Measurements of Coastal Winds and Temperature. Sensor Evaluation
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NTNU Trondheim Norges teknisk- naturvitenskapelige universitet Dr. sclent, avhandling Fakultet for fysikk, informatikk og matematikk Institutt for fysikk and Sensor Wind Evaluation, Structures v « "mew DataQu Measurements of Coastal Wind and Temperature Sensor Evaluation, Data Quality, and Wind Structures Tore Heggem Thesis submitted in partial fulfilment for the degree DOCTOR SCIENTIARUM NORWEGIAN UNIVERSITY OF SCIENCE AND TECHNOLOGY, TRONDHEIM Faculty of Physics, Informatics, and Mathematics Department of Physics March 1997 DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. “Deem traeng itj mal for a finn ut at det blaes her.” Fra “Viktor! Viktor!" av Fredrik Skagen Preface The present thesis has been worked out at the Norwegian University of Science and Technology, Trondheim (NTNU), Faculty of Physics, Informatics, and Mathematics, Department of Physics-Lade, and submitted as a partial fulfilment of the degree Doctor Scientiamm. The first five chapters of the thesis is a documentation of the measurement station at Skipheia. Chapter 6 and Chapter 7 describes the data base built up from measurements from 1982 and up to today. In Chapter 8 are temperature profiles and temperature spectra discussed. Chapter 9 contains a submitted manuscript with analysis of long-term time series. Construction and operation of the measurement station has been executed by the staff and by students at the Department of Physics. The leader of the project has been my supervisor, Associate Professor Jprgen Lpvseth. My connection to the measurement project started in 1986. When the station was rebuilt after a fire in 1992, Knut Mollestad, Svein Erik Aasen, and myself were central in the planning and rebuilding work. The thesis is partly a collaboration between Aasen and myself. Aasen completed his doctor degree with a thesis on the measurement station in 1995 (Aasen 1995). Chapter 2 and Chapter 3 of the present thesis is a result of the collaboration. The differences from the corresponding chapters in the work of Aasen are only editorial. Chapter 6 and Chapter 7 of the thesis concerning the data base and quality control of the data, have titles similar to corresponding chapters in Aasen ’s thesis. The content of these chapters are unique for the two theses, but since the Skipheia data base is used as basis in both works, there will be some similarities. A brief review of the data acquisition systems, and a description of the data base formate are found in both theses. Acknowledgements I would like to take the opportunity to express my deep appreciation to Associate Professor J0rgen Lpvseth who engaged my interest of environmental physics, and helped me carry out this work through his engagement and everlasting source of ideas. I wish to express my gratitude to the following persons who have contributed to the completion of this thesis: Dr. Scient. Svein Erik Aasen for his helpfulness and go-ahead spirit the time we worked together at the station and with the thesis. Rune Lende for enthusiastic collaboration on time series analyses, and careful reading of the manuscript. Thanks to Professor Anders Johnsson for helpful comments on the manuscript. Thanks to Knut Mollestad and Lars Einarsen for all the time we have spent together working with wind measurements. Thanks to the rest of the staff at the Department of Physics who havebeen a support in the work. Finally I want to thank my wife Ingvild and my children Ida and Esten for patience and support during the thesis work. Trondheim, March 1997 Tore Heggem viii ix Contents 1 Introduction 1 1.1 Motivation for wind and temperature measurements 1 1.1.1 Weather forecast 1 1.1.2 Wind energy production 2 1.1.3 Turbulence structure 2 1.1.4 Climatological studies 3 1.2 Measurements and data control 3 1.3 Presentation of the theses 4 2 The Skipheia Station 7 2.1 Background 7 2.2 Site 8 2.3 Masts and sensor locations 9 2.4 Instrumentation house 10 2.5 Historical review of the station 10 3 Wind Sensors 21 3.1 Introduction 21 3.2 Principles of sensor operation 22 3.2.1 Cup anemometer 22 3.2.2 Propeller 22 3.2.3 Vortex counting 24 3.2.4 Vane 25 3.2.5 Sonic senors 25 3.3 Evaluation of tested wind speed sensors 26 3.3.1 J-TEC wind speed sensor VA-320-2-1 26 3.3.2 Met-One 010b anemometer 27 3.3.3 Vaisala WAA12, WAA15 and WAA15A anemometers 27 3.3.4 Gill UVW Anemometer, Model 27005 29 3.3.5 Aanderaa Wind Speed Sensor 2740 29 3.4 Tested wind direction sensors 30 3.4.1 J-TEC Wind Direction Sensor VA-320-2-1 30 3.4.2 Met-One 022 Bivane 30 3.4.3 Gill Microvane, Model 12305 32 3.4.4 Gill UVW Anemometer, Model 27005 32 3.4.5 Teledyne Geotech Bivane, Model 1585 32 3.4.6 Vaisala WAA12 modified for resolver measurements 32 3.4.7 ED wind direction sensors 33 3.4.8 Aanderaa wind direction sensor 2053 33 3.5 Discussion 34 4 Temperature Sensors 35 4.1 Introduction 35 4.2 Sensor construction 36 X 4.2.1 Sensor housing 36 4.2.2 The thermistors 37 4.3 Measurement principle 38 4.4 Accuracy of measurements 39 4.4.1 Temperature drift in serial resistance 39 4.4.2 Self heating of thermistors 40 4.5 Testing of time response of the sensor 43 4.5.1 Experimental setting 43 4.5.2 Time response 44 4.5.3 Frequency response function 46 4.5.4 Influence from solar radiation 49 4.6 Discussion 49 5 Calibration of thermistors 51 5.1 Need for calibration 51 5.2 Calibration set-up 51 5.2.1 Reference thermometer 52 5.2.2 Temperature regulation bath 53 5.2.3 Thermistor preparation 53 5.3 Calibration measurements 54 5.4 Curve fitting 55 5.5 Conclusion 58 6 DataBase 59 6.1 Review of the data acquisition systems 59 6.2 Data format 60 6.3 Control of the data 63 6.3.1 Data acquisition monitoring 63 6.3.2 Inspection of data files 63 6.4 Missing data 66 6.4.1 Large gaps 66 6.4.2 Fillgap - a routine to fill small gaps in time series 67 6.5 Data survey 68 6.6 Distributions of wind and temperature 72 7 Quality of Data 79 7.1 Errors in wind speed measurements 79 7.1.1 Confidence in wind gust values 79 7.2 Wind direction measurements 87 7.3 Shading effects 89 8 Atmospheric Stability and Long-Term Spectra 97 8.1 Planetary Boundary Layer 97 8.2 Stability 98 8.3 Temperature profiles at Skipheia and Sletringen 99 8.3.1 Profile plots 101 8.3.2 Lapse rate at Sletringen 105 XI 8.3.3 Lapse rate at Skipheia 109 8.4 Temperature Spectra 111 9 Analysis of Long Time Series of Coastal Wind 115 References 137 Appendix A Data Survey A1 Appendix B Estimates of Power Spectral Density Bl Appendix C MATLAB Programs Cl xii Chapter 1 Introduction This chapter gives the motivation for wind and temperature measurements at the coast of Norway, and a short presentation of the thesis. 1.1 Motivation for wind and temperature measurements Precise and extensive measurements of meteorological quantities are required for several pur poses. To obtain data for reliable weather forecast is an obvious object of the measurements. Studies of wind loads on constructions, and mapping of potential wind energy resources are also important. In addition, studies of global climate require high quality long-term measure ments of wind and temperature. 1.1.1 Weather forecast Historically, the most important reason for meteorological measurements has been to provide information for weather forecasting. One of the largest disasters in the Norwegian fishing his tory hit the village Titrah, which is close to the measurement station at Skipheia, on 14 October 1899, when 150 fishermen were lost in a surprising storm. Fortunately, the forecasting and the communications has improved during the last century. The Norwegian Meteorological Institute (DNMI), which has official national responsibility for meteorological forecasts, has several meteorological stations at the coast of Mid-Norway. Data from some of the stations have been used to substitute for lacking data in some statistical analysis. 2 Introduction 1.1.2 Wind energy production The long Norwegian coastline has excellent sites for wind power production. The well developed hydro power system will even out the fluctuations in the wind power production, so combined with hydro power production the utilization of the wind power is optimal. The wind power production is in phase with the power consumption on an annual basis while the hydro power potential on the other hand is in opposite phase of the consumption, so the combination of water and wind energy will give a synergy effect. An intensive development of wind energy production can give an annual production of 30 TWh/year (Lpvseth, 1995). An objective of the measurements at Skipheia has been to provide suitable data for eval uation of the potential wind power production from large wind turbines. An important char acteristic of wind energy is that the power output of a wind turbine is proportional to the third power of the wind speed. Therefore the precision requirements of wind speed statistics for energy assessments are higher than for most other purposes. Knowledge of loads on wind turbines is also required. The effects of complex terrain on the loads on the wind turbine are not clearly identified.