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Offshore wind

In all there is over 230GW of wind-power capacity in place globally, nearly all on land, but offshore wind is moving ahead quite rapidly. The UK is in the lead with over 1.8GW operating, well ahead of Denmark and Germany, but China, the USA and Japan are now also in the race, although so far only China has any projects in operation, 234 MW so far. The US government has just announced a $180m 6-year plan to fund four offshore wind projects and Japan has plans for six 2 MW floating units and then possibly up to 80 by 2020 in a 1 GW offshore programme. Meanwhile France has plans for 6GW by 2020.

The costs are higher than for on-land wind, due to the difficultly of installing and maintaining machines offshore, and the need to have expensive undersea grid links back to shore. However new technology (including floating wind turbines) should be able to reduce the installation costs, and once there are multiple arrays in place the cost per turbine of shared grid links falls.

Studies by the Offshore Wind Cost Reduction Task Force, set up by the UK government, and by the Crown Estate, suggest that it should be possible to reduce the cost of offshore wind energy in the UK to £100 per megawatt hour within seven years with the right actions from the industry. As Wind Power Monthly reported, both studies conclude that the costs of offshore wind energy could be driven down by almost 30% by 2020, making it competitive with established forms of energy generation.

Given that the UK is targeting 18GW of offshore wind energy by 2020, the cut in costs envisaged in the two reports from the current £140/MWh to £100/MWh would save over £3 billion annually. The task force report sets out 28 separate actions required by industry and government to achieve the cuts, including supply chain, planning and consenting, finance and grid infrastructure.

There has been a lot of negative comment about the high cost of offshore wind recently, for example, from the governments advisory Climate Change Committee. So for offshore wind proponents these cost projections are good news, as long as it doesn’t give the government an excuse to cut support levels prematurely, as some argue they did when PV solar costs fell.

On land wind may be relatively cheap (it’s the cheapest major new renewable source), but, although we will need as much as we can reasonably get, there are obviously limits to how much can be installed. The current plan is to have around 13GW in place by 2020. By contrast the offshore resource is very large and less constrained - being offshore it’s less visually intrusive. Long term we could have 100GW or more, if we go further out to sea. Given larger machines and higher wind speeds, offshore wind also has higher capacity factors than on land wind, i.e. the actual energy out compared with installed capacity, sometimes also called the load factor (although there are subtle differences!). On-land wind projects in the UK typically achieve around 25% load factor averaged across the UK, although that’s moving up to 30% with new technology and of course it’s higher on good windy sites. But offshore wind is much more reliable and unaffected by topographical features. Recent results from Demmark show that its latest offshore wind farm, Horns Rev II, has attained a 47.7% capacity factor. The full list of actually measured ‘life time’ CF’s for Denmarks offshore wind farms is at: http://energynumbers.info/capacity-factors-at-danish-offshore-wind-farms

For the UK, DECC 2050 Pathways calculator uses a load factor of 45% for offshore wind. Given the new Danish data, that may turn out to be low, since by 2050 wind turbines will have improved further and will be further out to sea in windier locations. 50% seems a realistic possibility. For comparison, DECC quotes UK nuclear load factors as 69.3% (2006) 59.6% (2007) 49.4% (2008) 65.6% ( 2009) and 59.4% (2010). That averages out at 60%. Nuclear proponents say that new nuclear plants will do much better, with talk of 80-90%, but that has not yet been proven.

In my next blog I’ll look at some of the new technologies emerging for wind power, both on land and offshore. But as a taster, there were 104 offshore wind-turbine tower-support designs competing for support in the Carbon Trusts Offshore Wind Accelerator programme, which runs until 2014. Four were shortlisted for further development: Keystone’s wonderfully named ‘Inward Battered Guide Structure’ (IBGS), which is a ‘twisted jacket’ tripod tower design; SPTs Self Installing wind turbine; Harland and Wolff’s Universal Foundation design (basically a massive weighted bucket sitting on the sea bed ); and the Gifford BMT Freyssinet Gravity Base foundation. A version of Keystones IBGS tower/base has been installed for testing at Hornsea and there are plans for a full test with a wind turbine soon. The Universal Foundation design is also to be tested soon, on the Dogger Bank.

Meanwhile the HiPRWind, R&D programme with 60% (€11 m) EU funding is aiming to test a 1.5 MW wind turbine on a triangular floating structures off Spain. The Biscay Marine Energy Platform (Bimep) will be located 1.7 kilometres from the Basque Country in 50-metre deep waters. It’s predicted that the cumulative global market for floating wind turbine structures could exceed €200 billion by 2030. www.hyperwind.eu

Clearly offshore wind technology is moving ahead rapidly and we are likely to see major projects in the North Sea and elsewhere around the world. Some of them are already breathtaking. But ahead there could be even more dramatic developments, like the huge circular supergrid ring main around the edge of the North Sea, with nodal links to wind farm arrays, as proposed by the Dutch Society for Nature and Environment: www.we-at-sea.org/index.php?keuze=n&nummer=55

That’s some way off. For now, the UKs next big focus is the 1 GW London Array, around 7 miles off shore in the outer Thames estuary, in water up to 25m deep with 341 turbines. The government has also given a green light to projects off the north Norfolk coast, at, respectively, Race Bank (580 MW) and Dudgeon (550 MW). Plans for the 278 turbine Atlantic Array off N Devon/S Wales continue, while three 400-500MW arrays are planned off Scotland. There’s also a proposal for a huge 2.2 GW project in the Irish sea, to be called Rhiannon.

Major projects like this will obviously have to be carefully assessed in terms of environmental impacts. However, the studies carried out so far have not found significant problems. Crustaceans seem to like the foundations, sea mammals stay clear, as do birds. http://iopscience.iop.org/1748-9326/6/3/035101. But in some locations there can be problems. For example, the 500MW Docking Shoal project was refused over bird-impact fears, and the National Trust is opposing the proposed Atlantic Array wind farm, which it sees as being squeezed in between ‘two sensitive coastlines’.

Posted by Dave Elliott on September 1, 2012 2:18 PM | Permalink