Statistical analysis of winddata regarding long-term correction

Abstract: The procedure of determining if a site is suitable for wind power production requiresconvincing statistical data describing the long-term behavior of the average wind speed.This can be achieved by measuring the wind speed for a short time period, e.g. a year,and after that a Measure-Correlate-Predict (MCP) method can be performed. The shorttermmeasured wind data must be used in combination with a long-term referenceseries. This long-term reference series can be global reanalysis data reaching 20 to 30years back in time. In a MCP method different regression methods can be used. Aftercreating a long-term corrected wind data series, it is possible to analyze the conditionsat the investigated site. To be able to study the behavior of different reference series andregression methods, a model was created in MATLAB. As short-term wind speed dataVattenfall Wind Power supplied data from two measuring masts, Ringhals andOskarshamn, with maximum heights of 96 and 100 meters, respectively. From UppsalaUniversity data were supplied from a measuring mast near Marsta with maximummeasurement height of 29 meters.When creating these long-term corrected wind data series there were many methodsavailable. In this Master thesis methods such as Ordinary-Least-Square, Least-Absolute-Deviation and Reduced-Major-Axis regression methods have been used. With eachmethod three reference series were used in combination with the short-termmeasurement data. These were data from NCAR 850 hPa, NCAR 42-meter sigma leveland a confidential source.Regression methods in combination with reference series were studied and the deviationfrom mean wind speed was obtained for each of these cases. Studies were performed onhow the length of the short-term measurement series affected the deviation from themeasured mean wind speed. It was also investigated if the time of the year had anyinfluence on the measurements.The general conclusion drawn after performing the above-mentioned studies was thatthe NCAR 850 hPa wind speed data and the Reduced-Major-Axis regression methodgave the smallest deviation from the measured mean wind speed in most cases. It wasalso concluded that when a short-term measurement series reached 10 to 14 monthsthere was a significant decrease in deviation from the mean wind speed, regardless ofreference series or method used. Calculations from the model regarding seasonaldependence stated that there was a slight dependency on which period of the year ameasurement was performed.