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5 Apr 2017

Reading time 7 min

MacGregor innovations serve booming offshore wind energy market

Global investments in renewable energy have reached new heights and with a pipeline of long-term power-generation potential, MacGregor is well-positioned to support this burgeoning market

Setting a new record, last year developing countries invested more than developed economies in renewable energy, according to a report commissioned by the United Nations Environment Program (UNEP). It excludes large hydro projects, but includes China, India and Brazil committing a total of USD156 billion, up 19 percent on 2014, in comparison, developed countries invested USD130 billion. China placed the lion’s share and increased its investment in renewables by 17 percent to USD102.9 billion, or 36 percent of the world total.

Globally, the fastest growing renewable energy sector is the offshore wind farm industry. In Europe, the increase in 2015 was unprecedented, with the European Wind Energy Association (EWEA) recording 3,019MW of new offshore wind power capacity connected to the grid during the year. This represents a 108 percent increase over 2014 and the biggest annual addition to capacity to date.

Wind turbine orders for 2015 were up on 2014 figures, indicating good growth beyond 2016 and a year-on-year increase of 75 percent, says the EWEA. In Europe, there are currently 3,230 wind turbines installed and grid-connected, making a cumulative power generation capacity of 11,027MW. In the mid-term the EWEA expects the total installed grid-connected capacity to increase in Europe to 12.9GW. However, it has identified 26.4GW of consented offshore wind farms that could be constructed over the next decade. Of these, the UK has the largest pipeline of consented wind farm projects, standing at around 11.9GW.

MacGregor was chosen for the task because of its long history of designing and delivering very reliable mooring solutions for offshore operating in harsh North Sea conditions

– Jan Martin Grindheim

Pioneering new projects

MacGregor is well-positioned to serve this buoyant market. Most recently it has announced its participation in a pilot project pioneering the use of Nemos, an innovative system that generates electricity from waves. The system is ideally suited to work in combination with offshore wind farms, where it can share electrical infrastructure. This lowers the levelised cost of energy (LCOE) and smooths fluctuations in power-generation, therefore supporting greater commercial viability of renewable energy capture. For its part, MacGregor will supply highly-specialised winches.

“MacGregor is proud to be one of a few trusted, select partners for this ground-breaking project,” says Marcus Wolter, Director, Strategy and Business Development Offshore Deck Machinery, MacGregor. “As a result of MacGregor’s long-standing experience in winch technology, we were able to engineer a solution ideally suited to Nemos’ unique approach to converting wave energy into electricity.”

Nemos employs specially-shaped floating structures that move in a controlled trajectory to capture up to 80 percent of available wave energy, compared to 50 percent achieved by conventional rise and fall systems. Their associated generators and mooring winches can be located on any suitable offshore structure, such as a wind turbine.

MacGregor’s newly-developed mooring system winch delivers the optimum degree of movement to maximise energy capture

The Nemos mooring system employs two fibre ropes for each floating structure. These ropes are controlled by the MacGregor winches, which deliver the optimum degree of movement to maximise energy capture. Orientation of the floating structures can also be adjusted by the winches when wave direction changes. In extreme conditions, the winches can haul them down well below the surface to avoid storm damage.

“Combining Nemos with wind turbines can have a valuable smoothing effect on the power-generation profile of the overall installation, because the build up and decay of wave systems lags behind increase and subsequent decrease in wind strength,” explains Mr Wolter.

“Over the coming years, a large number of offshore wind farms will be built and within these farms there is considerable wave energy potential. Shared infrastructure, such as subsea cables and substations, could be better utilised, therefore the pro-rata costs for energy transport would also decrease,” he continues.

The first commercial Nemos pilot project will be located in the North Sea and should be fully operational in 2017.

As a result of MacGregor’s long-standing experience in winch technology, we were able to engineer a solution ideally suited to Nemos’ unique approach to converting wave energy into electricity

– Marcus Wolter

Securing the first floating wind farm

The Nemos project is one of many pioneering new approaches to the capture of renewable energy. At the end of 2015 MacGregor won an order for substructure connection mooring systems for the world’s first floating offshore wind farm, Statoil’s Hywind pilot park in Scotland, UK.

Hywind will cover an area of just over 4km² near Buchan Deep, 25km off Peterhead in Aberdeenshire, on Scotland’s North Sea coast. It is designed to demonstrate cost-efficient solutions that will enable the commercial capture of wind energy in deep-water environments.

MacGregor is contracted to deliver a Pusnes substructure mooring connection system to each of the pilot project’s five new floating wind turbines. The ballast-stabilised turbine structures will each be equipped with a three-point mooring system employing site-specific anchors. MacGregor plans to complete deliveries by the end of 2016 and installation of the wind turbines is scheduled for 2017.

“This contract represents a step change for MacGregor in terms of entering a new industry sector,” says Jan Martin Grindheim, Director, Floating Solutions at MacGregor. “The project hinges on applying proven technology in new applications. MacGregor was chosen for the task because of its long history of designing and delivering very reliable mooring solutions for offshore floating production units operating in harsh North Sea conditions.”

“Statoil is proud to develop the world’s first floating wind farm, further increasing the global market potential for offshore wind energy,” says Stephen Bull, Statoil’s Senior Vice President for Offshore Wind. “We are very pleased with this contract awarded to MacGregor. We are excited that high quality oil and gas suppliers in both Norway and Scotland are able to capture the growing opportunities offered through new renewables growth.”

The 6MW wind turbines will have a total power-generation capacity of 30MW and provide enough electricity for 20,000 UK homes. They will operate in waters over 100m deep which experience an average wave height of 1.8m. “To give some idea of the scale of the project, the wind turbines will stand at an overall height – from the seabed to the turbine blades – of around 258m, which is nearly three times the height of the Statue of Liberty in New York,” adds Mr Grindheim.

Keeping the turbines turning

Regardless of the difficulties imposed by their height and exposed positions, all wind turbines require regular inspections and maintenance. MacGregor is at the forefront of developing technology to deliver this vital service in a safe and efficient manner.

A notable example is a first-of-its-kind offshore crane that has a full three-axis (x, y and z) heave-compensation system that can keep a suspended load fixed in position relative to the seabed.

The crane was specifically developed to be able to land containers of tools and equipment to small platforms at the top of offshore wind turbine foundations with little margin for error.

“The landing platforms are about 20m above the water and they are only a few square metres, so precise load handling is necessary,” says Ingvar Apeland, Director, Load Handling at MacGregor. “Although MacGregor’s standard active heave compensation (AHC), supplied through a crane’s winch, compensates for a vessel’s vertical movements, a greater degree of precision was required in this case.

The crane is also ideally suited for maintenance work on wind turbines and other fixed installations.

“In addition to compensating for vertical motions with the winch, we needed to develop new technology to compensate for the vessel’s pitch and roll movements. If you can compensate for these motions, you can ensure that the crane’s pedestal remains vertical in relation to the sea bed, so that it is parallel to the windmill structure.”

MacGregor’s solution involves hydraulically tilting the crane’s foundation. The crane has an outer steel foundation welded to the deck at the centre line of the vessel. “Although all areas of the vessel experience the same angular movements in a seaway, positioning the crane at the centre of the vessel minimises the actual physical displacement of the crane and its load,” explains Mr Apeland.

MacGregor recognises that any investment must deliver distinct operational advantages

– Ingvar Apeland

The fixed foundation is connected to an internal foundation system supported by a hydraulically-actuated two-directional motion compensation system employing four high-speed hydraulic cylinders. These cylinders are arranged in two pairs; one pair is sufficient to provide full system functionality, so this provides a good level of redundancy. Each cylinder is fitted with a positioning sensor, to provide real-time feedback to the control system.

The crane has a safe working load of five tonnes at a 25m outreach and features a telescopic jib.

“In today’s challenging economic climate, MacGregor recognises that any investment must deliver distinct operational advantages,” adds Mr Apeland. “The three-axis heave-compensated subsea crane does exactly that, offering safe, quick, accurate load handling and unique operational capabilities, even in high sea states.”