It's a stainless-steel cooker that uses about 95% less fuel than conventional wood stoves, with minimal pollution. It would seem to be a can't-miss technology in a country where millions still cook with wood and most forests have been destroyed.
The device has garnered Nuñez a prestigious environmental prize. It has earned him a U.S. patent. And it has won fans among some Salvadoran peasants who no longer spend a good chunk of their days hunting for firewood and the rest inhaling cooking smoke.
It has also wrecked Nuñez's marriage, alienated two of his three children and swallowed his life savings. At 61, he lives with his mother to save on rent and drives a 1990 Kia. Nuñez knows some people think he's a fool to have poured $2.5 million of his and his family's money into his project with little to show for it.
"My ex-wife said: 'Man, you are an idiot. Poor people have no money. They are not going to buy your stoves,' " he said. "She was right."
Nuñez gambled that the government or nonprofit groups would finance production of the appliances to distribute to low-income people. But Salvadoran officials so far have shown scant interest in his invention. Environmental groups have offered praise but little financial backing.
Nuñez wonders if he'd get more respect if he hailed from Silicon Valley instead of this tiny Central American nation, where he toils in obscurity at a small private university in the capital. His "Advanced Combustion Laboratory of Menlo Park" -- he named it in honor of Thomas Edison -- is a converted storeroom fitted with a single fluorescent bulb. His annual budget is $10,000. Still, he perseveres.
Nuñez is convinced that his combustion method can save trees and reduce greenhouse gases. He figures the technology can be adapted to any fuel and put to industrial uses such as electricity generation. But saving the planet has become secondary to a more personal quest: winning back the love of his kids.
"If I could eliminate those emissions, then my children would be proud of me," Nuñez said. "That became the main motive of my invention. To let them know that I was right."
Nuñez married into one of the most powerful families in El Salvador, for whose business he designed industrial equipment. They helped him start his own small business building computer voltage regulators and power supplies. He drove a Range Rover and piloted a Piper Dakota plane. Why risk it all on a stove for the poor?
Intellectual curiosity is part of it. So are hubris and naivete. Then there are the words of the eccentric 20th century inventor Nikola Tesla, one of Nuñez's idols: "Science is but a perversion of itself unless it has as its ultimate goal the betterment of humanity."
It all started in the mid-1990s when a friend asked Nuñez to write a chapter on energy resources for a book about El Salvador's natural history. A voracious reader and compulsive tinkerer, Nuñez said he was stunned to find that 65% of his nation's 7 million people relied on wood for fuel.
In fact, half the planet cooks and heats much the way their ancestors did using solid fuels, according to the World Resources Institute, a Washington-based environmental think tank.
The environmental and health costs are staggering. Indoor pollution from cooking fires kills an estimated 1.6 million people a year worldwide, mostly women and children. Deforestation is a major source of carbon emissions and exacerbates both flooding and drought. The problem is particularly acute in El Salvador, where the nation's primary watershed is threatened by deforestation.
For Nuñez, a tall, aristocratic-looking engineer who speaks English with a vaguely British accent acquired during his student days in northern England, it all seemed an appalling waste.
"I thought: 'Well, if we don't fix that, we are going to convert this country into a complete desert,' " he said.
Petroleum-poor El Salvador has no ready replacement for wood. What was needed, Nuñez reasoned, was an ultra-efficient wood-burning cooker. Environmental groups have been pushing such projects for decades. Most involve the use of low-cost insulating materials such as mud or ceramic.
Nuñez dismisses these as "stone-age" technologies. He surmised that the key was a more efficient combustion chamber to get the combination of air, fuel and temperature just right. With the computer electronics business fast migrating to China, he decided to ditch that enterprise and reinvent his company to produce high-tech wood stoves.
Never mind that his wife wasn't crazy about the idea and the couple had three kids to support. Or that Nuñez knew little about combustion. With the help of textbooks and countless experiments, he slowly taught himself and his 10 employees.