system and a 260 kW irrigation pump. The idea is to optimize the energy usage of the overall system. The almond trees in the orchard require water during the hottest part of the day: from noon until 6 pm. The solar panels don’t provide all the power needed for the irrigation pump, even when at peak production, so the energy storage helps balance the total requirement and shift total load from costly peak periods to off-peak periods.
The EnerVault system provides the alternative of charging the batteries at night when power is cheap and even using solar power to further charge them in the morning hours. Then, during expensive peak periods, the power needs of the irrigation pumps can be fully met by a combination of the solar panels and the flow batteries.
"EnerVault Turlock is an important step in our path to provide large systems with 100's of megawatt-hours of storage," commented EnerVault CEO Ron Mosso. "Since completing commissioning, the system has been characterized, verified by 3rdparties, and allowed us to collect operations and reliability data. Going forward, we'll continue to operate the system and work with new customers in application development." In December 2014, EnerVault successfully completed testing per DOE test protocols for performance measurement of "Peak Shaving" applications.
The almond facility is a unique application but the basic principle of using storage to provide reliability and stability for renewable sources is far more general. Applications such as small island grids, military bases, and microgrids in general are all amenable to the EnerVault solution.
EnerVault expects to win additional grid-scale storage projects throughout the United States but is also looking a global opportunities. The company does not need a large factory. It builds cells and stacks for the batteries but uses partners such as Ascension for other parts of its systems. EnerVault believes that it is well-positioned for survival and success both in the near term and over the long haul.