Bill Gates has announced a $1 billion investment fund to back radical approaches to clean energy.

Last year, Gates established the Breakthrough Energy Coalition with more than 20 billionaires, among them Amazon's Jeff Bezos, Alibaba's Jack Ma, and Virgin's Richard Branson. At the time, they promised to invest at least $2 billion into new technologies.

The Breakthrough Energy Ventures fund is the first wave of that investment. Established to take a long-term approach to funding energy ideas, it will help startups considered to be too risky by regular venture capital firms. In a statement announcing the launch of the fund, John Arnold, who is one of the billionaire investors, explained that the "dearth of venture funding for clean energy technologies threatens to create a valley of death for the industry, with emerging ideas unable to find the necessary capital to reach commercialization."

The new fund plans to step in and bridge that gap. Its investments, which will take place over the next 20 years, won’t be limited to electricity production—they’ll also include new technologies for transportation, agriculture, manufacturing, and construction. It will fund projects that promise the biggest possible benefit to the planet’s future climate, as long as the science underlying the application has been proved in the lab and can plausibly be scaled up.

The 20-year fund length isn’t random. In an interview with MIT Technology Review earlier this year, Gates argued that in terms of carbon dioxide emission, “rich countries need to be net zero by 2050, if you really want just 2 degrees of warming.” Gates and his co-investors hope that they will be able to fund plans that are audacious enough to have a profound impact on the planet before then.

Not that it will be easy. In the same interview, Gates admitted that one of the biggest problems facing the fund was finding enough companies doing the right kinds of work to invest in. “I wish just writing a bigger check was the solution,” he explained. “I’ll be fascinated as we get this fund together how quickly we’ll be able to invest.” As will we, Bill.

(Read more: Breakthrough Energy Ventures, Telegraph, “Q&A: Bill Gates”)