Bill Gates reckons he has already dropped a cool $1 billion on investments in renewable energy technologies. Now he’s looking to double that.

Gates, who according to Forbes will still have at least $78 billion left even after he’s placed his new bets, said in an interview with the Financial Times that investing in radical, ‘wild-eyed’ energy tech companies is the only way that the world is going to get the solution to climate change at an affordable economic cost.

Current technologies, he said, were too expensive.

“The only way you can get to the very positive scenario is by great innovation,” he said. “Innovation really does bend the curve.”

Gates wasn’t impressed by those who claim their new battery and energy story technology can solve the problem of unpredictability that dogs renewable sources such as wind and solar.

“There’s no battery technology that’s even close to allowing us to take all of our energy from renewables and be able to use battery storage in order to deal not only with the 24-hour cycle but also with long periods of time where it’s cloudy and you don’t have sun or you don’t have wind,” Gates said. “Power is about reliability. We need to get something that works reliably.”

Gates said that the scale of the challenge and the extent of the possibilities demand that government puts “tens of billions” into researching and developing renewables. He drew comparisons with the vast resources thrown at the Manhattan and Apollo projects that made the atomic bombs and put men on the moon.

Gates has already invested “several hundred million dollars” in ‘nuclear recycling’ according to the FT, with much of that put in a company called TerraPower, which is trying to develop reactors that will run on depleted uranium, a waste product of today’s nuclear plants.

“Nuclear technology today is failing on cost, safety, proliferation, waste and fuel shortage, and so any technology that comes in has to have some answer to all of those things,” he said.

Other technologies Gates spoke warmly of included “solar chemical” power, which uses a process akin to photosynthesis to use sunlight to convert water into hydrogen fuel, and high-altitude wind power, which attempts to tap the energy of jet stream winds that blow 20,000 feet above the ground.