Ocean thermal energy’s big selling point is that it’s always on, and it’s always available. “Once you get the system going, it runs twenty-four/seven,” says Harry Jackson, president of Ocean Engineering and Energy Systems (OCEES), a company based in Honolulu, Hawaii, that designs OTEC plants. It’s consistent because the oceans act like a giant battery, storing up sunlight. “As an alternative energy source, it’s one of the few to provide baseload power,” says Reb Bellinger, vice president of Makai Ocean Engineering, also based in Honolulu, a firm that designs deep water pipes for OTEC.

The oceans’ thermal energy can be effectively harnessed wherever the temperature difference between the warm surface water and the cold deep water is at least 20°C — which covers about one-third of oceans’ area. OTEC’s major downside, however, is that most of the resource is marooned far from land and far from people. But scores of specially outfitted ships could float in the open ocean, grazing on the energy and using it to synthesize fuels and chemicals that get shipped to shore — a futuristic dream that could be the key to unlocking the technology’s potential.

Trial Niche

It won’t be easy. Even a simple test of OTEC, if it’s realistic, requires a huge system. “Unlike other renewables, it cannot be tested in small sizes,” says Girard Nihous of the Hawaii Natural Energy Institute. For one thing, even a proof-of-concept power plant still needs a wide pipe that reaches about a kilometer deep into the ocean. The up-front capital costs are also high, partly because of the sheer scale but also because of the difficulty of working with the sea. These systems have to contend with corrosive salt water and a slime of microorganisms that can grow inside the plumbing and clog it up. Violent weather can wreak havoc with the long cold-water pipes, especially if a storm hits when they’re in the midst of being installed. “The part that brings the risk is the ocean engineering,” Nihous says.

These obstacles have deep-sixed all efforts to date to build a practical OTEC system, though engineers have been trying for over a hundred years. Since the five-year run of an experimental plant in Hawaii ended in 1998, there hasn’t been a functioning OTEC plant anywhere in the world. However, several new plants are in various states of planning and the first could be switched on as soon as 2012.

That could be the plant the U.S. Navy has commissioned for its remote base on the island of Diego Garcia, in the middle of the Indian Ocean. The 8-megawatt plant — about 40 times bigger than any built so far — would float on a platform like those used for offshore oil drilling, about five kilometers from the coast. As a byproduct of the process of creating electricity, it would also desalinate nearly 5 million liters of drinkable water each day. “This is the first commercial project,” says Jackson of OCEES, the firm designing the plant. “A lot of people are watching to see how that goes. I think we’re going to learn a lot in this first project, and the technology will advance extremely fast.”

The base in Diego Garcia is now powered almost entirely by diesel fuel brought in by tanker. “There’s definitely an energy security issue,” says Christopher Tindal of the Navy’s Energy Policy Office. “Also, because of the price of energy these days, it’s prudent to go with alternative energy.” The new OTEC plant will save the Navy $290 million over 30 years, according to OCEES’s estimates — and that’s the main reason the Navy is going for it. “We won’t pay more for green power than for brown power,” Tindal says. “Any of the renewable projects we’re doing have to be cost-effective.” Getting the first commercial plant installed will be a major milestone, according to all the players in this field. “This is the golden egg,” as Tindal puts it. “Whether the Navy does it, or whether Lockheed Martin does it first, it doesn’t matter. I think it’s a wonderful concept.”

Other plants are in the works as well. The U.S. Navy is exploring the feasibility of an OTEC plant for its base on Guam, a South Pacific island. In November, the state of Hawaii concluded a deal with the Taiwan Industrial Technology Research Institute and Lockheed Martin that could pave the way for a 10-megawatt OTEC plant there. And the National Energy Laboratory of Hawaii Authority (NELHA) is also looking for companies interested in building an OTEC plant. “We’re issuing a request for proposals to build a 1-megawatt OTEC scale-up plant,” says Ronald Baird, NELHA’s chief executive officer. “The last one [at this site] was about 200 kilowatts, so this is five times bigger.”

Baird argues that OTEC is ideal for remote tropical islands like Hawaii, which gets over 90 percent of its energy from imported fossil fuels. “And our major sources of imported petroleum are very stable countries — Vietnam, Iraq, Iran, Yemen,” he adds sarcastically. “Hawaii’s electricity price is 44 cents per kilowat-thour — the highest in the U.S., and probably one of the highest electricity costs in the world.” But with a 1-megawatt OTEC plant, he said, the cost would be about half that, 22 cents per kilowatthour.

Serving this niche market of remote islands, where energy and drinking water are at a premium, could help OTEC get over a hump and move toward more widespread application, many of the technology’s supporters hope. “Great hope has been placed in military-controlled small islands, because the Department of Defense of the United States is richer than most countries, and they have discretion to do things that others can’t,” Nihous says. “So it makes sense to approach OTEC development this way.”

In part 3 of this series, we’ll explore other benfits of OTEC.

Mason Inman is a freelance science journalist currently based in Karachi, Pakistan.

This article originally appeared in World Watch Magazine May/June 2009 and is reprinted by permission.

But these words were actually spoken nearly 30 years ago in a video showing the deployment of a vast plastic pipe, first snaking along a Hawaiian beach and then being towed out to sea. This pipe was a crucial part of the first power plant of its kind to tap into the energy in the seas, through a process called ocean thermal energy conversion.

In 1979, when this power plant was built, oil prices were near an all-time high and the United States had been searching for alternative sources of energy for almost a decade. The main goal then was energy independence: U.S. policymakers wanted to ensure the country’s energy supply rather than rely on oil bought from hostile countries.

“We might very well have had a fleet of ocean thermal plants by now,” says Robert Cohen, who in the 1970s was the first manager of the U.S. Department of Energy’s research on ocean thermal energy. “We were headed toward that under the Nixon, Ford, and Carter administrations. But the Reagan administration was not friendly to renewables, especially ocean thermal. They pulled the rug on our funding.” Since then, plans for harnessing this technology have lain largely dormant. As Cohen puts it, “It’s become an orphan technology.”

But now the orphan is finally being adopted. With growing awareness of the vast amounts of clean energy that the planet needs to keep the global economy spinning while avoiding a climate catastrophe, companies and governments are again at work on harnessing ocean thermal energy. But this time these efforts are backed by new technologies—many from a seemingly unlikely sector, the offshore oil industry—that may finally make it practical and affordable. “Ocean thermal could become a big source, possibly the biggest global source of renewable energy,” Cohen says.

Estimates of the size of this energy source vary widely, but even a conservative tally figures it could sustainably produce more electricity than the whole world consumes today. The technology has some spin-offs that are already commercially viable, and others that could become so soon, including low-cost air conditioning for buildings, desalination for turning seawater into drinking water, and fish farms fed by the nutrient-rich water from the deep.

But ocean thermal energy conversion (OTEC) still has to prove itself. So far it has been tested only in small pilot projects, and no one has built a commercial power plant. Now, with a few plants in various stages of planning, OTEC may finally get a shot at competing with other sources of clean energy (such as solar, wind, geothermal, and tidal) to show whether it can match up, or even beat them.

Simply Difficult

In some ways, harnessing ocean thermal energy requires only the simplest of gadgetry: plastic and metal plumbing for carrying the water and exchanging heat between the warm and cold streams, and turbines for generating electricity. Yet in practice, building a robust power plant — one that can stand up to corrosive salt water, hurricanes, and microbial scum that seems to grow everywhere — requires a lot of ingenuity, patience, and money. Gérard Nihous, an ocean engineer at the Hawaii Natural Energy Institute, says, “The principle is elementary, but the practical application is a headache.”

The energy behind OTEC is sunlight. The oceans’ surface waters absorb it in prodigious amounts and store the energy as heat. In hurricanes, cyclones, and typhoons, this pent-up heat comes pouring back out in spiraling convulsions of wind and rain. To harness the energy for useful ends, OTEC systems need not just heat, but a way to make that heat move in a controlled way. That’s where one of the great challenges of ocean thermal energy conversion comes in: it requires large amounts of cold water as well. OTEC systems tap into a store of cold water that’s available around the world (see map, below).

“Here in Hawaii, it’s miraculous that if I drop a few hundred meters, it is so cold,” Nihous says. “It shouldn’t be. It’s only because of this deep circulation,” a vast current that winds around the whole globe, known as the great ocean conveyor. By sticking a very long pipe down into the conveyor’s depths, its cold water can be pumped up to the surface. When the cold and warm water are piped separately through a device called a heat engine — basically, a refrigerator that runs in reverse — it generates electricity.

The most likely way of doing this is the so-called closed system, in which the stream of warm surface water flows past a system of tubes containing some kind of refrigerant — a liquid that boils somewhere close to room temperature, such as ammonia. Shallow water in the tropics is warm enough to boil the refrigerant, producing a jet of vapor that pushes through a turbine, spinning it to generate electricity. Then the cold, deep-ocean water runs past the vaporized refrigerant to cool it and turn it back into a liquid, recycling it so it can run through the device again and again.

But to get much juice out of a system like this requires veritable rivers of both warm and cold water. A 100-megawatt OTEC plant (about one-tenth the size of a typical coal-fired power plant) would need several thousand liters of water flowing through it per second. According to Nihous’s estimates, producing electricity at the rate it’s used worldwide today — about 2 terawatts, or 2 trillion watts — would require a flow of cold water more than 10 times greater than that coursing down all of the world’s rivers combined. And in the future, if development continues at the current fast pace and the world moves from dirty fuels to green energy, we’ll need dozens of terawatts of clean electricity.

In part 2 of this article, we’ll look at some pilot OTEC installations around the globe.

Mason Inman is a freelance science journalist currently based in Karachi, Pakistan.

This article originally appeared in World Watch Magazine May/June 2009 and is reprinted by permission.

• Maseeh Rahman in New Delhi


• guardian.co.uk, Tuesday 4 August 2009 18.01 BST


• Article history

• From BusinessGreen.com, part of the Guardian Environment Network


• guardian.co.uk, Thursday 30 July 2009 11.59 BST


• Article history

• Tim Webb


• guardian.co.uk, Sunday 2 August 2009 19.29 BST


• Article history

The new zero-emission electric vehicle, Leaf, during the opening ceremony of the new Nissan headquaters in Yokohama on Sunday. Photograph: Kiyoshi Ota/Getty Images

Nissan has unveiled what it claims to be the world’s first mass-market electric car — a five-door hatchback called Leaf which its Sunderland plant is vying to build for the European market.

The family-sized car, which has a maximum range of 100 miles and a top speed of about 90mph, will be in showrooms in Britain, Europe, the US and Japan by the end of next year.

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The Leaf is the first of Nissan’s new range of fully electric powered cars, which produce no carbon emissions, unlike hybrid vehicles such as the Toyota Prius, which uses a petrol-powered engine as well as an electric battery. Nissan’s range of electric cars will include small, medium-sized and large saloon cars.

A Nissan spokeswoman would not disclose how much the Leaf would cost consumers, other than to say it would be similarly priced to other family-sized cars in the £10,000-£15,000 bracket. This excludes the cost of the electric battery, which drivers would have to buy at a cost of several thousands pounds, or lease for a monthly fee.

The Japanese carmaker announced last month that it had selected its Sunderland plant to make lithium-ion batteries for the European market at a new £200m factory. But the north-east plant is also bidding to make the cars. The factory is up against plants in France, Spain and Portugal also owned by Nissan and its French partner Renault.

Nissan is in discussions with the British government about what financial support could be offered because the economics of making electric cars on a large scale are unproved. The European Investment Bank has already offered the company a €400m (£340m) loan to build environmentally friendly cars in Europe but this needs to be guaranteed by the government for the UK to get a slice of production.

Business secretary Lord Mandelson has assembled a £2.3bn package of loan guarantees for the car industry but none have been extended yet, despite growing frustration from companies.

Nissan hopes that the Leaf will become the world’s first truly mass-market electric car. Unlike its Japanese rival Toyota, which makes the hugely popular Prius, Nissan is focusing its energies and investment on “pure electric” cars.

Electric cars currently on the market have a niche appeal with motorists put off by their limited range, size and speed. The tiny G-Wiz in Britain, for example, has been popular among commuters in large cities such as London, where it is exempt from the congestion charge. But even the latest model has a speed limit of only 51mph and a maximum range of 70 miles before it needs recharging, limiting its use.

High performance electric cars are prohibitively expensive. Tesla Motors, maker of the Tesla Roadster, has spent years trying to get costs down to about $100,000 (£60,000) for each sports car.

The Leaf car battery can be charged to 80% capacity in about 20 minutes, compared with almost three and a half hours needed for the G-Wiz. The first batch of cars, primarily for the Asian and North American markets, will be made in Japan and the US.

Miliband, an up-and-coming politician in the cabinet of besieged Prime Minister Gordon Brown, has done what was once unthinkable, put a British stamp of approval on feed-in tariffs as a policy mechanism for developing renewable energy.

The move has potentially far reaching ramifications in the English speaking world where there has been reluctance to use full-fledged systems of feed-in tariffs, sometimes on ideological grounds. Now that Britain, Ontario, and South Africa, two of Britain’s former colonies, have definitively moved toward implementing sophisticated feed-in tariff programs, there may be less reticence to do so elsewhere in the Anglophone world.

Of course, like politicians everywhere, Miliband had to rebrand feed-in tariffs to something more to his liking. His “clean energy cash back” creates yet another term for what everyone else calls, sometimes grudgingly, feed-in tariffs.

Nevertheless, the program’s designers took their task seriously and didn’t opt for a system of faux or false feed-in tariffs, what North American campaigners have begun derisively calling FITINOs, feed-in tariffs in name only.

The British proposal has also contributed several innovative new twists on feed-in tariff design that will mark the program as “made in the United Kingdom”.

One new feature is the inclusion of tariffs for Combined Heat & Power (CHP). While not a first, it is one of the few programs to do so. Another feature of the proposed program is a distinct tariff for small solar PV systems on new homes, and a separate tariff for existing homes.

Most significantly, program designers have included a mechanism to encourage homeowners and small businesses to reduce their electricity consumption. For example, a solar PV generator will be paid for all their generation. However, they will receive a bonus, currently at £0.05/kWh ($0.08 USD/kWh, $0.09 CAD/kWh), for electricity delivered to the grid over and above their domestic consumption. Thus, if a homeowner is able to cut their domestic consumption, and sell more electricity to the grid as a result, they are paid the bonus on top of the posted feed-in tariff.

The proposed program, like the successful programs it was modeled after, was designed to “set tariffs at a level to encourage investment in small scale low carbon generation.” This is in contrast to faux feed-in tariffs that set the tariffs on the “value” of renewable energy to the system as in the California Public Utility Commission’s largely ineffective program.

British designers were instructed to calculate tariffs not on ideology or economic theory but on the tariffs needed so “that a reasonable return can be expected for appropriately sited technologies” to meet the country’s renewable energy and carbon mitigation targets.

Unfortunately, the program’s targets are timid at best, two percent of Britain’s electricity consumption by 2020, and the tariffs are limited by law to projects less than 5 MW to protect the country’s stumbling Renewable Obligation, the preferred mechanism for developing larger projects.

The two percent target requires the generation of only 8 billion kWh (TWh) per year. For comparison, Germany generated 40 TWh in 2008 from wind energy and more than 4 TWh from solar PV. France, Britain’s longtime cross-channel rival, generated nearly 6 TWh from wind energy in 2008 from its system of feed-in tariffs.

Some of the proposed tariffs are not competitive with those on the continent, or those in Ontario. “For community-scale or larger on-site projects,” says David Timms, a senior campaigner with Friends of the Earth (UK), “the rates [tariffs] are inadequate.”

The tariff proposed for large wind turbines is low by international standards. Britain has some of the best winds in Europe. Nevertheless, many of the smaller projects that may be built under the feed-in tariff program may not be as advantageously sited as commercial projects under the Renewable Obligation. Consequently, the proposed tariff for wind projects from 500 kW to 5 MW may be insufficient to drive development.

Timms also adds that the “degression for solar PV is quite aggressive” at 7 percent per year and that the bonus payment of £0.05/kWh for export to the grid may not be bankable. Because the bonus payment will fluctuate with the “market price” it won’t necessarily have a fixed value and, consequently, it will be discounted by banks providing debt for projects financed under the feed-in tariff.

If implemented as proposed, though, the British program will offer some of the highest tariffs for small wind energy in the world. The tariffs will rival those in Italy, Israel, Switzerland, and Vermont, possibly reflecting the British government’s belief that it can encourage development of a domestic small wind turbine industry. For example, the tariff proposed for small wind turbines from 1.5 kW to 15 kW is £0.23/kWh ($0.38 USD/kWh, $0.42 CAD/kWh) about that paid in Italy and Israel.

The proposed program also includes a number of anti-gaming provisions to avoid breaking up bigger projects into several small ones to fit within the 5 MW project size cap. These will prevent companies from moving big wind projects from the Renewable Obligation to the feed-in tariff program.

Britain’s feed-in tariff program is expected to begin in early April, 2010 after an extensive consultation. Below is a summary of the program’s key elements.

• Program Cap: 2% of Supply, 8 TWh in 2020
  
• Project Cap: 5 MW
  
• Generator can be green field (doesn’t have to be a metered customer)
  
• Contract Term: 20 years, solar PV 25 years
  
• Program Review: 2013
  
• Costs for the program will be borne by all British ratepayers proportionally

While limited in scope, Britain’s proposed feed-in tariff program is as sophisticated, if not more so, as any proposed in the United States, and will put the country on the world map of innovative renewable energy policy.

Consultation on Renewable Electricity Financial Incentives 2009: Program Details

Consultation on Renewable Electricity Financial Incentives: Background Documents & Reports