Western Iberian offshore wind resources: More or less in a global warming climate?

Highlights: •Evaluation of offshore wind resource using state-of-the art regional climate modelling. •Present and future wind resource using multi-model ensembles. •Climate change signal on the Western Iberian offshore wind resource. •Significant decreases of wind power are projected for winter and autumn (up to 20%). •Projection of wind resource increases (up to 20%) in summer in northwestern areas. -- Abstract: Climate change is a major challenge for the energy sector, particularly for wind energy onshore and offshore. Climate models are the only tool which is able to produce physical-based projections of future changes in response to increasing greenhouse gas emissions. In the present study, the Western Iberian offshore wind resource is analysed for present and future climates, using a set of regional climate models (RCMs) simulations produced in the framework of the CORDEX experiment at 0.11° resolution (∼12 km), and a regional climate simulation produced with the WRF model at higher resolution (9 km). All these simulations are firstly, evaluated against wind buoy measurements and Cross-Calibrated Multi-Platform (CCMP) wind data, and used to generate two high quality multi-model ensembles based on the individual model's performance. The results of the WRF simulation and of the two multi-model ensembles are then used to describe the wind resource both for the present and future climates, according to the RCP4.5 and RCP8.5 emission scenarios. This allows the assessment of the climate change signal on the offshore wind and to provide an uncertainty measure of these projections. The vast majority of climate models project reductions of wind speed and wind power for all seasons, with the exception of summer. For the RCP8.5 emission scenario the multi-model ensembles project reductions in power density of around 7% for winter, 4% for spring and 12% for autumn, and increases of 5% for summer. In the latter, and increase up to 20% in power density is forecasted for the Iberian northwest coast. This is sufficient to offset the yearly balance, in as much as no change is expected at a yearly scale for this area. For the remaining west Iberian coast, a yearly reduction of less than 5% is estimated. These results are shared by the two multi-model ensembles and by WRF higher resolution simulation (9 km). The projected changes have the consequence of reducing the annual cycle of power density availability and of its yearly mean values. Finally, for the less aggressive scenario, RCP4.5, the changes have the same signal but with smaller values.