The Pacific Northwest National Laboratory says it’s about two years away from making hydrogen fuel cell cars more cost-effective — a 20-plus-year journey that once included a dream of going to Mars.

Researchers at the lab in Richland, Wash., have been working on a solar-reflector-based power source that they say is dramatically more efficient at generating electricity than a standard solar panel. The idea is to use the solar-reflector device to provide the power to convert natural gas into hydrogen fuel for vehicles.

A typical solar panel converts sunlight into electricity at a 20 percent efficiency rate, while the experimental solar-reflector device can reach a 70 percent efficiency rate, said Bob Wegeng, the engineer in charge of the PNNL project. As a comparison, photosynthesis in plants converts sunlight into energy at an efficiency rate of slightly less than 10 percent.

Why hydrogen? A kilogram of hydrogen (2.2 pounds) has about the same energy content as a gallon of gasoline (6.3 pounds). A hydrogen-fuel-cell car gets roughly 50 to 81 miles per kilogram, according to various estimates from the federal government and auto manufacturers.

We’re very close to a project that is commercial

With most of the solar-reflection power source completed, PNNL is now working on the engineering to use that power to create hydrogen fuel at a target cost of $2 per kilogram. That’s dramatically cheaper than the current conversion cost. A 2015 story from HybridCars.com cited a federal estimate of $13.50 per kilogram from a filling station dispensing hydrogen fuel. The same story quoted a Toyota official as putting the filling-station price at $10 to $12 per kilogram.

“We’re very close to a project that is commercial,” Wegeng said.

PNNL has been working at using cheap solar power to create fuels since the 1990s. At the turn of the century, that project received a tremendous boost when PNNL’s research meshed with NASA’s plans to use sunlight as a power source for Mars-bound spaceships. NASA’s research later diverged from PNNL project. But the idea of using solar-reflector technology to help create cheaper hydrogen fuel picked up momentum.

“Hydrogen cars have been such a tease. For decades, carmakers have held out the hope of clean energy, free of fossil fuels and tailpipe emissions, without telling us where the hydrogen will come from and what it will cost,” according to a story in IEEE Spectrum.

The economics of hydrogen-fueled cars and creating filling stations for them is still mostly uncharted territory. About two weeks ago, the U.S. Department of Energy issued a request for public feedback so it can begin to analyze the economics of hydrogen filling stations.

The theoretical upsides to hydrogen vehicles are that the fuel could be cheaper than gasoline, and essentially pollution-free. A major downside — besides still being in the experimental stage — is that hydrogen-powered cars are very expensive.

Two models are on American streets — the hydrogen-fueled version of the 2015 Hyundai Tucson and the 2016 Toyota Mirai. Their prices are in the range of $58,000 to $60,000. A third model is the 2017 hydrogen-fueled Honda Clarity, which carries a $60,000 price tag.

Today, hydrogen-fueled cars and the filling stations that provide hydrogen fuel are rare — essentially limited to the southern half of California in the United States along with small numbers in Europe and Japan. A July 2016 California Air Resources Board report said there are 20 hydrogen vehicles refueling stations in that state, with that number expected to grow to 38 by the end of this year, mostly in the Los Angeles area.

Although burning hydrogen fuel in automobiles is pollution-free, the current processes for creating hydrogen fuel produce their own greenhouse gases. That’s the downside that would be eliminated by the PNNL project.

The PNNL solar-reflector system would power a production device capable of creating 15 to 17 kilograms of hydrogen fuel per day. The idea is that hundreds, possibly thousands, of such devices could be installed at a fuel production site.