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INDUSTRY NEWS


After proving the concept (which is valid providing that the visibility sensor used for the intensity switching is completely reliable and highly accurate) Enercon trialled two sensors for over a year, namely Biral’s HSS VPF-710 visibility sensor and a well-known inexpensive competitor’s sensor. The trial not only looked at the measurements on the turbine but also how the sensors could be integrated into the existing electronics systems.


INTELLIGENT SWITCHING OF WARNING LIGHT INTENSITIES ON WIND TURBINES


Recently European Legislation modernised the aircraft warning light requirements for wind turbines with hub heights of 80m or more above ground level.


The aircraft warning lights that are used on these tall wind turbines have a very high light intensity of over 20,000 Candela*. This light is a great aid to navigation in poor weather but it can be quite intrusive in highly populated areas, especially when the visibility conditions are good. Until now, the warning lights were always required to be illuminated at full intensity in all conditions and this not only proves irritating to nearby residents but also restricts the number of wind turbines that can be placed in one location. This has a very negative impact on the amount of renewable energy that can be generated. The new legislation will help by allowing the intelligent switching of warning light intensity levels relative to local weather conditions.


For the past few years Biral has been working with Enercon GmbH (a leading wind energy turbine manufacturer in Germany) and the manufacturer of the warning lights to prove the validity of the concept of switching the light intensity intelligently to different intensity levels according to ambient visibility conditions. All considerations were taken into account for this study, including the difference in horizontal and diagonal visibility that pilots would have when flying and looking down at the land surface.


The Biral HSS sensors performed extremely well during this trial with the usual accuracy and reliability that these sensors are known for and the contract to supply visibility sensors for over 100 wind turbines was awarded to Biral.


The Biral HSS sensor performed particularly well in two key areas;


1 The Biral HSS sensors use several levels of hard and software filtering on the receiver optics that ensure they are able to work in close proximity to the tried and proven aircraft warning light sources without these same light sources affecting the measurements of the visibility sensor


2 The very large amount of vibration on a turbine with hub heights above 80m is quite difficult to deal with and the Biral sensors performed satisfactorily compared to the competitive models in this regard


For wind energy turbine applications the sensors are mounted next to the existing wind sensor on the rear of the turbine hub facing away from the blades (see picture).


Using the collected visibility data the aircraft warning lights can be adjusted to one of three intensity levels. The wind speed and direction data is used to alter the hub orientation and the alignment of the blades. The data is also archived and available for viewing along with the other operational parameters of the wind turbine.


The Biral HSS sensors have been used in many other visibility applications as well, from lighthouses to airports for over two decades.


* All the units for measuring and defining light are based on the candela, which is the unit defining the luminous intensity from a small source, in a particular direction. This unit was originally based on the light emission from a flame. (www.electrooptical.com/whitepapers/ca ndela.htm)


Bristol Industrial & Research Associates Ltd www.biral.com


Wind Energy NETWORK


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