For a little-known green technology, ocean thermal energy conversion once enjoyed something of a heyday. OTEC, as it is known, uses the difference in the temperature between the cold bottom and the warmer surface of the sea to generate electricity. In the later years of George W. Bush’s presidency and the early years of the Obama administration, constituencies in both major parties viewed the technology as an answer to their concerns.

For dovish progressives and nationalist conservatives, OTEC showed promise to wean the country from its reliance on coal and Middle Eastern oil. “The technology is still being developed in the laboratory, but if it succeeds on a large scale, it could eventually become an important tool in the nation’s battle against global warming and dependency on foreign oil,” New York Times reporter Kate Galbraith wrote in 2009.

For some environmentalists, OTEC showed more promise than better-known renewal energy technologies. The National Oceanic and Atmospheric Administration, the federal agency that oversees non-military-related maritime policy, boasted of OTEC's superiority to its wind and solar counterparts. OTEC “generates a constant, clean source of electricity,” NOAA wrote. “This constancy differs from the output of renewable resources such as wind and wave energy that sometimes produce intermittent electricity because of weather changes.”

Defense contractor Lockheed Martin has sought to build an OTEC power station for decades, and from 2008 to 2010 the company received repeated public votes of confidence. The firm received at least $14.72 million in federal support to build a 10 megawatt ocean thermal energy conversion pilot plant on Hawaii. Makai Ocean Engineering, a Hawaii-based firm, received funding to help design and develop the plant.

Smaller firms, too, gravitated to OTEC. The Ocean Thermal Energy Corp., a Pennsylvania-based firm, made a deal with the government of the Bahamas to build a fully commercial OTEC plant, according to The Economist, which wrote in 2012 that “the technology may at last come to fruition.”

Ask leaders of the two companies about OTEC today, and they still insist the technology will bear fruit, but that optimism is tempered by new economic realities.

Last month, Marillyn Hewson, the chairman, president, and chief executive officer of Lockheed Martin, termed OTEC a “leading-edge” clean energy technology. Hewson placed the technology ahead of better known technologies such as tidal energy and smart grid solutions. Earlier in the year, Lockheed signed a contract with the Reignwood Group, a private Chinese property developer, to build a 10 megawatt plant off the coast of southern China. The company has said officials expect the station to operate by 2016 or 2017.

James D. Greenberger, director and chief sustainability officer of the Ocean Thermal Energy Corp., said the firm expects to operate a plant that uses a similar technology -- seawater air conditioning -- in the Bahamas in 2016. Greenberger cited a quote from the firm’s executive chairman to emphasize OTEC's enduring appeal: “Many if not most customers in our markets are also driven by the need to have stable long-term predictable energy price … untethered to the on-going volatility of global oil prices. One solution for such customers’ basic needs is OTEC based 24/7 electricity, which will have an unlimited free supply of ‘fuel’ (solar energy stored in ocean surface waters) for as long as the sun heats the oceans.”

Recently, however, both firms have scrapped their more ambitious plans from years ago.

Geneva Greene, a spokeswoman for Lockheed Martin, said the defense contractor no longer works with Makai Ocean Engineering on the taxpayer-funded Hawaii contract. The pilot plant was to open in 2015. Greene referred a reporter to Makai to describe the state of the project. Reached at the office in Hawaii, a company secretary said executives were in meetings all day and could not comment.

Greenberger of the Ocean Thermal Energy Corp. did not mention the company building an OTEC plan in the Bahamas. He referred to a plant that uses seawater air conditioning as its “current lead project” in the Bahamas. (Seawater air conditioning uses one pipe to pull cold water from the ocean to the surface instead of two pipes -- one warm water pipe and one cold water pipe).

Other energy firms, too, have shied away from seeking public funding for OTEC. No companies have filed for a license under the Ocean Thermal Energy Act of 1980, according to NOAA spokesman Ben Sherman.

So why are energy companies dissuaded from pursuing public funding or even seeking to build OTEC?

The large cost of building the enormous pipes is one reason, according to federal officials and some industry representatives.

“OTEC power plants require substantial capital investment upfront,” the Department of Energy wrote in a white paper last August. “OTEC researchers believe private sector firms probably will be unwilling to make the enormous initial investment required to build large-scale plants until the price of fossil fuels increases dramatically or national governments provide financial incentives."

Makai Ocean Engineering, the former partner with Lockheed Martin, acknowledged that building the pipes is no easy feat. “OTEC has long been challenged by high capital costs in a world of cheap energy,” the company wrote on its website. Kerry Kehoe, the former head of OTEC activities at NOAA, told The Economist that building a pipe for a 100 megawatt plant would cost $1 billion. 

In the last 40 years, efforts to build a reliable OTEC power station received their biggest boost when oil prices skyrocketed. The Ocean Thermal Energy Act was created at the tail end of the oil-price shocks of the 1970s. The federal funding from the Bush and Obama administrations came after oil prices skyrocketed in 2007.

Officials with Lockheed Martin and Ocean Thermal Energy Corp. know the public is unlikely to provide public funding for their projects, and if they build an OTEC power station, they will do so alone. Their logic is undeniable. The price of a barrel of crude oil is $67.13. Last December, it was more than $100 a barrel.