Machbarkeitsstudie zur Bestimmung des sensiblen Wärmestroms von Gründächern

2021 ◽  
Author(s):  
Niels Wollschläger ◽  
Uwe Schlink ◽  
Armin Raabe
Keyword(s):  
Sonic Anemometer ◽  
Sonic Anemometers

<p>Die Eddy-Kovarianz-Methode ist ein bewährtes Verfahren zur Erfassung des fühlbaren Wärmeströms mit Hilfe dreidimensionaler Sonic Anemometer. <br />Diese Methode eignet sich jedoch nicht für kleinere Flächen wie Gründächer, da diese nicht mit den räumlichen Dimensionen des  <br />entsprechenden Footprints übereinstimmen. </p> <p>Als eine alternative Methode wird ein kürzlich konstruiertes akustisches Anemometer (Ly-ATOM) getestet, <br />das horizontal mit einer Ausdehnung von ca. 1 m und einer Datenerfassungsfrequenz von 1 Hz arbeitet. <br />Das Ly-ATOM ist in der Lage sowohl die akustische virtuelle Temperatur als auch die horizontalen Windkomponenten<br />eines dreidimensionalen Sonic Anemometers zuverlässig zu reproduzieren. <br />Da das Ly-ATOM viel näher am Boden angebracht werden kann, kann die Größe des Footprint erheblich reduziert werden (um den Faktor 25).</p> <p>Zwei Methoden werden verwendet, um den fühlbaren Wärmestrom aus den Schwankungen der Temperatur und <br />der horizontalen Windkomponenten, die vom Ly-ATOM aufgezeichnet wurden, zu ermitteln:<br />Die Kombination der Fluss-Varianz-Ähnlichkeits-Methode und der alternativen Fluss-Varianz-Methode <br />für die Anwendung bei labiler bzw. stabiler Schichtung führt zu guten Ergebnissen für die Sonic-Messungen. <br />Daher können diese Methoden auch auf duie Messungen des Ly-ATOMs angewandt werden.<br />Bei der Untersuchung der Senisitivität zur Detektion veränderter Oberflächeneigenschaften,<br /> insbesondere erhöhter Evapotranspiration und verringerter Oberflächenalbedo Albedo, <br />erweist sich das Ly-ATOM-Gerät als geeigneter im Vergleich zum Sonic Anemometer, welches vertikal weiter <br />von der zu untersuchenden Oberfläche entfernt ist.</p>

scholarly journals Wind Estimation in the Lower Atmosphere Using Multirotor Aircraft

2017 ◽  
Vol 34 (5) ◽  
pp. 1183-1191 ◽  
Author(s):  
Ross T. Palomaki ◽  
Nathan T. Rose ◽  
Michael van den Bossche ◽  
Thomas J. Sherman ◽  
Stephan F. J. De Wekker
Keyword(s):  
Wind Speed ◽  
Sonic Anemometer ◽  
Unmanned Aircraft ◽  
Lower Atmosphere ◽  
Promising Alternative ◽  
Atmospheric Structure ◽  
Structure And Dynamics ◽  
Sonic Anemometers ◽  
Vertical Profiling ◽  
Good Agreement

AbstractUnmanned aerial vehicles are increasingly used to study atmospheric structure and dynamics. While much emphasis has been on the development of fixed-wing unmanned aircraft for atmospheric investigations, the use of multirotor aircraft is relatively unexplored, especially for capturing atmospheric winds. The purpose of this article is to demonstrate the efficacy of estimating wind speed and direction with 1) a direct approach using a sonic anemometer mounted on top of a hexacopter and 2) an indirect approach using attitude data from a quadcopter. The data are collected by the multirotor aircraft hovering 10 m above ground adjacent to one or more sonic anemometers. Wind speed and direction show good agreement with sonic anemometer measurements in the initial experiments. Typical errors in wind speed and direction are smaller than 0.5 and 30°, respectively. Multirotor aircraft provide a promising alternative to traditional platforms for vertical profiling in the atmospheric boundary layer, especially in conditions where a tethered balloon system is typically deployed.

scholarly journals Note on the application of planar-fit rotation for non-omnidirectional sonic anemometers

2013 ◽  
Vol 6 (2) ◽  
pp. 221-229 ◽  
Author(s):  
M. Li ◽  
W. Babel ◽  
K. Tanaka ◽  
T. Foken
Keyword(s):  
Tibetan Plateau ◽  
Friction Velocity ◽  
Sonic Anemometer ◽  
Data Sets ◽  
The Tibetan Plateau ◽  
Open Part ◽  
Scalar Fluxes ◽  
Sonic Anemometers ◽  
Wind Velocities

Abstract. For non-omnidirectional sonic anemometers like the Kaijo-Denki DAT 600 TR61A probe, it is shown that separate planar-fit rotations must be used for the undisturbed (open part of the sonic anemometer) and the disturbed sector. This increases the friction velocity while no effect on the scalar fluxes was found. In the disturbed sector, irregular values of − u′w′ < 0 were detected for low wind velocities. Up to a certain extent these results can be transferred to the CSAT3 sonic anemometer (Campbell Scientific Ltd). This study was done for data sets from the Naqu-BJ site on the Tibetan Plateau.

scholarly journals Field intercomparison of prevailing sonic anemometers

2018 ◽  
Vol 11 (1) ◽  
pp. 249-263 ◽  
Author(s):  
Matthias Mauder ◽  
Matthias J. Zeeman
Keyword(s):  
Wind Speed ◽  
Sonic Anemometer ◽  
Three Dimensional ◽  
Buoyancy Flux ◽  
Horizontal Wind ◽  
Horizontal Wind Speed ◽  
Sonic Anemometers ◽  
Adjacent Structures ◽  
Mean Wind Speed ◽  
Field Intercomparison

Abstract. Three-dimensional sonic anemometers are the core component of eddy covariance systems, which are widely used for micrometeorological and ecological research. In order to characterize the measurement uncertainty of these instruments we present and analyse the results from a field intercomparison experiment of six commonly used sonic anemometer models from four major manufacturers. These models include Campbell CSAT3, Gill HS-50 and R3, METEK uSonic-3 Omni, R. M. Young 81000 and 81000RE. The experiment was conducted over a meadow at the TERENO/ICOS site DE-Fen in southern Germany over a period of 16 days in June of 2016 as part of the ScaleX campaign. The measurement height was 3 m for all sensors, which were separated by 9 m from each other, each on its own tripod, in order to limit contamination of the turbulence measurements by adjacent structures as much as possible. Moreover, the high-frequency data from all instruments were treated with the same post-processing algorithm. In this study, we compare the results for various turbulence statistics, which include mean horizontal wind speed, standard deviations of vertical wind velocity and sonic temperature, friction velocity, and the buoyancy flux. Quantitative measures of uncertainty, such as bias and comparability, are derived from these results. We find that biases are generally very small for all sensors and all computed variables, except for the sonic temperature measurements of the two Gill sonic anemometers (HS and R3), confirming a known transducer-temperature dependence of the sonic temperature measurement. The best overall agreement between the different instruments was found for the mean wind speed and the buoyancy flux.

scholarly journals A Bayesian model to correct underestimated 3-D wind speeds from sonic anemometers increases turbulent components of the surface energy balance

2016 ◽  
Vol 9 (12) ◽  
pp. 5933-5953 ◽  
Author(s):  
John M. Frank ◽  
William J. Massman ◽  
Brent E. Ewers
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Bayesian Model ◽  
Field Experiments ◽  
Sonic Anemometer ◽  
Vertical Wind ◽  
State Variables ◽  
Data Set ◽  
Sonic Anemometers ◽  
Posterior Correction

Abstract. Sonic anemometers are the principal instruments in micrometeorological studies of turbulence and ecosystem fluxes. Common designs underestimate vertical wind measurements because they lack a correction for transducer shadowing, with no consensus on a suitable correction. We reanalyze a subset of data collected during field experiments in 2011 and 2013 featuring two or four CSAT3 sonic anemometers. We introduce a Bayesian analysis to resolve the three-dimensional correction by optimizing differences between anemometers mounted both vertically and horizontally. A grid of 512 points (∼ ±5° resolution in wind location) is defined on a sphere around the sonic anemometer, from which the shadow correction for each transducer pair is derived from a set of 138 unique state variables describing the quadrants and borders. Using the Markov chain Monte Carlo (MCMC) method, the Bayesian model proposes new values for each state variable, recalculates the fast-response data set, summarizes the 5 min wind statistics, and accepts the proposed new values based on the probability that they make measurements from vertical and horizontal anemometers more equivalent. MCMC chains were constructed for three different prior distributions describing the state variables: no shadow correction, the Kaimal correction for transducer shadowing, and double the Kaimal correction, all initialized with 10 % uncertainty. The final posterior correction did not depend on the prior distribution and revealed both self- and cross-shadowing effects from all transducers. After correction, the vertical wind velocity and sensible heat flux increased  ∼ 10 % with  ∼ 2 % uncertainty, which was significantly higher than the Kaimal correction. We applied the posterior correction to eddy-covariance data from various sites across North America and found that the turbulent components of the energy balance (sensible plus latent heat flux) increased on average between 8 and 12 %, with an average 95 % credible interval between 6 and 14 %. Considering this is the most common sonic anemometer in the AmeriFlux network and is found widely within FLUXNET, these results provide a mechanistic explanation for much of the energy imbalance at these sites where all terrestrial/atmospheric fluxes of mass and energy are likely underestimated.

An analysis of  flow distortion in a multipath sonic anemometer

2021 ◽  
Author(s):  
Ebba Dellwik ◽  
Poul Hummelshøj ◽  
Gerhard Peters
Keyword(s):  
Vertical Velocity ◽  
Velocity Component ◽  
Sonic Anemometer ◽  
Three Dimensional ◽  
Turbulence Theory ◽  
Flow Distortion ◽  
Vertical Velocity Component ◽  
Ongoing Research ◽  
Sonic Anemometers

&lt;p&gt;Sonic anemometers provide point observations of the three-dimensional velocity field at high sampling rates and are crucial instruments for understanding and quantifying the fluxes of momentum, energy and scalars between the atmosphere and Earth&amp;#8217;s surface. Since the beginning of sonic anemometry 50 years ago, the characterization of flow distortion, i.e. how the instrument structure alters the flow, has been an ongoing research topic. Multi-path sonic anemometry provides a new opportunity to research and understand flow distortion on the vertical velocity component, since several positions in the small measurement volume can be measured simultaneously. In this work, we use data from a flat terrain measurement campaign in 2020, in which several sonic anemometers were mounted on 4m towers placed 4m apart. The analysis is focused on the Multipath Class-A sonic anemometer (Metek GmbH, Germany), which provides vertical velocity observations from three vertical paths 120 degrees and 0.1m apart. Vertical velocities are also calculated from several combinations of the tilted paths. We investigate how the vertical velocity component is altered depending on wind direction relative to different parts of the instrument structure. We demonstrate that by an optimal combination of the different paths, the vertical velocity variance and fluxes can be significantly enhanced. We also show spectra, and especially look at the high frequency end of the spectrum, where the relative behaviour of the velocity components is known from fundamental turbulence theory. Further, the relative importance of transducer shadowing and pressure-induced blockage effects is discussed.&lt;/p&gt;

scholarly journals Singularities and Undefinitions in the Calibration Functions of Sonic Anemometers

2004 ◽  
Vol 21 (12) ◽  
pp. 1868-1875 ◽  
Author(s):  
Alvaro Cuerva ◽  
Angel Sanz-Andrés ◽  
Oscar López
Keyword(s):  
Mathematical Model ◽  
Strong Influence ◽  
Sonic Anemometer ◽  
Design Parameters ◽  
Wind Vector ◽  
Implicit Function ◽  
Acoustic Path ◽  
Calibration Function ◽  
Good Design ◽  
Sonic Anemometers

Abstract A mathematical model of the process employed by a sonic anemometer to build up the measured wind vector in a steady flow is presented to illustrate the way the geometry of these sensors as well as the characteristics of aerodynamic disturbance on the acoustic path can lead to singularities in the transformation function that relates the measured (disturbed) wind vector with the real (corrected) wind vector, impeding the application of correction/calibration functions for some wind conditions. An implicit function theorem allows for the identification of those combinations of real wind conditions and design parameters that lead to undefined correction/ calibration functions. In general, orthogonal path sensors do not show problematic combination of parameters. However, some geometric sonic sensor designs, available in the market, with paths forming smaller angles could lead to undefined correction functions for some levels of aerodynamic disturbances and for certain wind directions. The parameters studied have a strong influence on the existence and number of singularities in the correction/ calibration function as well as on the number of singularities for some combination of parameters. Some conclusions concerning good design practices are included.

scholarly journals In Situ Calibration of Hot-Film Probes Using a Collocated Sonic Anemometer: Implementation of a Neural Network

2010 ◽  
Vol 27 (1) ◽  
pp. 23-41 ◽  
Author(s):  
E. Kit ◽  
A. Cherkassky ◽  
T. Sant ◽  
H. J. S. Fernando
Keyword(s):  
Neural Network ◽  
Sonic Anemometer ◽  
Input Voltage ◽  
Calibration Method ◽  
Calibration Procedure ◽  
Approximation Technique ◽  
Sonic Anemometers ◽  
Standard Calibration ◽  
Hot Film

Abstract Although the integral quantities of atmospheric turbulence are conveniently measured using sonic anemometers, obtaining relevant finescale variables such as the kinetic energy dissipation using conventional hot-film/wire techniques remains a challenge because of two main difficulties. The first difficulty is the mean wind variability, which causes violation of the requirement that mean winds have a specific alignment with the hot-film/wire probe. To circumvent this problem, a combination of collocated sonic and hot-film anemometers, with the former measuring mean winds and aligning the latter in the appropriate wind direction via an automated platform, is successfully designed and implemented. The second difficulty is the necessity of frequent and onerous calibrations akin to hot-film anemometry that lead to logistical difficulties during outdoor (field) measurements. This is addressed by employing sonic measurements to calibrate the hot films in the same combination, with the output (velocity) to input (voltage) transfer function for the hot film derived using a neural network (NN) model. The NN is trained using low-pass-filtered hot-film and sonic data taken in situ. This new hot-film calibration procedure is compared with the standard calibration method based on an external calibrator. It is inferred that the sonic-based NN method offers great potential as an alternative to laborious standard calibration techniques, particularly in the laboratory and in stable atmospheric boundary layer settings. The NN approximation technique is found to be superior to the conventionally used polynomial fitting methods when used in conjunction with unevenly spaced calibration velocity data generated by sonic anemometers.

scholarly journals Spatially Distributed Measurements of Platform Motion for the Correction of Ship-Based Turbulent Fluxes

2008 ◽  
Vol 25 (11) ◽  
pp. 2007-2017 ◽  
Author(s):  
Ian M. Brooks
Keyword(s):  
Motion Correction ◽  
Angular Rate ◽  
Sonic Anemometer ◽  
Angular Rate Sensor ◽  
Motion Sensing ◽  
Turbulence Measurements ◽  
Sensing Systems ◽  
Sonic Anemometers ◽  
Spatially Distributed ◽  
Rate Sensor

Abstract A method for determining the angular offsets between measurement axes for multiple motion sensing systems and a sonic anemometer using underway data is demonstrated. This enables a single angular rate sensor to be used with spatially separated accelerometers, collocated with sonic anemometers, for the motion correction of turbulence measurements on a mobile platform such as a ship. Effective motion correction of turbulence measurements at sea is demonstrated. The errors in instrument alignment are considered, and estimates are made of the resulting biases in wind stress estimates.

scholarly journals A method to assess the accuracy of sonic anemometer measurements

2019 ◽  
Vol 12 (1) ◽  
pp. 237-252 ◽  
Author(s):  
Alfredo Peña ◽  
Ebba Dellwik ◽  
Jakob Mann
Keyword(s):  
Power Spectrum ◽  
Sonic Anemometer ◽  
Three Dimensional ◽  
Distortion Correction ◽  
Inertial Subrange ◽  
Flow Distortion ◽  
Three Dimensional Flow ◽  
Sonic Anemometers ◽  
The Usa ◽  
Corrected Data

Abstract. We propose a method to assess the accuracy of atmospheric turbulence measurements performed by sonic anemometers and test it by analysis of measurements from two commonly used sonic anemometers, a Metek USA-1 and a Campbell CSAT3, at two locations in Denmark. The method relies on the estimation of the ratio of the vertical to the along-wind velocity power spectrum within the inertial subrange and does not require the use of another measurement as reference. When we correct the USA-1 to account for three-dimensional flow-distortion effects, as recommended by Metek GmbH, the ratio is very close to 4∕3 as expected from Kolmogorov's hypothesis, whereas non-corrected data show a ratio close to 1. For the CSAT3, non-corrected data show a ratio close to 1.1 for the two sites and for wind directions where the instrument is not directly affected by the mast. After applying a previously suggested flow-distortion correction, the ratio increases up to ≈1.2, implying that the effect of flow distortion in this instrument is still not properly accounted for.

scholarly journals Can LiDARs Replace Meteorological Masts in Wind Energy?

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3680 ◽  
Author(s):  
Jay Prakash Goit ◽  
Susumu Shimada ◽  
Tetsuya Kogaki
Keyword(s):  
Wind Speed ◽  
Wind Energy ◽  
Turbulence Intensity ◽  
Regression Line ◽  
Sonic Anemometer ◽  
Bending Moments ◽  
Wind Speeds ◽  
Acceptable Accuracy ◽  
Sonic Anemometers ◽  
Measured Wind Speed

This paper discusses whether profiling LiDARs can replace meteorological tower-based wind speed measurement for wind energy applications without severely compromising accuracy. To this end, the accuracy of LiDAR is evaluated in a moderately complex terrain by comparing long-term wind data measured by a profiling LiDAR against those obtained from tower-mounted cup and sonic anemometers. The LiDAR-measured wind speeds show good agreement with those measured using the sonic anemometer, with the slope of regression line being 1.0 and R 2 > 0.99 . Furthermore, the turbulence intensity obtained from the LiDAR has better agreement with that from the sonic anemometer compared to the cup anemometer which showed the lowest turbulence intensities among the three devices. A comparison of the turbulence intensity obtained from the 90th percentile of the standard deviation distribution shows that the LiDAR-measured turbulence intensities are mostly larger (by 2% or less) than those measured by the sonic anemometer. The gust factors obtained from both devices roughly converged to 1.9, showing that LiDAR is able to measure peak wind speed with acceptable accuracy. The accuracy of the wind speed and power distributions measured using the profiling LiDAR are then evaluated by comparing them against the corresponding distributions obtained from the sonic anemometer. Furthermore, the annual capacity factor—for the NREL 5-MW wind turbine—from the LiDAR-measured wind speed is 2% higher than that obtained from the sonic anemometer-measured wind speed. Numerical simulations are performed using OpenFAST in order to compute fatigue loads for the wind speed and turbulence distributions for the LiDAR and the sonic anemometer measurements. It is found that the 20 years lifetime Damage Equivalent Loads (DELs) computed for the LiDAR wind speed were higher than those for the sonic anemometer wind speeds, by 2%–6% for the blade root bending moments and by 11%–13% for the tower base bending moments. This study shows that even with some shortcomings, profiling LiDARs can measure wind speeds and turbulence intensities with acceptable accuracy. Therefore, they can be used to analyze wind resource and wind power potential of prospective sites, and to evaluate whether those sites are suitable for wind energy development.

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