Effect of Climate Change on Wind Persistence at Selected Indian Offshore Locations

摘要

The offshore wind energy is slated to meet world's energy demand significantly in future. In India three offshore regions along the eastern, southern and western parts of the coastline, namely, Rameshwaram, Kanyakumari and Jakhau, have been identified by the Government of India for offshore wind energy extraction. This is based on the wind power potential assessed with the help of historical data. One of the wind parameters that plays an important role in evaluating the energy resource is the persistence of mean wind, often known through the positive serial correlation in a given wind time series. The persistence observed through historical data however may not remain same in future due to the effect of climate change induced by global warming. In this paper, the wind speed persistence at the above mentioned three locations has been analyzed in the light of climate change. The daily wind speeds for the future time slice of 2006-2032 are derived from the Canadian General Circulation Model: CGCM4 run with RCP 4.5 warming scenario. Such projected wind information is compared with the historical wind over the time slice of 1979-2005 and belonging to the 'CGCM: 20C3M' model. The GCM data suffer from bias and this is removed using the quantile mapping method. The stationarity test of 'unit-root' indicates that the daily wind speed for each station is stationarity. In order to quantify the persistence at the turbine cut-in speed of 4 m/s, the wind speed duration curve (WSDC) is drawn. The results demonstrate a decrease in the persistence in future of the order of 3% and 8% at Rameshwaram and Jakhau, respectively and an increase in it by around 3% at Kanyakumari. These trends are further confirmed by the alternate autocorrelation function approach. From the wind persistence point of view alone therefore the power extraction at Kanyakumari may go up in future, which may not be the case with the two other sites. The variances across the three datasets are analyzed using the Levene's test, which showed that the cross-variance across the three locations might decrease in future, but the individual variance at Jakhau might increase and the same at Rameshwaram and Kanyakumari might remain the same in future, not much affecting the energy extraction over the latter two sites.