Application of optical measurement complex Pentalum SpiDAR for wind shear measurements onshore Baltic Sea

Transcription

1 Application of optical measurement complex Pentalum SpiDAR for wind shear measurements onshore Baltic Sea Valerijs Bezrukovs 1, 2, Vladislavs Bezrukovs 2, Aleksejs Zacepins 1, Vitalijs Komashilovs 1 1 Institute of Physical Energetics, Aizkraukles Street 21, Riga, LV-1006, LV, 2 Ventspils University College, Inzenieru Street 101, Ventspils, LV-3601, LV. elmag@inbox.lv Key words: complex Pentalum SpiDAR, wind speed, measurements, wind shear, quality. 1. Introduction While designing wind power parks (WPP) emphasis should be done on research of wind shear and evaluation of wind energy resource. Based on this research evaluation of annual energy production is done to define technical requirements of wind turbine (WT) and height of the mast. Today optical measurement complexes are used for wind energy flow monitoring up to 200 (m) height. In Latvia investigation of wind shear is done using the measurement complex Pentalum SpiDAR [1]. 2. Approach The measuring complex showed on Figure 1 is installed in the territory of the Ventspils International Radio-Astronomy Center at the height of 13.2 (m) above ground level and at a distance of 2.5 (km) from the sea shore on a platform with coordinates N 57º33 12ʺ and E 21º51 16ʺ. Figure 1. Location of the Pentalum SpiDAR measuring complex 1

2 Complex is powered from 230 (V) supply mains. For the data transmission an optical communication line is employed which connects the measuring complex with server at the Ventspils University College. The Pentalum SpiDAR performs 5 (s) measurements of wind speed and direction for ten height levels: 30, 40, 50, 80, 100, 120, 140, 160, 180 and 200 (m). Apart from that, the records are made for pressure, humidity, and temperature of the air. 3. Main body of abstract Results of wind parameter measurements for one year period using measuring complex Pentalum SpiDAR revealed its capabilities and limitations. Figure 2 presents the curves of average monthly wind speed values, V avg, which are calculated by averaging the bins, i.e. the measured wind speed values V accumulated within 10 minutes in the time period Т from to using the laser measuring complex Pentalum SpiDAR at the heights 30, 50, 100, 140 and 180 (m) above ground. Fig. 2. Distribution curves of the average wind speed values V avg (m/s) obtained using the laser measuring complex Pentalum SpiDAR for the heights 30, 50, 100, 140 and 180 (m) above ground in the measurement time T. Figure 3 demonstrates the distribution curves of the average wind speed V avg and the average cubic wind speed V avg cub (m/s) values along with the SD value for the wind shear up to the height of 200 (m). These values have been calculated based on analysis of the data accumulated during 14 months in 2014/

3 Fig. 3. Approximation curves for the measured values of wind speed V avg, V avg cub (m/s), and for the standard deviation, SD, depending on height h. The distribution of the obtained wind shear values is well approximated by the expression: where h r is the height of wind speed measurement, (m), h is the height of WT location, (m), α are approximation coefficients. V avg = V avg hr ( ) (m/s), (1) Using the power law function for approximation of the measurement results, expression (1) will assume the form: V avg =0.76 h 0.47 (m/s). (2) SD = 0.43 h 0.4. (3) V avg cub = 1.13 h (4) Not all results of 5 second measurements can be used for calculating the averaged 10 minute value of wind speed. Part of the 120 measurements, which are performed during 10 minute interval have errors, that s why each measurement is accompanied by a quality score. It is a number from 0 (very bad) to 100 (very good), that is determined based on the following criteria: percentage of raw results used to calculate 10 minutes average; 3

4 Relative amount of data relationship between current measurement and measurements in neighbouring heights and times; signal or equipment problems leading to quality=0. The selection of quality threshold affects both goodness of results, and data availability. An optimal quality threshold is both site and customer dependent. 4. Conclusion Analysis of collected measurement data shows, that quality of measurement results depends on height of measurement point. Figure 4 shows, that best measurement quality results are achieved on (m) height. At high altitudes the quality of measurement results is dropping. Analysis of quality of measurement results shows that they depend also on seasonal periods. Figure 5 shows that the best quality of raw results can be achieved during winter period. Fig. 4. Percentage of raw results for wind speed used to calculate 10 minutes average grouped by height. 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Spring Summer Fall Winter Season < 20 Fig. 5. Percentage of raw results for wind speed used to calculate 10 minutes average grouped by season. 4

5 5. Learning objectives Pentalum SpiDAR wind speed measurement results are presented on web site Measurement results are periodically added and updated and they can be used by specialist for analysis of wind energy flow in Latvia territory onshore of Baltic Sea. As well students can use this data for educational and research purposes. Related publication [1]. V P Bezrukovs, V V Bezrukovs and A J Zacepins. Comparative efficiency of wind turbines with different heights of rotor hubs: performance evaluation for Latvia. Journal of Physics: Conference Series 524 (2014). doi: / /524/1/