Slots, flaps, tabs - for control engineering
Andrew Garrad, board member, DNV GL/EWEA president
The development of turbine technology over the past three decades has been dramatic and almost any aspect of it could be chosen as the source for major development in the future. Right now, I choose control engineering. You cannot see it, but it is the nerve centre of a modern turbine.
Day and night the huge turbines are actively optimised to change speed, reduce noise, increase yield, extend lifetime and integrate with diverse grid requirement. The extraordinary sensitivity of the aerodynamics to pitch angle means that a small twitch to the blades produces a large change in load.
Great effort is now made to keep the aerodynamic conditions as linear as possible. But can it be a good idea to move an 80-metre structure through 0.5 degrees every few seconds for 20 years?
Aerodynamics is notoriously non-linear and, in the 1990s, we used to make good use of its stalling characteristics - now too blunt a tool.
Now I'd like to see radical development in the use of small non-linear devices - slots, slats, flaps and tabs - general "smartness". Large movements of small components can produce big changes in loads, just as small movements of large components can.
Work is under way in several research locations and could be industrialised. The real challenge is reliability under all weather conditions, but the prize for moving a few kilogrammes rather than a few tens of tonnes is big.
If I can look beyond the turbine for development themes then I choose short-term weather forecasting. We have made spectacular progress in the last decade, but there are rich pickings in slight improvements in accuracy, making wind energy more and more reliable.
Standardise condition monitoring systems
Nigel Parlour, contract relations, Romax Technology
The first technological contribution would be the development of amalgamated condition monitoring systems to handle the multitude of makes of turbines.
There are no industry standards in condition monitoring, and this means that there are almost as many systems as there are makes of turbine. For larger wind-farm fleets this results in control rooms with multiple monitoring screens and greater complexity for operators. The fallout from this will mean the next stage in system monitoring will be the development of software that takes multiple sources of information from different monitoring systems and presents this data in a single, easy format. This would make turbine management less complex and resource-intensive for wind-project operators.
The second major contribution that technology will bring to the wind energy sector is predictive maintenance. We have seen a number of exciting developments, and we are getting to the stage where we can peer two or three years ahead of the life of specific components and recommend appropriate changes in use to extend component lifespan.
A prognostic rather than diagnostic approach to maintenance would be a huge benefit and, if more wind turbine owners were able to take a longer view, their wind energy costs could be cut dramatically.
Finally, as the size of wind turbines has continued to increase, the development of medium-speed drivetrains will represent a big step forward. The current maturity of the market means that there is still the opportunity for significant step changes in reliability, turbine cost and the cost of energy. The development of improved, semi-integrated solutions that are built on a modular basis offer the best way to maximise flexibility and reduce capital expenditure in the future.
A mix of classical and innovative steps
Henrik Stiesdal, CTO, Siemens Wind Power
I don't believe there is a specific technological improvement that can be identified that is likely to make the single biggest contribution in the near future to cutting wind energy costs. The 35-year historical trend of cost of energy from wind turbines is a continuous reduction without clear steps, indicating, in the end, that the technology developed incrementally without real singularities.
In my opinion the cost reductions of the future will be the result of a range of technological improvements representing a mixture of classical and innovative steps. The classical cost-reduction steps include: increased turbine size, obviously including larger rotors; continued efforts on aerodynamic efficiency improvements; and traditional cost-cutting activities, which do not makes headlines but are highly efficient.
The innovative steps include: new, automated manufacturing methods, particularly for blades; low-cost tall towers - several concepts are known, but certain new concepts may provide even better potential; new redundancy concepts providing lower-maintenance turbines, particularly for offshore; and new systems for active rotor control, to allow for larger rotors without dimensional increases.
One should also consider technological improvements that complement wind-energy cost reduction by increasing the value of wind energy.
The likely steps required to increase the value of wind energy include grid-scale storage, and turbine and controller upgrades to enable the provision of classical ancillary services in accordance with the needs of system operators - regulation up/down, spinning reserve, full reactive power at no wind, frequency response, voltage control and black start capabilities.
Open source tools to advance technology
Dan Bernadett, chief engineer, AWS Truepower
Many organisations, including the National Renewable Energy Laboratory (NREL) to the US Department of Energy (DOE) have focused on cost reduction for several years now. Many of these efforts have most recently focused on losses - wake, availability, power curve, environmental. This recognises that 15-25% of possible production is lost to various sources. While advances in materials science and manufacturing can reduce the cost of blades, gearboxes and generators, the mature state of this science means that cost reduction potential is small. But, great potential lies in reducing losses and maximising performance.
Open source software is an interesting area of development. We have already created an open source geographical information system tool to optimise plant energy output, which can advance transparency while inviting others to participate in advancing the technology. The open-source element could be useful in other areas of the wind industry, to help share the knowledge of this still young industry.
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