Homer Electric Association Deploys Tesla Batteries in Soldotna
Thirty-seven Tesla Megapacks in Soldotna became part of the Homer Electric Association grid in January 2022.
Once a world record holder, the battery backup for Golden Valley Electric Association (GVEA) in Fairbanks has a new rival on the Kenai Peninsula. Homer Electric Association (HEA) recently installed a battery energy storage system (BESS) using new technology from Tesla to balance the flow of power every tenth of a second.
Playing with Power
Located at a generating plant on the outskirts of Soldotna, BESS is an array of thirty-seven Megapacks, each the size of a 40-foot shipping container and containing 200,000 lithium-ion cells. The system can store 93 MWh of energy, a far greater capacity than the nickel-cadmium batteries that GVEA has operated since 2003.
At the time it was installed, GVEA’s system was certified by the Guinness Book of World Records as the world’s most powerful battery. During one test it discharged all 46 MW in five minutes.
Larry Jorgensen, HEA’s director of power, fuels, and dispatch, says the Tesla system in Soldotna has a comparable discharge rate. However, the Fairbanks system was designed to operate for ten to fifteen minutes to prevent short-term power outages; HEA’s system can discharge for up to two hours.
“What we’re doing is making ourselves more robust, able to supply all of our reliability requirements and do it more cost effectively,” Jorgensen says.
HEA announced in 2019 that it selected Tesla to provide the Megapack, a scaled-up version of the automaker’s domestic battery spinoffs, the Powerwall and Powerpack. The components were scheduled for delivery last May but didn’t arrive until July, shipped from Seattle to Anchorage and then trucked to Soldotna. HEA technicians installed the units and conducted system integration until late November. BESS became operational in January 2022.
Each pack weighs 26 tons, Jorgensen says. That puts the entire system at 962 tons, a bit leaner than the 1,500-ton system in Fairbanks. GVEA’s batteries are made of 13,760 cells developed by Saft, plus a converter developed by ABB that changes direct current to alternating current.
The battery backup lets HEA avoid using a gas-fired power plant for reserves. When connected to the Railbelt grid, the reserve requirement is 10 MW, just in case of a large power draw, such as the huge motors at the Marathon refinery in Kenai. The reserve requirement increases to 40 MW when HEA is disconnected from the Railbelt grid, which happens regularly for maintenance up to a month out of the year.
Jorgensen explains, “What we would have to do before the BESS is whenever we were islanded we would have to run another unit at minimum load to provide those reserves. Now the BESS can do that.”
In addition to reserves, the second main function of BESS is to regulate the system, maintaining a steady AC frequency of 60 Hz. “Since we’re not trying to use it as a bucket that we fill into and pull out of, instead we’re allowing it to maintain a charge and we operate really close to that,” Jorgensen says. “By doing that we reduce the amount of charge/discharge cycles. That tends to extend its life.”
By contrast, the main function of the GVEA battery is to stabilize power for a few minutes until additional generators can pick up the slack, in case of an outage or disconnection from the intertie to Anchorage. Golden Valley says the system activated forty-nine times in 2019, preventing five outages for the average metered customer.
Included with Batteries
The 26-ton Megapacks arrived in summer 2021 and were lined up in rows at a Soldotna generating station.
Electricity storage opens the possibility of adding renewable energy sources, like wind turbines, to the HEA mix. (Homer Electric operates the state-owned Bradley Lake Hydroelectric Plant, the largest renewable energy source in Alaska, but the output is shared with other utilities, giving HEA 12 percent, or 14 MW.) Not right away, though; Jorgensen says the battery system would need to be ten times larger. However, he adds, “once we have that regulation ability, we can then bring the renewables on and try to make that all work. Otherwise, we are being very stretched to do so and actually make our system unstable because we wouldn’t have the capability to provide that regulation. BESS opens that door.”
One major difference between HEA’s and GVEA’s storage systems, apart from their underlying chemistry, is that the Fairbanks battery is contained indoors. The Megapacks are out in the weather. This exposure gives Tesla the opportunity to test the hardware in a cold climate.
“They want to make sure that they can make their product work in as many places as possible,” Jorgensen says. “Each environment has different challenges. The challenge here is to not let the batteries freeze because it really messes up the chemistry.”
Each Megapack has a fully integrated HVAC system, Jorgensen explains, and he expects the heater will be on most of the year. “Most of the Lower 48, they’re much more worried about getting them too hot, [which can] cause damage to them if they overheat,” he adds.
The bottom line is that BESS might save the utility $1.5 million in natural gas expenses each year, according to Keriann Baker, HEA director of member relations. Over the projected lifetime of the system, that should recoup the up-front capital expense of approximately $40 million.
Golden Valley paid $35 million for its battery in 2003 (or more than $50 million in 2022 dollars). That system had a minimum life of twenty years and is due for an update. According to GVEA, its batteries were noticeably losing performance by 2021 and the control system was not recharging and discharging as efficiently. The system has a maximum designed life until 2033. The GVEA board may decide this year how to refurbish or replace its batteries. And now lithium-ion is an option to explore.