The Influence of the North Atlantic Oscillation on diverse renewable generation in Scotland

The North Atlantic Oscillation (NAO) is an index measure of the pressure gradient between Iceland and Portugal, with the pressure gradient affecting the strength and track of storms across the North Atlantic and into Europe. This has implications for renewable generation, which are becoming increasingly important with higher renewable penetrations. To explore the impact of the NAO on renewables a hindcast of wave, onshore and offshore wind generation in Scotland was created for the most recent climate normal period (1981–2010).
These hindcast generation figures were compared to NAO monthly index values and showed a strong and significant positive correlation for the high energy portion of the year (October to March). The strength of this relationship is in some instances, most notably for wave generation, weakened by the higher energy positive NAO conditions causing increased device cut-out. The impact of the NAO was also modelled at a seasonal winter scale (December–March) as is usual in NAO analysis. The model showed the strongest influence on capacity factor for offshore wind, with each increase in NAO index of 1 causing a predicted increase of capacity factor of 3.17 (compared to 2.59 for onshore wind, 1.35 for wave, and 2.49 for the combined portfolio). In January and February, the NAO has a statistically significant impact on hindcast generation variability, at a 1–4 h time scale for all resources and 1–24 h timescale for onshore wind and wave, which will have implications for system management.