Noon Energy raises $28M for a whole new kind of long-duration storage

With its carbon-based storage tech, startup Noon could be among the first to commercialize clean energy storage that can power the grid for days.

Five workers around a CO2 tank
The Noon Energy team (Noon Energy)
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A former NASA scientist wants to break through the barriers to cheap long-duration energy storage. And he’s doing it with ingredients as basic as carbon and oxygen.

Chris Graves co-founded Noon Energy in 2018 after working on a tool for NASA’s Perseverance Mars rover that snatches carbon dioxide out of the red planet’s atmosphere and converts it into oxygen. Along the way, Graves realized that this process could be tweaked to store clean energy very cheaply for longer periods of time than what’s commercially viable with today’s lithium-ion batteries.

The 10-person team at Noon successfully scaled up a lab prototype’s storage capacity by a factor of 50 in the last 14 months, which gave them confidence that the core technology will work at the scale of a grid power plant. With that in hand, the company raised $28 million Series A financing announced Wednesday. It had previously raised a $3 million seed round while remaining coy about what its technology entailed.

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Clean Energy Ventures led the new round with Aramco Ventures’ Sustainability Fund (yes, that Aramco). Other investors included Emerson Collective, At One Ventures, Mistletoe and Doral Energy-Tech Ventures. 

The scientific risk is fully behind us,” Graves said. It’s a very low-cost and high-energy-density solution.” 

The next big goal is to build demonstration projects to test the technology in the field, Graves told Canary Media. To get there, he wants to triple headcount, hiring engineers, business development pros, product developers and HR staff.

This makes for a relatively new entrant into the increasingly well-funded field of long-duration energy-storage startups. They serve a market that doesn’t exactly exist yet, but which anticipates the needs of the grid as renewables deliver more and more of the electricity supply. Something needs to be able to take the bursts of clean power and make them available when they’re actually needed.

The phrase long-duration energy storage,” however, is a term of art that can mean whatever the speaker desires. Some entrepreneurs use it to hawk newfangled batteries that serve the exact same functions as lithium-ion, just without the track record or the manufacturing scale. Noon occupies a more rigorously defined space: It’s building batteries that can deliver a desired amount of power for 100 hours or more. 

That range, also called multiday storage, would allow a Noon-supplied power plant to store clean energy and deliver it through a prolonged period without sun or wind. It would take over a role typically served by fossil-gas plants, providing on-demand power that ramps up quickly when needed and can run for days. 

Wags on Twitter often dismiss long-duration attempts as slow batteries; you could take any battery and let out a trickle of power for a long time, but that’s not useful. What Noon is building would deliver a useful amount of capacity (determined by the customer’s needs), affordably, for days on end without running out of juice. The lithium-ion batteries that run the grid-storage show today can’t go for ultra-long duration without becoming prohibitively expensive.

If Noon delivers on that promise, it won’t have much competition. The leading contender for 100-plus-hour storage is the iron-air battery being developed by Form Energy, helmed by former Tesla storage exec Mateo Jaramillo. That startup has raised a staggering $650 million in the last two years alone, locked down a utility contract for its first deployment, and is building a factory in the West Virginia steel town of Weirton. (Incidentally, Aramco also went in on Form’s Series A in the long-ago days of 2018.)

Form picked iron as its key ingredient because it’s cheap and abundant compared to conventional battery materials. Noon similarly wanted cheap and abundant; it starts with a tank of carbon dioxide. Noon’s battery stores energy by using electricity to split the CO2 into solid carbon and oxygen gas; to discharge, it reverses the operation, oxidizing the powdery solid carbon. The active ingredients are so cheap that Noon pays more for the tanks to store them in, Graves said. 

Using something cheaper than lithium-ion batteries is table stakes for long-duration storage. But Noon has two qualities that few competitors in the space claim: energy density and high round-trip efficiency.

Long-duration technologies are almost always expected to be less energy-dense than lithium-ion. They aren’t trying to power sports cars, so they can sprawl out a bit and take up space in a field somewhere. But Graves says his carbon-based storage is in fact three times as energy-dense as lithium-ion. He theorizes it could one day power clean marine shipping or long-distance trucking, two applications where even lithium-ion isn’t energy-dense enough for the job.

Long-duration storage technologies, due to various laws of physics, tend to lose more power than typical batteries do in the round-trip conversion to storage and back. The refrain from the companies producing them is that losing half the energy you put into the device doesn’t really matter if the bulk storage is cheap enough. That could prove correct, but nobody’s had a chance to confirm that this isn’t wishful thinking. In any case, energy losses are a bug, not a feature. 

Noon differs from the pack in that it purports to have near lithium-ion levels” of round-trip efficiency.

We’re not in the camp of saying efficiency is not important,” Graves said. 

As for the question of serving a market demand for multiday storage that doesn’t palpably exist yet, Graves said it’s a matter of picking the places where the futuristic conditions are starting to materialize.

At the moment, the grid broadly is not asking for it,” he noted. Of course, the grid is not homogenous, and some locations need it sooner than others.” 

He thinks it will make a good fit for places like Hawaii, which has nation-leading rooftop solar penetration, shut down its last coal plant last year, and is building a renewables-only grid without any gas to keep the lights on after dark. Early markets could include other islands as well as remote microgrids, where cheap renewables with long-term storage can compete with pricey imported fossil fuels.

Julian Spector is senior reporter at Canary Media.