ERCOT’s battery fleet is the ‘first line of defence for the grid’ through Texas winter storms

Batteries can respond in milliseconds to grid operator or market signals, putting them at a distinct advantage over thermal power plants, which can take minutes, or hours—or perhaps even not start up at all—if both plant equipment and fuel supplies are not adequately weatherised.   

“The value of batteries is probably the highest during extreme weather, during a winter storm, because you might have gas power plants failing because the supply freezes up, or you might have transmission lines failing because of snow, ice load or falling trees,” Kairies told ESN Premium in an interview.

“At the same time, there are demand peaks, so during a cold storm, batteries really are the first line of defence for the grid.”

Whereas perhaps even as recently as five years ago, batteries might have been thought of as a nice-to-have, they have now become a “central pillar of grid resiliency, so they’re more important than ever”, Kairies said.

Battery storage assets are designed to capture volatility, essentially the mismatch between electricity supply and demand, helping bridge the gap that otherwise causes shortfalls of capacity and electricity prices to spike in wholesale markets.

Just this week, on the other side of the globe in Australia, which is experiencing one of its hottest summers on record, peak demand spiked on Monday (26 January), the Australia Day national holiday. Battery trading and dispatch analytics provider OptiGrid found that in South Australia, BESS participating in the National Electricity Market (NEM) entered a AU$1,000/MWh (US$700/MWh) price event for four hours in an extreme heatwave, a record high.

Lessons from past events

Ironically, in Texas, mild weather over the past couple of years has led to fewer volatility events in which BESS operators could capture extreme price spikes. Back in February 2021, when Winter Storm Uri struck the state and gas plants were less well prepared, relatively fewer battery systems were able to share the value of volatility. There were reports of assets achieving payback in timeframes of months or even weeks, not years.

“The players in the market really learned from Uri and some of the storms that we saw during that time. I think we’re better prepared against that now,” Kai-Philipp Kairies said.

“The gas infrastructure, apparently, was very vulnerable at the time, and I think they definitely fixed that. Then, of course, the additional batteries that we have right now are just a stronger defence against these sudden ‘grid swings.’ It’s really a positive development for grid stability that we have these additional capacities online now, and that the owners and operators have become more experienced with putting them to use in the best possible way.”

Even with ERCOT’s BESS assets being, on average, of relatively short duration and sized to capture volatility in regular operation without investors and owners overspending on Capex, Kairies said they can still provide a valuable buffer to the grid when demanding conditions strike.

“If you look at sudden failures of equipment, like a transmission line going down, or a gas power plant going down, an additional hour or one and a half hours of time to re-dispatch and maybe do a little bit of load shedding if needed, if there’s no additional generation capacities available nearby, it can save the system and it can prevent a small failure growing into a larger failure,” Kairies said.

“The additional flexibility in the grid definitely buys time, and can keep the system online. We’ve seen that in other parts of the world, where batteries stepped in and really prevented blackouts over the last couple of years, including Australia, including Europe.”

There is, however, a caveat to that. During extreme weather conditions, batteries can show their full value to the system, Kairies said, but at the same time, battery cells themselves “hate the cold”.

That requires what Kairies described as “a lot of good system engineering”, so that the BESS assets function properly during cold snaps.

Where analytics providers like ACCURE come into play is by using their cell-level monitoring software to help system operators not so much keep their systems working, but rather allow them to meet their full potential in capturing price spikes and keeping the lights on in ERCOT.

“We’re [ACCURE] almost exclusively looking into getting the most out of existing batteries, and through analytics, to make sure that you capture the full value. Days like these are really a test of true system performance. If you just look at the revenue potentials during these days, getting 5, 10, 15% more capacity out of a system really pays off.”

“Under extreme conditions, you just want to get 100% of the energy, because it’s probably the best revenue opportunity in the quarter, maybe even in the year, and all of a sudden you realise that you were 20% off in state of charge (SoC). The opportunity costs and penalties you’re running into during these phases could be an order of magnitude larger than in day-to-day operations,” Kairies said.

Why battery cells hate the cold

The CEO explained that the diffusion process that occurs when lithium ions move from the anode to the cathode, or vice versa, in a battery is strongly temperature dependent.

“At high temperatures, you have better diffusion, so the batteries work better. So, from that perspective, the warmer the battery, the better it will function.”

At temperatures above a certain level, performance will continue to improve, but the side effects will be harmful to the battery. Which is, of course, why industry conversation so often focuses on cooling systems, including HVAC and, in newer systems, liquid cooling.

Coming back to cold weather performance, however, diffusion can be reduced to the point that ions struggle to move between the cathode and the anode, so alongside cooling, thermal management equipment and auxiliary power can also be used to keep cells sufficiently warm.

“If you force a lot of electricity in or out of the battery, while the ions actually can’t move, they’re going to start to have side effects that are quite harmful, and the worst thing that can happen if you charge a battery that’s very cold [is that] then plating happens. That means the ions, instead of going into the anode, will just plate on the outside of it, forming metallic lithium. That can then cause thermal runaway, fires, nasty stuff. So it is critically important to manage the temperature of a cell,” Kairies said.

That is, of course, an extreme example, and in truth, it is more likely to be about optimising the technical performance of batteries as they continue to safely operate in extreme cold.  

That optimisation, without analytics, requires tracking millions of data points, which the CEO said can be difficult to do. Whereas analytics solutions monitor subtle changes in operating behaviour and extrapolate what they mean for future performance under different loads.

“We’re able to warn owners and operators about potential shortcomings in operation and performance and capacity before they become relevant,” he explained. “For the example of a winter storm, if we see that a couple of racks have had less coolant flow, for whatever reason, [such as] the pumps aren’t fully calibrated, or there might be some other hardware issues, that during normal operation, were still okay because ambient temperatures were regular, we can already anticipate that they’re not going to be able to keep the temperature as it should be when the ambient temperature goes down.”

“Predictive analytics will really tell you exactly what power and energy you can get out of your battery, and if it’s not 100% what you can do to unlock it before prices go up. If you only realise that when you’re already in the delivery phase, there’s nothing you can do. The payback for having a better view into the actual capacity and power, and the ability to fix it during low-price phases, to be ready for high-priced phases, is really good,” Kairies concluded.  

The Energy Storage Summit USA will be held from 24-25 March 2026, in Dallas, TX. It features keynote speeches and panel discussions on topics like FEOC challenges, power demand forecasting, and managing the BESS supply chain. ESN Premium subscribers can get an exclusive discount on ticket prices. For complete information, visit the Energy Storage Summit USA website.