Grid storage has turned into a big business with a short menu. When a utility buys a battery today, it pretty much orders rows of lithium-ion cells in containers, the same chemistry as your phone scaled up to the size of a parking lot. That works, but the supply chain runs mostly through China, and every so often one of these installations catches fire and stays in the news for a week.<\/p>\n
Back in August we dug into a company outside Boston working on a much stranger answer: graphite blocks heated until they glow white-hot<\/a>, with liquid tin carrying the heat and cells that work like solar panels turning the glow back into electricity. At the time, Fourth Power’s 1-megawatt demonstration unit was a promise with a 2026 deadline attached.<\/p>\n The promise now has a construction crew. Fourth Power announced on September 14<\/a> that its new Bedford, Massachusetts facility is open and the first full-scale demonstration of its system is going up inside, with phased commissioning underway. The Boston Globe<\/a> reported on September 23 that the build started earlier this month.<\/p>\n So what exactly are they putting up?<\/p>\n The Bedford unit is a 1-megawatt battery. It’s a proof run, the Globe says, built to show the concept works somewhere other than a lab bench. Fourth Power still calls it full-scale, because it’s assembled from full-size commercial components. There are just fewer of them than a real plant would carry.<\/p>\n Commissioning, if you haven’t spent much time around industrial hardware, is the polite word for switching a machine on very slowly. Crews power up one subsystem at a time and check it does what the drawings promised before touching the next one. With a machine that runs at up to 2,400 degrees Celsius, or 4,352 degrees Fahrenheit, I’d want it done slowly too.<\/p>\n One quirk in the coverage: the Globe puts the demo at one megawatt, while MIT News<\/a> described it in March as a 1-megawatt-hour system. Those aren’t the same measurement. Megawatts tell you how hard a battery can push, megawatt-hours tell you how much it holds, and neither outlet squares the two, so I’d hold the exact spec loosely. Either way, this is the small one.<\/p>\n The physics hasn’t changed since August, so here’s the short version. Cheap grid power heats the graphite until it glows at between 1,900 and 2,400 degrees Celsius, liquid tin gets pumped through the stack, and thermophotovoltaic cells mounted inches from the metal turn that light straight back into electricity, with lab cells already topping 40 percent efficiency. The insulated stack loses about 1 percent of its stored energy per day, and that slow bleed is what makes storing power for days instead of hours a sane idea.<\/p>\n The commercial unit is where the fresh figures live. Per the Globe, the standard block fills about one acre and puts out 25 megawatts, roughly what 18,000 typical households draw, and it can keep that up for as long as 50 hours.<\/p>\n That 50-hour figure needs a little unpacking. When MIT News wrote the company up in March, the base commercial block paired 25 megawatts with 250 megawatt-hours, which works out to 10 hours at full output. The system is modular, though. “One storage and one power module, and that’s a 10-hour battery,” MIT professor and company founder Asegun Henry told MIT News, and buyers stretch the duration by adding storage modules. So the 10-hour block is the entry point, and 50 hours is one of the longer builds a customer can order.<\/p>\nThe demo is small on purpose<\/h2>\n
The full-size battery finally has hard numbers<\/h2>\n