Round Robin Testing: Exploring Experimental Uncertainties through a Multifacility Comparison of a Hinged Raft Wave Energy Converter

Abstract

The EU H2020 MaRINET2 project has a goal to improve the quality, robustness and accuracy of physical modelling and associated testing practices for the offshore renewable energy sector. To support this aim, a round robin scale physical modelling test programme was conducted to deploy a common wave energy converter at four wave basins operated by MaRINET2 partners. Test campaigns were conducted at each facility to a common specification and test matrix, providing the unique opportunity for intercomparison between facilities and working practices. A nonproprietary hinged raft, with a nominal scale of 1:25, was tested under a set of 12 irregular sea states. This allowed for an assessment of power output, hinge angles, mooring loads, and six-degree-of-freedom motions. The key outcome to be concluded from the results is that the facilities performed consistently, with the majority of variation linked to differences in sea state calibration. A variation of 5–10 % in mean power was typical and was consistent with the variability observed in the measured significant wave heights. The tank depth (which varied from 2–5 m) showed remarkably little influence on the results, although it is noted that these tests used an aerial mooring system with the geometry unaffected by the tank depth. Similar good agreement was seen in the heave, surge, pitch and hinge angle responses. In order to maintain and improve the consistency across laboratories, we make recommendations on characterising and calibrating the tank environment and stress the importance of the device–facility physical interface (the aerial mooring in this case).

Laboratory investigation on short design wave extreme responses for floating hinged-raft wave energy converters

“…The paper is structured such that Section 2 establishes the experimental case study, environmental test conditions and SDW approaches considered; Section 3 presents the results for the short-term irregular sea states; Sections 4, 5 present the results for the single and constrained SDWs, respectively; Section 6 discusses the performance of the various techniques with suggestions on future improvements that could be made; and finally, the recommendations and conclusions are drawn in Section 7. 10.3389/fenrg.2022.1069108 2 Physical modelling campaign Experiments are conducted in the Ocean Basin at the COAST Laboratory; a facility that is 35 m in length, 15.5 m wide and has an adjustable floor to allow for a range of operating water depths up to a maximum of 3 m. The operational water depth is set to 1.5 m in this work, based on the EMEC Billia Croo Wave Test Site and consistent with previous work conducted on a similar device through the Marinet-2 project (Davey et al, 2021).…”

Experimental investigation into laboratory effects of an OWC wave energy converter

“…More recently and relevantly, the MaRINET2 project coordinated round robin tests for generic wave, floating wind, and tidal energy converters tested in multiple hydrodynamic test laboratories. Regarding wave energy, a deep water hinged raft WEC was tested in irregular waves across four laboratories [6]. Findings showed mean values of sea states, motions, power, and mooring loads results were consistent across laboratories to within 5-15%, but maximums sometimes varied significantly (35%+).…”

Numerical Investigation of the Scaling Effects for a Point Absorber

“…This staged approach has been adopted in the latest international standards [13] to provide a development pathway with research and development processes appropriate to the Technology Readiness Level (TRL) of the project. Understanding the uncertainties in the laboratory is key to understanding the significance of the measured data and results [14,15]. Small scale hydrodynamic model tests are usually performed according to Froude's scaling law [16,17].…”