SmartBlades2: field measurement campaign on wind turbine in Colorado begins

Longer service life, greater yield

Rotor blades equipped with bend-twist coupling are able to adapt to variating wind conditions on their own – at higher wind speeds the rotor blades can bend or twist, thus offering the wind a smaller impact surface. This reduces the overall load on the system, thus increasing the service life of the wind turbine as well as its power yield. In order to be able to fully capture the structural and aerodynamic behaviour of the newly developed blades during the field experiment, the project partners integrated specially developed measurement systems into the blades' structure already during production at the DLR Center for Lightweight-Production-Technology (ZLP) in Stade, Germany.

First analysis under real weather conditions

"We are very excited to observe and find out how our rotor blades behave during these field assessments. This measurement campaign represents the first practical trial for our blade technology", says SmartBlades2 Project Manager Zhuzhell Montano Rejas of the DLR Institute of Composite Structures and Adaptive Systems. The findings will also be used to improve simulation models for next-generation wind turbines. Fraunhofer IWES is leading the measurement campaign. "We are using several measurement systems that will allow us to monitor the entire length of the blades in order to capture the deformations, accelerations and loads they are subjected to. In addition, the air flow around the rotor blades will be recorded at the surface using an aerodynamic measurement system,” reports Christian Kress of IWES, who is responsible for the campaign. Inside the rotor blades, various systems designed by DLR, IWES and SSB Wind Systems will continuously control how the blades behave under the diverse wind loading conditions to which the turbine will be subjected. Furthermore, the turbine’s tower and the nacelle made available by NREL are also equipped with extensive measuring technology, enabling the team to measure the behaviour of the entire system in detail.

The resulting measurements will be correlated with data on wind conditions, which will be recorded by the NREL data acquisition systems present on the NWTC’s field and a SpinnerLIDAR (LIght Detection And Ranging) measurement device from the Center for Wind Energy Research (ForWind) at the University of Oldenburg. This LIDAR is normally installed in the spinner of a wind turbine, but in this case it is set up on top of the nacelle to be able to analyse the wind field both in front and behind the turbine. With a laser system, the SpinnerLIDAR scans an area of wind field in front of or behind the turbine. "In this section, the SpinnerLIDAR can measure over 300 points per second," says ForWind scientist Martin Kühn. "This enables us to measure wind speeds, wind directions, vertical wind shear components, and local turbulences with a spatial resolution that cannot be met with conventional LIDAR devices."

The comparison of the structural behaviour measured by the sensors with the wind data will show whether the developed rotor blades achieve the desired behaviour. At the beginning of the measurement campaign, the SpinnerLIDAR will measure the incoming wind field while at the end it will also measure the wake flow behind the wind turbine to better understand the influence of the blades on the surrounding environment. Unlike systems used for commercial power generation, the measurements in the three-bladed Controls Advanced Research Turbine (CART3) provided by NREL will allow the scientists to conduct various validation scenarios, such as an abrupt deceleration of the rotor. On site – on the edge of the Rocky Mountains – the wind conditions can range from very low speeds to powerful gusts in winter and early spring. This will make it possible for the researchers to assess the SmartBlades2 rotor blades under a variety of environmental conditions. “We are delighted to be able to validate the new rotor blades at our research turbine at the NWTC. We are also eager to find out how these rotor blades, designed with bend-twist coupling, perform under real world conditions,” says Andrew Scholbrock, who is responsible for the measurement campaign with the CART3 turbine at NREL.