Big batteries blooming

By Ken Wicker

Pages: 1 2 3 4

NiCad batteries: Less costly than they seem

Nickel-cadmium (NiCad) batteries have powered portable electronic devices for decades. However, their relatively high capital cost has prevented their widespread use in large stationary applications. Nevertheless, there are certain utility market niches in which NiCads can compete on a lifecycle-cost basis with conventional lead-acid batteries because the former can work in extreme temperatures and deliver lots of current over a short period.

Indeed, a phenomenon related to discharge speed is what prompted the Golden Valley Electric Association (GVEA; Fairbanks, Alaska) to choose nickel-cadmium units to power its Battery Energy Storage System (BESS). Commissioned in late 2003, the GVEA system (Figure 3) is the biggest of its kind in the world. With the internal NiCad units connected in series to create a 5,000-VDC battery, BESS is capable of providing 27 MW of AC current for 15 minutes, or up to 46 MW for long enough to start up a backup generator to replace one that fails. Tim Devries, GVEA's manager of engineering services, expects about 30 of these events per year in Alaska's unforgiving climate.

3. Big BESS. At the heart of the Golden Valley Electric Association's Battery Energy Storage System are racks holding 13,760 nickel-cadmium modules. Connected in series, the modules function as a 5,000-VDC battery.
Courtesy: Golden Valley Electric Association

GVEA chose NiCad batteries to power BESS (which happens to be in a controlled-temperature facility) because their capacity degrades slowly and linearly when they are discharged rapidly. During the selection process, Devries realized that meant he wouldn't have to replace the NiCads at all during the system's 20-year expected life. Over that period, had he chosen lead-acid batteries to power BESS, they would have to be replaced at least once. Add the capital and shipping costs of the new batteries to the cost of sending the old ones down to the Lower 48 for recycling, and you can see why the NiCads should end up costing less over two decades. Even better, Jim McDowall of Saft America Inc. (North Haven, Conn.), which provided the NiCads, expects that GVEA will be able to use BESS for more than 20 years, but at a lower output.

Perhaps vanadium redox

The two major suppliers of vanadium redox batteries are Tokyo-based Sumitomo Electric Industries Ltd. (SEI) and the aforementioned VRB Power Systems Inc. (VPS). Both companies rely on intellectual property held by Sydney-based Pinnacle VRB Ltd., in which VPS owns a controlling share. In addition, a third company—Reliable Power Inc. (Arlington, Va.)—is authorized by Sumitomo to sell vanadium redox batteries in the U.S.

SEI has been developing vanadium redox batteries since 1985 and manufacturing and marketing them since 2001. SEI markets megawatt-scale systems directly in Japan, where 11 projects representing more than 3.7 MW and 13.8 MWh are in operation.

To date, VPS has installed only two systems. One is a 200-kW/1,000-kWh battery connected to a hybrid wind/diesel-powered microgrid on King Island off the south coast of Australia. The other is a 350-kVA/2.4-MWh system (Figure 4) that provides peak shaving and voltage support for a 200-mile-long, 25-kV feeder on the PacifiCorp grid near Moab, Utah; it began operation in March 2004 (POWER, July/August 2004, p. 8). According to VPS President Vince Sorace, "Since the project has been up and running, feeder deviations have improved by 2% and the power factor improvement has reduced line losses by 40 kW."

4. On the job. VRB Power Systems dedicated this 350-kVA/2.4-MWh vanadium redox battery near Moab, Utah, in March 2004. It provides peak shaving and voltage support on a 200-mile-long PacifiCorp feeder.
Courtesy: VRB Power Systems Inc.

Consider zinc-bromide

Currently, ZBB Energy Corp. is the only company working to commercialize the zinc-bromide flow battery. The firm has its headquarters and a new production facility in Menominee Falls, Wis., but its research, development, and marketing efforts are based in Perth, Australia. Greg Nelson, the company's chief operating officer, characterizes the company's efforts as being in the small-scale demonstration phase.

To date, ZBB has largely focused on demonstrating the technology in the utility market. The company has built energy storage systems whose outputs range from 50 to 500 kWh for PG&E, Melbourne-based United Energy Ltd., Detroit Edison Co., Osaka-based Daihen Corp., and Sandia National Laboratories.

In the new factory, ZBB Energy soon will be able to build up to 100 MWh of battery systems per year—five times its current production limit. A commercially available 500-kWh grid-interactive storage system is the company's basic building-block product. One system should satisfy most industrial energy storage needs, and several can be combined into multi-megawatt-hour sizes for utility applications (Figure 5). For example, four of the trailer-mounted systems are scheduled to be installed this year to provide 2 MW of peak-shaving support to a stressed PG&E substation.

5. One-stop shopping for moving and storage. This turnkey zinc-bromide flow battery from ZBB Energy Corp. can supply 250 kW for up to two hours. Delivered inside a standard shipping container, it is trailer-mounted, making it relocatable.
Courtesy: ZBB Energy Corp.