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Offshore Wind Turbines Keep Growing in Size

Mammoth wind turbines may soon dot the shallow coastal seas of the world



Photograph by phault, courtesy Flickr

Whipped by winds exceeding 90 mph and battered by 15-foot waves, hundreds of wind turbines produce electricity off the coast of the North Sea and send it onshore to power homes and businesses in the United Kingdom, Germany and Denmark. Thousands more will be erected in the next 15 years, and bigger will be better as far as turbine makers are concerned.

The top offshore turbine makers, Vestas and Siemens, are preparing for rapid market growth and are developing 7-megawatt and 6 MW turbines, respectively. And General Electric Co. is working on a turbine that could be as big as 15 MW -- five times larger than existing offshore machines.

There's big money to be made in the North Sea, where the U.K. government aims to install 32 gigawatts in offshore wind capacity in its third licensing round between 2015 and 2025. That's more than 10 times the offshore capacity currently installed in the entire world. The U.K. Carbon Trust estimates the offshore wind market will be worth $52 billion by 2020.

"The opportunities in the wind industry are enormous," said Finn Strøm Madsen, president of Vestas Technology R&D. "It's a technology-driven business. From a research and development perspective, it is a very interesting area. Vestas is spending 5.5 percent of its revenue on research and development, which is comparable with Airbus or Boeing."

The 7 MW Vestas V164 turbine has more than double the capacity of the biggest offshore machines today, which are 3 MW. It weighs 800 tons without taking into account the underwater foundation, and its 164-meter (538-foot) rotor sweeps an area three times the size of a football field.

"This is a dramatic technology development because the rotor is so much bigger than anything on the market today," Madsen said. "The control systems and the software are totally new, and the control mechanisms are very sophisticated and advanced compared with existing wind turbines. The blade shape is different and much more efficient. Overall, it drives down the cost of energy by about 40 percent, which is a very important parameter for our customers."

The technical challenge, though, remains daunting.

"These products are standing outside for 25 years, and the speed of the tip of the blade on the V164 is 320 kph [199 mph]" Madsen said. "Nothing else on this planet is experiencing the same enormous stress as this turbine. It's very different from an airplane, which flies 15 hours and then lands again to be serviced. You don't take a turbine down for months."

Bigger is cheaper, but more complex
Bigger turbines generate electricity at a lower cost per kilowatt-hour. Taller is also better because wind speed and consistency increase with altitude. So offshore, you want as big a turbine as possible, with as big a rotor as possible that will run longer. That's impossible onshore, where manufacturers are constrained by the size of roads and bridges over which the turbine parts will have to be transported.

"Producing electricity with wind offshore is more expensive than onshore, just due to the complexity of it," Madsen explained. "This new turbine is dramatically more efficient, so it's narrowing the gap but still not closing it. The cost of energy is still cheaper onshore."

On the other hand, offshore parks generate more power than those on land because winds blow 40 percent more often at sea, according to the European Wind Energy Association.

While Vestas won't have a prototype ready for the V164 until next year, Siemens is already testing its first 6 MW turbine offshore from Denmark, and serial production is expected to begin in 2014.

Aside from the different capacities, the two rival manufacturers are also betting on different technologies. The Vestas machine will be a conventional geared turbine, while the Siemens one operates with direct drive.

In a conventional geared turbine, the rotor turns a large gear, which turns a smaller one, which turns the generator. With direct drive, the turbine directly turns the generator at the same speed as the blades. The generator converts the mechanical energy generated by the blades into usable electrical power. How effective the generator is directly affects how much wind can be converted into electric power. Today, most wind turbines have generators connected to a gearbox.

Several turbine makers sell direct drive machines onshore. Siemens itself has two models. Germany's Enercon is the only company to succeed with a direct-drive turbine so far, but its models are only built for onshore installation.

Vestas looked into using direct drive on the V164 but decided against it. The company says a geared solution is more efficient, uses a lot less rare earth materials and will need to be serviced less often compared with a direct drive turbine. On the other hand, direct drive weighs less.

While in the past the gearbox was the main cause of turbine failures in the industry, now it is electrical systems. And a direct drive turbine has to have four times more electrical components than a geared turbine, which would increase the chance of a malfunction.

It's not only expensive to send technicians to repair turbines at sea, but also physically impossible during bad weather. And a turbine that is not running is costing its operator a lot of cash in energy that it is unable to produce. Siemens says its direct drive machine will require less maintenance than existing models.

Offshore wind turbines cost much more to install and maintain than onshore ones, so reliability is paramount. The machines require special ships to anchor the turbine foundations and build the towers. The Siemens 6 MW prototype even has a helicopter-hoisting platform integrated in the back of the nacelle to allow easy access for service technicians.

GE enters the turbine power race
GE announced last month that it had begun a two-year project to develop a direct drive wind turbine as big as 10 to 15 MW using superconducting magnets. The project received a $3 million subsidy from the U.S. Department of Energy.

"With the industry's desire for higher-megawatt machines to maximize clean wind power opportunities in the U.S. and around the globe, new technologies will be needed to support larger-scale wind platforms," said Keith Longtin, wind technology leader at GE Global Research. "The key challenge will be delivering solutions that achieve the right scale and cost."

GE has experience with superconducting magnets from magnetic resonance imaging (MRI) applications in its health-care equipment business. "For MRI systems, we're applying superconducting magnets to make lower-cost systems with higher image quality," Longtin said. "For wind turbines, we want to apply them to generate more wind power at a lower cost of electricity. The applications are different, but the basic technology is the same."

Geared turbines are extremely effective today, but they will incur higher costs as they are scaled up to larger wind platforms because of additional weight and maintenance needs, Longtin said. The additional power will come with an increase in the cost of electricity, he said, explaining why GE is betting on direct drive. GE did not give an expected date for when it would have a new turbine ready to sell to customers.

Meanwhile, DONG Energy, the world's biggest operator of offshore wind farms, will test both the Vestas and the Siemens models.

"According to our discussions with DONG, the new turbine from Vestas seems to be the best offshore offering on the market at present," said Patrik Setterberg, a senior analyst at Nordea Bank. "This turbine will be very hard to overlook if it delivers what it promises. However, DONG emphasized that everything depends on the performance of the prototypes. A new offshore turbine is a must for Vestas if it wants to keep its leading market position."

Vestas installed 60 percent of the offshore wind turbines erected last year in Europe, while Siemens had 35 percent of the market. But the German company has continued to pick up orders in Europe, while Vestas has said it won't install any offshore turbines this year in the region. Siemens will supply turbines to Cape Wind, off Cape Cod, Mass., the first American offshore wind farm. It has not yet signed any firm contracts for its direct drive model.

"Vestas will now have the largest and most efficient offshore turbine ahead of the U.K. round three," Setterberg said. He estimated Vestas will need at least two new factories to produce the V164 -- one for blades and one for nacelles. In its expansion in the United States, Vestas built four plants in Colorado, betting the demand would materialize, then had to temporarily lay off workers there at the height of the financial crisis.

By contrast, the company says it won't build the V164 plants until it has a pipeline of firm orders for the larger turbine.

Vestas wants a reasonable amount of certainty that the market for its V164 will be there when mass production begins in 2015. That means a feed-in tariff for offshore wind in the United Kingdom, improvements on the grid that would take the wind energy produced in the North Sea to the rest of Europe, and operators' making progress on securing permits for the offshore wind farms.

Chinese and South Korean companies will also compete
There will be offshore wind opportunities also in Germany, which needs to increase its renewable energy output as it phases out all its nuclear power plants by 2022. A smaller German wind turbine maker, Nordex, is also working on a 6 MW offshore turbine.

Germany plans offshore wind parks totaling 25 GW by 2030, which would be the equivalent of 20 nuclear reactors, but so far the effort has gotten off to a slow start. The German grid needs big investments before it can support significant wind energy from the North Sea. To protect coastlines and tidal flats, Germany requires wind turbines to be located as far offshore as 40 kilometers (25 miles).

This means the turbines must be installed in water as deep as 160 feet, unlike in Denmark or the United Kingdom, where they can be placed in shallow waters within view of the mainland. Some environmental groups worried about the effect of construction noises on porpoises are lobbying for construction to be halted between May and August -- exactly the time of the year with the most auspicious weather for installing offshore turbines.

Vestas, Siemens and Nordex will see tough competition coming from South Korea, where shipbuilder powerhouses Samsung, Daewoo and Hyundai are making a push to expand into wind. Samsung is building a wind turbine factory near one of its shipyards in South Korea. Daewoo bought turbine maker DeWind and is building a plant in Canada. Hyundai is developing a 5.5 MW offshore turbine and is considering making a 10 MW machine. It may open factories in the United States and South America.

The three Korean companies' fledgling wind businesses could get a significant boost from their government, which will invest $8.4 billion in a 2.5 GW offshore wind farm, Asia's largest. Bidding will take place next year, with Samsung, Daewoo and Hyundai likely to tout their experience with building oil rigs and laying underwater pipelines, even though they have yet to supply any offshore wind turbines. Foreign companies will be barred from bidding.

Chinese wind turbine markers are also eyeing the offshore market. Goldwind and Sinovel are working on 6 MW turbines, while Shanghai Electric is developing a 5 MW machine. Their current products are technically inferior to those of Siemens or Vestas, but they're learning fast, and they have a cost advantage due to cheaper labor and financing. China already makes more electricity from wind than any other country.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500

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