On Wednesday, hydrogen fuel cell company Plug Power announced that Amazon would be changing its battery-operated forklifts to hydrogen fuel cell-powered ones at 11 of its fulfillment centers. According to Reuters, Amazon secured the right to buy up to 23 percent of the company as well, which would make the online retailer one of the largest shareholders in the fuel cell company.

Plug Power said in a press release that Amazon would be spending about $70 million in 2017 to purchase Plug Power’s GenKey systems, which include fuel cells for forklifts, stationary fuel cells for backup power, hydrogen fueling infrastructure and fuel, as well as customer support.

Hydrogen fuel cells are seen as interesting alternatives to batteries because batteries can take a long time to recharge, whereas fuel cells are simply refilled, like filling up the gas tank in a car. There’s also no real waste or emissions associated with using hydrogen to power a vehicle, besides harmless H 2 O. But there are downsides, too. Making hydrogen often relies on burning greenhouse gases, so critics say it’s not truly a carbon-neutral fuel. And transporting hydrogen is more difficult than transporting, say, gasoline, as it often needs to be compressed or kept at very cold temperatures.

Still, fuel cell technology is being developed by GM in partnership with the Army and the Navy, as well as Toyota and Shell. Companies like Walmart and Kroeger have deployed Plug Power fuel cell forklifts in their warehouses. Back in 2015 we reviewed the Toyota Mirai, one of the first production cars to use a hydrogen fuel cell.

In its press release, Plug Power noted that its partnership with Amazon will be unique, as the fuel cell company will collaborate with the retail giant on “exploring the expansion of applications for Plug Power's line of ProGen fuel cell engines,” which could include applications in cars and trucks.

According to the Albany Times Union, Plug Power had $85.9 million in revenue last year, so the Amazon deal could nearly double that figure this year. Plug Power has not yet seen a profitable quarter.

Correction: Headline was changed to clarify that the old forklifts used batteries to provide electricity, and the new forklifts use hydrogen fuel cells to provide electricity.