What’s better than a big battery? How about a big battery you can move around

Study after study has shown that the power grid of the future is going to need a lot of batteries. To meet that need without breaking the bank, those batteries must be as affordable as possible. But they also need to be deployed in the right places.

Shihab Kuran, CEO of Power Edison, argues that mobile batteries hit the sweet spot in many use cases. They entail extra costs and complications, but their value is maximized by the ability to move them from place to place and quickly interconnect them with the grid.

Over the past five years, Power Edison has built up the equipment and expertise to make mobile, utility-scale batteries a reality, from early-stage pilots with New York utility Con Edison to a gigawatt-scale pipeline of projects with utilities whose identities have not yet been made public by the company.

Last month, the company announced its biggest project yet: an electric-vehicle charging hub in its home state of New Jersey. At its peak, the hub aims to support up to 200 megawatts of heavy-duty electric vehicles serving one of the country’s busiest seaport complexes, making it one of the biggest EV charging facilities announced to date in the U.S.

It could take years for a utility to upgrade the local power grid to support that kind of EV charging load. But batteries can get the job done much quicker — and mobile batteries mean it can be done with a high level of flexibility.

Putting batteries on truck trailers or barges, instead of installing them on concrete pads, enables a site to be more nimble in terms of matching different amounts of storage to shifting charging demands, Kuran said. It also allows depleted batteries to be replaced by ones recently recharged at sites without grid constraints.

Eventually, if and when the grid infrastructure is expanded to meet a site’s charging needs, those mobile batteries can be moved on to the next location, he said. That’s valuable not only to the sites that need batteries but also to the owners and financial backers of the batteries.

After all, every battery that’s permanently installed at a site is making a bet that its value is going to hold firm for years into the future. But with a fast-evolving set of grid needs and the vagaries of matching energy-storage values to individual sites, that’s not always a safe bet, he said.

“Financing mobile systems is much safer compared to stationary systems,” Kuran said. ​“Storage sometimes has a limited economic outlook at a particular location. Mobility — if you can do it cost-effectively — can perform multiple services and stack up revenues not just at one location, but at multiple locations.”

Mobility to serve the energy storage value stack 

Energy storage analysts have identified dozens of use cases for batteries, as well as how these use cases can be ​“stacked” to make more money from a single battery installation, as this chart from the utility-backed nonprofit Electric Power Research Institute indicates.

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.”