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Delay of flow separation and stall on Aerofoils using a Passive Flow control Technology which will improve aerodynamic performance and stability of wind turbines increasing their range of operation

Periodic Reporting for period 1 - Aeropaft (Delay of flow separation and stall on Aerofoils using a Passive Flow control Technology which will improve aerodynamic performance and stability of wind turbines increasing their range of operation)

Reporting period: 2014-11-01 to 2015-04-30

This programme has been undertaken to assess the feasibility of passive air jet vortex generators, requiring no active energy input, to the performance enhancement of large scale wind turbines. Previous work has demonstrated that these simple devices, properly designed and implemented according to the principles identified in the literature, can provide worthwhile performance benefits for large diameter wind turbines. In particular, this study shows that they can increase the maximum output power coefficient, reduce the cut-in wind speed and improve power output at the lower wind speeds, while reducing the sensitivity of power output in gusty conditions.
The objective of the study has been to assess industry’s reaction to the opportunity and the maturity of the technology. We have been to conferences, investigated the market and spoken to all the major wind turbine manufacturers. As far as we have been able to ascertain, industry is not yet ready to buy into the technology, citing immaturity and lack of evidence. This view should be set against a complex scenario whereby competitive pressures are forcing turbine manufacturer to look at cost reduction. We have also found that some companies have full schedule of development programmes ongoing so they are not open to new investigations.
Despite this view, a number of companies appear open to further discussion if the technology can be proven in the field. This remains the challenge since to convert a turbine and ideally to compare one turbine against another is an expensive undertaking and with normal match funding rules not one that Jarilo is able to undertake.
We have followed two work streams – technical performance and commercial interest. We have investigated the technical opportunity and shown that the PVJGs can be accommodated within a turbine blade without affecting the strength of the wing. This is because the PVJGs do not need to penetrate the structural components in the blade, namely the web spars and spar caps.
An experimental study has been performed to assess the feasibility of passive air jet vortex generators, requiring no active energy input, to the performance enhancement of a domestic scale wind turbine. It has been demonstrated that these simple devices, properly designed and implemented according to the principles identified in the literature, can provide worthwhile performance benefits for domestic wind turbines of the type investigated in this study. In particular, this study shows that they can increase the maximum output power coefficient, reduce the cut-in wind speed and improve power output at the lower wind speeds, while reducing the sensitivity of power output in gusty conditions. A theoretical performance analysis of a 500kW stall regulated wind turbine, based on simple Blade Element Momentum Theory, indicates that passive air jet vortex generators would be capable of recovering some of the power loss resulting from boundary layer separations over the blade surface, thereby allowing attainment of rated power output at slightly lower average wind speeds. Such devices would therefore provide the benefit of traditional vane vortex generators with much reduced excrescence drag penalty.
The data obtained from the Blade Momentum theory has then been combined with a Weibull distribution describing wind speed for a typical location in Europe. It shows a competitive improvement in annual energy recovery but is conservative compare to the headline internet view of vane vortex generators. This has hampered interest from major organisations such as LM Wind, Siemens and Vestas, despite our assertion that the technology will generate the benefits of vane vortex generators but without the drag associated with those devices.
In terms of commercial interest we have been in contact with most of the world’ major wind turbine organisations and a number of smaller ones.
Table 1 refers
Company Scope/Interest

1 Alstom Power Power and generating group
2 Windnovation Since starting out in 2007, WINDnovation has successfully completed more than 100 projects across the entire spectrum of modern wind turbine technology
3 SenvionSE The wind turbine manufacturer Senvion SE (“Senvion”), previously part of the Indian group Suzlon Energy Limited (“Suzlon”)
4 GE Power and Water Power and generating group, makes its own turbines
5 Frauhofer IWES German technology institute, equivalent to the UK catapults
6 Gamesa Spanish turbine group
7 Dekumed Dekumed has been established in 1974 as a plastic processing company.
8 Acciona Acciona, S.A. is a Spanish conglomerate group dedicated to the development and management of infrastructure and renewable energy
9 Blade Dynamics UK-based innovation group
10 Polytech
11 Renewable Advice.net
12 Biomedesign Turbine design group
13 ETA Wind Blade Solutions Italian group focussed on reblading
14 Sinoi GmBH – EU rep for LZ 4th largest Chinese manufacturer of turbines
15 Structeam Ltd Structural analysis group
16 LM WindPower Probably the world’s largest blade manufacturer
17 Pontis Smaller Netherlands turbine group
18 SE Blades Technology SE (Suzlon Energy Ltd) Blades Technology is responsible for the development and production of composite products.
19 NAREC UK Catapult wind turbine development group
20 SSP Technology A/S Wind turbine blades; design, development and optimization
21 EDP Renewables Energy company with interest in wind turbine
22 Siemens Power Major supplier – buys blades from LM Wind
23 Vestas Vertically integrated turbine manufacturer, currently focussed on offshore
24 Goldwing Goldwind (officially Goldwind Sc
The expected outcome with the product and its impact within the industry is that industry is curious and indeed in some instances interested in what we truly believe is exciting technology. Currently, the product of the conservative calculations and the immaturity of the technology means that we have not yet found a company to invest in the technology until such time as the technology has been proven to TRL6 on full size turbines. Unless investment is found to take the technology further there is as a consequence an impasse and the technology remain where it is.
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