RELATIONSHIP BETWEEN THE ENERGY AND THE CHANGE OF DIRECTIONS OF THE WIND

摘要

In the process of wind energy production the efficiency of the wind turbine or wind machine decreases if the change of wind directions is more frequent. It may be supposed that the specific wind power as a potential quantity also depends on the variability of the wind directions. In this paper we investigate the relationship between the average specific wind power and the daily change of wind directions. The database of our investigations consists of hourly wind directions and speeds of five Hungarian meteorological stations from the period 1991-1995. It has 16 wind directions according to the climatological practice. The analysis was made for the whole data set and the different subsets of the period. The method of the examinations is that we create elemental events from the hourly wind directions. The wind direction of the t hour of a day of a given period (subset) is compared to that of the previous (t-1) hour. If these are uniform then the t hour is considered to be a stable point of time from the aspect of the change of the wind directions. Otherwise the t hour is an instable point of time. From this we can calculate the average daily number of instable points of time and the so called instability index of the wind directions. Since the specific wind power is in proportion to the cube of the wind speed we used the average of the hourly wind speed-cube to characterize the daily wind energy. First we analyze the time periods (subsets) on the basis of the average specific wind power, than we compare the instability indexes. At least we construct a special linear correlation-regression model to investigate the sensitivity of the potential wind energy to the change of wind directions.