Roughness Parameter of the Land Verification of Values Based on Measurements Obtained Through the Use of Anemometers Poles
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Recent Researches in Environment, Energy Planning and Pollution Roughness Parameter of the Land Verification of Values Based on Measurements Obtained Through the Use of Anemometers Poles IOAN ION, VIOREL CAMPIAN ADRIAN CUZMOS, COSMIN DUMBRAVA Center for Research in Hydraulics, Automation and Thermal Processes – CCHAPT “Eftimie Murgu” University of Resita Traian Vuia Square, No. 14, 320085 Resita ROMANIA [email protected] http://www.cchapt.ro Abstract: The investment management of a fleet of air-electrical generators, the most important activity that takes place in the opening phase is to assess the wind potential of the area which will have wind turbines. If the evaluation is only based on general information from weather stations, wind speed at heights above calculation is made taking into account the "roughness of the zone characterized by specific parameters recommended by the literature. Based on experimental data, their values can be verified. Key-words: Wind, wind speed, wind potential, specific energy / power of the wind, graphic variation, roughness parameter 1 Introduction. General Specifications - which will be the cost price (production) of Every project involves risk. In large projects, such electricity when connected to the download as the one seeking to achieve a park of wind network? generators, the risk should be minimized. In fact, the - which is the average lifespan of the turbine itself project of a wind turbine park, involves both certain and related facilities, thereby being able to factors and elements that are characterized as safe, estimate the rate for the investments recovery but also factors which by definition are and its economic profit? unpredictable and can lead to positive results, but The safety of the response to the first question is also failures. in inverse correlation with the risk assumed under Most technical products have a behavior that can the project to build a wind generator park. be anticipated with high probability. Since their Evaluation of wind potential, in a point or an area design phase (even experimental models and can only be based on the measurement of prototypes) their technical characteristics can be parameters (factors) of those atmospheric spots. estimated with great precision because, in general, The values of atmospheric parameters can be the operation does not depend only to a limited obtained from weather stations (if they exist in the extent by climatic conditions. area) an indication by the websites which provide In the case of the generators in question, they information on movements of air masses and/or have well-established technical characteristics, but using the facilities and specialized equipment for the electricity they produce is entirely dependent on monitoring the atmosphere and which are mounted atmospheric stability and wind speed in particular. on special poles with different heights. We can say with certainty that the risk management, Background difference between data recorded at in this case involves a thorough assessment of weather stations and those obtained from potential wind measurements consist of the following aspects: The intention of investment in wind energy at the - from weather stations single values are initial stage of implementation, must find the answer obtained for size and wind direction. In to some questions: addition, generally anemometers from weather - which is the wind energy potential in the future stations are placed at low heights, of several location of wind turbines? meters, which make wind power to be impacted - how much electricity will be produced in a time (reduced) significantly from the roughness of by a single plant (elected) whose technical and site. Until the use of modern equipment, wind structural characteristics are known? direction and intensity values are read from a certain period by time, mediation was made somehow subjective, there are no recorded data ISBN: 978-1-61804-012-1 216 Recent Researches in Environment, Energy Planning and Pollution base for fixed time intervals, allowing a - relative air humidity in [%]; calculation and hence an objective assessment . - air temperature [o K] × 10; Obs. For a general estimation, to conduct tests for - Atmospheric pressure [hPa]; determining the place of the arrangement of Storing data in columns was made with a Data anemometric columns maps with weather Logger 32 and was used for transmitting mobile information on the intensity of the wind are more telephone network. than welcome and necessary. Downloading data was done daily for all - the anemometric pillars (specialized) may have columns, followed by validation and processing several anemometers at heights pre-established, values. with which the wind force can get the Each data file with file extension. row (for each measurements averaged over the desired time day and location) was transformed into an Excel file intervals (pre-established); to validate both the performance and subsequent - disposal sites in the field, the anemometric poles calculations. can be chosen depending on the land It is noted that by setting the equipment was configuration, by access roads, electricity intended and achieved an average of values for a transmission networks and distribution of period of 10 minutes per day resulting in 144 lines existing and especially curves (based on the of eight fields containing values of parameters existing primary information’s) for the existing tracked. potential in the area . In Figures 1 and 2 were presented the measured The county of Caras-Severin, integrating the values (in m/s) of wind speeds (at h=50m) for all 10 objectives and priorities of the National locations (July 2009). Development Plan, namely the Joint Programming 12 Document Romania, Serbia, has realized the project viteza măsurată [m/s] "Assessment of wind potential in the south of la h=50m Anina 10 Banat from the perspective of sustainable Bolvasnita Brebu Nou development." The project provided specialized Buchin Gradinari technical support (as plants and transmission 8 Moldova Noua characteristics of weather values, and pillars) for the Pojejena Resita Semenic following ten locations: Anina BolvaşniŃa, Brebu 6 Nou Buchin, Gradianri, Moldova Noua, Pojejena, Vrani Resita, Semenic and Vrani. Installation of 4 equipment was conducted in summer 2009 and then started collecting the measurements. 2 The lack of equipment with which the monitoring of atmospheric parameters is made, zilele lunii iulie 2009 0 there can be used approximate methods of work 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 which can be determined based on average wind Fig. 1. Speeds measured in 10 locations h = 50m speed chart for the location of interest. Material object is to make a check (and possibly 6 viteza medie măsurată [m/s] a correction) of values by roughness of parameters, 5.167 la h=50m which are presented in the literature, based on actual 5 measurements obtained by using columns 4.024 anemometric. 4 3.882 3.892 3.252 3.12 3.027 3 2.744 2.761 2 The Measuring of Weather 2.376 Characteristics with Anemometric 2 Pillars. Parameters and Units 1 The equipment, which was disposed, the monitoring was done by measuring the weather characteristics 0 as follows: Anina Bolvasnita Brebu Nou Buchin Gradinari Moldova Pojejena Resita Semenic Vrani Noua - wind speed at three heights (50, 25 and 15 m) in Fig. 2. Averaged speeds measured in 10 locations [dm / s]; h=50m - wind direction at two heights (50 and 25 m) in sexagesimale degrees; ISBN: 978-1-61804-012-1 217 Recent Researches in Environment, Energy Planning and Pollution 3 Calculations for Wind Potential 3.2.2 Math Computing Assessment The above assumptions can be analytically written as follow: 3.1 Commercial Software ⋅vm 2 E = (1) There are commercial software that can estimate the c 2 wind potential for higher heights then column height (which is properly placed and anemometer). m Vp ⋅⋅=⋅ TR (2) Depending on the results we can estimate the M power/energy and also specific wind generator can be chosen optimally. α v h = (3) v hrr 3.2 Own Software Based on the reasoning of the underlying where: Ec is air mass kinetically energy; phenomenon which transforms kinetic energy (air m – air mass that spin the turbine runner; masses) into electrical energy, taking into account v – air speed at height h corresponding to the measurements of anemometric columns was turbine shaft; prepared a program that can determine the wind p – measured atmospheric pressure; potential at the desired height (usually the upper V – air volume corresponding to air mass pole height ). that spin the turbine runner; M – air molar mass; 3.2.1 Working Assumptions R – ideal gas constant; The following assumptions were made: T – measured air temperature; - the wind exposed area, for which the kinetic vr – reference air speed; energy are computed, is perpendicular by wind hr – reference height; direction; h – turbine shaft height; - is considered that the air mass which spin the α - boundary layer exponent. generators propeller, have the same velocity (on The coefficient that characterized the exponential entire propeller surface) and is equal with the profile of the boundary layer for a height h > hr = 50 measured or computed (based on extrapolation) m can be computed using the determined for the height at which the rotor shaft are coefficients for height interval that the wind speed installed; was measured (h1 = 15 m, h2 = 25 m i hr = 50 m). - the pressure and temperature variation of free The