Electricity for Later: Storage Technology Extends Grid Capabilities
Looking to stabilize and balance their electrical grids as more renewable generation is connected, Alaska’s Railbelt utilities are turning to gigantic storage batteries comparable to those used in electric cars, cellphones, and laptop computers.
Homer Electric Association (HEA) flipped the switch in January 2022 on its Battery Energy Storage System (BESS), an array of thirty-seven Megapacks made by Tesla. Chugach Electric Association (CEA) and Matanuska Electric Association (MEA) have jointly installed a twenty-four Megapack BESS, scheduled to be charged and operational by fall 2024.
Because wind and solar energy are usually not available at the exact time consumers need power, other sources must fill the gap. Utility-scale BESS systems provide a tool that allows transition between renewables and conventional generation to occur seamlessly due to their ability to respond quickly. Thus, storage helps utilities better balance their grid while also enabling new methods of harnessing energy sources.
Energy Storage Technologies
Storing energy is not a new concept to Alaska.
When Golden Valley Electric Association (GVEA) activated its BESS in Fairbanks twenty years ago, it was the largest battery in the world, earning a place in the Guinness Book of World Records. Used mainly for preventing blackouts, the system is capable of briefly supplying 40 MW to the co-op’s grid when problems occur.
GVEA’s nickel-cadmium battery system is nearing the end of its useful life and, because fuel savings made possible by the existing BESS has proven extremely valuable, GVEA officials are looking at options for upgrading or replacement.
Under consideration is a BESS system that takes advantage of recent improvements in lithium-ion technology, enabling more wind and solar generation to be cost-effectively integrated into GVEA’s portfolio.
GVEA serves 100,000 Interior residents in Fairbanks, Delta Junction, Nenana, Healy, and Cantwell in addition to some customers along the Steese and Elliot highways and Chena Hot Springs Road. The utility has operated Eva Creek Wind Farm since 2012 and a solar farm since 2018 and is actively working to expand the use of renewables.
The Railbelt electric grid stretches approximately 700 miles from Fairbanks through Anchorage to the Kenai Peninsula. The four member-owned electric cooperatives and one municipal utility—HEA, CEA, MEA, GVEA, and Seward Electric Department—share and sell power to Railbelt customers.
Since going into operation more than forty years ago, the energy systems have undergone significant change, with increased loads, aging assets, and growing stakeholder interest in clean energy generation to reduce emissions. Cost-saving power sales between utilities have increased, demanding more of the transmission system. The push for implementing renewable resources into the grid has utilities looking for economical ways to store that energy.
Many Forms of Energy Storage
Depending on the location, energy storage can take on many forms.
According to Dan Bishop, GVEA’s director of engineering, each form of energy storage has advantages and disadvantages, so utilities work to optimize the mix.
“For example, the fast response of BESS systems is very valuable because it can keep the lights on when conventional generation or power lines are damaged, so other generation has time to ramp up or get started,” says Bishop.
In terms of sheer amount of energy stored, hydroelectric energy storage is more widely used than any other in Alaska’s Railbelt. The Bradley Lake Hydroelectric Project near Homer is, thanks to the Railbelt intertie, GVEA’s largest source of stored energy.
“Although it does not produce as much instantaneous power as GVEA’s BESS, it can provide power over much longer durations,” says Bishop. “GVEA also stores energy in the form of fossil fuels: tanks full of oil and piles of coal.”
Racks of nickel-cadmium batteries were world-class when Golden Valley Electric Association activated its BESS in 2003, but newer lithium-ion technology is an attractive replacement.
Testing has been done on flow batteries, supercapacitors, and flywheels. Tests on a liquid-metal battery fell through a few years ago when the manufacturer was unable to scale up the system for commercial use.
“And that can often be a challenge: what works on a benchtop scale doesn’t necessarily work at full commercial scale, at least not economically,” Holdmann says.
The flywheel that ACEP tested was successfully deployed to a remote gold mine in northern Canada to integrate wind energy. The ACEP Energy Technology Facility recently tested a new lithium-titanate battery system that will be installed in Saint Mary’s, a village on the Lower Yukon River, to operate the local grid without diesel generators when enough wind power is available.
“And that’s where real savings can come in for the community,” says Holdmann. “It takes a lot of fuel to run a generator even on standby, so if you can reduce the number of hours it is operating, the savings can be significant.”
In Alaska’s rural areas, energy is generally stored as diesel fuel. But future innovative technologies such as batteries using liquid metal, sodium-ion, iron-air, nickel-hydrogen, and storage options utilizing pumped hydro, thermal energy, geologic pressure, and others are likely to be more widely used, he adds.
“Technology is advancing very quickly, and it is difficult to predict where the next breakthrough will be,” Bishop says.
Healy is the site of a cutting-edge facility that Westinghouse Electric Co. is proposing. The storage medium is concrete slabs. Surplus electricity would heat the insulated concrete, and heat pumps could extract the energy when needed. The facility is designed to store energy for 2,000 homes for up to a month, and it easily scales up by adding more slabs.
GVEA helped Westinghouse apply to the US Department of Energy for a possible $50 million grant. The facility would be co-located with the utility’s coal plant, but GVEA has not committed any money toward the project. If phase one demonstrates feasibility at grid scale, GVEA has expressed interest in a power purchase agreement. The Westinghouse storage project is expected to be built by 2028.
Golden Valley Electric Association’s solar farm, operational since 2018, charges the utility’s battery storage when the sun shines in Fairbanks so that the energy is available during darker hours.
Megapacks Get a New Look
Unlike GVEA’s nickel-cadmium batteries, lithium-ion batteries are currently the technology of choice due to their cost-effectiveness and high efficiency. Tesla’s response to HEA’s request for proposals offered the best value for the amount of storage and system capability, says Larry Jorgensen, HEA’s director of power, fuels, and dispatch.
Part of the company’s purchase agreement with Tesla is returning the batteries for recycling at the end of their operating life.
“Recycle all those rare earth minerals and not lose them,” says Jorgensen. “That’s an advantage to all of us.”
Homer Electric Association was the fifth rural electric cooperative in Alaska, according to Jorgensen.
“In 1946, a 75 kW Caterpillar generator supplied electricity to fifty-six members. Today, 80 MW of generation from several sources is needed to fulfill all the electric needs,” Jorgensen says.
Those megawatts and generation sources must be carefully balanced against fluctuating demand, not just in terms of volume but in frequency and phase. The principal function of HEA’s BESS is to regulate the system.
“Running the electrical grid is like having a car that you’re trying to keep at the same speed, but you have a trailer that you’re pulling, and people are adding on and taking off things all the time,” he gives as an analogy. “You constantly have to adjust.”
“When a generator across the Railbelt has an unplanned outage and trips offline, the frequency of the entire Railbelt system drops.”
When there are deviations to the grid, the BESS either absorbs energy or delivers enough to maintain the balance, he adds.
HEA also uses the BESS as a backup power source if the system goes off-line. If transmission lines are damaged, the batteries have stored energy for immediate use.
Installing a Megapack takes a bit of planning.
Each Megapack weighs 52,000 pounds and contains more than 200,000 smaller battery cells providing 2.5 MW of energy storage, according to Jorgensen. “That’s equivalent to 970 Tesla cars parked out here, charging and discharging. The concrete has to extend down in the ground a long ways in order to make a stable, earthquake-proof foundation,” he adds.
Before utilizing the BESS, HEA used fuel combustion turbines during system glitches with nowhere near as fast a response time as the BESS.
“We don’t have to use fuel to do that,” says Jorgensen. “Instead, we use stored energy.”
Energy stored in batteries is very short term, usually good for a few hours at best, according to Jorgensen. HEA also relies on Bradley Lake as another form of stored energy.
“The BESS is a short-term solution but very effective in how it does it,” he adds.
Alternative to Natural Gas
“There are a lot of ways we can store energy, and the options available can be site-specific,” Holdmann observes. “If you think about it, fossil fuels are one way of storing energy in a pretty inert form for a long time—either in a tank or underground for millions of years. It is basically the perfect form of dense energy storage, ready for use when you need it.”
CEA and MEA, the two largest electric utilities in the state, depend largely on natural gas produced in Cook Inlet for electrical generation. But the Cook Inlet basin is aging, according to the state’s leading gas producer, Hilcorp. Shortfalls could begin surfacing in a few years. Current contracts between Hilcorp and the two utilities will end in 2028.
Water behind the dam at Bradley Lake, north of Homer, stores the energy that lifted rain and snow against gravity. Releasing that energy through a hydroelectric turbine, though, is not ideal for moment-to-moment grid balancing.
Southcentral Alaska has been burning more natural gas than Cook Inlet produces for years, yet everyday customers haven’t noticed an interruption thanks to another storage mode.
Cook Inlet Natural Gas Storage Alaska (CINGSA) is Alaska’s first commercial natural gas storage facility. Located in a depleted natural gas reservoir on the eastern side of Cook Inlet, CINGSA provides a means to store gas during the summer months when availability exceeds demand. Five horizontally drilled wells allow up to 150 million cubic feet of gas per day to be injected or withdrawn. The stored gas is then available for withdrawal during winter months.
“The facility can be switched from injection to withdrawal within a three-hour time period, allowing CINGSA to meet its customers’ needs on short notice,” says Julie Hasquet, CEA’s senior manager of corporate communications.
Holy Grail of Energy Storage
To provide more economical system support previously provided by natural gas generators, CEA installed twenty-four Megapacks next to its Southcentral Power Project generators near Midtown Anchorage at a cost of $63 million. MEA is a 25 percent owner.
“When a generator across the Railbelt has an unplanned outage and trips offline, the frequency of the entire Railbelt system drops and initiates a period of dynamic response to replace that lost generation,” Hasquet explains. “If the frequency isn’t stabilized almost immediately, it can cause load shed, or outages. To avoid load shed, the lost generation must be replaced on a time frame which can be as small as 1.5 seconds. A large BESS like our Tesla Megapack is very effective at responding to events like this because it can react instantly to inject or absorb necessary power and stabilize the grid.”
The real value of battery storage is helping utilities stabilize the grid without having to burn fossil fuels, with big savings on cost and emissions, says Hasquet.
The utilities have lofty hopes for new renewable energy projects to meet carbon emission reduction goals. CEA is aiming for 50 percent renewables by 2040 and MEA the same percentage by 2050.
Both utilities depend approximately 15 percent each on the Bradley Lake and Eklutna Lake hydroelectric projects, according to Julie Estey, MEA’s senior director of external affairs and strategic initiatives. The Fire Island Wind Farm, owned by Cook Inlet Region Incorporated, provides 3 percent. And MEA recently added power from Alaska’s largest solar farm, an 8.5 MW array in Houston, through a partnership with Renewable Independent Power Producers.
According to Holdmann, “Affordable long-duration energy storage is sort of the Holy Grail for enabling variable renewable resources like wind and solar.”