This study evaluates the performance of a counter-rotating dual rotor wind turbine (CR-DRWT) with 2 m2 rotor radius equipped with a double rotational armature in an open jet wind tunnel. With only one similar-sized design previously assessed in a wind tunnel, this study offers valuable validation material for the literature. Through wind tunnel testing, the CR-DRWT confirmed earlier findings in literature and achieved a 15% to 50% increase in power output and a 10% increase in efficiency (CP) compared to a single rotor configuration at higher wind speeds (> 7 m/s). Though these gains were not observed at lower wind speeds (4–7 m/s). The simplified mechanics of a double rotational armature show promise for SWTs, as financial viability depends on reducing LCOE through efficiency improvements that maximize energy capture. The design's maximum CP values were below those achieved in previous field tests at larger scale highlighting potential for improvement for smaller sized turbines. To further explore the aerodynamics of CR-DRWT's, computational fluid dynamics (CFD) simulations are recommended, as they could provide insights into optimizing flow dynamics around CR-DRWT's. Finally, the study emphasizes the need for precise pitch angle and rotational speed measurements to improve the value of future measurements.
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This article discusses results from an international contest, open for university student teams (bachelor and master), involving the design, construction, and testing of small wind turbines in a large wind tunnel. The wind tunnel has an outlet of 2.85 x 2.85 m allowing a maximum rotor swept area of 2 m2 without significant tunnel effects. Both horizontal and vertical axis wind turbines are part of the competition. The turbines are evaluated by an external jury of industry experts based on criteria such as Annual Energy Production, cut-in wind speed, innovations, design, and sustainability. Although the contest has been initiated in 2013 with an educational focus, it has also evolved into a valuable database for scientific purposes by providing a decade worth of performance measurements for roughly 9-10 various turbine concepts each year. The collected data may serve as a unique validation resource for assessing the accuracy of design codes in modelling diverse turbine concepts thanks to detailed design reports with model descriptions accompanying each turbine (such turbine descriptions are often considered confidential for field measurements). The paper aims to explore the scientific value of this database by comparing calculations with measurements, offering explanations where possible, and reporting intriguing findings on unconventional concepts' performance. Even though not all observations could be explained fully they provide food for thought. Recommendations are provided for both students to enhance their designs and for contest organizers to elevate the scientific value of the measurements in future contests.
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tract Micro wind turbines can be structurally integrated on top of the solid base of noise barriers near highways. A number of performance factors were assessed with holistic experiments in wind tunnel and in the field. The wind turbines underperformed when exposed in yawed flow conditions. The theoretical cosθ theories for yaw misalignment did not always predict power correctly. Inverter losses turned out to be crucial especially in standby mode. Combination of standby losses with yawed flow losses and low wind speed regime may even result in a net power consuming turbine. The micro wind turbine control system for maintaining optimal power production underperformed in the field when comparing tip speed ratios and performance coefficients with the values recorded in the wind tunnel. The turbine was idling between 20%–30% of time as it was assessed for sites with annual average wind speeds of three to five meters per second without any power production. Finally, the field test analysis showed that inadequate yaw response could potentially lead to 18% of the losses, the inverter related losses to 8%, and control related losses to 33%. The totalized loss led to a 48% efficiency drop when compared with the ideal power production measured before the inverter. Micro wind turbine’s performance has room for optimization for application in turbulent wind conditions on top of noise barriers. https://doi.org/10.3390/en14051288
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