Optimising wind farm performance through efficient asset management

Minor adjustments to wind farm asset operations can make a significant difference to its financial performance in the long run.
Published: Thu 08 Sep 2016

Numbers show that the wind market is maturing which means that wind farm owners and operators want to optimise operations and enhance returns. This can be done through effective asset management.

It would be safe to say that there is still a great deal of research and development around the wind energy industry as perhaps the relationship between the wind and the turbine is not yet fully understood and the benefits not completely harnessed.

As a result, there is a drive to mitigate risk and deliver optimal financial performance at both ends of the wind farm development life cycle. Project developers find themselves under pressure to cut the levelised cost of energy from new projects. 

Optimising performance through modern technology

Over the design life of a wind farm, making minor adjustments to asset operations can make a significant difference to its financial performance in the long run.

According to David Cunningham, Principal Cleantech & Renewables Analyst at SgurrEnergy, there are a number of ways in which to optimise wind farm operation and financial performance. With modern technology and industry-leading analytical techniques, some significant results are possible.

Firstly, fix the yaw misalignment. Turbines should directly face the wind to maximise the power they generate. Unfortunately this doesn’t always occur due to the limitations of traditional wind direction measurement techniques. This can be addressed by using lidar to measure wind speed and direction across the whole rotor area to enable optimal turbine positioning. By implementing more effective measurements this can push up annual energy production (AEP) by 2%, and raise the absolute project internal rate of return (IRR) by 0.3%. He suggests that developers also control the wind farm as a single unit because then wake effects can be dealt with in real time more effectively, thereby providing grid support to meet regulatory requirements. This can boost AEP by 1%-4%, and increase IRR by 0.1%-0.6%.

In fact recently, the first ever demonstration of a ‘total wind farm control’ approach with wake steering resulted in some pretty significant wind turbine performance improvements.The ground-breaking study, pioneered by Prof. Dr. Carlo L. Bottasso, Chair of Wind Energy, Wind Energy Institute, Technical University of Munich (TUM), used wind lidars originating from ZephIR Lidar to demonstrate the potential that total wind farm control offers the industry. Wakes were deflected along a line of wind turbines resulting in an increase of 15% actual power output from the combined wind farm production.

According to TUM, this was the first ever closed-loop demonstration of wake deflection control, developed within a collaborative project funded by the German Federal Ministry for Economic Affairs and Energy (BMWi). The demonstration consisted of 3 turbines and, by yawing two of the upwind turbines to laterally deflect their wakes, the rearmost turbine was able to increase production leading to a net 15% gain in power across the ‘wind farm’. 

The lidars, provided by Danish Technical University (DTU) Wind Energy, measured the wind speed across the full flow field of the experiment, providing a clear visualisation of the deflected wakes and reduced interferences among the wind turbines.

Total wind farm control looks at the most effective method of turbine operation to benefit the overall production output from the site, rather than on an individual turbine-by-turbine basis. One key cause of overall site underproduction can be the wakes affecting all turbines downwind of the leading edge of the wind farm. The wake effects build and propagate through the wind farm with the potential for those turbines sited at the very back of the wind farm to be heavily limited in output.

ZephIR Lidars remotely measure wind speed from the ground or installed on turbines out to ranges of 300 metres in order to inform wind studies or to characterise a wind turbine’s true potential by reducing yaw misalignment and accurately measuring power curves in free wind flow. Measurements are taken across the full rotor swept diameter, rather than just at or up to hub height as typical met masts and more basic turbine mounted remote sensors provide.

Aerodynamics and forestry effects

Other factors that should be considered, according to Cunningham is the importance of making aerodynamic improvements.

Vortex generators are small fins that help to improve blade performance by reducing flow separation and improving lift. The use of effective scanning technology means owners can apply vortex generators in an optimum manner to match real site conditions. This can increase the annual production by an estimated 2%-3%, with a boost of 0.3%-0.4% to IRR.

Effective individual blade control is also critical to ensure the wind turbines meet their design life in addition to improving energy output. Wind turbines age and degrade, their optimum control set-points also change over time.  With a more robust and adaptive turbine control system, improvements in output will be achieved. This can increase the production by 1%-4%, and project IRR by 0.1%-0.6%.

Lastly, understand the real effects of forestry on performance. Locating a wind farm near a wooded area will clearly have an effect on turbine performance but the exact effect is difficult to quantify. Scanning lidar can help developers better understand the real effects of forestry on project performance. This can be used to manage the environment around a wind farm more effectively through selective forestry felling and restructuring which can boost production by up to 15%, delivering an increase in the project IRR of up to 3%.

It is evident that the adoption of optimisation activities can enhance developer, investor and owner returns at every stage of the development cycle and should form a core part of M&A, design and operational activity. Without this approach, projects will quickly become unviable and true potential will not be harnessed.

Wind generation (on and offshore) provides its own myriad of complex challenges to the smart grid and grid connection. Join our webinar, Large Scale Wind Integration-Case Study. This webinar is part of our 'Renewable Integration' In Focus track on Engerati. Follow this link for more insights!

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