Calpine grid-scale battery, image courtesy of Calpine

Swapping An 800 MW Gas Generator For A 680 MW/2720 MWh Grid-Scale Battery

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We often think nothing ever changes, and then wham! Everything changes. Take grid-scale battery storage, for instance. A decade ago, GE installed what was at the time a state of the art combined cycle methane-fired turbine at a generating station in Menifee, California, southeast of Los Angeles. Combined cycle captures some of the exhaust heat from the combustion process and uses it to produce even more electricity. That makes the process significantly more efficient at converting methane into electricity than a standard gas-fired facility.

Here’s how GE explains things on its website:

Gas turbine burns fuel:

  • The gas turbine compresses air and mixes it with fuel that is heated to a very high temperature. The hot air-fuel mixture moves through the gas turbine blades, making them spin.
  • The fast-spinning turbine drives a generator that converts a portion of the spinning energy into electricity.

Heat recovery system captures exhaust:

  • A heat recovery steam generator (HRSG) captures exhaust heat from the gas turbine that would otherwise escape through the exhaust stack.
  • The HRSG creates steam from the gas turbine exhaust heat and delivers it to the steam turbine.

Steam turbine delivers additional electricity:

  • The steam turbine sends its energy to the generator drive shaft, where it is converted into additional electricity.

The video below from GM explains things in more detail.

At the time, it was expected that the spiffy new combined cycle facility would be in service for at least 30 years, and maybe more. Fast forward to 2024, and the gas-fired plant has been demolished. In its place, a $1 billion grid-scale battery storage facility known as Nova is under construction by Mortenson for Calpine. When completed, it will be able to store 680 MW of electricity and discharge it back to the grid for four hours. That works out to a total of 2720 MWh of juice to meet the late afternoon and early evening demand for electricity.

Grid-Scale Battery Storage Happens

What happened to make that combined cycle facility obsolete? Solar energy. California has lots of it, and most of it is generated in the afternoon. If you can store it for a few hours and then send it back to the grid as the sun begins to set, the grid is distributing zero emissions electricity, which, if you are at all interested in addressing carbon dioxide pollution, is a very good thing.

So why not just crank up a combined cycle generating station to take over when the solar power begins to wane? Because it takes up to 12 hours to fire up a combined cycle plant. That means it would have to be kept spinning all day long just to be able to use its electricity between 4 and 8 pm. The bottom line is it is just too expensive to do that. Ah, hello, Adam Smith. Welcome to the conversation.

“A lot of us remember what was here just a year ago with the two big smokestacks,” Menifee Mayor Bill Zimmerman told Canary Media. ​“It would take all day just to get that thing up to speed and running, and they would have to anticipate whether or not they would need it. This is going to be ten times better and ten times more efficient, without all that extra work.”

Houston-based Calpine previously dabbled in grid-scale battery technology with two California projects, but Nova’s price tag and power capacity catapult it into the upper echelons of storage developers and owners. Federal analysts predict 2024 will be the biggest year ever for grid-scale battery installations across the US and they highlighted Calpine’s project as one of the single largest projects. The 680 megawatts the company plans to energize this year represents more than 4% of the industry’s total expected new additions.

Grid-Scale Storage Means Big — Really Big!

The Nova installation is comprise of 1,096 total battery containers holding a total of 26,304 battery modules. Inside those modules are 3 million battery cells manufactured by BYD,  Robert Stuart, an electrical project manager with Calpine, told Canary Media. That’s enough electricity to supply 680,000 homes for four hours, Calpine says.

Another advantage of grid-scale battery storage is how quickly it can be installed. Construction began last August and is expected to reach 510 MW of fully operational capacity over the course of this summer, even as installation continues on other parts of the plant. Erecting a conventional gas plant of comparable scale would have taken three or four years of construction labor due to the complexity of the systems and the many different trades required for it, Stuart said.

One of the major reasons why Calpine chose Menifee was because the all-important connection to the electrical grid was already in place. Emily Precht, strategic origination manager at Calpine, said, “Given the fact that this plant was retiring and there was all of this existing infrastructure on this site, batteries really helped with grid reliability in the face of all of these intermittent renewables. They are instantaneous ramping. You can start and stop them whenever you need to and it just made a whole lot of sense.”

All US utility companies are developing strategies to deal with the spike in electricity demand expected as the “electrify everything” movement adds more heat pumps and electric cars to American homes. In the Southeast, most of those utilities are  planning to build a fleet of new fossil gas plants to deal with this predicted surge. However, if time is of the essence, the Menifee project demonstrates that grid batteries have the clear advantage.

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The Policy Piece Of The Puzzle

Grid-scale battery installations can be built quickly due to their modular nature. The battery in Menifee is composed of identical modules that have the same inverters and battery enclosures inside. Everything connects via standardized substations to the grid. Building a battery storage plant involves wiring up the same design over and over again until it’s done. That’s why Calpine can energize swaths of the project as they become ready — something not possible for a gas turbine. “When Phase One is completed, operators will take it over, while we’re still working on Two, Three, and Four,” Stuart said. ​“We’ll be actively building these and then turning them over right away as they’re ready.”

California is experiencing a rapid battery build-out now, but all of this construction has its roots in the state’s much earlier decision to mandate battery storage for its utility companies. That 2013 policy kicked off a decade long project to bring an energy storage market into existence through methodical policies and regulations to support the effects of building the nation’s foremost solar fleet. Those energy storage policies succeeded in jumpstarting the modern grid battery market.

California leads the nation with more than 7 gigawatts of batteries installed as of last year, although Texas is poised to overtake California in battery installations this year, not as the result of any particular policy efforts other than a general openness to building the cheapest energy projects possible .Yet despite all those policy initiatives, California hasn’t actually closing many gas  generating stations. The state had years to prepare for a 2020 deadline to shutter ​“once through cooling” plants that use ocean water, only to flip at the last minute and ask those targeted plants to keep burning gas to avoid a grid calamity.

Today, despite its best-in-the-nation renewables build-out, methane is still the leading source of electricity generation in California. But the state’s interlocking climate regulations effectively rule out new gas construction. Its energy road map instead calls for massive expansion of battery capacity. These trends, along with the falling price of batteries and maturing business model for storage, nudged Calpine to get into the battery business in a big way.

Learning From Others’ Mistakes

Menifee is Calpine’s first battery project that is even close in total capacity to its legacy gas projects. The sheer size of this project means it will control more battery capacity than all but a handful of other California operators once online. “There was a need in California for making the grid cleaner and adding more dispatchable resources, and we felt that it was an opportune time to start developing this site,” Precht said. ​“All the pieces came together.” Calpine is developing a portfolio of 2,000 megawatts of California battery capacity, including Menifee, she noted.

Calpine was able to take advantage of the lessons learned about grid-scale battery storage by one of its competitors. Vistra, another top gas power producer, which embraced the battery revolution before Calpine when it built the nation’s largest grid battery at a former gas-fired facility at Moss Landing south of San Francisco. Vistra expanded that facility over multiple phases to hold 750 megawatts and 3,000 MWh as of last June. But Moss Landing’s reputation for bolstering the grid suffered due to multiple fires that not only halted operations but temporarily locked down the surrounding region.

Two of those separate Moss Landing fires weren’t actually caused by its lithium-ion batteries. Faulty sprinkler systems set them off, meaning the pipes intended to suppress fires actually caused them. Calpine took a different approach to fire safety. The company rebuilt the fire hydrant system to expand its capacity, but elected to not connect the water system to the battery containers, Stuart explained. No water in the pipes means no accidental fires from trigger happy sprinklers. But if a battery fire ever happens, alarms will sound and first responders can hook up a hydrant to the enclosure in question and flood it entirely, or isolate the fire and let it burn itself out safely.

In other words, the Nova project benefits from the many iterations in large-scale battery development that came before. The engineering firm Mortenson handled the actual construction on behalf of Calpine, and applied techniques it has honed building big batteries elsewhere in the West. “It’s only getting faster, and you know, this isn’t Mortenson’s first project,” said Stuart. ​“They do have good communication within their company, they talk to each other to make sure that all their battery projects are going at the same rhythm, and lessons learned aren’t lost on one project.”

The Takeaway

680 MW/2720 MWh is a pretty big battery by any standard. The ability to plan it, build it, and turn it on fairly quickly is a huge advantage over thermal generation, as is the stable price of electricity for decades. Who knows what the price of methane gas will be next year or five years from now? You would think based on purely economic considerations, battery storage would be the preferred choice in most cases.

But policy considerations do play a big role as well. The southeastern states are all in on thermal generation because their governments are in thrall to fossil fuel interests — despite the fact that those states are most likely to suffer the most from the effects of an overheated planet. When beliefs take priority over facts, weird things happen. In this case, it is ratepayers who will bear the brunt of those poor decisions.


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Steve Hanley

Steve writes about the interface between technology and sustainability from his home in Florida or anywhere else The Force may lead him. He is proud to be "woke" and doesn't really give a damn why the glass broke. He believes passionately in what Socrates said 3000 years ago: "The secret to change is to focus all of your energy not on fighting the old but on building the new." You can follow him on Substack and LinkedIn but not on Fakebook or any social media platforms controlled by narcissistic yahoos.

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