We present a modelling study of the impact of coastal breeze regimes on prospective wind farms offshore at two sites similar in position but located in different climate zones: the Central Mediterranean Sea, Lamezia Terme, Italy, and the Western North Sea, Høvsøre, Denmark. Both sites are located at the west coast of a peninsula with a north-south oriented coastline and a main westerly synoptic flow aligned to the breeze system.
The increasing growth of the height of wind turbines, and of the extension of future clusters of wind farms in coastal offshore areas, demand a careful study of the characteristics of the coastal flow in both vertical and horizontal dimensions respectively. The sea breeze cell extent is of special interest because it might include only part of a wind farm thus affecting its production pattern. Numerical Weather Prediction models, NWP, and specifically, meso-scale models are ideal to investigate spatial variation but their limitations in spatial resolutions does not allow to accurately locating the coastline.
Observations from Lamezia Terme, at the west coast of the peninsular Calabria region in Italy, include an intensive summer campaign in July 2009, and observations from a wind lidar for a three-year period starting from 2014. The Høvsøre test centre for large wind turbines, at the west coast of the Jutland peninsula in Denmark, has more than ten years of measurements from tall masts and from different wind lidars.
Two previous studies at Lamezia [1,2] showed that: (i) coastal breeze develops during the summer creating the daily stability cycle over land; (ii) coastal breeze develops in sunny days all year around with different strength; (iii) during moderate westerlies and sunshine, the sea breeze modulates the background wind while the weak nocturnal return flow is blocked. In Jutland, sea-land breeze systems at the west coast of Jutland  are difficult to separate from the persistent westerly flow that blocks the night cell development and the variable weather conditions during the day. Two cases were found and work in progress focuses on finding other occurrences to attempt developing a statistics in Denmark.
To study the extent of sea breezes, we use data from: the upcoming database from the New European Wind Atlas, NEWA, model chain over Europe at a spatial resolution of 1 km, and time resolution of 30 minutes for a period of 30 years; and simulations over the whole period of the intensive campaign in Lamezia at a space and time resolution of 3 km and one hours. For both Lamezia and Høvsøre, a transect of 5 points perpendicular to the coast was chosen, and correlations between the different points was estimated to observe the wind speed and direction variation with the distance to the coast during sea breezes days. Power production of a prospective wind farm will be estimated using different combination of the wind speed along the transect.
As far as we know, this study is a seldom study on sea breezes development in Denmark.