Researchers from the National Renewable Energy Laboratory (NREL) and other institutions have recently evaluated the performance of a widely-used wave measurement buoy, the Datawell DWR-MkIII, in monochromatic waves. The study, led by Xuepeng Fu and colleagues, aimed to quantify the buoy’s measurement accuracy, particularly for wave elevation and energy flux estimation, which are crucial for marine energy resource characterization, device design, and project development.
The team conducted experiments using a large-amplitude six-degree-of-freedom motion platform at the National Laboratory of the Rockies. They subjected the buoy to prescribed monochromatic heave motions and validated these motions with an optical motion tracking system. The buoy’s elevation and raw acceleration data were recorded and analyzed using four different methods: one frequency-domain method and three time-domain methods. The researchers also applied Bayesian optimization for the design of experiments and evaluated records from three test sites.
The results revealed two error regions within the buoy’s nominal period range of 1.6 to 30 seconds. For wave periods between 5 and 25 seconds, the buoy provided accurate wave height measurements. However, for short periods of less than 5 seconds, the buoy’s 1.28Hz sampling frequency induced sub-Nyquist artifacts, leading to biased elevation measurements and maximum energy flux estimation errors exceeding 100%. For long periods exceeding 25 seconds, the buoy underpredicted elevation, with errors depending on the period but relatively independent of wave height. The maximum wave height and wave energy flux errors in this range reached 64% and 87%, respectively.
The analysis of field data also suggested that the currently recommended method for estimating wave energy flux may underestimate the actual wave energy flux. This finding has significant implications for the marine energy sector, as accurate wave energy flux estimation is vital for resource assessment and project planning.
The research was published in the journal Applied Energy, providing valuable insights into the performance of a widely-used wave measurement buoy and highlighting areas for improvement in wave energy flux estimation methods. This study underscores the importance of accurate wave measurements for the advancement of marine energy technologies and the development of reliable wave energy projects.
Source: Fu, X., Driscoll, F., Fao, R., Kenny, C., Griffin, K.P., Murphy, M., & Lambert, S. (2023). Performance evaluation of an offshore wave measurement buoy in monochromatic waves. Applied Energy, 335, 120754.
This article is based on research available at arXiv.