After already receiving a controversial $1.6 billion construction loan from U.S. taxpayers, the wealthy investors of a California solar power plant now want a $539 million federal grant to pay off their federal loan.

"This is an attempt by very large cash generating companies that have billions on their balance sheet to get a federal bailout, i.e. a bailout from us - the taxpayer for their pet project," said Reason Foundation VP of Research Julian Morris. "It's actually rather obscene."

The Ivanpah solar electric generating plant is owned by Google and renewable energy giant NRG, which are responsible for paying off their federal loan. If approved by the U.S. Treasury, the two corporations will not use their own money, but taxpayer cash to pay off 30 percent of the cost of their plant, but taxpayers will receive none of the millions in revenues the plant will generate over the next 30 years.

"They're already paying less than the market rate," said Morris, author of a lengthy report detailing alleged cronyism and corruption in the Obama administration's green energy programs. "Now demanding or asking for a subsidy in the form of a grant directly paying off the loan is an egregious abuse."

NRG doesn't see it that way, telling Fox News the money is there for the taking."NRG believes in a clean and sustainable energy future and therefore participates in available government programs to develop and expand the use of clean energy to accelerate America’s energy independence." In 2013, the Obama administration handed out $18.5 billion in renewable energy grants, with $4.4 billion going to solar projects.

Ivanpah is the largest concentrated solar power plant in the world. It was unveiled in February with great fanfare. Dr. Ernest Moniz, the U.S. Secretary of Energy, justified taxpayers' investment at the time, saying, "We want to be technology leaders. It's good for our economy and it’s also good for helping stimulate the global transition to low carbon."

But since then the plant has not lived up to its clean energy promise. According to the U.S. Energy Information Administration, the plant produced only about a quarter of the power it's supposed to, a disappointing 254,263 megawatt-hours of electricity from January through August, not the million megawatt-hours it promised.

A NRG spokesman blamed the weather, saying the sun didn't shine as often as years of studies predicted. However by the four-year mark, NRG has "every confidence that the plant will function as anticipated for the life of the facility,"according to the company.

Touted as a clean, green energy, some environmentalists have turned against concentrated solar as a technology, deeming it dangerous and a threat to wildlife. Unlike solar photovoltaics, which turn sunlight directly into electricity, CSP uses thousands of large mirrors to concentrate reflected sunlight into powerful beams aimed at “power towers.” The heat generates steam to turn turbines that create electricity.

The problem is that birds see the mirrors as water. As they approach, the 800º F solar beams roast any bird that happens to fly by. A recent study released by the California Energy Commission conducted by the Center for Biological Diversity called Ivanpah a “mega-trap” that will kill up to 28,000 birds a year.

The plants' owner at the time, BrightSource Energy, said it will likely kill only a thousand birds a year. BrightSource came under scrutiny by the House Oversight and Government Reform Committee and investigators found the company received direct “guidance and support from the White House” for how it obtained its $1.6 billion in federal loans.