Impacts of Spatial and Temporal Windspeed Variability on Wind Energy Output

Abstract

Modern applications of wind energy include water pumping and, for supply of electricity, grid-connected wind turbines and wind/direct stand-alone systems. In Britain, wind energy has been found to be particularly suited to isolated communities where the costs of transporting diesel fuel are such that it is prohibitively expensive to provide a constant source of electricity. The impact of long-term climate variability on wind energy production has been almost totally neglected in wind energy studies. The 1898?1954 Southport windspeed record is analyzed and it is shown that the annual mean varies between 7.3 and 5.2 m s?1. Depending on the turbine characteristics, this can represent a 50% mean reduction in output. A principal components analysis (PCA) was performed on forty-two monthly windspeed records for the years 1962?81 and the scores of the fist component (PC1) were used to analyze temporal variability in the wind field. It was found that the period 1962?81 has three phases alternating high-low-high winds over Britain. The time series of windspeed PCI scores is shown to be highly correlated with the PCI scores of a PCA of the Lamb Catalogue, an index of the atmospheric circulation systems affecting Britain. In meteorological terms, the relative frequency of westerly and anticyclonic conditions is related to the strength of the wind field. By correlation of station wind speeds with an index of westerly/anticyclonic frequency, it is shown that west mast stations are strongly affected by the relative frequency of these two weather types, whereas the relationship at east coast stations is much weaker.