Clean energy journalism for a cooler tomorrow

This startup’s energy storage tech is essentially a giant toaster’

Antora Energy has raised millions for its super-heated graphite blocks that can deliver grid power, industrial heat or both.
By Julian Spector

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Workers are shown at an industrial structure containing 6 graphite blocks that is sited at wind and solar farm
A rendering of Antora Energy's storage array (Antora)

Startup Antora Energy knows the power of the light side.

The iconoclastic Bay Area company approaches the problem of how to store carbon-free energy very differently from other startups. It doesn’t tinker with new or improved batteries, harness gravity, or pump air or water.

Instead, Antora stores energy by heating metal blocks to extremely high temperatures. The super-heated blocks glow so brightly that a beam of that light can produce electricity on demand or directly heat energy-intensive industrial processes. Antora fits this mechanism inside a modular box about the size of a shipping container.

If that sounds bizarre and fantastical, then you’re paying attention. Nobody’s done anything quite like it before.

But Antora’s team has been honing the concept since launching in 2018 and this year secured $50 million from Bill Gates’ Breakthrough Energy Ventures, Lowercarbon Capital and other established climatetech investors. (Antora Energy is also a portfolio company of climate accelerator Third Derivative. Third Derivative and Canary Media are both affiliates of think tank RMI.)

Those backers are betting that Antora can make a dent in the planet-warming gases generated by industrial activities, which have thus far proven hard to clean up. Overall, industry contributes roughly 30 percent of U.S. greenhouse gas emissions, counting factory processes and the electricity they consume.

Antora already has prototypes that can store up to 500 kilowatt-hours of electricity. The Series A financing will fund the creation and installation of a 5-megawatt-hour storage prototype, to be deployed at a customer site in Fresno, California. That could be the jumping-off point for building large-scale facilities that store cheap renewable electricity and deliver it when factories need heat or the grid needs clean power.

I spoke with Antora founder and CEO Andrew Ponec in March to find out more about the company’s unique approach to the well-known challenge of turning intermittent wind and solar into dependable clean energy whenever it’s needed.

Get incredibly hot

Using heat to store energy isn’t new. Concentrated solar power plants, which reflect sunlight at a central tower to collect energy, often use molten salts” to store that energy for several hours.

But thermal storage has been relegated to the fringes of a booming grid storage industry, as unprecedented amounts of money flowed to other quixotic technologies. When the Antora team surveyed potential methods for storing clean energy, they homed in on thermal storage as an overlooked area with great potential.

And if you’re using heat for energy storage, you may as well go big.

Previously commercialized molten salt technology typically tops out below 600 degrees Celsius. Instead of reflecting sunlight with mirrors, Antora runs electricity through blocks of graphite, causing them to heat up. It’s essentially a giant toaster,” Ponec explained. Except that the heating elements in this toaster reach 2,000 degrees Celsius.

That kind of heat unlocks capabilities that clean energy otherwise cannot serve. Industrial tasks such as smelting metals, forging glass, producing cement and concocting fertilizer all require ferociously high temperatures. Antora could take a burst of solar power on the grid and channel it into the kind of volcanic heat that those glassmakers and fertilizer factories demand.

By going big on heat, Antora could chip away at the really troublesome emissions” from industry that clean technologies haven’t yet been able to tackle.

Unleash the power of light

That white-hot toaster energy only matters, though, if Antora can deliver it from the insulated box into something useful. And handling 2,000 degrees Celsius with normal heat-transfer tools is no walk in the park.

Heat transfer often happens through circulating liquids, but the conventional paradigm for how to move heat within a system goes away at high temperatures,” Ponec explained. What fluid are we going to use?”

Instead of engineering some elaborate new heat-transfer fluid, Antora took a cue from the sun, which transmits massive amounts of energy through, well, light.

We have shutters open up and blast intense light” straight from the glowing blocks, Ponec said.

By releasing controlled blasts of high-intensity light, Antora says it can deliver heat at 1,500 degrees Celsius directly into its customers’ industrial facilities, taking the place of heat from fossil fuel combustion. Or Antora’s device can blast specially designed solar panels to generate emissions-free electricity on demand to power a factory or the broader electrical grid.

Struggling to visualize that kind of energy moving via the force of light, I had to ask how it would feel to stick your hand in the beam. 

Don’t do that,” Ponec replied.

No need for a new supply chain

Novel storage technologies must be proven to work, and then be easily scaled up to a global supply chain that delivers high volume at low cost. If a new battery is so obscure and complicated that only one little startup knows how to make it, it will be hard to reach mass adoption at the pace the climate crisis demands.

We don’t want to have to scale a supply chain for our storage,” Ponec said, hence the value of the graphite blocks, which Ponec likens to Lego bricks — that is, if Lego made meter-long blocks that each weighed more than a ton.

Tens of millions of these blocks change hands every year, Ponec said, and are subsequently melted to manufacture various metal products.

They’re made all over the world because they’re used in aluminum and steel, which are made all over the world,” Ponec explained. There are no resource constraints.”

That’s especially valuable as Russia’s invasion of Ukraine upends the markets for key minerals used in other clean energy technologies.

Other storage startups have similarly chosen readily available materials as a tool to store energy. Form Energy uses iron pellets and has a major iron conglomerate as a backer. ESS makes flow batteries out of iron powder too. Zinc is also popular among storage startups. Others employ turbines and compressors from conventional industrial suppliers, engineering them into new configurations for clean energy storage.

But Antora is the first to try to build a successful grid storage business around graphite blocks.

Serve industry and the grid at the same time

Antora started off looking for ways to store cheap and abundant clean electricity. But the more the team explored heat as a storage medium, the more valuable heat itself seemed to be.

We were surprised at how big the industrial heat side of things was,” Ponec said, noting that large industrial facilities typically use far more energy for heat than for electricity. There’s no go-to solution for industrial heat right now.”

By offering both heat and electricity outputs, Antora expands its business options. It can serve customers who need clean power or high heat on demand, or those who need both (there’s already a robust market for heat and power served by gas-burning cogeneration” plants).

Startup Rondo Energy sees similar potential in converting clean energy into industrial-grade heat. That company raised a $22 million Series A in February for its super-heated brick technology. But Rondo doesn’t offer electricity as a product.*

Heliogen claims to offer both heat and electricity by digitally focusing a field of mirrors at a central tower, which hits 1,000 degrees Celsius. It’s an update to the otherwise moribund concentrated solar power genre, which lost out to mass-produced solar panels years ago as a cheap clean-power generator. Heliogen listed on the New York Stock Exchange last year but expects to sell its first two or three modules this year.

Prioritize energy density

Batteries in electric cars have to fit into a narrow footprint while packing a big storage punch. Storage for the grid doesn’t face the same constraints, so up-and-coming technologies for grid storage tend to sprawl out a bit. Antora’s tightly packed modules are an exception.

There’s still value in energy density, Ponec said, because it reduces all sorts of costs associated with getting a power plant online.

Ponec previously worked in the solar industry, where he learned that when the costs of solar panels plummeted, the business quickly became about managing costs for everything else that goes into a project: real estate and labor and wiring and racks and inverters.

Keeping a tight footprint with thermal storage means less land and less material are needed to deliver the needed capacity. It’s a way of looking ahead to a time when multiple technologies are competing for the budding role of long-term energy storage.

We can do quite a bit better than lithium-ion on energy density,” Ponec said, referring to the current most popular battery technology. We can’t do that on a car scale, so we’re not going to be the next electric vehicle, but at large scale, we can.”

Measuring this energy density is a little complicated because Antora can deliver either heat or electricity. One shipping-container-sized module can deliver 1 megawatt of heat for 50 hours straight for industrial customers. Or it can be geared for electricity, with a capacity of 200 kilowatts for 100 continuous hours. Antora plans to string together as many modules as needed to meet a customer’s energy requirements.

For comparison, 5 to 10 acres of large-scale solar are required to produce 1 megawatt of power, according to the Solar Energy Industries Association. Antora could take solar power produced out in vast desert facilities and store it near the point of consumption where land is scarce, given its small footprint.

But a lot of things need to happen before this becomes a meaningful advantage. Antora needs to prove its technology works in the field and close some deals with customers. The broader long-duration industry needs to get beyond pilot projects, too. But if, down the road, various technologies compete in a thriving advanced storage marketplace, Antora can brag about fitting a lot of capacity into a tight space.


*This article originally stated that Rondo Energy’s Series A funding totaled $20 million, not $22 million. We regret the error. 

Julian Spector is a senior reporter at Canary Media. He reports on batteries, long-duration energy storage, low-carbon hydrogen and clean energy breakthroughs around the world.