In August, California experienced its worst electricity crisis in nearly two decades. From PG&E to San Diego Gas & Electric, blackouts rotated across the state as millions of Californians, housebound by a pandemic, tried to stay cool during record-breaking heat.
The crisis showed the limits of the existing electrical grid, which buckled under too much demand and too little supply when it was needed. Problems arose late in the day, when the output from solar power declined. As the state looks to further increase the share of renewables on the grid to cut greenhouse gas emissions, the risk of supply shortages could increase. State energy leaders wrote in a letter to the governor: “Our changing electricity system may need larger reserves.”
Three years ago, the cofounders of Antora Energy anticipated this very problem.
“Wind and solar are the cheapest electricity in many places around the world already. They beat fossil fuels on raw economics—but they’re not dispatchable,” says Justin Briggs, chief science officer of the venture. “So, how do you build a stable, clean energy grid where you can have affordable power at the snap of your fingers, independent of the weather or time of day?”
That’s the question Antora Energy set out to answer.
Cofounders Andrew Ponec, ’17, and Justin Briggs, PhD ’17, might seem like an unlikely pair. In 2017, Briggs was wrapping up a PhD in applied physics—and wanted to apply his knowledge to the urgency of climate change. Meanwhile undergrad Ponec, by age 21, had already cofounded and sold Dragonfly Systems, a successful solar startup, and was ready for his next project.
They approached their collaboration thoughtfully. Before looking for solutions, they started by asking: What are the biggest problems in energy? Where could we have the biggest impact?
“We were technology-agnostic in a way,” says Briggs.
As the cost of solar had dropped precipitously in recent years, they realized that storage was, and continues to be, the limiting factor. Finding a way to hold and dispatch sun or wind power for future use.
But how, exactly?
Currently 96 percent of the world’s energy storage is in what is called pumped hydropower, essentially two lakes separated by a steep incline with pipes to move the water back and forth. Yet this technology requires specific geography, often far from urban centers where energy is consumed, and has environmental consequences on the landscape.
Lithium-ion batteries, which are broadly used in electric vehicles and consumer goods, are one alternative to pumped hydropower. Their use for grid storage has grown rapidly in recent years, including an expected six-fold increase in capacity for California in 2020 alone. However, lithium ion batteries have significant drawbacks that limit their ability to supply the reserves needed for a clean energy grid. Most can only hold up to four hours of charge, they are made using metals with supply chain challenges, their capacity reduces over time, and they are flammable—all in all making them a pricey and risky bet.
The Stanford grads took a summer to think it over independently. By fall 2017, they reconvened and discovered they had landed on the same conclusion: thermophotovoltaics.
During his PhD, Briggs had begun exploring ways to, as he phrases it, time-shift energy—to bottle up sunshine at noon and save it for midnight. Or, more likely, 6 p.m., when the air conditioner, television, washer, and stove are operating all at once.
“I had identified that you could pair thermophotovoltaics with a thermal energy storage system—so you could store energy as heat and then convert it to electricity. But I had no real notion of the cost of that,” says Briggs.
Like photovoltaics, thermophotovoltaics, or TPV for short, harness light and convert it into electricity, but rather than collecting energy from the sun, they collect it from a closer object that is hot enough to radiate light. Picture a blacksmith’s tools burning red-hot in the fire.
“Independent of my academic musing, Andrew had been diving deep into the technology, carefully calculating the economics of thermal storage systems, and examining alternative solutions to see: Does this pencil out?” says Briggs, giving credit to his cofounder. “He really was the progenitor of the technology and the core concepts.”
By January 2018, the duo got to work, earning a TomKat Center Innovation Transfer grant. Only two months later, this funding helped them gain entrance into the Cyclotron Road incubator program at Lawrence Berkeley National Laboratory.
There, they soon connected with third cofounder David Bierman, a PhD from MIT, who was advancing similar technology—whose name, in fact, Briggs knew well from the scientific literature. By summer 2018, the trio merged into one team.
As California ramps up to meet its targets of 60 percent renewable electricity by 2030 and 100 percent emissions-free energy by 2045, a stable grid will require energy storage that can span weeks to months.
Antora is developing just that by designing modular units at scales for an office building to a metropolis. The technology uses renewable electricity to heat insulated carbon blocks that get incredibly hot—over 1,000ºC—hot enough that they radiate light. Then when electricity is needed, a TPV panel is used to harvest the radiated light and generate electricity for consumers. The system can connect directly to solar panels or wind turbines adjacent to a customer, or to the electrical grid, depending on the user needs.
The TPV approach provides benefits over solar cells due to its ability to leverage a broader spectrum of light. Semiconductors can only harvest a narrow band of the available light—the reason why most solar photovoltaics are typically limited to 20 to 30 percent efficiency. The same issue arises with TPV, but in this case, the leftover light is reflected back into the thermal source.
“You don’t lose the energy at incompatible wavelengths, you recycle it. You reabsorb it into the thermal source, so instead of losing that light back into space, you can keep reusing it over and over,” says Briggs.
For hospitals and data centers in need of reliable backup power, the system could provide a clean, affordable choice. This matters all the more as California enters into wildfire season, a time when emergency shutoffs of the electrical grid sometimes happen.
Today Antora Energy has grown to a team of 13 employees. Right as the venture was graduating from Cyclotron Road in March 2020, the global COVID pandemic made clear that securing a new headquarters would need to wait. Instead the team is spread out from West Coast to Midwest to East Coast, carefully advancing their prototypes in stages along the way.
Despite the hurdles, this year Antora won a $2 million grant from the California Energy Commission to build out its first pilot installation, and the venture also closed on a round of seed funding with private investors for an undisclosed amount. By 2021, the team plans to construct the pilot system—which will store between 5 and 10 megawatt hours of energy—with an independent power producer in California’s Central Valley.
“For a long time, I was—and I still am—pretty skeptical about capitalism as it currently exists. I spent many years trying to improve things outside of that system through my personal actions and advocacy. But I’ve recognized that personal behaviors are hard to scale,” says Briggs.
“The most important thing about Antora Energy is that we’re fundamentally motivated by improving human well-being through stopping climate change. The reason we are doing this as a commercial endeavor is because we believe this is the fastest and best way to have a big impact.”