Wave exploitability index and wave resource classification

The selection of areas for wave energy development requires a thorough characterisation of the resource. For all its importance, wave power should not be the only criterion, and overly emphasising its role to the detriment of other aspects may mislead developers to the wrong areas. In this work, a new approach is presented based on a combination of two elements: the Wave Exploitability Index (WEI), defined ad hoc, and a classification of the resource based on mean wave power. These elements are applied at a global scale using the ERA-5 database, which spans the period 1979–2019. The highest WEI values (0.14–0.22) are found to occur in the Tropics and mid-latitudes, which highlights their potential for wave energy exploitation. The lowest WEI values (below 0.06) are located in (semi)-enclosed seas, such as the Mediterranean Sea or the Gulf of Mexico. As regards the classification of the resource, Classes IV and V, with mean wave power over 40 kWm−1, occur in areas which have aroused great interest but which often do not have high WEI values due to the resource variability (e.g., Western Europe); these areas are hardly ideal from the resource standpoint. Class I (below 10 kWm−1), typical of enclosed seas, is of little interest. Finally, Classes II and III (10–40 kWm−1) occur in areas open to the ocean in the lower and lower-middle latitudes (e.g., Chile, SW Australia); they present the highest WEI values, thus showing great potential, and have received scant attention so far. •A new wave exploitability index (WEI) is proposed and calculated globally.•A new classification of the wave resource is defined and applied globally.•Areas for wave energy so far mainly decided on basis of mean wave power.•We show quantitatively that the resource is more exploitable in other areas.•Areas with high WEI values and significant resource are Chile, SW Australia.