Editor's Note: This month, the Energy Services Bulletin introduces a new column featuring innovative equipment, systems and applications utilities around the nation are using to save energy and improve service.
What's This? A Supply Side UPS?
by Johnny Douglass
Most of us are familiar with battery-powered uninterruptible power supply systems electric customers use to keep up critical loads. Customers commonly use them to keep their computers and critical processes running until power is either restored or on-site generation can be started. Golden Valley Electric Association of Fairbanks, Alaska, has taken this to another level—to the utility supply system.
Fairbanks can be fiercely cold in winter, so critical loads are not just computers and sensitive industrial processes, but building heating systems. With typical nighttime lows of around -19°F in January and record lows of below -50°F, electric power is a matter of life safety.
GVEA has local backup generation to provide power when there are problems with the transmission and distribution system that normally brings power in from Anchorage; however, that backup generation takes up to 15 minutes to start. This led the GVEA to implement a monster battery-powered UPS system that seamlessly fills the time gap.
The Battery Energy Storage System is currently the world's largest. It was a joint endeavor for the utility, with Saft Batteries supplying and maintaining the nickel cadmium batteries, and the ABB Group supplying the primary design and controls. BESS consists of 13,760 liquid-filled Ni-Cad cells, and has a total weight of 1,500 tons. Maximum output capacity is 46 MVA, and the system is currently capable of sustaining 27 MW for 15 minutes. It can be expanded to sustain 40 MW for 15 minutes.
From November 2003, when it began service, through February 2004, BESS sustained power through 10 outages totaling an hour and 40 minutes. In the three years between 1994 and 1997, GVEA suffered 111 outages. Of those, 73 were within the current 27-MW capability of BESS, and 10 more were within the ultimate 40-MW capability. For this Fairbanks utility, the UPS system has become an important supply-side tool.
(Note: Douglass is a registerd professional
engineer with the Energy Services Clearinghouse.)
