'It used to be that we talked about wind farms – even offshore. Now we are looking at wind power plants, 500 MW up to maybe 800 MW in one big cluster', says Christina Aabo. As senior manager for Wind Assets and Concepts, her role at DONG Energy is to head up the department that ensures the long-term business case for offshore wind developments.
DONG Energy, a utility based in Denmark, has a rapidly expanding portfolio of offshore wind developments alongside its onshore ones. Most of its established offshore plants are in Denmark, including Horns Rev (64 MW), Horns Rev 2 (209 MW) and Nysted (132 MW), along with UK developments such as Gunfleet Sands 1 (108 MW) and 2 (65 MW). UK waters are also home to much of DONG's portfolio of current offshore construction work, which includes shares in the London Array (315 MW), Walney 1 (184 MW), Walney 2 (184 MW) and Westermost Rough (180-200 MW). But the company has its eye on other countries as Europe's offshore wind markets develop, says Aabo.
DONG views wind power as an asset into which it is investing, and needs to ensure that the investment will be sound, says Aabo. While controlling capital expenditure is important, a key focus is to ensure that operational expenditure will not run out of control - and that's over an operating lifetime of 20 to 25 years. So how does DONG go about this? Aabo says planning is the key – DONG is developing tools and methods to carry out careful calculations beforehand and ensure that assets are invested in the right way. It's essential to avoid major design errors and to ensure all equipment is operating safely and is well maintained.
As everyone knows, offshore is a tough environment – and continues to be over a long operating lifetime. For most of DONG's offshore assets in the UK or Denmark the expected lifetime is 24 years, says Aabo. 'So we make sure all parts – foundations, turbines, cables, etc. are reliable for 24 years'. That kind of operating lifetime goes well beyond manufacturers' warranty periods for all kinds of asset. So it is essential to make sure that the appropriate maintenance can be carried out beyond the period of guarantee.
One issue every offshore operator must face is the difficulty of access, especially for unscheduled maintenance – and as offshore wind power plants move further from the shore, this becomes even more of an issue. Bad weather and large waves can make even relatively small repairs impossible. So maximising reliability is a real essential. For a business like DONG, working closely with suppliers, especially turbine manufacturers, to eliminate potential problems is increasingly important. 'We are integrated into suppliers' design reviews,' says Aabo. The situation has now moved way beyond the point 'where you just buy turbines and put them offshore', she adds.
Another really important shift in thinking has occurred over the past few years. At one time people thought in terms of wind turbines, collected together in a wind farm - onshore or off. Now, as a power utility, explains Aabo, we are looking at a full wind power plant which has individual turbines as 'components'.
It means, says Aabo, that in investment and performance DONG looks beyond kilowatt hours output and much more at operating as a power plant. It means, for example, that the company accepts the need to build a certain amount of redundancy into the system – which increases capital expenditure but brings savings later on in terms of operating expenditure, explains Aabo. 'It needs to be the best product from a full lifetime point of view.'
From the operational point of view, she explains, the company no longer looks at one project or asset as one unit. Having more assets allows the company to benefit from certain synergies - for example with service vessels and crews maintaining several projects to bring on the volume and scale they are looking at offshore.
One trend as offshore wind power plants increase in size is multiple ownership. DONG is now starting to own projects jointly with other utilities or other large investors, which can add significantly to the complexity of project planning. The chance that ownership of a share in a project may pass from one party to another necessitates due diligence with very careful documentation and agreements. 'Further on we may sell off parts of it [an offshore wind plant] and that brings in more severe due diligence on how we have spent money, our business case,' says Aabo. 'New ways of working are emerging - small practical things like having to give access to technical documentation, agreeing what kind of service will be offered to owners. It means everything needs to be much more legally strict. We need to be much more transparent and have much stronger processes.'
Christina Aabo trained as a wind turbine engineer and worked with several leading manufacturers before moving on to her current role. So how does she view developments in offshore wind turbines themselves – does she think the latest generation of turbines will be able to run problem-free, with only occasional, planned maintenance? 'This is a difficult area to predict, but players at many parts of the value chain are working to ensure turbines are reliable from day one,' she says. But Aabo anticipates a delay between the introduction of new turbines and their application on a large scale, during which investors and manufacturers will co-operate on development, 'maturing the product together'.
What's absolutely essential is for turbines to work from the start and through their lifetimes. Companies like DONG Energy are not building into their business case the eventuality that turbines might fail and have to be replaced in the first years. 'Those days are over,' she says.
In January this year, after this interview took place, DONG Energy signed up with Siemens Wind Power to test two new 6 MW offshore turbines and one 3.6 MW turbine from Siemens as part of a demonstration programme for offshore turbines based on direct drive technology. It's understood the 3.6 MW turbine will be tested at DONG's test site in Denmark, while the 6 MW turbines may be installed in Denmark or the UK. DONG and Siemens say they expect direct drive technology to make the turbines easier to maintain. Siemens embraced direct drive technology in 2009.
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