Canadian startup e-Zn has raised money to store clean energy far longer than currently available batteries allow, using cheap and abundant zinc.

On Wednesday, the company received CAD $2 million ($1.5 million) in non-dilutive grant funding from Sustainable Development Technology Canada, a federally funded body charged with vetting and funding cleantech hardware innovation. E-Zn used an earlier CAD $700,000 SDTC grant to build a demonstration that paired the zinc storage with a solar array. The new funding is to turn the current product iteration into a containerized package, test it in the field and refine it for manufacturing.

That builds on a CAD $3.4 million seed round announced last week. Chicago-based evergreen fund Energy Foundry led the round, joined by Toronto’s MaRS Investment Accelerator Fund, Sustainable Chemistry Alliance and Emeraude Capital. 

“We’ve got the funds, now it’s about execution,” said CEO James Larsen.

The long duration storage sector writ large has an execution problem; technologies that work in the lab, like flow batteries, have had trouble breaking into a market at price points competitive with mass-produced lithium-ion batteries. When exactly market demand will pick up for longer-term energy storage is an open question, though the proliferation of intermittent renewables will make it more valuable over time.

E-Zn’s strategy is to keep costs low with an unconventional design based on a cheap active ingredient. The current form factor is geared toward 24-hour storage or longer, and the company will go to market in remote communities that stand to benefit by offsetting diesel generator usage.

“When you can engage customers with an economic proposition that eliminates the fossil fuel, cleans their local environment, and delivers energy in a more affordable way, it’s a no brainer,” Larsen said.

From there, e-Zn will pursue resilience applications in developed markets, and in the latter part of the decade, chase bulk grid balancing in high renewables markets.

Turning electricity into metal

The zinc energy storage device invented by scientist and e-Zn founder Gregory Zhang differs from both typical batteries and flow batteries.

“I’d be willing to guess we’ve seen hundreds of storage ideas,” said Energy Foundry Managing Director Sara Chamberlain. “When I saw what they were doing, I had never seen anything like that.”

It consists of a cell slightly larger than a desktop computer. Charging happens at the top, where an electric current precipitates pellets of zinc out of an alkaline electrolyte solution. Windshield wiper-like elements scrape off the pellets, which fall to the bottom of the cell. To discharge, the device pulls in air and dissolves the zinc back into solution.

Each cell currently packs 100 watts of power capacity, capable of 24-hour or 48-hour discharge, depending on size. The power and energy ratios can be customized by adjusting the surface area of the charging and discharging electrodes, and the volume of electrolyte and zinc, respectively. That quality helps keep long duration storage costs down compared to lithium-ion batteries, which have a fixed ratio of power to energy capacity. 

The design is notable for two other features. It does not need a membrane to separate the charging and discharging areas, because it uses gravity; the wipers dislodge the zinc nuggets and they fall to the bottom, where they sit until discharge.

That’s important, Chamberlain noted, because membranes have proven costly and complicated to develop for other long duration technologies, including flow batteries. Side-stepping that kind of engineering lowers costs for e-Zn and simplifies the development cycle.

The nature of the cell also ensures that the storage device won’t lose its charge over time, Larsen explained.

Lithium-ion cells inevitably self discharge, so they’ll lose their charge after sitting around for a while. But the zinc cell can’t dissolve the metal bits unless the device introduces air and draws the charge out. That means any renewable electricity stored inside will still be waiting when the owners need it. The e-Zn cell also does not suffer capacity fade like lithium-ion batteries, Larsen added.

Burden of proof

After years of big aspirations and limited success, mere promises of low-cost and competitive alternatives to lithium-ion count for very little. Like bits of zinc floating in solution, they hold potential, but need additional steps to convert it.

For e-Zn to deliver, it needs observable field deployments that convince initial customers to take a risk on a new technology. E-Zn has a pathway to initial deployments with the SDTC grants.

The first demonstration connected a 5-kilowatt solar array to a 1 kilowatt/24 kilowatt-hour stack of cells; it’s been operating since April 2018. The newly granted $2 million will help bring the cells into commercial manufacturing, and package them into a 5 kilowatt/240 kilowatt-hour containerized unit.

The next step will be translating the prototypes into an efficient manufacturing process. This is where Chamberlain believes the relative technical simplicity of the Zn Reactor will give it an edge against better known and more highly funded long-duration ventures.

“It’s a solution with a charge that runs through it and it precipitates out metal or dissolves it,” she said. “It was much more of a manufacturing play than an electrochemical play.”

That simplicity also convinced Larsen, when he was considering whether to join the company as CEO in the summer of 2018.

“I assessed the technology component by component — Can this actually be as cheap as the founders claim?” he recalled. “Yes. It’s commodity materials and tried, tested and true engineering processes.”

Assuming e-Zn clears those hurdles, it will have to hope that an actual market for long-duration storage greets it on the other side. Utilities are buying batteries that can go for four, five, sometimes six hours, but little traction has emerged for longer duration systems.

The economics are more favorable in remote or island grids, where renewables and storage are beating imported diesel on price. And the more solar and wind pack into mature energy markets, the more incentive developers will have to save the booms in production for hours when generation peters out.

“We fundamentally had the thesis that there was a need for long duration,” Chamberlain said. “If you want to get to that future state, you have to make the investments now.”

At least some customers are starting to share that view, and have requested proposals for storage beyond what conventional batteries can offer, Larsen said. As he sees it, the needle already is starting to move toward long duration. Conditions should only be more favorable in a year or two, when e-Zn hopes to push into the market.