Reduction of the capture width of wave energy converters due to long-term seasonal wave energy trends

Abstract

This paper presents a pioneering attempt to evaluate the impact of long-term seasonal wave energy trends on hydrodynamic capture by wave energy converters (WECs) over the 20th century. The ERA20c reanalysis generated by the European Centre for Medium-Range Weather Forecasts is calibrated against the ERA-Interim reanalysis via the quantile matching technique, and validated against buoy measurements across the Northeast Atlantic Ocean. The study focus is the seasonal variation of wave resources over the 20th century, so the calibration is performed using seasonally classified reanalysis and measured data. Results show that wave energy flux increased to 3 and 2 kW/m per decade in winter and spring/autumn, respectively, and that the frequency of off-limit events, defined as sea-states with significant wave height of over 5 m, has doubled over the 20th century. The impact of such wave energy trends is analysed in this paper using an oscillating wave surge converter, which shows steadily increasing power absorption over the 20th century. However, as a result of higher decadal trends and the increase in off-limit events, the hydrodynamic efficiency of the WEC, referred to as the capture width ratio, decreases up to 20%.1. The wave energy flux and its inter-annual variability (analysing the seasonal cycle), 2. The bi-dimensional probability density function, or scatter diagram, given by the wave period and the wave height, and 3. The probability of occurrence of off-limit events, where the WEC needs to activate its survival mode.In general, wave data from previous one, two or three decades are used for assessing the resource and power production capabilities of WECs in a given location [9][10][11][12][13][14][15]. However, by only considering data

A review of wave energy technology from a research and commercial perspective

“…However, extreme events also increase, requiring more focus on WEC survivability [87]. In addition, increase in off‐limit events () can significantly reduce the capture width ratio of an OWSC in the Irish sea, up to a level of 20% [92]. Thus, long‐term trends of wave climate should be considered for commercial planning [29, 73].…”

Variability of Wave Power Production of the M4 Machine at Two Energetic Open Ocean Locations: Off Albany, Western Australia and at Emec, Orkney, UK

“…We note that the two above formulations are equivalent. Analogous methods for evaluating WEC performance on a sea-state basis were used by Carballo et al (2015) and Morim et al (2019) for example, who used sea-state power matrices from the literature or provided by the WEC developer, while Penalba et al (2018) and Ulazia et al (2019) for example calculated the absorbed power using the authors' own time-domain hydrodynamic models of the studied WECs.…”

“…They also note that the magnitude of the inter-annual variations in the power production (for suitably downsized WECs) is generally lower than the inter-annual variability in the wave resource. Penalba et al (2018) and Ulazia et al (2019) consider decadal changes in WEC performance in the North-East Atlantic, off the western European coast. They note a progressive increase in the incident wave energy flux and the mean annual WEC power yield, respectively up to 40% and 30% higher values during 1980-2000 compared to 1900-1920. When the survival behaviour of the WECs is taken into account (i.e.…”

On the impact of long-term wave trends on the geometry optimisation of oscillating water column wave energy converters

“…The validation of the E1 and E2 gridpoints was not considered in this paper, but was previously described in [34] and [35], respectively.…”