Is ‘ocean thermal’ power ready for its day in the sun?
Posted on February 11th, 2009Saqib Rahim, E&E reporter
Climatewire: HONOLULU, Hawaii — Ted Johnson has flown to Hawaii so many times he can’t even put a number on it. Like most visitors, he checks into a beach hotel and unpacks a loose-fitting Hawaiian T-shirt, the kind that the islands are known for. There’s a label over his breast pocket: “OTEC.”
Johnson isn’t here for a sunny vacation. He’s laying the groundwork for a project his company, Lockheed Martin, is plying on this island, Oahu. It’s an “ocean thermal” power plant, an attempt to generate power by reaping the temperature difference between Hawaii’s famously balmy surface water and the ocean’s chilly depths.
If it works, Johnson says, it would be the perfect renewable energy source: constant, inexhaustible and zero-emission. Using the warm waters surrounding the islands, it could easily power Hawaii. And it could yield fresh water, nutrients for fertilizer and even hydrogen to use in fuel cells.
So Johnson doesn’t pull any punches when he describes his hopes. “What is the ultimate solution to our energy problems? The ultimate solution is OTEC,” he says.
This isn’t the first time someone has sought energy’s Holy Grail in the ocean’s warm shallows. Engineers have known of ocean thermal energy technology, or OTEC, for more than a hundred years. Over that century, efforts to prove its viability have been hobbled by bad planning and bad luck, leaving a technology of high hopes to await its time once more.
A cadre of OTEC supporters, many of them involved with America’s first effort in the 1970s, is watching Johnson’s effort. The stars seem aligned this time, some say, as energy prices are high, climate fears are growing, and Hawaii has set an aggressive renewable-energy target. They don’t question whether a company with Lockheed’s reputation can build a 10-megawatt pilot plant off Oahu’s shore.
A long trail of trials
But for a technology that seemed sure-fire to so many for so long, few are expecting tomorrow to be OTEC’s day in the sun.
The basics are well-accepted. With 23 million square miles of surface area — 70 percent of the Earth — the ocean is the world’s biggest sunbather. The amount of heat it absorbs each day is equal to burning hundreds of billions of oil barrels. Tapping into even one-tenth of a percent of that energy, the National Renewable Energy Laboratory says, would yield 20 times as much electricity as the United States uses in a day.
Engineers have two main ways to mine this resource. In the first, hot surface water is pumped from the ocean and used to heat a working fluid that boils at low temperatures. As the vapor expands, it pushes a turbine to generate electricity. Then exposing the vapor to cold deep-ocean water turns it back into fluid, ready to be boiled again.
The second way is called “open-cycle,” and it can make more than electricity. Warm, salty water is piped into a vacuum, where it becomes water vapor and turns a turbine, generating power. When it meets cold ocean water, it becomes fluid again — but since the salt was lost during boiling, the process has a side-product of fresh water.
In either case, OTEC offers something that few renewable resources can — baseload power. While wind and solar are known to be fickle, ocean thermal backers say it can provide hundreds of megawatts every minute of the day.
Making these processes work, though, requires a large temperature difference between the ocean surface and the depths. The spread is about 36 degrees Fahrenheit, and it can’t be found just anywhere: The best-suited regions are in a band 20 degrees latitude north or south of the equator. That describes Hawaii, where most of the world’s major OTEC demonstrations have taken place.
‘Edison of France’ fizzles in Cuba and Brazil
It also describes Cuba and Brazil, which were home to the first ill-fated OTEC efforts 70 years ago. They were proposed by Georges Claude, an eccentric inventor whom some called the “Edison of France” for inventing the neon light near the turn of the 20th century.
Intrigued by ocean power’s massive potential, Claude dedicated his personal fortune to showing it was possible to harness. But the inventor’s eagerness eventually took hold of him. An effort in 1930 on Cuba’s north shore was hindered by technical errors and pummeling storms. The result was a plant that spent more energy pumping up the water than it generated.
Undaunted, Claude pursued another project off the coast of Brazil. It would be a floating power plant, its thousand-foot pipe dangling from a barge. But Claude’s vision was beyond the ocean-engineering knowledge of the day. Bankrupted by storms and technical flaws, Claude had to abandon the project in 1935. He returned to France, where, as a Nazi sympathizer, he would be arrested after the war.
OTEC drew little attention until the 1970s oil crisis. With Washington growing more aware of the country’s energy conundrum, Lockheed and Hawaii set up a tiny pilot plant on board a Navy barge, a mile off the big island of Hawaii, in 1979. “Mini-OTEC” produced a meager 15 kilowatts, but within months, Congress had authorized funds for more research.
Slumping oil prices stop Navy-Lockheed venture
Then oil prices dropped. Ted Johnson wasn’t with Lockheed yet — he would join in 1988 to continue work on mini-OTEC — but he remembers what that did to the technology. “All the research, all the government money, stopped.”
OTEC research didn’t completely disappear over the next 25 years of the cheap-oil era. Engineers continued to make advances where Georges Claude had failed: better turbines, better pipes, better models of the ocean’s movements. But none came any closer to delivering OTEC’s promise of reliable power in the hundreds of megawatts, enough to supply a population with massive energy needs.
Then, a couple years ago, oil prices began their drastic upswing. Johnson and his Lockheed colleagues, some of whom had worked on the 1979 project, began to dig up their old files. “We didn’t turn up the flame on this thing until a couple years ago,” he says.
Now his phone is ringing. Puerto Rico and Florida, whose waters may fit the bill, have called. A U.S. Navy project, testing OTEC for use on warships, has caught the attention of India. “I’m getting interest from all over the world on this thing,” he says.
Poor countries, especially, find OTEC’s many uses appealing, Johnson says. The fresh water from OTEC’s open cycle could be used for farming, not just for land crops but also for seafood. Biomass sucked up from the ocean floor, like algae or kelp, could be used to make cheap biofuels. Ammonia extracted from the water could be used in fertilizer. “It’s really, I think, the game-changer in energy, can really do good in the world,” Johnson says.
A puzzle that may be ready for final assembly
As Georges Claude might warn, there’s just one hurdle left: executing the project.
Johnson is confident. “The technology’s really been proven,” he says, likening it to everyday devices like refrigerators and heat pumps.
OTEC experts agree. In the 70 years since Claude’s failures, they say, new discoveries and methods have come to light, making his vision more robust. Offshore oil drilling, for example, has gained ample experience with Claude’s bogeyman, the cold-water pipe.
What remains, Johnson says, is for someone to put it all together. Lockheed won’t put its name on something that isn’t held to the highest engineering standards, he says. But he retreats from specifics, explaining that it’s “kind of a proprietary project.”
Johnson’s visit to Hawaii comes in late January, when gas prices are sagging below $2.50 per gallon — a bargain in this oil-starved state. Energy observers here say there’s every reason to think renewable energy will survive the dip. There’s the stinging memory of gas prices that reached $5 and $6 per gallon. There’s the memory of how OTEC starved when cheap oil came to roost. There’s the urgency of climate change and the islands’ impending laws to promote renewable energy.
And there’s the ocean, thrashing and timeless. Johnson gazes out at the water as it welcomes another perfect Hawaiian sunset. A breeze flutters his collar. “This is it,” he says. “I think we learned our lesson the first time. We’re going to stick to it.”