In the March 2011 issue of Transmission & Distribution World, American Electric Power’s Emeka Okafor described how the utility has deployed battery energy storage across its distribution system. The potential benefits of implementing battery energy storage systems (BESS) at the substation were described as improving reliability both through supporting aging electrical infrastructure and providing backup power for customers. The BESS delivers these benefits through peak shaving and islanding.
Peak shaving is a function that allows the battery to discharge at times of high demand, thus reducing the peak load through the system and consequent stress on substation components. In addition to potentially extending the life of an asset, this function can defer the need for capital upgrades required to meet increasing demand. Islanding allows the battery to supply power to a portion of the distribution network when disconnected from the main grid because of a planned or unplanned outage. In this state, the battery is effectively acting as a backup power source.
In January 2010, BC Hydro initiated a project in partnership with Natural Resources Canada to install BESS on its distribution system in Golden, British Columbia, Canada, in the hopes of achieving both of these benefits.
The two mountain communities of Golden and Field, in the East Kootenay region of British Columbia, have had significant reliability issues in the past.
Both towns receive power from the Golden substation, which uses four radial distribution feeders to supply the town of Golden and surrounding areas. In early 2010, the load forecast for the area predicted substation capacity would be exceeded by the winter peak of 2013-2014. The town of Field, located approximately 50 km (31 miles) to the east of Golden, is supplied by a single 25-kV feeder from Golden. This distribution line experiences frequent and prolonged outages because of the heavily forested environment and cold, snowy conditions of Yoho National Park, in which the town of Field is located. The feeder does not always follow the road, and the rugged terrain makes it especially difficult for crews to locate faults and restore power.
To provide both peak-shaving functionality at Golden and backup power to Field, BC Hydro’s team reviewed several alternatives including battery storage and diesel generation. The financial cost of deploying battery storage was weighed against the cost of diesel generation at both sites. Although the cleaner battery option was preferred, diesel generation was significantly cheaper. It was only with a matching funds award from the Canadian government’s Clean Energy Fund that a business case could be made for battery storage.
In the business case, the utility is expected to derive benefits from the batteries over a 15-year life cycle and defer the cost of transformer upgrades at the substation for two years. BC Hydro and the Canadian government had three main
- Prove the business case
- Gain knowledge in the deployment of battery energy storage for peak shaving and islanding (for backup power)
- Understand the additional challenges of the Canadian climate and environment.
Early on, the BC Hydro team determined 2 MW of storage was required to mitigate the capacity risk at Golden substation. In locating 1 MW at Field and implementing an islanding scheme, BC Hydro expects to reduce the number of extended outages for the community by up to 80%.