Blade Test Centre A/S – better known as BLAEST – was founded as an independent company on 1st May 2005. But our history started long before - together with the modern wind energy industry.
Wind turbine blades have been tested for many years. Contrary to steel constructions composite structures are more complex and analytical verification is very complicated with lots of uncertainties. In the early days of the modern wind energy business many turbines lost their blades or experienced serious blade failures. Therefore, it was realised from the very beginning that full-scale testing was necessary to ensure the structural integrity. Furthermore, testing was used to prove that blades in mass production would meet the design assumptions.
One of the first Danish activities in the emerging wind energy business was the manufacture of two 630 kW wind turbines in 1979 which were both placed close to the town Nibe not far from Aalborg. The wind turbines were stall- and pitch-regulated respectively and they formed part of the wind power demonstration plant of the energy companies.
During this period RISØ National Laboratory also launched wind energy research activities, including test of wind turbine blades where the first static test took place in 1981 and the first fatigue test was performed in 1984 at Risø.
Static Test at Risø using sand bags
Apart from the public initiatives several private activities were emerging. During the years from 1977 to 1981 one of these private initiatives was the serial production of wind turbine blades (Økær Vindenergi) in the small village Sparkær located between the cities Viborg and Skive in the western part of Denmark. Later these blades were manufactured under the brand name Aerostar in Denmark and the USA. In 1986 the license-holder Erik Grove-Nielsen established the Sparkær Blade Test Centre as a private test centre. Before the test centre was built, blade tests were in fact performed in the open field which was later to hold the foundation of the test hall. The test rig was built to carry 4 blades at the same time. The test rig was in operation until the shutting down of the Sparkær Centre in 2014.
The first test rig in Sparkær
Wind turbine blades development expended rapidly and RISØ ran out of space. Consequently, in 1990 RISØ took over the Sparkær Centre and in 1996/97 a new test hall for large wind turbine blades was built. The new hall meant a period with plenty of room for testing blades up to enormous 30 meters! But the development continued and from a spacious environment the test hall soon became too small. In 2001/02 the test hall was extended by 10 meters.
The test hall in Sparkær
The development of blade testing was not only a matter of length. Test demands kept increasing accordingly. These demands were both to methods, measurements and not least the quality. Consequently, the test centre was accredited in 1998 as a test laboratory by the Danish national accreditation body DANAK (TEST reg. No. 427). Now the test centre could write accredited test reports for Static tests, Fatigue tests and Determination of natural frequencies. Later the accreditation also included Modal analysis and Conductivity measurement on the Lightening Protection System.
The test centre in Sparkær
The development of wind turbines and the size of blades continued growing and resulted once more in lack of space. Further expansion was needed, but the operation of BLAEST had reached a state of commercialisation that did not fit the basic research idea of RISØ National Laboratory. Therefore, it was decided to separate the blade testing activities in Sparkær into an independent fully commercial company. This led to the foundation of Blade Test Centre A/S (BLAEST) 1st May 2005 with RISØ, Force Technology and Det Norske Veritas as shareholders.
In 2006 a new blade test facility at Aalborg East Harbour was established in the former ship construction hall of Danyard. Now the problem with shortage of space had been solved and the Sparkær test centre could still to be used for small blades. However, in 2014 the test centre in Sparkær was closed, partly because the hall was too small for the blades of the future of 50-70 m, and partly because the financial crisis and a general downturn in the wind energy business led to a decreasing demand for blade testing.
Test hall in Aalborg before extension
The test centre at Aalborg worked fine. The capacity was good and there were lots of primarily overseas customers. The test hall allowed blades with a length of 60 m, which sufficed over a long period. But an extension was inevitable and in 2014 the hall was extended by approximately 25 meters which would allow blades of 85 meters to be tested. The development continued and already in 2016 part of the blade tip had to be cut off the world’s longest blade – LM Wind Power’s LM 88.4P blade – to fit the blade into the test hall.
Static test of LM88.4P in Aalborg
Test hall in Aalborg after the extension
Before BLAEST was established as an independent company it formed part of the RISØ National Laboratory. In this institution BLAEST formed part of the Test and Measurements Department at the Test Laboratory for Small Wind Turbines and later an independent unit under the Wind Technique department. Within RISØ Erik Grove-Nielsen started as manager of the Sparkær Centre. From 2000 to 2005 Carsten Skamris managed the Sparkær Centre and when BLAEST was established as an independent company Carsten took the role as Managing Director. In 2015 Erik Steen Jensen replaced Carsten as Managing Director.
The staff has always included a mix of engineers and technicians with very different backgrounds. The engineers could be everything from autodidact to engineers with a Ph.D. background. Likewise, the technicians could also be everything from unskilled to technicians with an advanced technical education. The common interest has always been the ability and the will to learn some of the special disciplines which are required to test wind turbine blades.
The BLAEST staff June 2016
The demands to both equipment and methods have developed rapidly since the very first tests were performed in the early 80ties. The first static tests were done by placing sand bags onto the blade corresponding to the extreme load. Today these tests are done by means of an electro mechanic load system which is both much faster and enables a much more uniform/standardized load with very little variation. In the beginning the fatigue test was done with a rotating mass mounted on top of the blade. The only important thing was a sufficient root moment. Today fatigue loads on large blades are induced by a floor-based exciter system and various dead loads, and the load level is achieved within a very narrow tolerance from the target load along the entire blade length.