The ability of a battery to stack use cases depends on multiple factors. Those include whether a battery is installed in a building or connected to the larger grid, as well as who owns the battery and the regulations that determine how they’re allowed to make money.

 

A battery’s usefulness is also highly dependent on where it is and when it’s available. That’s particularly true for batteries being used to mitigate peak loads and stresses on grid circuits or substations that would otherwise need major capital upgrades, a use case known as transmission and distribution (T&D) upgrade deferral or a ​“non-wires alternative.”

 

But those T&D upgrade deferral values are hard to predict years in advance. Maybe loads increase faster than expected, forcing a utility to pay well ahead of schedule for the upgrades the battery was meant to defer. Permanently installed batteries at that location aren’t as valuable anymore — but if they can be moved, that value can be put to use somewhere else.

 

Conversely, a utility may foresee the need to build grid infrastructure for a new subdivision or factory, but it isn’t sure when or if that new grid demand will actually show up. ​“The utility would love, if they were able, to delay the upgrade decision until they knew for sure you were building a factory,” Kuran said. ​“Mobile batteries allow a utility to defer, defer, defer” until the need actually materializes.

 

EV charging represents the latest manifestation of this chicken-or-egg problem for utilities trying to plan their future grid infrastructure needs. But the massive scale of EV growth needed to meet decarbonization goals could rapidly overwhelm utilities’ ability to deliver enough power.

 

Existing grid constraints are already driving an increasing number of EV charging sites to include batteries. Power Edison has launched a new subsidiary, EV Edison, specifically targeting that market, Kuran said.\

 

“Even if the utility is working 24/7, you’re dealing with eminent-domain issues, siting, digging up the streets,” he said. ​“But you can do it in a modular fashion — and if the uptake happens faster than the utility upgrade, our truck and barge mobile solution is there.”

 

Given these advantages, Power Edison has ​“had a number of business partners say, ​‘Why would we ever buy a stationary storage system?’” 

 

The challenges of making batteries mobile 

 

Analyst Daniel Finn-Foley has an answer to that rhetorical question. There are still plenty of use cases that favor permanently sited batteries, said Finn-Foley, an energy transition and energy storage specialist with PA Consulting.

 

“Energy storage is a game of tight margins,” he said in an interview. ​“If you know there’s going to be a need for 20 years in a location, then you’re going to lock it down because it just makes more sense.” The tens or hundreds of megawatts of energy storage being added to solar and wind farms demonstrate a prime use case for stationary batteries.

 

Moving batteries from site to site also isn’t as easy as it might sound, he said. ​“There are hurdles around moving batteries to meet those locational needs. Do the benefits of making the technology mobile outweigh the costs?”

 

Kuran acknowledged those challenges, which Power Edison has spent the past five years working on. ​“To do this cost-effectively, you have to have properly engineered mobile solutions,” he said. ​“A makeshift solution is not going to work.”

 

First of all, batteries are heavy, Kuran said. Many of the containerized systems Power Edison transports require specially designed trailers with multiple axles, as well as designs that distribute the weight of the battery cells and supporting equipment in ways that don’t violate federal and state-by-state transportation regulations.

 

Second, batteries need to be handled carefully to avoid damage or disruption. Many battery manufacturers will void warranties if they’re moved without proper precautions, he said. Power Edison has subjected its transport systems to vibration and bracing tests to ensure battery chemistries and power electronics connections aren’t harmed in transit.

 

Third, mobile batteries have to be engineered to be interconnected at their host sites quickly and with a minimum of complications, Kuran said. ​“If you’re mobile, you don’t want to have a month of connecting” at the end of each relocation. Power Edison has engineered switchgear and interconnection equipment to make the process as seamless as possible. ​“We even have patents filed for quick connect and disconnect, whether on barges or trucks,” he said.

 

All of this comes at a cost premium compared to containerized batteries destined for permanent installation. ​“On a variable cost, we might be 30 percent more from an equipment perspective,” he said. But the engineering and construction costs of preparing sites for stationary storage can eat away at that cost difference, he said.

 

In fact, he says, ​“we’ve found our solution is more cost-effective than a stationary solution, even if it stays in one place,” he said. ​“Now, if you move it even once, you’re ahead of the game.”

 

Mobile batteries could also help utilities get double duty out of the same batteries for changing seasonal needs. Some parts of the grid are stressed by summer air-conditioning demand, while others are stressed by winter heating demand, he noted. ​“Why not keep yourself open to the possibility that if a battery is being used in one place in the summer, I can use it somewhere else in the winter?”

 

Bottlenecks can still slow this approach, Finn-Foley noted. ​“Interconnection costs and delays are key barriers for energy storage development,” he said. Adding megawatts of batteries to a utility’s power grid requires extensive interconnection studies that can take six months to a year, whether those batteries are stationary or mobile.

 

But in some cases, Power Edison’s batteries can start working at a site before those interconnections are approved if it’s cost-effective to shuttle discharged batteries out and replace them with batteries charged elsewhere, Kuran said.

 

That’s an expensive proposition, compared to delivering electricity over the grid, Finn-Foley noted. ​“We don’t usually drive tractor-trailers full of water or natural gas from one part of the city to another.”

 

Still, given the immense pressure on utilities to support fast-growing EV charging loads, these kinds of options may become tenable, Finn-Foley said. The big question is whether mobile batteries can find enough value in being moved from place to place over their operating lifetime to make them worthwhile.

 

“I wouldn’t say that the locational value of storage has been fully recognized yet,” Finn-Foley continued. ​“If that happens, and when that happens, will be the key.”