Chris Sacca’s venture firm Lowercarbon Capital is raising a second fund to back nuclear fusion energy hopefuls, the VC said at the SOSV Climate Tech Summit on Thursday, as reported by Bloomberg.  

The firm has backed leading fusion startup Commonwealth Fusion Systems, as well as others like Pacific Fusion. It raised a $250 million, fusion-geared fund in 2022. Fusion believers, who include a number of well-known climate VCs beyond Sacca (like Vinod Khosla), still hold faith that a breakthrough needed to make it commercially viable is just around the corner. And several advances are showing promise of delivering one.

In the meantime, building fusion reactors is expensive. Commonwealth raised $863 million earlier this year, after raising a $1.8 billion Series B four years ago. TechCrunch has documented a dozen fusion startups that have raised over $100 million. 

Sacca didn’t say how big this second fund will be, but a source told Bloomberg that it’s intended to be bigger than the first.