T. Boone Pickens might not be building the world's biggest wind farm anymore – at least not until the money comes back.

But the Texas oil billionaire and clean energy evangelist hasn't let the stalling of his energy plan stop him from keeping up his screed against America's reliance on imported oil – and a solution that might benefit his own natural gas business interests.

The idea is to convert about 350,000 heavy-duty trucks so they can run on natural gas instead of diesel, and he's seeking up to $28 billion in federal economic stimulus incentives to do it.

"We have an abundance of natural gas in America," Pickens said said Wednesday at the Cleantech Investor Summit in Palm Springs. "It's cheaper, its cleaner, and it's ours."

Pickens said he's met twice with the transition team of President Barack Obama and with leading Democrats in Congress to push his plan. Converting that many diesel trucks to natural gas could save the country 4 percent of its annual oil imports, he said.

It's also essentially the second half of an energy plan Pickens launched in July with the hope of weaning the United States from its reliance on foreign oil (see T. Boone Pickens Has a Plan).

The idea was to build enough wind turbines in the Midwest to provide about 4 gigawatts of power -- what would be the world's largest wind farm. That would free up natural gas now used to run power plants for use as a transportation fuel instead. The combination could reduce the United States' reliance on foreign oil by one third in 10 years, he said.

By July, Pickens said he had spent $2 billion on the project so far and planned to invest $10 billion more, with the goal of producing electricity by 2011.

But the economic downturn and the rapid fall in oil prices crashed those plans. Pickens' hedge fund, BP Capital, had lost about $2 billion by October as a result of slumping oil and natural-gas prices (see Knocking the Wind Out of Pickens).

"That's where you are on that biggest wind farm right now," Pickens said Wednesday. "There's no money."

Pickens' company, Mesa Wind, has a big wind turbine order with General Electric, he said. But for the future of the wind farm itself, "We'll see what happens in the next few years."

So Pickens has turned to the second half of his plan – using natural gas to fuel transportation, particularly big rigs. The proposal he's seeking federal support for would spend about $75,000 per vehicle and build 2,000 filling stations, creating more than 400,000 jobs, in the process, he said.

It also would likely benefit the company he co-founded, Clean Energy Fuels (NDSQ: CLNE), a natural gas distributor in Seal Beach, Calif. with investments in natural gas-powered transportation (see Clean Energy Fuels Buys Landfill Gas Plant).

Clean Energy Fuels spent $17 million to back a failed California ballot initiative this fall, Proposition 10, which called for the state to raise $5 billion in bonds to fund rebates for buying and retrofitting vehicles to run on alternative fuels including natural gas (see States Tackle Green Ballot Initiatives).

Pickens acknowledged that substituting natural gas for oil wasn't an ideal solution from an environmental standpoint, though he did note that using natural gas as a fuel produces about 60 percent less greenhouse-gas emissions than the equivalent of diesel fuel.

He also said he supports the use of battery-powered electric cars and other light-duty vehicles. But he disparaged the idea that battery technology was advanced enough at this point to power heavy-duty trucks.

"Al Gore and I discussed these things, and Al of course would like to go to the battery on Monday morning," Pickens said. "But the technology is not there."