By Rory Carroll and Nichola Groom

IVANPAH DRY LAKE, Calif./LOS ANGELES (Reuters) - One of the world's largest solar projects, which uses heat from the sun to generate power in California, opened on Thursday but may be the last of its kind in The Golden State.

Sprawling across 3,500 acres in the Mojave desert near the California-Nevada border, the $2.2 billion Ivanpah solar thermal power plant has more than 300,000 mirrors that reflect sunlight onto boilers housed in the top of three towers, each of which is 150 feet taller than the Statue of Liberty.

The sun heats water inside the towers, creating steam that moves turbines and produces enough emissions-free electricity to power 140,000 homes, or about 392-megawatts.

Though Ivanpah is an engineering marvel, experts doubt more plants like it will be built in California. Other solar technologies are now far cheaper than solar thermal, federal guarantees for renewable energy projects have dried up, and natural gas-fired plants are much cheaper to build.

From a distance, the mirrors - known as heliostats - look like a pristine lake rising from the desert. Ivanpah, about four times larger than New York City's Central Park, can even be seen from the International Space Station.

The Ivanpah plant was partially backed by a $1.6 billion loan guarantee from the U.S. Department of Energy, the same controversial program that supported failed solar panel maker Solyndra.

The opening of the Ivanpah plant marks a big step in federal and state renewable energy efforts, but government funds for such projects under President Barack Obama have been largely tapped out.

That means the private sector must fill the gap at a time when building a natural-gas fired power plant costs about $1,000 per megawatt, a fraction of the $5,500 per megawatt that Ivanpah cost.

"Our job was to kickstart the demonstration of these different technologies," Energy Secretary Ernest Moniz said in an interview high up on one of the plant's three towers.


The solar market has changed dramatically since Ivanpah was approved by California regulators in 2010.

Traditional solar panels, based on photovoltaic technology that uses the sun's light to generate electricity, have undergone a massive drop in price in the last few years, leaving solar thermal far costlier.

Ivanpah developer BrightSource Energy Inc has failed to secure a permit for any other solar thermal projects in California in part due to environmental concerns, including fears that the intense heat and energy around its plants would harm or kill desert birds.

Ivanpah is jointly owned by privately-held BrightSource, power plant owner NRG Energy Inc and Google Inc.

Aside from Ivanpah, NRG has invested in two other massive, government-backed solar power plants in the U.S. West, but said smaller photovoltaic (PV) solar panel installations are the future of the industry as it shifts toward distributed generation on rooftops and away from large solar farms.

"There's no doubt that in terms of price competitiveness solar photovoltaic is cheaper," NRG Chief Executive David Crane. "What really gets me excited in the morning is that there are 50 million American buildings that should have solar PV on them."

Solar thermal projects like Ivanpah are more likely to crop up overseas in places like India, where land and sun are plentiful and cheap natural gas is not abundant as it is in the United States, said Andy Gillespie, project manager for Bechtel, the engineering and construction contractor for Ivanpah.

Late last year, Oakland-based BrightSource said it would focus increasingly on markets outside the United States and in using its technology for industrial applications like enhanced oil recovery, desalination and augmenting existing fossil fuel power plants. The market for solar thermal power will reach 30 gigawatts globally by 2020, up from 2.5 GW at the end of 2012, BrightSource said at the time.

"We will have failed as a company if the last project we build is Ivanpah," BrightSource CEO David Ramm said at the plant's opening.

BrightSource is more than 20 percent owned by French power equipment maker Alstom SA. Other investors include venture capital firms VantagePoint Capital Partners and DBL Investors, Goldman Sachs Inc GS.N, Chevron Technology Ventures and BP Ventures.

(Reporting by Rory Carroll in Ivanpah Dry Lake and Nichola Groom in Los Angeles; Editing by Terry Wade and Marguerita Choy)