What does energy have to do with ending poverty? Bill Gates -- whose philanthropic largesse has made him one of the most prominent advocates for the world's poor -- should know.

At the recent Wall Street Journal ECO:nomics forum, Gates made a pitch for making energy cheap and clean around the world.

"If you want to improve the situation of the poorest two billion on the planet, having the price of energy go down substantially is about the best thing you could do for them," Gates said. "Energy is the thing that allowed civilization over the last 220 years to dramatically change everything."

Just as access to reliable and modern energy sources has laid the foundation for the wealth of developed countries, energy poverty impedes the progress of the world's poor. And it's no small problem: as energy demand soars in the developing world, approximately 1.3 billion people lacked access to electricity and around 2.7 billion relied on traditional biomass for heating and cooking in 2011, according to the International Energy Agency.

WHO estimates that indoor air pollution -- caused primarily by burning biomass fuels such as wood, crop waste and dung, or coal in inefficient and poorly ventilated stoves -- is "responsible" for a staggering 1.6 million deaths annually.

Moreover, lack of access to reliable and modern energy inhibits education for children who cannot study after dark, medical treatment for doctors with tenuous electricity, and access to markets for farmers.

But it's not enough to make energy cheap -- we have to also make it clean, Gates said. He warned that global warming could be a "disaster" for the global poor because it would make agriculture in tropical areas "virtually impossible."

That's why he called for massive investments in energy research to spur innovation.

"I think the world needs to invest a lot more in energy R&D to provide the energy breakthroughs that can get down to near zero carbon emissions in the next 75 years," Gates wrote after the conference.

View Breakthrough Institute research on how we can make clean energy cheap and accessible around the globe here.

View the rest of Gates' talk on energy here: