Seasonal Correction of Offshore Wind Energy Potential due to Air Density: Case of the Iberian Peninsula

Alain Ulazia,Gabriel Ibarra-Berastegi,Jon Sáenz,Santos J González-Rojí,Sheila Carreno-Madinabeitia

doi:10.3390/su11133648

Abstract

A constant value of air density based on its annual average value at a given location is commonly used for the computation of the annual energy production in wind industry. Thus, the correction required in the estimation of daily, monthly or seasonal wind energy production, due to the use of air density, is ordinarily omitted in existing literature. The general method, based on the implementation of the wind speed’s Weibull distribution over the power curve of the turbine, omits it if the power curve is not corrected according to the air density of the site. In this study, the seasonal variation of air density was shown to be highly relevant for the computation of offshore wind energy potential around the Iberian Peninsula. If the temperature, pressure, and moisture are taken into account, the wind power density and turbine capacity factor corrections derived from these variations are also significant. In order to demonstrate this, the advanced Weather Research and Forecasting mesoscale Model (WRF) using data assimilation was executed in the study area to obtain a spatial representation of these corrections. According to the results, the wind power density, estimated by taking into account the air density correction, exhibits a difference of 8% between summer and winter, compared with that estimated without the density correction. This implies that seasonal capacity factor estimation corrections of up to 1% in percentage points are necessary for wind turbines mainly for summer and winter, due to air density changes.

Highlights

Energy and environment are strongly related subjects that explain the patterns of the global crisis from the geopolitical viewpoint or from the perspective of climate change
A previous study carried out by the authors [53] demonstrated that this simulation, including data assimilation, is effective for improving the results provided by the numerical integrations where only the boundary conditions drive the model, for variables such as the precipitation, evaporation and precipitable water over the Iberian Peninsula
The authors would like to stress that the paper deals with seasonal changes in the air density (Figures 4 and 5), the close agreement between density calculated from model and observations (Figure 6, Figure 7 and Table 3), and the consequent results on Wind Power Density (Figure 8) and seasonal capacity factors for winter and summer (Figure 9)

Summary

Introduction

Energy and environment are strongly related subjects that explain the patterns of the global crisis from the geopolitical viewpoint or from the perspective of climate change. Offshore winds usually present higher speeds than onshore winds, and the available working hours near the rated power of the turbines are higher offshore. Wind farms cover large areas of land or sea. Danish Anholt offshore wind power plant covers a sea area of 88 km. Danish Anholt offshore wind power plant covers a sea area of 88 km2 This is another huge advantage for offshore wind energy, since onshore land occupation of this level presents important ecological and legal problems [3]. The authors have developed different offshore wind resource assessment studies in sea areas with different bathymetry such as the Bay of Biscay, Scotland and the Mediterranean taking into account this restriction in the selection of the available area [4,5,6]

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