Investigation of wind potential variation at three measurement sites based on atmospheric stability and power production Lavan Kumar Eppanapelli Master of Science Thesis KTH School of Industrial Engineering and Management Energy Technology EGI-2012-2013 Division of Heat & Power SE-100 44 STOCKHOLM -2- Master of Science Thesis EGI 2012:2013 Investigation of wind potential variation at three measurement sites based on atmospheric stability and power production Lavan Kumar Eppanapelli Approved Examiner Supervisor Prof. Torsten Fransson Miroslav Petrov Commissioner Contact person AQSystem, Sweden Lasse Johansson Abstract As tapping energy from wind expands rapidly worldwide, it is a common procedure to locate a practicable site to extract power from abundant wind energy by building wind farms. Comprehensive understanding of wind resource at a site is important to perform the main activities such as wind flow modeling, wind turbines micro siting, annual energy yield calculation and cost of energy estimation. The present study progressed by focusing on the variation of wind potential at three measurement sites to investigate the possible factors that influence the wind at each location. Three measurement units, one 100m met mast and two AQ500 SoDAR systems are used for the present study for collecting wind measurements for one year duration. This report outlines the working principle of remote sensing instrument AQ500 SoDAR, thermal stratification of the atmosphere and land-sea breezes effects along with the data filtering methods, statistical methods and annual power production. The results of the inter-comparison study between two nearby (800m) locations are given as an orientation to assess the differences that will be introduced into two faraway (5515m) locations due to the distance, the complexity of surrounding terrain and stability classes influence. Variation of diurnal and seasonal wind speed has taken as a basis to explain the stability influence on the measurements, furthermore, variables such as potential vertical temperature difference and Richardson number are considered to derive the stability classes. Statistical method has derived based on the wind speed distribution to calculate the annual power production and capacity factor values at the three locations. MATLAB is used for developing data filtering techniques, Richardson number, power production and inter-comparison calculations. Key words: AQ500, SoDAR, Met mast, statistical analysis, atmospheric stability, wind shear, annual wind power production -3- Preface and acknowledgement This report submitted as a master thesis for the two-year master’s program in Sustainable energy engineering at the energy technology department at KTH. It is written in close supervision with AQSystem, Sweden. Deserving of special mention is my industrial supervisor Lasse Johansson, who had given extensive support and refreshed my wind energy expertise to a higher level. I would like to express my gratitude to AQSystem for giving me the opportunity to develop this thesis project. It was an excellent opportunity to acquire industrial and real-time experience by working with the AQSystem and by being to the wind farm field trips. I would especially like to thank my supervisor at KTH, Miroslav Petrov for his kind assistance during the project time and suggestions for finalizing the report. This thesis would not be what it is now without his moral support and encouragement. I owe a great thank you to my examiner Prof. Torsten Fransson for officially examining and evaluating my thesis report. -4- Table of Contents Abstract ........................................................................................................................................................................... 3 Preface and acknowledgement .................................................................................................................................... 4 List of Figures ................................................................................................................................................................ 7 List of Tables .................................................................................................................................................................. 9 Glossary .......................................................................................................................................................................... 9 1 Introduction ........................................................................................................................................................11 1.1 Background ................................................................................................................................................11 1.2 Problem statement ....................................................................................................................................12 1.3 Scope of this work ....................................................................................................................................13 1.4 Overview of existing literature ................................................................................................................13 1.5 Structure of the report ..............................................................................................................................13 1.6 About AQSystem ......................................................................................................................................14 2 Theory ..................................................................................................................................................................14 2.1 Atmospheric boundary layer ...................................................................................................................14 2.1.1 Vertical wind profile ........................................................................................................................14 2.2 Thermodynamics and stability conditions ............................................................................................15 2.2.1 Unstable stratification .....................................................................................................................17 2.2.2 Stable stratification...........................................................................................................................17 2.2.3 Neutral stratification ........................................................................................................................17 2.2.4 Stability conditions parameters ......................................................................................................18 2.3 Analysis of wind behavior........................................................................................................................18 2.3.1 Local effects ......................................................................................................................................18 2.3.2 Wind shear ........................................................................................................................................18 2.3.3 Atmospheric turbulence..................................................................................................................20 2.4 Mathematical formulation of wind resource.........................................................................................21 2.4.1 Wind data frequency distribution ..................................................................................................21 2.5 Wind measuring campaign systems ........................................................................................................21 2.5.1 Met Mast ............................................................................................................................................22 2.5.2 Remote sensing methods ................................................................................................................24 3 Methodology .......................................................................................................................................................26 3.1 Project location ..........................................................................................................................................26 3.2 Method of attack .......................................................................................................................................26 3.3 Wind resource data ...................................................................................................................................27 3.3.1 Data collection and quality control of the data ...........................................................................27 3.3.2 Filtering and Data correction .........................................................................................................30 4 Results and Analysis ...........................................................................................................................................33 -5- 4.1 Wind speed measurements with respect to the time ...........................................................................33 4.2 Wind profile and shear .............................................................................................................................34 4.3 Wind speed measurements difference ...................................................................................................35