Wind plants are playing an increasingly important role in the generation of electricity worldwide. But there's one obvious downside to wind power: the wind strength varies dramatically and unpredictably. This means that the power output from a wind plant can change very rapidly, causing problems in the transmission network.

In January 2006, Hawaiian Electric Co. Inc. (HECO) and S&C Electric Co. installed the PureWave Electronic Shock Absorber (ESA), an innovative grid-stabilizing device for wind plants designed to overcome these problems, at Lalamilo Wind Farm, near Waikoloa on the Big Island of Hawaii. Wind conditions at Lalamilo provide an ideal location to prove out the system. The installation will demonstrate the potential for increasing the amount of wind power that can be generated for small, remote or stand-alone electrical grids like those on each island of Hawaii.

The PureWave ESA can provide short-term electrical energy storage and improve voltage support and overall stability of the transmission system. In addition, for larger, interconnected grids, the ESA has the ability to smooth out fast-changing wind-power outputs, called ramp rates. Smoothing wind-power output reduces the amount of conventional generation “spinning reserve” that is otherwise needed to stabilize the grid, reducing fuel and maintenance costs. These are the potential added costs of applying wind power to the electrical grid; and minimizing them will lead to the increased use of wind-power generation.

S&C received exclusive rights from HECO to design, build and commercialize the ESA. The system is based on S&C's DSTATCOM Distributed Static Compensator, with the addition of ultracapacitor energy storage provided by BOOSTCAP Ultracapacitors from Maxwell Technologies.

Ultracapacitors are zero-maintenance energy-storage devices that can be charged and discharged thousands of times. They can deliver much higher power output than rechargeable batteries and can operate over a wider temperature range, making them ideal for this application.