Offshore wind technology gets better every year with more innovative turbine and blade designs. But no matter how well they design a wind turbine, engineers perpetually confront the unique difficulties of exporting electricity back to shore.
Subsea power cables are built with the demands of open ocean in mind. Multiple layers of alloy and fiber strengthen and protect the power-conducting cables inside. In the open ocean, far from ship anchors and fishing nets, deep-sea communication cables can last for decades without a fault.
Power cables installed near dry land have it much tougher because they are so much closer to the ocean surface, where turbulent weather and heavy machinery can cause havoc. Indeed, an article at RenewableEnergyFocus.com estimated that export cable damage surged by 500 percent in the past 12 months.
Survivability is the central concern of cable manufacturing because oceans bring peril with every wave. Typhoons, fishing trawlers, corrosion — it’s always something. Here’s a quick look at the key challenges with power cables that export electricity from offshore wind farms:
Finding the Damage
Occasionally, a ship anchor will snag a cable and snap it in two. This is bad news because it shuts off a revenue source for the offshore wind operator, but it could be much worse.
A pure break location is somewhat easy to track down because engineers can measure the resistance in a length of power cable and calculate with a fair degree of precision where the electricity cuts off. Then it’s a matter of sending a ship to the estimated location of the break, pulling up the broken cables and using splicing gear to reconnect them.
The much more daunting challenge happens when a cable starts developing significant losses in transmission — often because the cable was damaged and exposed to the corrosion of seawater. This kind of damage is less likely to leave telltale hints about its location, which can bog down the pace of attempted repairs.
Windfarm designers have figured out how to build towers and turbines that can withstand gale-force winds and furious storms. Unfortunately, the worst weather may damage even the most well-built cables, which requires ships to locate the problem and try to fix it.
Repair crews cannot do their jobs in storms that toss their giant vessels around like corks. So they have to wait for the weather to calm down. It might take days; it might take months.
It’s not unheard of for a ship to be at sea for three months in pursuit of a single repair if severe storms continually blow it off course. There are only so many ships available, and they can fix only so many damaged cables.
Once a repair ship locates a cable problem, it has to pluck the cable from the ocean floor and pull it up to the surface. If all goes well, this process won’t damage the cable even more.
After the damaged area of cable arrives at the surface, the next step is to recondition the broken areas, rejoin any damaged conductors, then seal the assembly with heavy-duty splicing equipment. The techniques for repairing and rejoining subsea power cables are well understood. But repairs are still hostage to the first two problems: finding the cable fault and waiting out the weather.
This is Why Subsea Cable Accessories Must be the Best of the Best
All these challenges give offshore wind operators plenty to worry about. The accessories that attach and connect their power cables should not be another source of anxiety.
At PMI, we aim to provide the most durable, practical subsea power cable accessories on the market. We’re big believers in the promise of offshore wind and other marine renewable power sources, but we’re also realistic about the depth of the challenges facing the industry.
It may turn out that difficult cable repair jobs are the price we have to pay for offshore renewables. If so, we’ll do our part to make sure those fixes stay fixed.
- Damage to Subsea Cables a Huge Risk to Offshore Wind Farms
- Challenges in the Installation and Repair of Offshore Wind Turbines
- Offshore Wind Farms Still Learning How to Handle Cables
- Vision for Offshore Wind Energy Market
The future of the offshore wind market depends on where you’re standing.
- In Europe, the offshore wind market is so well established that new generations of equipment are replacing obsolete machinery.
- In North America, the industry is so new that it exists largely on the drawing boards of offshore-wind developers.
- In Asia, it’s somewhere in the middle as China ramps up its offshore wind capacity.
Installing and maintaining offshore wind turbines is an incredibly complex undertaking full of daunting logistical challenges.
For starters, ships built to install turbines can cost $100 million or more. Stormy weather can delay installations and thwart repairs. Weather and erosion exact a long-term cost on turbine blades, and turbine engines must be painstakingly designed for always on-operation for decades.
Here’s a quick look at some of the difficulties in installation and repairs in offshore wind installations:
Placing a foundation on the sea floor is a sophisticated, highly complex job. A gravity-base foundation uses a large volume of reinforced concrete and must be moved to a carefully prepared spot on the seafloor. All this requires specialized ocean vessels and specific expertise.
Sea floors vary widely around the world. For instance, the sea bed off the coast of China is a lot different than the sea bed of European waters, so foundation expertise gained in Europe might not apply in China — adding to the complexity (and expense) of China’s ambitious offshore-wind agenda.
Once the foundation is installed, it becomes vulnerable to saltwater corrosion and underwater species that attach themselves and may have to be eventually removed at considerable cost.
Longer turbine blades produce much more energy than shorter ones, so the blades keep getting longer and longer as the offshore-wind industry evolves. Obviously, longer blades will create extra complications in transport and installation.
But the bigger challenge is in maintenance. Blades suffer substantial erosion from constant exposure to the wind that decreases their efficiency. They often also suffer lightning strikes that cause considerable damage below the wind-facing surface.
And the manufacturing processes of turbine blades are not completely standardized, so maintenance processes for one kind of blade can be substantially different than those on another variety. This adds to the difficulty of finding and training people to perform maintenance on turbine blades
Turbine engines are large mechanical devices suspended high in the air. Installation is fairly straightforward because the offshore wind industry is so mature in European waters. But it’s still a non-trivial job to install a wind turbine engine in the open ocean because of the usual weather pressures.
Because they run 24 hours a day for years on end, turbine engines must be carefully designed and manufactured to close tolerances to minimize breakdowns. An article in Forbes magazine likened running a wind turbine for 20 years to getting 3 million miles from a car engine.
Turbine engines have lots of moving parts including bearings and gears that eventually wear out. This cannot be entirely avoided, but it can be monitored with increasingly sophisticated computer software that can predict when critical parts will fail, and allow them to be removed before they give out and cause serious damage to the machinery.
The technology for laying transmission cables is mature and the techniques are well understood. At PMI, we’ve been building premium, high-performance subsea cable accessories for decades, so we’ve seen these developments up-close.
The biggest maintenance challenges for transmission cables happen if they get snagged by ship anchors or fishing-trawler equipment, or if they’re damaged in subsea landslides. These mishaps require sending highly trained crews to the site of the break and fashioning a repair at sea. That will always be expensive and time-consuming.
Costs cannot be ignored
Offshore wind remains very expensive to install, maintain and operate. WindEurope (formerly EWEA) reports that offshore wind LCoE must be reduced in order for it to “remain a viable option in the long-term.”
This places a lot of pressure on offshore-wind operators to find ways to reduce these kinds of costs. Using cheaper materials may be attractive in the short run, but if it adds to long-run maintenance costs, it’ll be a bad bargain because fixing things at sea is so much more complex.
Offshore wind in the U.S. got a nice boost in June when the U.S. government announced that 81,130 acres off the coast of New York will be opened to leasing for offshore wind power projects.
Commercial offshore wind providers will have an opportunity to bid for leases they will need to develop wind farms in an area 11 miles south of Long Island. Although the U.S. does not have a single offshore wind farm up and running right now, the first project is expected to be operational by the end of 2016 and many more are on the way.
The U.S. Bureau of Ocean Energy Management has already awarded 11 commercial offshore wind leases worth $16 million and covering more than a million acres of U.S. waters, according to the BOEM website.
Nine of those leases have been sold through competitive bidding: Two each in New Jersey, Massachusetts and Maryland; two for an area between Rhode Island and Massachusetts; and one for Virginia.
Offshore wind power has a long way to go in the U.S., especially compared to Europe, which has over 3,000 wind turbines up and running. But U.S. several projects are in the works:
- A pair of six-megawatt wind turbines is proposed off the coast of Virginia. The BOEM has awarded a research lease for the project and approved a research action plan in March.
- An offshore wind project planned for Maryland could install as many as 125 turbines. It’ll still be a couple more years before construction starts, and two more years after that to complete the project.
- A more preliminary project is slated for the coast of New Jersey. That project is only in the opening stages. U.S. Wind, headquartered in Boston, is developing the New Jersey and Maryland projects.
- Another New Jersey project is being developed by Fishermen’s Energy, which won a Department of Energy grant to start a demonstration project near Atlantic City.
- DONG Energy, a Danish company that has done large projects in Europe, acquired the rights last year to develop a wind farm about 25 miles off the shore of Martha’s Vineyard.
The bottom line is that offshore wind will at least have demonstration projects up and running by the end of this decade to establish what works and what doesn’t.
The slow pace of adoption in the United States may frustrate advocates of renewable energy, but it’s important to remember that there was a time not so long ago when there were no wind farms in Europe. If oil prices jump and the political climate changes in ways that make offshore wind more attractive, we could see a lot more wind-power projects popping up off American shores.
After all, the technology is mature, thanks to the experience gained building Europe’s wind-power systems. A lot could change very quickly if all the right factors come together at the same time.
While more than 3,000 offshore wind turbines push electricity to power-hungry Europeans, the number of towering turbines in U.S. waters is precisely zero. But that’s about to change.
The first U.S. offshore wind farm is slowly rising in the Atlantic Ocean south of the state of Rhode Island and east of New York’s Long Island. It could be up and running by the end of 2016, according to media reports.
The five-tower farm is small in scale and enormous in price: the $290 million project will provide energy to 1,000 year-round residents of a remote tourist stop called Block Island, where energy costs are extremely high because the island is more than 10 miles from the mainland. Developers of the project hope it will establish a toehold for offshore wind energy in the United States.
Once this project starts delivering power, it may be able to provide insights on economies of scale that will enable an industry to take root on the Eastern Seaboard. The relatively shallow Atlantic Shelf provides the only viable choice for the U.S. because the Pacific Shelf hugs the coastline and drops off sharply, making the waters are far too deep for wind farm development.
The large offshore wind farms of Europe rely on government subsidies and policies designed to push more and more European energy consumption into the green-energy sector, but such policies are far more rare in the United States. While investors have made wind turbines a common sight across the broad open plains of the nation’s interior, finding folks brave enough to try the untested waters of offshore wind energy in the U.S. another matter altogether.
High up-front costs, investor skepticism and lack of public-sector support equal slow going for offshore wind the U.S. Low fuel prices also are discouraging development of renewable energy sources. But eventually, hydrocarbon costs will rebound and make these kinds of projects more attractive.
The five towers of the Block Island project will be 600 feet high and designed to withstand a category 3 hurricane. Because the winds are stronger at higher altitudes and farther away from shore, wind farm developers have an incentive to build taller towers in ever-more-remote locations. The Block Island towers must be installed on platforms that sit on the seabed in several hundred feet of water — dramatically adding to the project’s costs. In the decades to come, floating platforms anchored to the seabed may provide a much more economical base for offshore wind energy projects.
Whatever the future holds, we’ll be providing the durable cable hardware that enables the offshore wind energy industry to transmit energy to people on land.
More on the Block Island project:
• First US Offshore Wind Energy Projects Could Deliver Jolt Of Momentum To Struggling Sector
• America’s First Offshore Wind Farm Quietly Takes Shape
Fundy Bay is famous for pictures of fishing boats tilted on their hulls — run aground by the immense power of the world’s largest tides.
The waters of this scenic coastal inlet along Canada’s Nova Scotia and New Brunswick provinces rise and fall by more than 50 feet twice a day, every day of the year. That predictability is one of the key reasons why green-energy researchers are fascinated with the potential of converting tidal movements into electricity. Solar power goes dark after sunset and wind power rises and falls with moving weather patterns. But tides rise and fall like clockwork, creating the potential for an extremely reliable stream of electric power.
The Trouble with Tidal Energy
Unfortunately, the ocean is one of the worst places on earth to install mechanical equipment. Saltwater is extremely corrosive, and working on machinery underwater is incredibly dangerous and expensive.
Some wave and tidal energy projects are mounting turbines on the sea floor. This keeps the turbines out of sight, which is a boon to coastal views, but it also dramatically increases the costs of upkeep precisely because they are so difficult to access.
Floating Platforms: A Tidal Energy Alternative
Fundy Bay’s epic tides have made it a hub for working out these kinds of challenges in wave and tidal energy research. One alternative researches are exploring is mounting a turbine beneath a floating platform that’s moored to the ocean floor via cables. A turbine connected to a floating platform could have all of its machinery easily accessible from the platform rather than mounted on the sea floor, where the only way to reach it is with scuba divers or remote-operated vehicles (or both).
In March 2016, a Canadian firm called Dynamic Systems Analysis (DSA) helped launch a floating research platform called EcoSPRAY that will document how highly turbulent tides work. This, in turn, will provide clues to the best ways to deploy floating tidal energy platforms that have been moored to the ocean floor.
The platform is operating in the Grand Passage between Freeport and Westport, Nova Scotia, in the Outer Bay of Fundy. Sensors on the EcoSPRAY will track wind speeds, tidal currents and wave actions. A drag plate mounted on the bottom of the platform will simulate the thrust of an underwater turbine, DSA says.
Protecting tidal ecosystems
While floating tidal power platforms would be less visually pleasing than turbines mounted on the sea floor, they have the potential to be less disruptive to underwater environments. Mounting an underwater turbine is a major construction project, whereas placing anchor points on the sea floor for mooring cables could be far less disruptive to the coastal environment.
Protecting that environment is very much on the minds of Fundy Bay researchers. Fundy Ocean Research Center for Energy (FORCE), the Offshore Energy Research Association (OERA) and the Nova Scotia Department of Energy are all working together on a half-million-dollar program to determine the effects of tidal energy turbines this year.
This points to the future of wave and tidal energy, which may well depend on finding the best mix of high energy output, low cost and minimal impact on the subsea environment.
The offshore wind industry made significant strides in Europe last year, according to the European Wind Energy Association (EWEA). This growth has broad implications both for the renewables industry and the subsea cable market.
EWEA’s “Wind in Power: 2015 European Statistics” report published in February 2016 said European offshore wind installations more than doubled in 2015 from the year before. Germany had by far the most wind-power activity in 2015, adding 6,013 megawatts of generating capacity — and 38.4% of that was offshore.
Offshore wind installations accounted for 33.4 percent of all installations in 2015, according to EWEA’s data, up from 13.7% year before. Furthermore, investments in wind power hit an all-time high in 2015, EWEA said, with offshore wind leading the charge.
“Financial commitments in new assets reached a total of €26.4 billion, a 40 percent increase from 2014,” the report said. “While investments in new onshore wind generating assets increased by 6.3% in 2015, those in the offshore wind sector doubled compared to the previous year.”
A summary of the report in the website OffshoreWIND.biz notes where most of the capacity was added in 2015:
- Germany: 2,282 megawatts (75.4%), a four-old jump from the year before
- UK: 566 MW (18.7%)
- Netherlands: 180 MW (5.9%)
Another EWEA report, “The European Offshore Wind Industry — Key Trends and Statistics 2015,” drills deep into the details of the continent’s offshore power industry. It notes that “total investments for the construction and refinancing of offshore wind farms and transmission assets hit a record level of €18 billion.”
At PMI, we’re watching the growth of offshore wind closely because it has the potential to affect all the players in the subsea cable market. After all, those wind turbines depend on offshore cables to transmit power back to the mainland (the average turbine site was 43.3 kilometers from shore in 2015, in 27.1 meters of water). As sites near shore become more fully developed, offshore sites will inevitably move farther away and into much deeper water.
Those developments mean offshore cables and equipment like subsea cable terminations will need to be extremely tough and reliable — the two signature qualities of PMI cable equipment.
Any young, new industry will have growing pains, and the offshore wind farm industry is no different. Among other issues with offshore wind farms, one of the biggest problems to affect the industry are issues with subsea cables. Failures and issues during installation and maintenance of subsea cables have cost companies millions of dollars and have caused many delays in this new and quickly rising industry.
While much information on cable issues is closely guarded, there have been some high profile cases as well as some studies done regarding damage to offshore wind farms. One of these studies, conducted by the Bureau of Safety and Environmental Enforcement (BSEE), partially delves into issues specific to subsea cables. Failure statistics have shown that third party mechanical damage to cables is three to five times more likely that the risk of internal cable failures. A few examples of third-party subsea cable damage include:
- Jackup “Jacked Up” On a Cable:
One issue is the risk of Jackups “Jacking Up” on a cable. A Jackup is a floating barge fitted with long support legs that can be raised or lowered to service oil and gas platforms or wind turbines. According to the study by the BSEE, there have been issues with cables getting caught in the jackup and being damaged in the equipment.
- Anchors Damage To Cable:
Another common issue is damage from third party anchors. Often times, anchors of laying vessels will tangle with the cable being laid and cause damage to the cable.
- Cable Kinked
Perhaps one of the most common issues with subsea cables is their tendency to kink or bend. It is very easy to get a kink into the line when preparing to install cables and unkinking is a major exercise requiring special skills.
In addition to these issues, other common problems to cable installation can include: damage to cable during installation, weather or soil-related damage, cable or joint failure, or sediment movement that can lead to cable exposure.
Subsea cables are complicated pieces of equipment and need to be handled with care and should only be used with only the best cable hardware to promote longevity and fortification. PMI is ready to equip your cables with the highest quality cable hardware.
For more information regarding subsea cable vulnerability, read our blog: Why the growing renewable energy market should be concerned about subsea cable vulnerability or call us today to schedule a meeting.
The shift towards sustainable and renewable energy sources has made a real change in the energy industry. As we previously reported on our blog, Europe and Asia lead in wind energy production globally – Denmark itself uses wind power for almost 40% of Danish domestic electricity. The United States continues to grow in the market as well, with the U.S. Department of Energy reporting that by 2030, wind power could supply 20% of all U.S. electricity. However, as more wind turbines are being created, the more people are beginning to speak up about them being an eyesore. The solution? Offshore wind farms.
Offshore wind farming has proven to be a successful solution, not just for eyesore issues, but for productivity. Outside of populated areas and buildings, wind blows more steadily over the water, thus creating more energy for consumption. Moreover, studies are being done to use wind farms to temper violent hurricanes and other large scale weather incidents that can cause devastation.
For more information, watch this great video on Why the Future of Wind Energy Lies Offshore
Despite all these solid moves in the right direction, offshore wind is still a new and growing industry. Carrying power to and from wind turbines miles out in the ocean requires proven subsea hardware and cables. PMI’s years of experience and knowledge of subsea conditions and high quality equipment is the solution to many problems that can develop in the harsh waters off shore. PMI is ready to help your company solve your subsea cable and engineering issues. Contact us today to schedule an appointment to talk to our experts.
While it appears as thought the U.S. is falling far behind Europe in the Offshore Wind and Wave Energy department, you really need to understand the lay of the land – literally.
The U.S. coastline, with a relatively small continental shelf, is not quite as amenable as Europe’s North Sea for offshore wave and wind. Conventional offshore wind turbines are limited to a depth of around 50 meters. In these depths, foundations are typically open truss frame structures that are anchored to the seabed. They are expensive to build and aimed at supporting extremely large turbines. The larger the turbine, the more energy it produces, keeping the overall cost per kilowatt-hour down.
But as the water depth increases, foundation costs increases. So along the U.S. coast, floating structures similar to the ones deep-water oil and gas industry use are nearly the only option.
The U.S. would benefit from not only looking at floating offshore wind but also wave energy, both of which are economically equal in extracting energy from the marine environment.
But what is most important is that these types of projects get in the water soon, generate interest and start working towards lowering costs. We need to work to achieve lower costs through simplicity, reliability and economies of scale.
Today it appears that we are likely only to employ only a tiny fraction of this available resource and offset the needs within the U.S. The problem we truly face is not obtaining the resource; it is the practical deployment and the economical conversion of it into electricity.
We need to look at the most viable methods of capture it at the lowest cost.
Our years of experience in the offshore oil and gas industry will benefit offshore renewable energy companies that are navigating along the U.S. shoreline.
Want to know more? Read Ocean/Tidal/Stream Power: Wave Power’s Path to Commercial Acceptance – A Comparison with Deepwater Wind by Timothy R. Mundon.