Out at sea, a forest of steel and ingenuity

February 17, 2013 by  
Filed under Wind Energy Tips

At first, there is nothing to be seen but grey sky, grey clouds and grey, sullen seas.

On a clear day – a rare enough phenomenon at this time of year in England – the view out across the mouth of the Thames estuary from the modest heights of the greensward at Frinton-on-Sea can carry the eye as far as the north Kent coast, about 50 kilometres to the south.

On this February day, however, even the lifeboat station at the end of the 800-metre pier jutting out into the inhospitable soup from the neighbouring town of Walton-on-the-Naze is lost to view.

But this is East Anglia on the east coast of England, where sky and sea have always conspired to surprise with sudden, dramatic changes of scenery that have frustrated the aspirations of lesser artists and inspired the likes of Turner and Constable. Quite suddenly, the seemingly impenetrable murk is pierced and parted by shafts of light angling in from the low morning sun.

The sea, shimmering silver as though with the scales of a million surfacing fish, begins to reclaim the horizon. And then, out of the retreating Stygian gloom, appearing one by one in ranks as perfectly ordered as the headstones in a military graveyard, rise what at first, improbably, appears to be the advance guard of a titanic marine forest.

In fact, this is a forest of steel and ingenuity, a vast manmade plantation of hope for the future of a power-hungry planet and, in scale and ambition, without doubt one of the wonders of the modern world.

The 175th and final turbine of the London Array windfarm, a joint enterprise by the Danish company Dong Energy, the gas and electricity group E.ON UK and Abu Dhabi’s future-energy initiative Masdar, was installed on December 13.

Together, they have created the world’s largest offshore windfarm. More than 80 of the 175 turbines are already online and, when the last of them is commissioned, some time this spring, the windfarm will be pumping 630 megawatts into the national grid. That’s enough electricity to power 470,000 homes – about two thirds of all the households in the southeastern English county of Kent.

Part of the wonder is the speed at which the project has been completed. Groundwork on the onshore substation, through which all the power flows into the national grid along cables buried in the seabed, began in July 2009. The foundations for the first turbine were driven into the seabed in March 2011 and, right on schedule, all major construction was completed by the end of last year.

In just 21 months, in other words, a vast seascape has been utterly reshaped.

The scale of the windfarm, more than 20 kilometres off the coasts of Kent and Essex, can be glimpsed only from the shore. But it is only from the air or up close – as seen by passing ships, fishing vessels and yachtsmen, cautiously learning to thread their way through the trunks of the mighty forest, each trunk mathematically spaced between 750 and 1,000 metres from the next, to take best advantage of the wind – that it can be properly appreciated.

Each of the three-bladed turbines, the tips of which reach up to 147 metres above mean sea level, is marginally larger in height and diameter than the London Eye, the giant Ferris wheel on the city’s South Bank. Occupying 100 square kilometres, the windfarm is built on an area of seabed more than one and a half times the size of Abu Dhabi island.

It has, says Mohamed Al Khawaja, an electrical engineer with Masdar, been “an amazing project to be involved with. You can look at pictures, but when you actually see the scale of the project it is unbelievable. It just goes on and on”.

Mr Al Khawaja, from Dubai, joined Masdar in December 2009, and spent three years working on some of Masdar’s pilot alternative-energy projects, including the Sir Bani Yas onshore windfarm and the Nour 1 solar plant near Al Ain.

Promoted to senior electrical engineer, he was seconded in June 2011 to the Array, where he has worked as an interface engineer on the all-important offshore and onshore electricity substations, through which the power generated by the windfarm is marshalled and channeled into the UK’s national grid.

When he first arrived in England, the first foundations for the windfarm were being put in place. After two years in the UK, Mr Al Khawaja is due to return to fresh challenges in the UAE at the end of March, and among his souvenirs is a treasured photograph of himself, taken out at sea in December in front of the project’s final turbine as it was being installed.

“I will take with me the experience of this great opportunity,” he says. “The international experience gained from this project, through working with E.ON and Dong, I could not have gained anywhere else.”

The challenges for Mr Al Khawaja and everyone else who has worked on the project, says Joanne Haddon, spokeswoman for the London Array, have been considerable.

“This is a major engineering and building project – at sea,” she says. “Any major building project is complex, but we obviously have had the added complexity of the weather, which is out of our control.”

Which doesn’t tell the half of it.

Remarkably, given the vagaries of wind, weather and tides, the project has been on schedule from day one, thanks to extensive preparations including surveys, mapping of the seabed and the study of wind patterns over several seasons, using specially designed data buoys. It has taken between 36 and 72 hours to install each of the 175 foundations, and between 24 and 48 hours to mount upon them each of the turbines. Weather permitting, work progressed 24 hours day, but during the winter months, when the notorious North Sea gales blow through, the schedule allowed for 30 per cent downtime.

Of course, the wind that has made life so testing for the construction teams is the very reason the farm is where it is in the first place. The turbines start generating power from wind speeds as low as 11kph, achieve full power at 46kph and shut down, automatically, only when the wind speed reaches 90kph – a force-10 storm on the mariners’ Beaufort scale.

Each turbine has had to be connected to the next, and thence to the two unmanned, three-storey offshore substations, by subsea cables. The four export cables, which carry the power from the sea to the shore, are each continuous lengths 54km long and, weighing 4.5 tonnes each, are the heaviest single item on the windfarm.

Using specialist vessels, it took four to six weeks to run each of the cables from shore to windfarm. The contractors, the Dutch company Visser and Smit Marine Contracting, worked in depths ranging from 23 metres to the mudflats of the intertidal area near the Kent shore.

The windfarm straddles two huge sandbanks that for centuries have posed a serious navigation hazard to mariners entering and leaving the River Thames. Long Sand and Kentish Knock, and the 20-metre-deep Knock Deep channel that runs between them, are names that have spelled ruin for generations of ships’ masters, and death for unknown numbers of passengers and crew.

Know something of the wrecks that litter the seabed where the windfarm now stands, its underwater cables a vast shroud of a net thrown over the buried remnants of the past, and the notion of the turbines as regimented tombstones seems more than merely fanciful.

Somewhere beneath the blade-shadowed waves, for example, lie the wreck and many of the dead of the SS Deutschland, a steamer lost here while carrying emigrants from Bremen, Germany, bound for a new life in the New World. If she foundered on a day like today, she would be clearly visible from the greensward at Frinton. But on December 6, 1875, the fog and snowstorm that confused her navigator and led the ship on to Kentish Knock also blinded those on the shore to her distress rockets.

When help finally arrived the following day, 57 people had been lost. Many were found frozen to death in the ship’s rigging, where they had sought sanctuary from the waves that swept the stricken vessel’s sunken hull. Only a dozen bodies were recovered.

The site of the wreck was lost for years. Then, in the summer of 2005, at a depth of 11 metres in the sand at the edge of the Knock Deep, a German marine archaeologist recovered tableware bearing the shipping company’s crest, a broken candelabra and a button. The button commemorated the World’s Fair, due to be held in Philadelphia the following year – a pre-ordered mass-produced souvenir that never made it to America.

The Deutschland, whose loss was commemorated in a poem by the English Victorian poet Gerard Manley Hopkins, is just one of countless ships lost on the Long Sand and Kentish Knock. That this wild place, so close to shore and yet, for so many lost souls, so far from safety, has finally been mastered by human beings is perhaps the greatest achievement of all.

And there is a kind of perfect circularity about this enterprise. It was the wind, of course, that first drove British seafarers out into the world, where they helped themselves to its riches. Now, post-empire, that same, timeless wind is being harvested as the engine of a new age of power.

As vast as it is, the London Array is just part of a network of offshore windfarms from which the UK is already producing more electricity than the rest of Europe combined – and it will soon by dwarfed by other projects under development.

Offshore developments have two advantages: more wind, and they avoid the not-in-my-backyard protests that dog the developers of onshore projects. There are currently 22 offshore windfarms around the coast, generating a total of 3,000 megawatts of electricity. In the pipeline are a further 29 projects, many much bigger than the London Array, promising a further 47,000 megawatts of power – or enough electricity at peak production to power a majority of the homes in the UK.

So what’s in it for the UAE?

For Masdar, the experience gained by Mr Al Khawaja and other Emiratis on the London Array project has made a vital contribution to its mandate to develop homegrown expertise through the development of large-scale, clean-energy projects at home and around the world.

Masdar itself, in the words of its chairman, Ahmed Ali Al Sayegh, is seen as “a key pillar in Abu Dhabi’s much broader vision towards sustainable economic development and diversification, and the fostering of knowledge-intensive industries”. The success of the London Array project sees that vision writ large on the world stage.

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