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With an increasing number of naturally ventilated dairy barns (NVDBs), the emission of ammonia and greenhouse gases into the surrounding environment is expected to increase as well. It is very challenging to accurately determine the amount of gases released from a NVDB on-farm. Moreover, control options for the micro-climate to increase animal welfare are limited in an NVDB at present. Both issues are due to the complexity of the NVDB micro-environment, which is subject to temporal (such as wind direction and temperature) and spatial (such as openings and animals acting as airflow obstacles) fluctuations. The air exchange rate (AER) is one of the most valuable evaluation entities, since it is directly related to the gas emission rate and animal welfare. In this context, our study determined the general and local AERs of NVDBs of different shapes under diverse airflow conditions. Previous works identified main influencing parameters for the general AER and mathematically linked them together to predict the AER of the barn as a whole. The present research study is a continuation and extension of previous studies about the determination of AER. It provides new insights into the influence of convection flow regimes. In addition, it goes further in precision by determining the local AERs, depending on the position of the considered volume inside the barn. After running several computational fluid dynamics (CFD) simulations, we used the statistical tool of general linear modeling in order to identify quantitative relationships between the AER and the following five influencing parameters, the length/width ratio of the barn, the side opening configuration, the airflow temperature, magnitude and incoming direction. The work succeeded in taking the temperature into account as a further influencing parameter in the model and, thus, for the first time, in analysing the effect of the different types of flow convection in this context. The resulting equations predict the barn AER with an
E. Doumbia; David Janke; Qianying Yi; Alexander Prinz; Thomas Amon; Martin Kriegel; Sabrina Hempel. A Parametric Model for Local Air Exchange Rate of Naturally Ventilated Barns. Agronomy 2021, 11, 1585 .
AMA StyleE. Doumbia, David Janke, Qianying Yi, Alexander Prinz, Thomas Amon, Martin Kriegel, Sabrina Hempel. A Parametric Model for Local Air Exchange Rate of Naturally Ventilated Barns. Agronomy. 2021; 11 (8):1585.
Chicago/Turabian StyleE. Doumbia; David Janke; Qianying Yi; Alexander Prinz; Thomas Amon; Martin Kriegel; Sabrina Hempel. 2021. "A Parametric Model for Local Air Exchange Rate of Naturally Ventilated Barns." Agronomy 11, no. 8: 1585.
The tracer gas method is one of the common ways to evaluate the air exchange rate in a naturally ventilated barn. One crucial condition for the accuracy of the method is that both considered gases (pollutant and tracer) are perfectly mixed at the points where the measurements are done. In the present study, by means of computational fluids dynamics (CFD), the mixing ratio NH
E. Doumbia; David Janke; Qianying Yi; Guoqiang Zhang; Thomas Amon; Martin Kriegel; Sabrina Hempel. On Finding the Right Sampling Line Height through a Parametric Study of Gas Dispersion in a NVB. Applied Sciences 2021, 11, 4560 .
AMA StyleE. Doumbia, David Janke, Qianying Yi, Guoqiang Zhang, Thomas Amon, Martin Kriegel, Sabrina Hempel. On Finding the Right Sampling Line Height through a Parametric Study of Gas Dispersion in a NVB. Applied Sciences. 2021; 11 (10):4560.
Chicago/Turabian StyleE. Doumbia; David Janke; Qianying Yi; Guoqiang Zhang; Thomas Amon; Martin Kriegel; Sabrina Hempel. 2021. "On Finding the Right Sampling Line Height through a Parametric Study of Gas Dispersion in a NVB." Applied Sciences 11, no. 10: 4560.
The direct measurement of emissions from naturally ventilated dairy barns is challenging due to their large openings and the turbulent and unsteady airflow at the inlets and outlets. The aim of this study was to quantify the impacts of the number and positions of sensors on the estimation of volume flow rate and emissions. High resolution measurements of a naturally ventilated scaled building model in an atmospheric boundary layer wind tunnel were done. Tracer gas was released inside the model and measured at the outlet area, using a fast flame ionization detector (FFID). Additionally, the normal velocity on the area was measured using laser Doppler anemometry (LDA). In total, for a matrix of 65 × 4 sensor positions, the mean normal velocities and the mean concentrations were measured and used to calculate the volume flow rate and the emissions. This dataset was used as a reference to assess the accuracy while systematically reducing the number of sensors and varying the positions of them. The results showed systematic errors in the emission estimation up to + 97%, when measurements of concentration and velocity were done at one constant height. This error could be lowered under 5%, when the concentrations were measured as a vertical composite sample.
David Janke; Qianying Yi; Lars Thormann; Sabrina Hempel; Barbara Amon; Štěpán Nosek; Philippe Van Van Overbeke; Thomas Amon. Direct Measurements of the Volume Flow Rate and Emissions in a Large Naturally Ventilated Building. Sensors 2020, 20, 6223 .
AMA StyleDavid Janke, Qianying Yi, Lars Thormann, Sabrina Hempel, Barbara Amon, Štěpán Nosek, Philippe Van Van Overbeke, Thomas Amon. Direct Measurements of the Volume Flow Rate and Emissions in a Large Naturally Ventilated Building. Sensors. 2020; 20 (21):6223.
Chicago/Turabian StyleDavid Janke; Qianying Yi; Lars Thormann; Sabrina Hempel; Barbara Amon; Štěpán Nosek; Philippe Van Van Overbeke; Thomas Amon. 2020. "Direct Measurements of the Volume Flow Rate and Emissions in a Large Naturally Ventilated Building." Sensors 20, no. 21: 6223.
A reliable quantification of greenhouse gas emissions is a basis for the development of adequate mitigation measures. Protocols for emission measurements and data analysis approaches to extrapolate to accurate annual emission values are a substantial prerequisite in this context. We systematically analyzed the benefit of supervised machine learning methods to project methane emissions from a naturally ventilated cattle building with a concrete solid floor and manure scraper located in Northern Germany. We took into account approximately 40 weeks of hourly emission measurements and compared model predictions using eight regression approaches, 27 different sampling scenarios and four measures of model accuracy. Data normalization was applied based on median and quartile range. A correlation analysis was performed to evaluate the influence of individual features. This indicated only a very weak linear relation between the methane emission and features that are typically used to predict methane emission values of naturally ventilated barns. It further highlighted the added value of including day-time and squared ambient temperature as features. The error of the predicted emission values was in general below 10%. The results from Gaussian processes, ordinary multilinear regression and neural networks were least robust. More robust results were obtained with multilinear regression with regularization, support vector machines and particularly the ensemble methods gradient boosting and random forest. The latter had the added value to be rather insensitive against the normalization procedure. In the case of multilinear regression, also the removal of not significantly linearly related variables (i.e., keeping only the day-time component) led to robust modeling results. We concluded that measurement protocols with 7 days and six measurement periods can be considered sufficient to model methane emissions from the dairy barn with solid floor with manure scraper, particularly when periods are distributed over the year with a preference for transition periods. Features should be normalized according to median and quartile range and must be carefully selected depending on the modeling approach.
Sabrina Hempel; Julian Adolphs; Niels Landwehr; Dilya Willink; David Janke; Thomas Amon. Supervised Machine Learning to Assess Methane Emissions of a Dairy Building with Natural Ventilation. Applied Sciences 2020, 10, 6938 .
AMA StyleSabrina Hempel, Julian Adolphs, Niels Landwehr, Dilya Willink, David Janke, Thomas Amon. Supervised Machine Learning to Assess Methane Emissions of a Dairy Building with Natural Ventilation. Applied Sciences. 2020; 10 (19):6938.
Chicago/Turabian StyleSabrina Hempel; Julian Adolphs; Niels Landwehr; Dilya Willink; David Janke; Thomas Amon. 2020. "Supervised Machine Learning to Assess Methane Emissions of a Dairy Building with Natural Ventilation." Applied Sciences 10, no. 19: 6938.
Airflow inside naturally ventilated dairy (NVD) buildings is highly variable and difficult to understand due to the lack of precious measuring techniques with the existing methods. Computational fluid dynamics (CFD) was applied to investigate the effect of different seasonal opening combinations of an NVD building on airflow patterns and airflow rate inside the NVD building as an alternative to full scale and scale model experiments. ANSYS 2019R2 was used for creating model geometry, meshing, and simulation. Eight ventilation opening combinations and 10 different reference air velocities were used for the series of simulation. The data measured in a large boundary layer wind tunnel using a 1:100 scale model of the NVD building was used for CFD model validation. The results show that CFD using standard k-ε turbulence model was capable of simulating airflow in and outside of the NVD building. Airflow patterns were different for different opening scenarios at the same external wind speed, which may affect cow comfort and gaseous emissions. Guiding inlet air by controlling openings may ensure animal comfort and minimize emissions. Non-isothermal and transient simulations of NVD buildings should be carried out for better understanding of airflow patterns.
Chayan Kumer Saha; Qianying Yi; David Janke; Sabrina Hempel; Barbara Amon; Thomas Amon. Opening Size Effects on Airflow Pattern and Airflow Rate of a Naturally Ventilated Dairy Building—A CFD Study. Applied Sciences 2020, 10, 6054 .
AMA StyleChayan Kumer Saha, Qianying Yi, David Janke, Sabrina Hempel, Barbara Amon, Thomas Amon. Opening Size Effects on Airflow Pattern and Airflow Rate of a Naturally Ventilated Dairy Building—A CFD Study. Applied Sciences. 2020; 10 (17):6054.
Chicago/Turabian StyleChayan Kumer Saha; Qianying Yi; David Janke; Sabrina Hempel; Barbara Amon; Thomas Amon. 2020. "Opening Size Effects on Airflow Pattern and Airflow Rate of a Naturally Ventilated Dairy Building—A CFD Study." Applied Sciences 10, no. 17: 6054.
The application of naturally ventilated pig buildings (NVPBs) with outdoor exercise yards is on the rise mainly due to animal welfare considerations, while the issue of emissions from the buildings to the surrounding environment is important. Since air pollutants are mainly transported by airflow, the knowledge on the airflow characteristics downwind the building is required. The objective of this research was to investigate airflow properties downwind of a NVPB with a roofed outdoor exercise yard for roof slopes of 5°, 15°, and 25°. Air velocities downwind a 1:50 scaled NVPB model were measured using a Laser Doppler Anemometer in a large boundary layer wind tunnel. A region with reduced mean air velocities was found along the downwind side of the building with a distance up to 0.5 m (i.e., 3.8 times building height), in which the emission concentration might be high. Additional air pollutant treatment technologies applied in this region might contribute to emission mitigation effectively. Furthermore, a wake zone with air recirculation was observed in this area. A smaller roof slope (i.e., 5° slope) resulted in a higher and shorter wake zone and thus a shorter air pollutant dispersion distance.
Qianying Yi; David Janke; Lars Thormann; Guoqiang Zhang; Barbara Amon; Sabrina Hempel; Štěpán Nosek; Eberhard Hartung; Thomas Amon. Airflow Characteristics Downwind a Naturally Ventilated Pig Building with a Roofed Outdoor Exercise Yard and Implications on Pollutant Distribution. Applied Sciences 2020, 10, 4931 .
AMA StyleQianying Yi, David Janke, Lars Thormann, Guoqiang Zhang, Barbara Amon, Sabrina Hempel, Štěpán Nosek, Eberhard Hartung, Thomas Amon. Airflow Characteristics Downwind a Naturally Ventilated Pig Building with a Roofed Outdoor Exercise Yard and Implications on Pollutant Distribution. Applied Sciences. 2020; 10 (14):4931.
Chicago/Turabian StyleQianying Yi; David Janke; Lars Thormann; Guoqiang Zhang; Barbara Amon; Sabrina Hempel; Štěpán Nosek; Eberhard Hartung; Thomas Amon. 2020. "Airflow Characteristics Downwind a Naturally Ventilated Pig Building with a Roofed Outdoor Exercise Yard and Implications on Pollutant Distribution." Applied Sciences 10, no. 14: 4931.
The application of naturally ventilated pig buildings (NVPBs) with outdoor exercise yards is on the rise mainly due to animal welfare considerations, while the issue of emissions from the buildings to the surrounding environment is important. Since air pollutants are mainly transported by airflow, the knowledge on the airflow characteristics downwind the building is required. The objective of this research was to investigate airflow properties downwind of a NVPB with a roofed outdoor exercise yard for roof slopes of 5°, 15°, and 25°. Air velocities downwind a 1:50 scaled NVPB model were measured using a Laser Doppler Anemometer in a large boundary layer wind tunnel. A region with reduced mean air velocities was found along the downwind side of the building with a distance up to 0.5 m (i.e. 3.8 times building height), in which the emission concentration might be high. It was found that a smaller roof slope (i.e. 5° slope) resulted in a higher and shorter wake zone and thus a shorter air pollutant dispersion distance. It was concluded that a smaller roof slope could contribute to the dilution of air pollutants and a lower air pollutant concentration near the ground.
Qianying Yi; David Janke; Lars Thormann; Guoqiang Zhang; Barbara Amon; Sabrina Hempel; Štěpán Nosek; Eberhard Hartung; Thomas Amon. Airflow Characteristics Downwind a Naturally Ventilated Pig Building with a Roofed Outdoor Exercise Yard and Implications on Pollutant Distribution. 2020, 1 .
AMA StyleQianying Yi, David Janke, Lars Thormann, Guoqiang Zhang, Barbara Amon, Sabrina Hempel, Štěpán Nosek, Eberhard Hartung, Thomas Amon. Airflow Characteristics Downwind a Naturally Ventilated Pig Building with a Roofed Outdoor Exercise Yard and Implications on Pollutant Distribution. . 2020; ():1.
Chicago/Turabian StyleQianying Yi; David Janke; Lars Thormann; Guoqiang Zhang; Barbara Amon; Sabrina Hempel; Štěpán Nosek; Eberhard Hartung; Thomas Amon. 2020. "Airflow Characteristics Downwind a Naturally Ventilated Pig Building with a Roofed Outdoor Exercise Yard and Implications on Pollutant Distribution." , no. : 1.
The mandate to limit global temperature rise calls for a reliable quantification of gaseous pollutant emissions as a basis for effective mitigation. Methane emissions from ruminant fermentation are of particular relevance in the context of greenhouse gas mitigation. The emission dynamics are so far insufficiently understood. We analyzed hourly methane emission data collected during contrasting seasons from two naturally ventilated dairy cattle buildings with concrete floor and performed a second order polynomial regression. We found a parabolic temperature dependence of the methane emissions irrespective of the measurement site and setup. The position of the parabola vertex varied when considering different hours of the day. The circadian rhythm of methane emissions was represented by the pattern of the fitted values of the constant term of the polynomial and could be well explained by feeding management and air flow conditions. We found barn specific emission minima at ambient temperatures around 10 °C to 15 °C. As this identified temperature optimum coincides with the welfare temperature of dairy cows, we concluded that temperature regulation of dairy cow buildings with concrete floor should be considered and further investigated as an emission mitigation measure. Our results further indicated that empirical modeling of methane emissions from the considered type of buildings with a second order polynomial for the independent variable air temperature can increase the accuracy of predicted long-term emission values for regions with pronounced seasonal temperature fluctuations.
Sabrina Hempel; Diliara Willink; David Janke; Christian Ammon; Barbara Amon; Thomas Amon. Methane Emission Characteristics of Naturally Ventilated Cattle Buildings. Sustainability 2020, 12, 4314 .
AMA StyleSabrina Hempel, Diliara Willink, David Janke, Christian Ammon, Barbara Amon, Thomas Amon. Methane Emission Characteristics of Naturally Ventilated Cattle Buildings. Sustainability. 2020; 12 (10):4314.
Chicago/Turabian StyleSabrina Hempel; Diliara Willink; David Janke; Christian Ammon; Barbara Amon; Thomas Amon. 2020. "Methane Emission Characteristics of Naturally Ventilated Cattle Buildings." Sustainability 12, no. 10: 4314.
Environmental protection efforts can only be effective in the long term with a reliable quantification of pollutant gas emissions as a first step to mitigation. Measurement and analysis strategies must permit the accurate extrapolation of emission values. We systematically analyzed the added value of applying modern machine learning methods in the process of monitoring emissions from naturally ventilated livestock buildings to the atmosphere. We considered almost 40 weeks of hourly emission values from a naturally ventilated dairy cattle barn in Northern Germany. We compared model predictions using 27 different scenarios of temporal sampling, multiple measures of model accuracy, and eight different regression approaches. The error of the predicted emission values with the tested measurement protocols was, on average, well below 20%. The sensitivity of the prediction to the selected training dataset was worse for the ordinary multilinear regression. Gradient boosting and random forests provided the most accurate and robust emission value predictions, accompanied by the second-smallest model errors. Most of the highly ranked scenarios involved six measurement periods, while the scenario with the best overall performance was: One measurement period in summer and three in the transition periods, each lasting for 14 days.
Sabrina Hempel; Julian Adolphs; Niels Landwehr; David Janke; Thomas Amon. How the Selection of Training Data and Modeling Approach Affects the Estimation of Ammonia Emissions from a Naturally Ventilated Dairy Barn—Classical Statistics versus Machine Learning. Sustainability 2020, 12, 1030 .
AMA StyleSabrina Hempel, Julian Adolphs, Niels Landwehr, David Janke, Thomas Amon. How the Selection of Training Data and Modeling Approach Affects the Estimation of Ammonia Emissions from a Naturally Ventilated Dairy Barn—Classical Statistics versus Machine Learning. Sustainability. 2020; 12 (3):1030.
Chicago/Turabian StyleSabrina Hempel; Julian Adolphs; Niels Landwehr; David Janke; Thomas Amon. 2020. "How the Selection of Training Data and Modeling Approach Affects the Estimation of Ammonia Emissions from a Naturally Ventilated Dairy Barn—Classical Statistics versus Machine Learning." Sustainability 12, no. 3: 1030.
In the last decades, a global warming trend was observed. Along with the temperature increase, modifications in the humidity and wind regime amplify the regional and local impacts on livestock husbandry. Direct impacts include the occurrence of climatic stress conditions. In Europe, cows are economically highly relevant and are mainly kept in naturally ventilated buildings that are most susceptible to climate change. The high-yielding cows are particularly vulnerable to heat stress. Modifications in housing management are the main measures taken to improve the ability of livestock to cope with these conditions. Measures are typically taken in direct reaction to uncomfortable conditions instead of in anticipation of a long-term risk for climatic stress. Measures that balance welfare, environmental and economic issues are barely investigated in the context of climate change and are thus almost not available for commercial farms. Quantitative analysis of the climate change impacts on animal welfare and linked economic and environmental factors is rare. Therefore, we used a numerical modeling approach to estimate the future heat stress risk in such dairy cattle husbandry systems. The indoor climate was monitored inside three reference barns in central Europe and the Mediterranean regions. An artificial neuronal network (ANN) was trained to relate the outdoor weather conditions provided by official meteorological weather stations to the measured indoor microclimate. Subsequently, this ANN model was driven by an ensemble of regional climate model projections with three different greenhouse gas concentration scenarios. For the evaluation of the heat stress risk, we considered the number and duration of heat stress events. Based on the changes in the heat stress events, various economic and environmental impacts were estimated. The impacts of the projected increase in heat stress risk varied among the barns due to different locations and designs as well as the anticipated climate change (considering different climate models and future greenhouse gas concentrations). There was an overall increasing trend in number and duration of heat stress events. At the end of the century, the number of annual stress events can be expected to increase by up to 2000, while the average duration of the events increases by up to 22 h compared to the end of the last century. This implies strong impacts on economics, environment and animal welfare and an urgent need for mid-term adaptation strategies. We anticipated that up to one-tenth of all hours of a year, correspondingly one-third of all days, will be classified as critical heat stress conditions. Due to heat stress, milk yield may decrease by about 2.8 % relative to the present European milk yield, and farmers may expect financial losses in the summer season of about 5.4 % of their monthly income. In addition, an increasing demand for emission reduction measures must be expected, as an emission increase of about 16 Gg of ammonia and 0.1 Gg of methane per year can be expected under the anticipated heat stress conditions. The cattle respiration rate increases by up to 60 %, and the standing time may be prolonged by 1 h. This causes health issues and increases the probability of medical treatments. The various impacts imply feedback loops in the climate system which are presently underexplored. Hence, future in-depth studies on the different impacts and adaptation options at different stress levels are highly recommended.
Sabrina Hempel; Christoph Menz; Severino Pinto; Elena Galán; David Janke; Fernando Estellés; Theresa Müschner-Siemens; Xiaoshuai Wang; Julia Heinicke; Guoqiang Zhang; Barbara Amon; Agustín del Prado; Thomas Amon. Heat stress risk in European dairy cattle husbandry under different climate change scenarios – uncertainties and potential impacts. Earth System Dynamics 2019, 10, 859 -884.
AMA StyleSabrina Hempel, Christoph Menz, Severino Pinto, Elena Galán, David Janke, Fernando Estellés, Theresa Müschner-Siemens, Xiaoshuai Wang, Julia Heinicke, Guoqiang Zhang, Barbara Amon, Agustín del Prado, Thomas Amon. Heat stress risk in European dairy cattle husbandry under different climate change scenarios – uncertainties and potential impacts. Earth System Dynamics. 2019; 10 (4):859-884.
Chicago/Turabian StyleSabrina Hempel; Christoph Menz; Severino Pinto; Elena Galán; David Janke; Fernando Estellés; Theresa Müschner-Siemens; Xiaoshuai Wang; Julia Heinicke; Guoqiang Zhang; Barbara Amon; Agustín del Prado; Thomas Amon. 2019. "Heat stress risk in European dairy cattle husbandry under different climate change scenarios – uncertainties and potential impacts." Earth System Dynamics 10, no. 4: 859-884.
Air flow assessment in animal husbandry is an important issue in the context of welfare and emission. The aim of this study was to implement a porous medium approach for the numerical simulation of air flow in the animal occupied zone (AOZ) of a dairy building. Computational fluid dynamics (CFD) was used to determine the flow resistance properties, where cow geometry was simplified by a six-cylinder geometry. Three different AOZ were identified and parametric studies were performed to determine the pressure drop depending on the air inlet angle. Viscous and inertial loss terms were calculated by non-linear regression and added to the Navier-Stokes equations for each AOZ as a subdomain. Simulations of the air flow in a barn segment containing the three AOZ (standing, resting and resting in double line) indicated that in most configurations, inertial forces dominated and pressure drop was dependent on the air inlet angle. The viscous and inertial loss terms changed depending on the AOZ. The total pressure drop predicted using the porous medium approach taking into account the different AOZs was in good agreement with the results obtained by simulations using the fully resolved, simplified cow bodies.
Jaime Daniel Bustos-Vanegas; Sabrina Hempel; David Janke; Moustapha Doumbia; Judith Streng; Thomas Amon. Numerical simulation of airflow in animal occupied zones in a dairy cattle building. Biosystems Engineering 2019, 186, 100 -105.
AMA StyleJaime Daniel Bustos-Vanegas, Sabrina Hempel, David Janke, Moustapha Doumbia, Judith Streng, Thomas Amon. Numerical simulation of airflow in animal occupied zones in a dairy cattle building. Biosystems Engineering. 2019; 186 ():100-105.
Chicago/Turabian StyleJaime Daniel Bustos-Vanegas; Sabrina Hempel; David Janke; Moustapha Doumbia; Judith Streng; Thomas Amon. 2019. "Numerical simulation of airflow in animal occupied zones in a dairy cattle building." Biosystems Engineering 186, no. : 100-105.
Sabrina Hempel. Reply to review 2. 2019, 1 .
AMA StyleSabrina Hempel. Reply to review 2. . 2019; ():1.
Chicago/Turabian StyleSabrina Hempel. 2019. "Reply to review 2." , no. : 1.
Sabrina Hempel. Reply to review 1. 2019, 1 .
AMA StyleSabrina Hempel. Reply to review 1. . 2019; ():1.
Chicago/Turabian StyleSabrina Hempel. 2019. "Reply to review 1." , no. : 1.
In the last decades, an exceptional global warming trend was observed. Along with the temperature increase, modifications in the humidity and wind regime amplify the regional and local impacts on livestock husbandry. Direct impacts include the occurrence of climatic stress conditions. In Europe, cows are economically highly relevant and are mainly kept in naturally ventilated buildings that are most susceptible to climate change. The high-yielding cows are particularly vulnerable to heat stress. Modifications in housing management are the main measures taken to improve the ability of livestock to cope with these conditions. Measures are, however, typically taken in direct reaction to uncomfortable conditions instead of in anticipation of a long term risk for climatic stress. Moreover, measures that balance welfare, environmental and economic issues are barely investigated in the context of climate change and are thus almost not available for commercial farms. Quantitative analysis of the climate change impacts on the animal welfare and linked economic and environmental factors are rare. Therefore, we used a numerical modeling approach to estimate the future heat stress risk in such dairy cattle husbandry systems. The indoor climate was monitored inside three reference barns in Central Europe and in the Mediterranean region. An artificial neuronal network (ANN) was trained to relate the outdoor weather conditions provided by official meteorological weather stations to the measured indoor microclimate. Subsequently, this ANN model was driven by an ensemble of regional climate model projections with three different greenhouse gas concentration scenarios. For the evaluation of the heat stress risk, we considered the amount and duration of heat stress events. Based on the changes of the heat stress events various economic and environmental impacts were estimated. We found that the impacts of the projected increase of heat stress risk vary dependent on the region respectively the barn, the climate model and the assumed greenhouse gas concentration. There was an overall increasing trend in number and duration of heat stress events. At the end of the century, the number of annual stress events can be expected to increase by up to 2000 hours while the average duration of the events increases by up to 22 h compared to the end of the last century. This implies strong impacts on economics, environment and animal welfare and an urgent need for mid-term adaptation strategies. We anticipated that up to one tenth of all hours of a year respectively one third of all days will be classified as critical heat stress conditions. Due to heat stress, milk yield may decrease by about 3.5 % relative to the present European milk yield and farmers may expect financial losses in the summer season of about 6.6 % of their monthly income. In addition, an increasing demand for emission reduction measures must be expected, as an emission increase of about 16 Gg ammonia and 0.1 Gg methane per year can be expected under the anticipated heat stress conditions. The cattle respiration rate increases by up to 60 % and the standing time may be prolonged by 1 h. This promotes health issues and increases the probability of medical treatments. The various impacts imply feedback loops in the climate system which are presently underexplored. Hence, future in-depth studies on the different impacts and adaptation options at different stress levels are highly recommended.
Sabrina Hempel; Christoph Menz; Severino Pinto; Elena Galán; David Janke; Fernando Estellés; Theresa Müschner-Siemens; Xiaoshuai Wang; Julia Heinicke; Guoqiang Zhang; Barbara Amon; Agustín Del Prado; Thomas Amon. Heat stress risk in European dairy cattle husbandry under different climate change scenarios – uncertainties and potential impacts. Earth System Dynamics Discussions 2019, 1 -38.
AMA StyleSabrina Hempel, Christoph Menz, Severino Pinto, Elena Galán, David Janke, Fernando Estellés, Theresa Müschner-Siemens, Xiaoshuai Wang, Julia Heinicke, Guoqiang Zhang, Barbara Amon, Agustín Del Prado, Thomas Amon. Heat stress risk in European dairy cattle husbandry under different climate change scenarios – uncertainties and potential impacts. Earth System Dynamics Discussions. 2019; ():1-38.
Chicago/Turabian StyleSabrina Hempel; Christoph Menz; Severino Pinto; Elena Galán; David Janke; Fernando Estellés; Theresa Müschner-Siemens; Xiaoshuai Wang; Julia Heinicke; Guoqiang Zhang; Barbara Amon; Agustín Del Prado; Thomas Amon. 2019. "Heat stress risk in European dairy cattle husbandry under different climate change scenarios – uncertainties and potential impacts." Earth System Dynamics Discussions , no. : 1-38.
Gaseous emissions from livestock buildings have been a research focus for many years. In particular, quantifying emissions from naturally ventilated buildings is not trivial because it requires accurately determining the air exchange rate (AER) and representative gaseous concentration values in the exhaust and in the incoming air. Improvements are required for the method for estimating AERs and for selecting representative sampling points and locations in naturally ventilated dairy buildings (NVB). The objective of this study was to investigate the magnitude and sources of uncertainties in calculating AERs. A long-term experiment was performed in an NVB located in north-east Germany. CO2 concentrations were continuously measured inside the barn at eight uniformly distributed points and outside the barn at four points. Sensitivity studies on the calculation of AER were performed by varying the indoor and outdoor sampling points, sampling duration and animal parameters used for the calculation. The sensitivity results were compared to the best available data approximation (BADA), which is based on the best knowledge of these parameters. All factors were evaluated and ordered in terms of their influence on AER calculation and uncertainty. The results show that the sampling duration and the number and location of indoor sampling points have the largest effects on AER uncertainty. Data on milk yield and days since insemination have the lowest influence on AER uncertainty. The information collected in this long-term study is very important for planning measurement campaigns in the future.
Marcel König; Sabrina Hempel; David Janke; Barbara Amon; Thomas Amon. Variabilities in determining air exchange rates in naturally ventilated dairy buildings using the CO2 production model. Biosystems Engineering 2018, 174, 249 -259.
AMA StyleMarcel König, Sabrina Hempel, David Janke, Barbara Amon, Thomas Amon. Variabilities in determining air exchange rates in naturally ventilated dairy buildings using the CO2 production model. Biosystems Engineering. 2018; 174 ():249-259.
Chicago/Turabian StyleMarcel König; Sabrina Hempel; David Janke; Barbara Amon; Thomas Amon. 2018. "Variabilities in determining air exchange rates in naturally ventilated dairy buildings using the CO2 production model." Biosystems Engineering 174, no. : 249-259.
Well-understanding indoor air movement with respect to openings in naturally-ventilated buildings is essential to provide healthy and comfortable indoor climate for livestock. This study investigated the effects of the sidewall opening configurations on internal airflow fields and air velocity characteristics within the animal occupied zone (AOZ). Eight cases with varied opening ratios and locations were tested under 8 m•s-1 free wind speed and wind direction perpendicular to the sidewalls. The ‘up-jet’ airflow pattern was observed when the opening ratio was no greater than 62.71% and the openings located beneath the eaves. Air went across the AOZ without circulating with the surrounding air when no sidewalls were installed below the AOZ height. Both air speed and turbulent kinetic energy increased when the opening was bigger with Pearson's correlation coefficients of 0.8 and 0.9 respectively, but the relationship between the opening size and the turbulence intensity was more complex. Uniform air speed distributions were observed in the AOZ with high sidewalls on bottom. By contrast, the air speed heterogeneity in the AOZ was found when sidewall heights were below the AOZ height. We conclude that care should be taken when using these kinds of opening configurations during extreme cold windy weather conditions.
Qianying Yi; Marcel König; David Janke; Sabrina Hempel; Guoqiang Zhang; Barbara Amon; Thomas Amon. Wind tunnel investigations of sidewall opening effects on indoor airflows of a cross-ventilated dairy building. Energy and Buildings 2018, 175, 163 -172.
AMA StyleQianying Yi, Marcel König, David Janke, Sabrina Hempel, Guoqiang Zhang, Barbara Amon, Thomas Amon. Wind tunnel investigations of sidewall opening effects on indoor airflows of a cross-ventilated dairy building. Energy and Buildings. 2018; 175 ():163-172.
Chicago/Turabian StyleQianying Yi; Marcel König; David Janke; Sabrina Hempel; Guoqiang Zhang; Barbara Amon; Thomas Amon. 2018. "Wind tunnel investigations of sidewall opening effects on indoor airflows of a cross-ventilated dairy building." Energy and Buildings 175, no. : 163-172.
It is important to estimate the ventilation rate of animal houses accurately for the purpose of reducing emissions and providing comfortable indoor climate. The orifice equation is widely applied for estimating the airflow rate of naturally ventilated dairy barns. However, to regard openings’ discharge coefficient (Cd) as a constant maybe not true for large openings. To gain basic knowledge of the opening size effects on Cd values, experiments with a scaled model were carried out in a large boundary layer wind tunnel. Seven cases with different sidewall opening ratios, varying from 18.6% to 81.4%, were investigated under 8 m/s wind speed conditions. The airflow rates, Cd values of windward openings and airflow patterns were analysed. It was found that the Cd value was considerably dependent on the opening size and varied from 0.67 to 0.94 when the opening ratio increased from 18.6% to 62.7%. This is due to the assumptions of pure pressure-driven flow and uniform velocity distributions in the opening were not satisfied for large opening cases. Our study suggests that Cd should be regarded as a variable under different opening size conditions when using the orifice equation to determine the airflow rate of large openings.
Qianying Yi; Guoqiang Zhang; Marcel König; David Janke; Sabrina Hempel; Thomas Amon. Investigation of discharge coefficient for wind-driven naturally ventilated dairy barns. Energy and Buildings 2018, 165, 132 -140.
AMA StyleQianying Yi, Guoqiang Zhang, Marcel König, David Janke, Sabrina Hempel, Thomas Amon. Investigation of discharge coefficient for wind-driven naturally ventilated dairy barns. Energy and Buildings. 2018; 165 ():132-140.
Chicago/Turabian StyleQianying Yi; Guoqiang Zhang; Marcel König; David Janke; Sabrina Hempel; Thomas Amon. 2018. "Investigation of discharge coefficient for wind-driven naturally ventilated dairy barns." Energy and Buildings 165, no. : 132-140.
Sabrina Hempel; Marcel König; Christoph Menz; David Janke; Barbara Amon; Thomas M. Banhazi; Fernando Estellés; Thomas Amon. Uncertainty in the measurement of indoor temperature and humidity in naturally ventilated dairy buildings as influenced by measurement technique and data variability. Biosystems Engineering 2018, 166, 58 -75.
AMA StyleSabrina Hempel, Marcel König, Christoph Menz, David Janke, Barbara Amon, Thomas M. Banhazi, Fernando Estellés, Thomas Amon. Uncertainty in the measurement of indoor temperature and humidity in naturally ventilated dairy buildings as influenced by measurement technique and data variability. Biosystems Engineering. 2018; 166 ():58-75.
Chicago/Turabian StyleSabrina Hempel; Marcel König; Christoph Menz; David Janke; Barbara Amon; Thomas M. Banhazi; Fernando Estellés; Thomas Amon. 2018. "Uncertainty in the measurement of indoor temperature and humidity in naturally ventilated dairy buildings as influenced by measurement technique and data variability." Biosystems Engineering 166, no. : 58-75.
Discharge coefficient of the opening is one of the most important parameters in accurately estimating ventilation rate of a building when applying orifice equation, which maybe not suitable to be taken as a constant value for wind-driven cross ventilated dairy barns. This study aims to investigate the impact of wall porosity and wind speed on discharge coefficient by means of wind tunnel tests and a 1:40 scaled building model. Air velocity at the windward opening and the pressure drop across it were measured by Laser Doppler Anemometer and differential pressure transducer respectively. The experimental result reveals that larger wall porosity and slower wind speed result in higher discharge coefficient. Its value was between 0.67 and 0.94 for wall porosity ranging from 0.22 to 1.61 under wind speed of 8 m/s, and decreased slightly from 0.75 to 0.6 for wall porosity of 0.33 when the wind speed increased from 6 m/s to 12 m/s. These findings indicate that the discharge coefficient of an opening cannot be generalized by a fixed value when predicting ventilation rate of a wind-driven cross ventilated building equipped with large openings.
Qianying Yi; Guoqiang Zhang; David Janke; Thomas Amon; Sabrina Hempel. Determining Discharge Coefficient of Large Openings of Wind-driven Cross Ventilation Barns by Wind Tunnel Tests. 2017 Spokane, Washington July 16 - July 19, 2017 2017, 1 .
AMA StyleQianying Yi, Guoqiang Zhang, David Janke, Thomas Amon, Sabrina Hempel. Determining Discharge Coefficient of Large Openings of Wind-driven Cross Ventilation Barns by Wind Tunnel Tests. 2017 Spokane, Washington July 16 - July 19, 2017. 2017; ():1.
Chicago/Turabian StyleQianying Yi; Guoqiang Zhang; David Janke; Thomas Amon; Sabrina Hempel. 2017. "Determining Discharge Coefficient of Large Openings of Wind-driven Cross Ventilation Barns by Wind Tunnel Tests." 2017 Spokane, Washington July 16 - July 19, 2017 , no. : 1.
Ammonia (NH3) and methane (CH4) emissions from naturally ventilated dairy barns affect the environment and the wellbeing of humans and animals. Our study improves the understanding of the dependency of emission rates on climatic conditions with a particular focus on temperature. Previous investigations of the relation between gas emission and temperature mainly rely on linear regression or correlation analysis. We take up a preceding study presenting a multilinear regression model based on NH3 and CH4 concentration and temperature measurements between 2010 and 2012 in a dairy barn for 360 cows in Northern Germany. We study scatter plots and non-linear regression models for a subset of these data and show that the linear approximation comes to its limits when large temperature ranges are considered. The functional dependency of the emission rates on temperature differs among the gases. For NH3, the exponential dependency assumed in previous studies was proven. For methane, a parabolic relation was found. The emissions show large daily and annual variations and environmental impact factors like wind and humidity superimpose the temperature dependency but the functional shape in general persists. Complementary to the former insight that high temperature increases emissions, we found that in the case of CH4, also temperatures below 10 °C lead to an increase in emissions from ruminal fermentation which is likely to be due to a change in animal activity. The improved prediction of emissions by the novel non-linear model may support more accurate economic and ecological assessments of smart barn concepts.
Sabrina Hempel; Chayan Kumer Saha; Merike Fiedler; Werner Berg; Christiane Hansen; Barbara Amon; Thomas Amon. Non-linear temperature dependency of ammonia and methane emissions from a naturally ventilated dairy barn. Biosystems Engineering 2016, 145, 10 -21.
AMA StyleSabrina Hempel, Chayan Kumer Saha, Merike Fiedler, Werner Berg, Christiane Hansen, Barbara Amon, Thomas Amon. Non-linear temperature dependency of ammonia and methane emissions from a naturally ventilated dairy barn. Biosystems Engineering. 2016; 145 ():10-21.
Chicago/Turabian StyleSabrina Hempel; Chayan Kumer Saha; Merike Fiedler; Werner Berg; Christiane Hansen; Barbara Amon; Thomas Amon. 2016. "Non-linear temperature dependency of ammonia and methane emissions from a naturally ventilated dairy barn." Biosystems Engineering 145, no. : 10-21.