While hardly a catch phrase in the government's multi-billion-dollar energy technology sweepstakes, OTEC - Ocean Thermal Electric Conversion - has evolved quietly to where it can be counted on to produce solar-generated electricity at commerical rates in the mid-1980s.

That at least is the judgment of senior Energy Department officials, Lockheed, Bechtel, TRW and other industrial giants urging Congress and the Carter administration to spend tens of millions of dollars on an OTEC demonstration plant.

They are not alone. Last year, the President's Council on Environmental Quality projected that OTEC could generate the equivalent of 1 quadrillion to 3 quadrillion BTUs (quads) by the year 2000 compared with the 3 quads that the nation today gets from hydroelectric power.

OTEC utilizes the temperature differences between warm ocean surface water and cold subsurface water pumped through an almost totally submerged 7-story pipe to form steam and power a turbine.

From the tower, which is tethered to the ocean floor, electrical current is transmitted ashore by submarine cable into the electrical grid.

OTEC is simply an engine that draws on the ocean's heat. It is based on concepts formulated in 1881 by Jacques d'Arsonval, a French scientist.

"What we really have is a very rudimentary power plant, with low temperatures and low pressures," said the Energy Department's Robert Cohen, adding, "It's not that exotic." Cohen and others such as Lockheed's James Wenzel also say that OTEC draws largely on off-the-shelf technology and many of the same engineering principals utilized in building offshore oil rigs.

Most important of all, however, OTECuses solar energy, requiring no oil, natural gas or coal to generate electricity.

Still another positive point is that OTEC is one of the few solar technologies under consideration by DOE that can be used in the near term to generate electricity on a large-scale basis.

Not everyone is unabashedly optimistic.Energy Secretary James R. Schlesinger is said to have expressed "nothing more than a distracted interest," according to administration officials. And, on Capitol Hill, a seenior Senate aide dismisses it out of hand as "pork barrel for the aerospace companies who designed Skylab."

Although OTEC is one of the few solar technologies that promises early commercial-scale operations, it receives the smallest share - about $33 million - of the 8 solar technologies funded in DOE's budget of nearly $600 million.

Part of the reason for this is that OTEC has a limited political consitutency due to its limited regional application. Congressmen outside of the Gulf Coast states, Puerto Rico and Hawaii see little gain from funding OTEC research or demonstration projects.

Still, another drawback is that OTEC's political fortunes have not benefited from the emerging power of the sprawling solar lobby. "All the (OTEC) pipes and aerospace companies (OTEC contractors) simply spook the Small-is-Beautiful People," says one scientist working on a DOE-funded OTEC project.

DOE's Cohen is quick to admit there are some obstacles. "We have a perception gap in OTEC; there are still a lot of misconceptions that have to be overcome," he said.

This doesn't mean there hasn't been fierce lobbying. CAPTION: Picture, Ocean Thermal Energy Conversion plant built on cold-water pipe tethered to the ocean floor includes above-water living quaters for the crew. Warm surface waters turn a fluid such as ammonia or propane into a vapor that expands, turning a turbine that drives an electric generator. Exposure to cool deep-sea water turns the vapor back into a liquid so it can be reused in the process. Lockheed Missiles & Space Co.