Winds of change
The UK currently has more offshore wind power than anywhere else in the world. We are becoming increasingly dependent on this clean, safe, energy source for a significant proportion of our electrical needs.
Further, rapid growth in this sector is expected and is actively encouraged by Governments, industry and many green groups. As a result, turbine reliability, and being able to predict and prevent problems at these remote sites, is becoming more important.
Alison Laing met Loughborough University’s Dr Simon Watson, whose research is focusing on just that.
Offshore wind power operators have two key problems they are keen to solve. One is reliability. Onshore wind turbines typically operate at 97 per-cent availability, with only three-per-cent down time for problems or maintenance, scheduled or unscheduled. The offshore environment is obviously more hostile, with strong winds, waves and corrosion to contend with. Offshore turbines at some sites are seeing just 80 per-cent availability.
The other problem for wind power operators is high maintenance costs, which often run at about 25 to 30 per-cent of the energy generation costs. A large percentage of this is caused by unexpected and catastrophic failures, leading to corrective and expensive repairs. Also, offshore turbines are more remote to access (some more than 20 kilometres out to sea), so if one stops operating, it could be down for several months.
Costs must be reduced, and reliability improved, in order to increase the economic competitiveness of offshore wind power, which is why research into early failure detection and diagnosis of wind turbines, has become such an important area.
Dr Watson is head of wind and water power research at the Centre for Renewable Energy Systems Technology (CREST), part of the Department of Electronic and Electrical Engineering at Loughborough University. He has spent the past six years investigating pro-active condition monitoring for turbines, to help wind power operators develop robust operations and maintenance strategies – and save them time and money.
Dr Watson said: “Although turbines have monitoring systems built-in that cause the machine to shut down if there is a major problem – rather like a trip-switch in a domestic home – operators don’t always know what the problem is, or why it happened.
The most common problems tend to be electrical, but they can be fixed generally quickly. Some of the more mechanical problems associated with gearboxes and generators take longer, however.
“For example, gearboxes, while not the most common subassembly to fail, take a long time to fix. The procurement time to get one from the factory is lengthy, and then you must have the right conditions to crane the part, and transport the maintenance crew, to the offshore wind farm by boat.
“If you can detect bearing problems in a generator or gearbox, and manage to replace them before you have a catastrophic failure of the entire subassembly, you could save £100,000s, per turbine. That’s why proactive condition monitoring and maintenance of wind turbines is so critical.”
Techniques for condition monitoring are rather new in wind power engineering, but Dr Watson and his team, in collaboration with worldwide research institutions, university partners, and industry giants such as E.ON and Scottish Power, have been testing different systems on wind turbines to see if they can detect various component failures, ahead of time. They have also been working as part of the UK Supergen Wind Energy Technologies Consortium, funded by the Engineering and Physical Sciences Research Council (EPSRC), on programmes to increase the availability of turbines to ensure they operate for a larger fraction of time.
Dr Watson said: “The strategic monitoring of various components on a wind turbine can detect potential problems, including bearing failure, up to several months in advance. This will save operators money and help them plan their maintenance programmes.
“We have done a lot of work trying to predict failures in generators and gearboxes, with some success. We’ve been looking at cleverer ways of interpreting things, like monitoring power output and how that can indicate problems, such as a misalignment of a generator shaft. It works like this; a particular frequency can indicate whether the shaft inside the generator is not spinning around exactly in the centre, because when that happens, it vibrates. This vibration movement affects the electromagnetic field inside the generator, and we can measure that. We’ve actually detected problems and noted a misalignment this way, and three months later the bearings did fail in the generator.
“We are also looking at historic data, because maintenance engineers produce logs. We look to see where there’s an increase in a particular component of the power signal, and what it related to when the maintenance engineer noted a problem.
And we have also done a lot of work focussing on large numbers of turbines, looking statistically to see if we can tell which turbines within the farm are likely to fail.
The first phase of the £2.5m EPSRC Supergen Wind project is due to end in March 2010, but the consortium of which Dr Watson’s team are part has already applied for follow-on funding of £3.5m to continue their work.
Dr Watson concluded: “What the wind power companies want is an automatic system that will alert them to a problem, but also be specific as to what that problem is. A system that engineers can quickly interpret, without ploughing through tons of data.
“The wind speed, the power, and particular vibrations – these are the key things that tell us there are going to be problems. It’s complex, but that’s where we are all aiming to go.
“We’ve had a good deal of success in terms of the research work we’ve been doing so far. Through our engagement with companies such as E.ON and Scottish Power, we know precisely what their issues are, and we are determined to develop technology and methods that can help them in the operation and running of their turbines now, and in the future.”
Want to know more?
- Website: www.lboro.ac.uk/crest
- Contact: Dr Simon Watson
- Email: S.J.Watson@lboro.ac.uk
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