MIT professor Yet-Ming Chiang has launched his latest storage bet, a flow battery startup designed to make renewable energy directly competitive with fossil fuels (see “24M’s Batteries Could Better Harness Wind and Solar Power”).
The scale of the company's ambition—and challenge—is telegraphed in the name: Baseload Renewables. The Cambridge, Massachusetts-based startup's stated mission is to produce batteries that are capable of producing reliable grid power from renewable sources around the clock, and cost at least five times less than where lithium-ion batteries are likely to plateau.
That’s approaching the price point where the idea of “seasonal storage” becomes economically feasible—meaning arrays of these batteries could store enough solar power during times of excess generation through the summer to continue meeting regional demand through the long, cloudy winter, Chiang says.
Baseload is housed at the Engine, MIT's new accelerator, which recently provided the company nearly $2 million in funding (see “Developing a Tough, Time-Consuming Technology? This Investor Is Interested”).
Baseload isn't providing many technical details at this stage, but the key to its low cost is relying on sulfur. That's because the material is very abundant and energy-dense, Chiang says. Indeed, it's a waste product of oil and gas production that costs as little as 10 cents per kilogram.
"Based on the charge stored per dollar, sulfur was more than a factor of 10 better than the next best thing," says Chiang, a materials science professor who previously cofounded lithium-ion battery startups A123 Systems, 24M, and three other startups.
Baseload's other cofounders include Ted Wiley, previously a vice president at Aquion Energy, as well as Marco Ferrara and Billy Woodford, both of whom previously worked with Chiang at 24M (see “Why Bad Things Happen to Clean-Energy Startups”).
Better, cheaper, longer-lasting storage technologies are crucial for enabling renewable sources to meet a greater portion of energy demand, and significantly lower greenhouse gas emissions.
For all the hopeful commentary and coverage of wind and solar prices nearing parity with fossil fuels, the truth is it's an apples-to-oranges comparison. Because the sun doesn't always shine and wind doesn't always blow, those sources can't be used as reliably and flexibly as coal or natural gas unless they're backed up by fossil fuel plants, balanced out through demand-response programs or long-distance transmission lines, or paired with some form of abundant storage. The options for the latter are generally limited to cheap pumped hydroelectric storage—which is tightly geographically restricted since it requires a pair of water reservoirs—or batteries and similar technologies that are still too expensive, short-lived, or both.
The lithium-ion batteries that run our smartphones and electric vehicles are increasingly being used in limited ways to balance renewable generation. But many battery experts believe that their high cost and limited life cycles place hard limits on how big a role they can play on the grid.
Flow batteries, on the other hand, can be designed with a very high energy-to-power ratio, which means they can hold a lot of energy, and continue delivering it over long periods, says Michael Aziz, a professor of materials and energy technologies at Harvard University.
Most flow batteries include two tanks of electroactive materials dissolved in liquids, known as the anolyte and catholyte. They're pumped into a central cell divided by a membrane permeable to one common ion, allowing atoms with a positive or negative charge to pass through. This current flow, in turn, charges the positive and negative electrodes on either side of the cell.
In the case of Baseload, the anolyte appears to be a "polysulfide solution," which simply means it contains chains of sulfur atoms, according to a patent application for "air-breathing aqueous sulfur rechargeable batteries" filed by MIT in late 2016. The application lists Chiang as an inventor. The catholyte is an unspecified metal salt dissolved in water. It’s called "air-breathing" because oxygen is generated in the catholyte during charging, and consumed while discharging.
Chiang, serving as the company’s chief scientist, expects the batteries to boast a “multi-day or longer” discharge duration, and last 20 years in the field.
“We are still working on selecting the ideal chemistry for this approach,” Chiang says.
He says the company is still in an early stage, noting it could take three to five years before there are significant projects in the field. Getting there will almost certainly take more than $2 million, and Chiang says the company continues to look for additional funding.
His early research on this approach began under the U.S. Department of Energy’s Joint Center for Energy Storage Research. George Crabtree, the program’s director, says sulfur batteries could eventually be cheap and long-lasting enough to replace the carbon-dioxide emitting gas turbines that are currently throttled up when wind and solar power flags, or even hydroelectric storage facilities.
Harvard’s Aziz says it's the first storage system he's heard of targeting such long discharge durations, other than pumped hydroelectric, and that it appears the company is trying to break new ground on kilowatt-hour pricing as well.
He says it's difficult to assess the technical viability without additional details, but adds that Chiang's track record as an inventor and scientist suggest the company is on a promising research path.
Chiang’s earlier venture, A123, was an early bet on building lithium-ion batteries for electric vehicles that earned wide press attention. But the company was forced to file for bankruptcy in 2012 after overbuilding its manufacturing facilities in anticipation of business that didn’t come. It was ultimately purchased by Wanxiang, a major Chinese auto parts manufacturer, and appears to be on solid financial footing again, according to some reports. He remains chief scientist at 24M.
Chiang says he learned crucial lessons in his earlier ventures that he intends to apply to Baseload Renewables. Among other things, he says, the company will very likely look to partner with established manufacturers rather than build out its own factories, a strategy that other battery ventures like Aquion and CAMX Power have also come to embrace.
“Startups aren’t equipped to tackle it, and investors aren’t fond of paying for it,” Chiang says.