Assessment of electricity production and coastal protection of a nearshore 500 MW wave farm in the north-western Portuguese coast

Abstract

Wave energy can contribute towards the “green” energy transition, but complementary applications like coastal protection are equally pertinent. However, viable commercialization should entice large wave energy farms of significant capacity, which may raise conflicts with coastal industries and/or protected areas. Such matters are addressed in this paper's numerical case study of a dual wave farm for a nearshore Portuguese site. It incorporates two parks of 75 bottom-fixed oscillating flap units, each. The farm's configuration, orientation, layout, and rating were evaluated for varying wave conditions and water levels, based on a statistically representative clustering technique. The farm's location was selected to minimize marine space conflicts. The numerical modelling was executed with SNL-SWAN, from which it was found that a staggered configuration – “W” – would yield better results than an aligned configuration – “III”. The “shadowing” effect of one park onto the other was equally observed, but with limited impact. Greater farm unit spacing and rated power benefited the annual energy production, with values of nearly 345 GWh/yr being achieved. However, the capacity factors were generally greater for lower power ratings, as pondered mean values varied between 0.078 (3.332 MW) to 0.144 (1 MW). Wave power absorption ratios between wave farms and cumulative standalone units (q-factors) were always below 1, pointing towards a destructive interference pattern. Important significant wave height reductions were observed (above 30 %, at times), albeit increments were punctually identified near two shallow water areas. Lastly, increasing the tidal level did not impact the farm's performance considerably, but benefited the nearshore impact.