In a recent letter posted on his website, Gates said no current clean-energy technology will enable the world to eliminate carbon dioxide emissions by 2100.

Nothing is consistent or inexpensive enough, but the world must find a magic bullet, or magic bullets, to reduce greenhouse gas emissions by 80% by 2050 to avoid catastrophic climate change, and it must then stop emissions entirely by 2100, Gates said.

That might be terrible news for the as-yet unborn petroleum leaders and coal barons of tomorrow, but it is potentially good news for scientists looking to make clean energy breakthroughs.

Last year Gates announced last year that he was committing $1 billion of his own money over five years to invest in clean-energy technology, and he has been pushing governments to increase their funding of cheap, scalable clean-energy sources.

Gates personally prefers next generation nuclear, which he describes as “a very promising path”, and he is backing efforts to improve battery technology, so that energy from intermittent clean sources such as solar and wind can be affordably stored at large scale for use over time.

“It would help, of course, if we had a great system for storing solar and wind power,” the Gates wrote.

“But right now, the best storage option is rechargeable batteries, and they are expensive.

“Lithium-ion batteries like the one inside your laptop are still the gold standard. If you wanted to use one to store enough electricity to run everything in your house for a week, you would need a huge battery—and it would triple your electric bill.

“Within the next 15 years I expect the world will discover a clean-energy breakthrough that will save our planet and power our world.”

It seems likely that the silver bullet could come from the US Department of Energy’s Advanced Research Projects Agency-Energy (Arpa-E), which believes one of the technologies it has invested in is on the cusp of becoming the next-generation system of large-scale energy storage systems beyond current lithium-ion batteries.

Arpa-E was founded in 2009 under US president Barack Obama’s economic recovery plan to fund early stage research into the generation and storage of energy.

It claims to have developed a new approach to a battery technology that could transform America’s electrical grid.

Since 2010, Arpa-E has invested approximately $1.3 billion across more than 475 projects through 30 focused programs and three open funding solicitations, with many showing early indicators of technical and commercial success, but it wants to accelerate development by partnering with private industry.

Last week Arpa-E announced 45 projects had secured more than $1.25 billion in private sector follow-on funding, 36 projects had formed new companies, 60 projects have partnered with other government agencies for further development and an ever increasing number of technologies have already been incorporated into products that are being sold in the market.