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The best wind locations are nowadays often occupied by old, less efficient and relatively small wind turbines. Many of them will soon reach the end of their operating lifetime, or lose financial support. Therefore, repowering comes to the fore. However, social acceptance and land use restrictions have been under constant change since the initial expansions, which makes less area available for new turbines, even on existing sites. For the example of Germany, this study assesses the repowering potential for onshore wind energy in high detail, on the basis of regionally differentiated land eligibility criteria. The results show that under the given regional criteria, repowering will decrease both operating capacity and annual energy yield by roughly 40% compared to the status quo. This is because around half of the wind turbines are currently located in restricted areas, given newly enacted exclusion criteria. Sensitivity analyses on the exclusion criteria show that the minimum distance to discontinuous urban fabric is the most sensitive criterion in determining the number of turbines that can be repowered. As regulations on this can vary substantially across different regions, the location-specific methodology chosen here can assess the repowering potential more realistically than existing approaches.
Jan Frederick Unnewehr; Eddy Jalbout; Christopher Jung; Dirk Schindler; Anke Weidlich. Getting more with less? Why repowering onshore wind farms does not always lead to more wind power generation – A German case study. Renewable Energy 2021, 180, 245 -257.
AMA StyleJan Frederick Unnewehr, Eddy Jalbout, Christopher Jung, Dirk Schindler, Anke Weidlich. Getting more with less? Why repowering onshore wind farms does not always lead to more wind power generation – A German case study. Renewable Energy. 2021; 180 ():245-257.
Chicago/Turabian StyleJan Frederick Unnewehr; Eddy Jalbout; Christopher Jung; Dirk Schindler; Anke Weidlich. 2021. "Getting more with less? Why repowering onshore wind farms does not always lead to more wind power generation – A German case study." Renewable Energy 180, no. : 245-257.
To reduce the negative implications associated with the use of conventional energies on the environment and human health, intensified renewable energy expansion is inevitable. Wind energy is one of the most promising renewable energies since the theoretical technical wind energy potential is far enough to cover the global electricity consumption. However, various geographical barriers reduce the wind potential to contribute to a more sustainable power supply. The main goal of this study was to quantify the percentage reduction of the theoretical technical wind energy potential due to geographical barriers. The geographical barriers were derived from seven land use models and an elevation model and classified into the restriction categories: (1) inaccessible areas (natural), (2) inaccessible areas (artificial), (3) protected areas, (4) missing infrastructure, and (5) consideration criteria. The theoretical technical wind energy potential was estimated by wind speed distributions from the Global Wind Speed Model and assuming a dense global onshore network of wind turbines within 500 m distances. The results reveal that the most significant theoretical technical wind energy potential loss results from missing infrastructure and soft consideration criteria. The global percentage energy reduction is 96.1 %. In most developing countries, lacking infrastructure was identified as the restriction category resulting in the most notable theoretical technical wind energy potential reduction. This result emphasizes the need to improve the accessibility to wind resources in developing countries by improving the electricity grid. In industrialized countries, consideration criteria (e.g., forests, agricultural areas, proximity to urban areas) cause the greatest theoretical technical wind energy potential reduction. Thus, the extent to which the theoretical technical wind energy potential is exploitable greatly depends on regulations, public acceptance, and agreements on competitive land use. By identifying the most relevant geographical barriers, the results of this study contribute to the development of country-specific frameworks for wind energy expansion.
Christopher Jung; Dirk Schindler. Distance to power grids and consideration criteria reduce global wind energy potential the most. Journal of Cleaner Production 2021, 317, 128472 .
AMA StyleChristopher Jung, Dirk Schindler. Distance to power grids and consideration criteria reduce global wind energy potential the most. Journal of Cleaner Production. 2021; 317 ():128472.
Chicago/Turabian StyleChristopher Jung; Dirk Schindler. 2021. "Distance to power grids and consideration criteria reduce global wind energy potential the most." Journal of Cleaner Production 317, no. : 128472.
Interactions between wind and trees control energy exchanges between the atmosphere and forest canopies. This energy exchange can lead to the widespread damage of trees, and wind is a key disturbance agent in many of the world's forests. However, most research on this topic has focused on conifer plantations, where risk management is economically important, rather than broadleaf forests, which dominate the forest carbon cycle. This study brings together tree motion time-series data to systematically evaluate the factors influencing tree responses to wind loading, including data from both broadleaf and coniferous trees in forests and open environments. We found that the two most descriptive features of tree motion were (a) the fundamental frequency, which is a measure of the speed at which a tree sways and is strongly related to tree height, and (b) the slope of the power spectrum, which is related to the efficiency of energy transfer from wind to trees. Intriguingly, the slope of the power spectrum was found to remain constant from medium to high wind speeds for all trees in this study. This suggests that, contrary to some predictions, damping or amplification mechanisms do not change dramatically at high wind speeds, and therefore wind damage risk is related, relatively simply, to wind speed. Conifers from forests were distinct from broadleaves in terms of their response to wind loading. Specifically, the fundamental frequency of forest conifers was related to their size according to the cantilever beam model (i.e. vertically distributed mass), whereas broadleaves were better approximated by the simple pendulum model (i.e. dominated by the crown). Forest conifers also had a steeper slope of the power spectrum. We interpret these finding as being strongly related to tree architecture; i.e. conifers generally have a simple shape due to their apical dominance, whereas broadleaves exhibit a much wider range of architectures with more dominant crowns.
Toby D. Jackson; Sarab Sethi; Ebba Dellwik; Nikolas Angelou; Amanda Bunce; Tim van Emmerik; Marine Duperat; Jean-Claude Ruel; Axel Wellpott; Skip Van Bloem; Alexis Achim; Brian Kane; Dominick M. Ciruzzi; Steven P. Loheide Ii; Ken James; Daniel Burcham; John Moore; Dirk Schindler; Sven Kolbe; Kilian Wiegmann; Mark Rudnicki; Victor J. Lieffers; John Selker; Andrew V. Gougherty; Tim Newson; Andrew Koeser; Jason Miesbauer; Roger Samelson; Jim Wagner; Anthony R. Ambrose; Andreas Detter; Steffen Rust; David Coomes; Barry Gardiner. The motion of trees in the wind: a data synthesis. Biogeosciences 2021, 18, 4059 -4072.
AMA StyleToby D. Jackson, Sarab Sethi, Ebba Dellwik, Nikolas Angelou, Amanda Bunce, Tim van Emmerik, Marine Duperat, Jean-Claude Ruel, Axel Wellpott, Skip Van Bloem, Alexis Achim, Brian Kane, Dominick M. Ciruzzi, Steven P. Loheide Ii, Ken James, Daniel Burcham, John Moore, Dirk Schindler, Sven Kolbe, Kilian Wiegmann, Mark Rudnicki, Victor J. Lieffers, John Selker, Andrew V. Gougherty, Tim Newson, Andrew Koeser, Jason Miesbauer, Roger Samelson, Jim Wagner, Anthony R. Ambrose, Andreas Detter, Steffen Rust, David Coomes, Barry Gardiner. The motion of trees in the wind: a data synthesis. Biogeosciences. 2021; 18 (13):4059-4072.
Chicago/Turabian StyleToby D. Jackson; Sarab Sethi; Ebba Dellwik; Nikolas Angelou; Amanda Bunce; Tim van Emmerik; Marine Duperat; Jean-Claude Ruel; Axel Wellpott; Skip Van Bloem; Alexis Achim; Brian Kane; Dominick M. Ciruzzi; Steven P. Loheide Ii; Ken James; Daniel Burcham; John Moore; Dirk Schindler; Sven Kolbe; Kilian Wiegmann; Mark Rudnicki; Victor J. Lieffers; John Selker; Andrew V. Gougherty; Tim Newson; Andrew Koeser; Jason Miesbauer; Roger Samelson; Jim Wagner; Anthony R. Ambrose; Andreas Detter; Steffen Rust; David Coomes; Barry Gardiner. 2021. "The motion of trees in the wind: a data synthesis." Biogeosciences 18, no. 13: 4059-4072.
An important metric for quantifying the greenhouse gas saving potential of wind turbine types is the greenhouse gas payback time. Previous studies revealed that wind speed and wind turbine size are negatively correlated with greenhouse gas payback times. However, so far, payback times were mostly estimated for wind turbine types with a hub height of less than 100 m and rated power below 2000 kW at coarse spatial resolution. It is unclear if the negative correlation with turbine size continues to hold at greater heights since, in general, the change in wind speed increase reduces with higher altitude. Thus, the hypothesis that the size of more giant wind turbine types is not negatively correlated with greenhouse gas payback times was tested. The main goal was to develop a high spatial-resolution atlas of European greenhouse gas payback times considering the small-scale wind resource variability for 33 generic wind turbine types. The greenhouse gas payback times were estimated by first calculating the average monthly energy yields for the wind turbine types with hub heights from 60 to160 m and rated power from 800 to 4200 kW at a 250 m × 250 m spatial resolution grid. Secondly, the wind turbine types’ anticipated greenhouse gas emissions were estimated based on their hub height and rotor diameter. The wind turbine type-related net greenhouse gas emissions were compared with the mean emissions of a natural gas-fired power plant (0.5 kg CO2,eq/kWh). It was found that wind turbine types with rated power and hub height of {2400 kW, 60 m} and {3600 kW, 80 m} have the shortest greenhouse gas payback times. The European median greenhouse gas payback time was estimated at 6.1 months including the wind turbine types with lowest payback times. In the hub height range of 60 to 160 m, the correlation between greenhouse gas payback times and hub height was found to be significantly positive.
Christopher Jung; Dirk Schindler. Modeling wind turbine-related greenhouse gas payback times in Europe at high spatial resolution. Energy Conversion and Management 2021, 243, 114334 .
AMA StyleChristopher Jung, Dirk Schindler. Modeling wind turbine-related greenhouse gas payback times in Europe at high spatial resolution. Energy Conversion and Management. 2021; 243 ():114334.
Chicago/Turabian StyleChristopher Jung; Dirk Schindler. 2021. "Modeling wind turbine-related greenhouse gas payback times in Europe at high spatial resolution." Energy Conversion and Management 243, no. : 114334.
The preconditions for wind farm installation and operation are high energy yields and accessibility. However, so far, no attempts were made to develop a global scale index integrating energy yields and accessibility of wind farms. Thus, the goal of this study was to create a universally applicable wind farm potential index that enables finding productive and accessible wind farm sites around the world. The wind farm potential index was developed at a very high horizontal resolution (2000 m × 2000 m) using the Global Wind Speed Model and comprehensive land use data. The wind farm capacity factor's global pattern was estimated based on Kappa and Wakeby distributions, and a generic 3.3 MW wind turbine power curve yielding the resource potential index. The geographical potential index integrates 16 geographical restrictions, including the accessibility to the power grid. The correlation coefficients between the resource potential index and geographical potential index were below 0.10 in many countries (61%). The areas with high resource potential and geographical potential were often divergent, e.g., in areas with poorly developed infrastructure. Applying the new wind farm potential index allows a global, consistent assessment of areas suitable for installing and operating wind farms.
Christopher Jung; Dirk Schindler. A global wind farm potential index to increase energy yields and accessibility. Energy 2021, 231, 120923 .
AMA StyleChristopher Jung, Dirk Schindler. A global wind farm potential index to increase energy yields and accessibility. Energy. 2021; 231 ():120923.
Chicago/Turabian StyleChristopher Jung; Dirk Schindler. 2021. "A global wind farm potential index to increase energy yields and accessibility." Energy 231, no. : 120923.
Among the renewable energy sources, the highest share of European net electricity generation comes from wind power. However, the European onshore wind resource’s volatile nature is a significant challenge in ensuring a constant national electricity supply. Therefore, this study examined the potential of complementary use of national wind resources available in 33 European countries. The complementarity of the national wind resources was assessed for 1971–2010 by identifying the time scales explaining the largest part of the variance in the time series of daily wind energy yield. The results of a novel combination of wavelet analysis, graph models, and dynamic time warping indicate that the wind energy yield shows the most substantial variations at the annual, seasonal, and multi-day scales. Geographical proximity is a critical factor in the complementarity of national wind energy yields. At all evaluated time scales, the wind energy yield in most central and western European countries is strongly correlated, forming a large supranational network with low potential for complementary use of national wind resources. Although the seasonal component of daily wind energy yield is shifted between the European countries by up to several weeks, which would create potential for complementary use, domestic electricity consumption often exceeds the usable wind resources. Domestic electricity consumption was found to be a major barrier to the transboundary exchange of wind energy. Based on the results obtained for the European onshore wind resource’s spatiotemporal dynamics, it must be assumed that the potential for regular complementary transboundary use of wind resources is limited.
Dirk Schindler; Sophia Schmidt-Rohr; Christopher Jung. On the spatiotemporal complementarity of the European onshore wind resource. Energy Conversion and Management 2021, 237, 114098 .
AMA StyleDirk Schindler, Sophia Schmidt-Rohr, Christopher Jung. On the spatiotemporal complementarity of the European onshore wind resource. Energy Conversion and Management. 2021; 237 ():114098.
Chicago/Turabian StyleDirk Schindler; Sophia Schmidt-Rohr; Christopher Jung. 2021. "On the spatiotemporal complementarity of the European onshore wind resource." Energy Conversion and Management 237, no. : 114098.
Wind energy in Germany is awarded a crucial role in increasing the share of renewable energies in the electricity mix to 65% until 2030, especially in light of the federal government’s recent decision to phase out coal-based electricity until 2038. In addition to the targeted expansion of wind energy, Germany will be struggling with thousands of wind turbines at the end of their service life in the next years. To advance the expansion of wind energy and to increase its efficiency, repowering is deemed a promising way to deal with the upcoming changes in wind energy use. This study assesses Germany’s repowering potential in 2021–2040. It estimates how many of the existing wind turbine sites in Germany can be used for repowering without violating recently recast geographical restrictions while at the same time meeting proper spacing criteria for repowered wind turbines. The results from fifteen scenarios indicate the repowering potential in Germany to be highly impacted by the recast geographical restrictions and wind turbine categories used to repower. Compared to the energy contributed by onshore wind in the baseline year 2021, the best-case scenario could provide 110%. In contrast, the worst-case scenario could provide 40% of potential wind energy generation in 2040. The highest potential wind energy generation is reached under low distance restrictions of 500 m to surrounding settlement areas. The results indicate repowering alone to be unable to substantially increase the share of wind energy in Germany’s energy mix over the next two decades. Without expansion, the contribution of wind energy to Germany’s energy mix will diminish. However, despite the growing number of old wind turbines in Germany, repowering still offers more efficient exploitation of the wind resource.
Leonie Grau; Christopher Jung; Dirk Schindler. Sounding out the repowering potential of wind energy – A scenario-based assessment from Germany. Journal of Cleaner Production 2021, 293, 126094 .
AMA StyleLeonie Grau, Christopher Jung, Dirk Schindler. Sounding out the repowering potential of wind energy – A scenario-based assessment from Germany. Journal of Cleaner Production. 2021; 293 ():126094.
Chicago/Turabian StyleLeonie Grau; Christopher Jung; Dirk Schindler. 2021. "Sounding out the repowering potential of wind energy – A scenario-based assessment from Germany." Journal of Cleaner Production 293, no. : 126094.
The anticipated climate change during the next decades is posing crucial challenges to ecosystems. In order to decrease the vulnerability of forests, introducing tree species’ mixtures are a viable strategy, with deep-rooting native Silver fir (Abies alba) being a primary candidate for admixture into current pure stands of European beech (Fagus sylvatica) especially in mountainous areas. Such a change in forest structure also has effects on the regional scale, which, however, have been seldomly quantified. Therefore, we measured and modeled radiative balance and air chemistry impacts of admixing Silver fir to European beech stands, including changes in biogenic volatile organic compound emissions. An increased fraction of Silver fir caused a smaller albedo and a (simulated) larger evapotranspiration, leading to a dryer and warmer forest. While isoprene emission was negligible for both species, sesquiterpene and monoterpene emissions were larger for fir than for beech. From these differences, we derived that ozone concentration as well as secondary organic aerosols and cloud condensation nuclei would increase regionally. Overall, we demonstrated that even a relatively mild scenario of tree species change will alter the energy balance and air quality in a way that could potentially influence the climate on a landscape scale.
Boris Bonn; Jürgen Kreuzwieser; Ruth-Kristina Magh; Heinz Rennenberg; Dirk Schindler; Dominik Sperlich; Raphael Trautmann; Rasoul Yousefpour; Rüdiger Grote. Expected Impacts of Mixing European Beech with Silver Fir on Regional Air Quality and Radiation Balance. Climate 2020, 8, 105 .
AMA StyleBoris Bonn, Jürgen Kreuzwieser, Ruth-Kristina Magh, Heinz Rennenberg, Dirk Schindler, Dominik Sperlich, Raphael Trautmann, Rasoul Yousefpour, Rüdiger Grote. Expected Impacts of Mixing European Beech with Silver Fir on Regional Air Quality and Radiation Balance. Climate. 2020; 8 (10):105.
Chicago/Turabian StyleBoris Bonn; Jürgen Kreuzwieser; Ruth-Kristina Magh; Heinz Rennenberg; Dirk Schindler; Dominik Sperlich; Raphael Trautmann; Rasoul Yousefpour; Rüdiger Grote. 2020. "Expected Impacts of Mixing European Beech with Silver Fir on Regional Air Quality and Radiation Balance." Climate 8, no. 10: 105.
An important aspect of planning the future expansion of wind energy is the consideration of changes in available wind resources due to climate change. In previous studies simulations of the future behavior of wind resources were derived from regional climate models at coarse spatial resolutions not suitable for wind energy potential assessment at the wind turbine scale. Thus, this study investigates the hypothesis that changes in future wind resources initiated by climate change will influence important aspects of small-scale wind resource assessment. A new approach is introduced that can be used to quantify the (1) spatial wind resource availability, (2) temporal wind resource availability, and (3) geographical complementarity under climate change at the wind turbine scale. The assessment of the future spatiotemporal variations in wind resources is based on an ensemble of near-surface (10 m) wind speed time series at a daily resolution for the period 1981–2099 from 35 different regional climate models. Using the highly resolved (horizontal resolution: 200 m × 200 m) Wind Speed-Wind Shear model, the near-surface wind speed time series were bias-corrected and extrapolated to a wind turbine hub height of 140 m at the sites of the current wind turbines in Germany. Bias correction was carried out by matching the quantile distributions from the regional climate models and the Wind Speed-Wind Shear model. Afterward, a power curve of a modern 3.45 MW wind turbine was applied to calculate daily capacity factors. The results indicate small long-term changes in the wind resource availability under the representative concentration pathways 4.5 and 8.5. It was found, that the influence of the interannual variability of the German wind resource exceeds the influence of climate change on the wind resource. The newly developed approach goes beyond previous wind resource assessments under climate change because it offers the opportunity for the spatially explicit investigation of different aspects of wind resource assessment which allows to develop more sophisticated wind energy expansion plans. Although the results are valid only for the study area, the proposed methodology is portable to any other region around the world.
Christopher Jung; Dirk Schindler. Introducing a new approach for wind energy potential assessment under climate change at the wind turbine scale. Energy Conversion and Management 2020, 225, 113425 .
AMA StyleChristopher Jung, Dirk Schindler. Introducing a new approach for wind energy potential assessment under climate change at the wind turbine scale. Energy Conversion and Management. 2020; 225 ():113425.
Chicago/Turabian StyleChristopher Jung; Dirk Schindler. 2020. "Introducing a new approach for wind energy potential assessment under climate change at the wind turbine scale." Energy Conversion and Management 225, no. : 113425.
The anticipated greater penetration of the variable renewable energies wind and solar in the future energy mix could be facilitated by exploiting their complementarity, thereby improving the balance between energy supply and demand. Based on the hypothesis that a complementary use of wind and solar is possible, this investigation provides information about the spatiotemporal scales on which there is potential for the synergistic use of wind and solar in Germany. The results show that the wind-solar complementarity depends very much on the time scale under consideration. Regardless of the spatial scale, potential for complementarity is greatest on the seasonal scale, where the annual cycles of surface incoming solar radiation and surface wind speed show the strongest anti-correlation. On all other scales studied, including daily and inter-annual scales, the potential for wind-solar complementarity is significantly lower with wind and solar being usually very weakly anti-correlated or being uncorrelated. On these scales, there is hardly any compensation of times with low solar resource by the wind resource and vice versa. There is also hardly any solar-solar or wind-wind complementarity in different regions because their regional inter-regime dynamics are similar and do not show any significant differences. From the results, it is therefore concluded that there is little potential for the complementary use of wind and solar in Germany, except on the seasonal scale. Germany’s low complementarity potential reinforces the need to systematically advance other options for mitigating the individual volatilities of wind and solar such as energy storage systems and transboundary exchange of renewable power in a pan-European electricity grid. Although the results are limited to a single country, the proposed novel data-driven approach can be readily transferred to study wind-solar complementarity in other parts of the world. It enables for the first time the consistent small-scale assessment of wind-solar complementarity in large, transnational areas and has the potential for being established as an essential tool to improve electrical grid operability.
Dirk Schindler; Hein Dieter Behr; Christopher Jung. On the spatiotemporal variability and potential of complementarity of wind and solar resources. Energy Conversion and Management 2020, 218, 113016 .
AMA StyleDirk Schindler, Hein Dieter Behr, Christopher Jung. On the spatiotemporal variability and potential of complementarity of wind and solar resources. Energy Conversion and Management. 2020; 218 ():113016.
Chicago/Turabian StyleDirk Schindler; Hein Dieter Behr; Christopher Jung. 2020. "On the spatiotemporal variability and potential of complementarity of wind and solar resources." Energy Conversion and Management 218, no. : 113016.
A new model for mapping the near-surface wind speed L-moments on a high spatial resolution scale (250 m × 250 m) is introduced (GloWiSMo). The target variables are the first five L-moments of 6146 globally distributed wind speed time series. ERA5 reanalysis wind speed available on a 0.25° × 0.25° grid was used as predictor representing the large-scale wind field. Eleven predictors derived from a land cover model and a digital elevation model were applied to integrate the influence of small-scale surface properties on the wind field. The model is based on a least-squares boosting approach which is a machine learning algorithm. The parameters of the Kappa and Wakeby distribution were estimated based on the modeled L-moments. By applying the power law, the near-surface wind speed distribution can be extrapolated to any hub height. Here, we selected a typical wind turbine hub height of 120 m to demonstrate the potential of GloWiSMo. It was found that the relevance of a predictor on the spatial variability of the wind resource changes with the size of the investigation area. While the roughness length is a decisive factor for the large-scale spatial variability of the wind resource, the relative elevation is an important factor for the small-scale spatial variability. Rigorous model evaluation was performed using a validation dataset containing 598 globally distributed wind speed time series. The coefficient of determination calculated for the first L-moment was found to be 0.83. Based on the evaluation results, we argue that the developed model enables accurate and spatially explicit wind resource estimates at a very high spatial resolution.
Christopher Jung; Dirk Schindler. Integration of small-scale surface properties in a new high resolution global wind speed model. Energy Conversion and Management 2020, 210, 112733 .
AMA StyleChristopher Jung, Dirk Schindler. Integration of small-scale surface properties in a new high resolution global wind speed model. Energy Conversion and Management. 2020; 210 ():112733.
Chicago/Turabian StyleChristopher Jung; Dirk Schindler. 2020. "Integration of small-scale surface properties in a new high resolution global wind speed model." Energy Conversion and Management 210, no. : 112733.
The parameterization of hybrid-mechanistic storm damage models is largely based on the results of tree pulling tests. The tree pulling tests are used for imitating the quasi-static wind load associated with the mean wind speed. The combined effect of dynamic and quasi-static wind loads associated with wind load maxima is considered by either linearly increasing the quasi-static wind load by a gust factor or by using a turning moment coefficient determined from the relationship between maxima of wind-induced tree response and wind speed. To improve the joint use of information on dynamic and quasi-static wind loading, we present a new method that uses the coupled components of momentum flux time series and time series of stem orientation of a plantation-grown Scots pine tree. First, non-oscillatory tree motion components, which respond to wind excitation, are isolated from oscillatory components that are not coupled to the wind. The non-oscillatory components are detected by applying a sequence of time series decomposition methods including bi-orthogonal decomposition and singular spectrum analysis. Then, the wind-excited tree response components are subjected to dynamic time warping, which maximizes the coincidence between the processed data. The strong coincidence of the time-warped data allows for the estimation of the wind-induced tree response as a function of the effective wind load using simple linear regression. The slope of the regression line represents the rate of change in the tree response as the effective wind load changes. Because of the strength of the relationship, we argue that the method described is an improvement for the analysis of storm damage in forests and to individual trees.
Dirk Schindler; Sven Kolbe. Assessment of the Response of a Scots Pine Tree to Effective Wind Loading. Forests 2020, 11, 145 .
AMA StyleDirk Schindler, Sven Kolbe. Assessment of the Response of a Scots Pine Tree to Effective Wind Loading. Forests. 2020; 11 (2):145.
Chicago/Turabian StyleDirk Schindler; Sven Kolbe. 2020. "Assessment of the Response of a Scots Pine Tree to Effective Wind Loading." Forests 11, no. 2: 145.
A new approach for modeling daily precipitation (RR) at very high spatial resolution (25 m × 25 m) was introduced. It was used to develop the Precipitation Atlas for Germany (GePrA). GePrA is based on 2357 RR time series measured in the period 1981–2018. It provides monthly percentiles (p) of the large-scale RR patterns which were mapped by a thin plate spline interpolation (TPS). A least-squares boosting (LSBoost) approach and orographic predictor variables (PV) were applied to integrate the small-scale precipitation variability in GePrA. Then, a Weibull distribution (Wei) was fitted to RRp. It was found that the mean monthly sum of RR ( R R ¯ s u m ) is highest in July (84 mm) and lowest in April (49 mm). A great dependency of RR on the elevation (ε) was found and quantified. Model validation at 425 stations showed a mean coefficient of determination (R2) of 0.80 and a mean absolute error (MAE) of less than 10 mm in all months. The high spatial resolution, including the effects of the local orography, make GePrA a valuable tool for various applications. Since GePrA does not only describe R R ¯ s u m , but also the entire monthly precipitation distributions, the results of this study enable the seasonal differentiation between dry and wet period at small scales.
Christopher Jung; Dirk Schindler. Precipitation Atlas for Germany (GePrA). Atmosphere 2019, 10, 737 .
AMA StyleChristopher Jung, Dirk Schindler. Precipitation Atlas for Germany (GePrA). Atmosphere. 2019; 10 (12):737.
Chicago/Turabian StyleChristopher Jung; Dirk Schindler. 2019. "Precipitation Atlas for Germany (GePrA)." Atmosphere 10, no. 12: 737.
Christopher Jung; Dirk Schindler. Changing wind speed distributions under future global climate. Energy Conversion and Management 2019, 198, 1 .
AMA StyleChristopher Jung, Dirk Schindler. Changing wind speed distributions under future global climate. Energy Conversion and Management. 2019; 198 ():1.
Chicago/Turabian StyleChristopher Jung; Dirk Schindler. 2019. "Changing wind speed distributions under future global climate." Energy Conversion and Management 198, no. : 1.
Long-term gust speed (GS) measurements were used to develop a winter storm atlas of the 98 most severe winter storms in Germany in the period 1981–2018 (GeWiSa). The 25 m × 25 m storm-related GS fields were reconstructed in a two-step procedure: Firstly, the median gust speed ( G S ˜ ) of all winter storms was modeled by a least-squares boosting (LSBoost) approach. Orographic features and surface roughness were used as predictor variables. Secondly, the quotient of GS related to each winter storm to G S ˜ , which was defined as storm field factor (STF), was calculated and mapped by a thin plate spline interpolation (TPS). It was found that the mean study area-wide GS associated with the 2007 storm Kyrill is highest (29.7 m/s). In Southern Germany, the 1999 storm Lothar, with STF being up to 2.2, was the most extreme winter storm in terms of STF and GS. The results demonstrate that the variability of STF has a considerable impact on the simulated GS fields. Event-related model validation yielded a coefficient of determination (R2) of 0.786 for the test dataset. The developed GS fields can be used as input to storm damage models representing storm hazard. With the knowledge of the storm hazard, factors describing the vulnerability of storm exposed objects and structures can be better estimated, resulting in improved risk management.
Christopher Jung; Dirk Schindler. Historical Winter Storm Atlas for Germany (GeWiSA). Atmosphere 2019, 10, 387 .
AMA StyleChristopher Jung, Dirk Schindler. Historical Winter Storm Atlas for Germany (GeWiSA). Atmosphere. 2019; 10 (7):387.
Chicago/Turabian StyleChristopher Jung; Dirk Schindler. 2019. "Historical Winter Storm Atlas for Germany (GeWiSA)." Atmosphere 10, no. 7: 387.
In a large number of previous studies, the technical wind energy potential was estimated from national to global scale. Usually, it was assumed that the underlying meteorological potential remains constant over time. However, the wind resource greatly varies on different temporal scales including inter-annual and multi-decadal scales. In this study, the long-term variability of national and global technical wind energy potentials was assessed for the period 1971–2010 based on wind speed data from the coupled atmosphere/land-surface/ocean-wave model ERA-20C. Within this period, the annual national and global wind energy generation was reconstructed assuming an average number of 0.01–0.25 wind turbines per km2 sited on geographically non-restricted areas. The applied wind turbines have an average rated power of 3.67 MW and a hub height of 100 m. While no significant trend in technical wind energy potential was found in the majority of the countries studied, the Mann-Kendall and Cox-Stuart trend tests revealed significantly increasing trends in 37 countries and significantly decreasing trends in 10 countries. In addition, the results show that the inter-annual variability of the wind energy potential is influenced not only by the wind resource itself, but also by the rate of wind turbine expansion. From the presented results it is clear that the quantification of the long-term variability of the wind energy potential is an important prerequisite for controlling and adapting the expansion of wind energy on national and global scales to future electricity consumption.
Christopher Jung; Diana Taubert; Dirk Schindler. The temporal variability of global wind energy – Long-term trends and inter-annual variability. Energy Conversion and Management 2019, 188, 462 -472.
AMA StyleChristopher Jung, Diana Taubert, Dirk Schindler. The temporal variability of global wind energy – Long-term trends and inter-annual variability. Energy Conversion and Management. 2019; 188 ():462-472.
Chicago/Turabian StyleChristopher Jung; Diana Taubert; Dirk Schindler. 2019. "The temporal variability of global wind energy – Long-term trends and inter-annual variability." Energy Conversion and Management 188, no. : 462-472.
Empirical forest storm damage models can assist in identifying the key factors of the occurrence of storm damage in order to develop locally adapted measures to minimize damage in forests. Yet, there is a significant lack of knowledge in these models concerning the correlation between storm damage and high-impact near-surface airflow. To improve our understanding in this field, we built Random Forests (RF) and Generalized Linear Models (GLM) for evaluating the association between high resolution gust speed data and long-term, multi-event forest storm damage data from long-term permanent forest growth and yield plots. The tested gust speed data were derived from two different gust speed models: a numerical non-hydrostatic mesoscale model and a statistical model. In all RF and GLM models gust speed was a statistically significant predictor. The performance of the evaluated empirical models was very high (area under the receiver operating characteristic curve values AUC = 0.86–0.99). Depending on the type of model, the relative importance of gust speed was moderate to very high (up to 35%). However, starting from models using all significant predictors and excluding gust speed, the performance loss was almost negligible in all models. Furthermore, modeling long-term storm damage for each storm event individually performed better compared to modeling average long-term, event-unspecific storm damage. Our results demonstrate that empirical storm damage models using only gust speed as a predictor can reach moderate (GLM) to very high (RF) performance, even without any other information on terrain and forest attributes. However, if detailed terrain and forest data are available, empirical storm damage models may have such a high performance that adding gust speed data improves them very little. The correlation between gust speed and storm damage in the coupled modeling system is a fundamental first step in being able to evaluate potential changes of forest storm damage in a changing climate with potentially changing wind regimes. Additionally, further improvements could be achieved by improved representation of airflow in complex forest.
Axel T. Albrecht; Christopher Jung; Dirk Schindler. Improving empirical storm damage models by coupling with high-resolution gust speed data. Agricultural and Forest Meteorology 2019, 268, 23 -31.
AMA StyleAxel T. Albrecht, Christopher Jung, Dirk Schindler. Improving empirical storm damage models by coupling with high-resolution gust speed data. Agricultural and Forest Meteorology. 2019; 268 ():23-31.
Chicago/Turabian StyleAxel T. Albrecht; Christopher Jung; Dirk Schindler. 2019. "Improving empirical storm damage models by coupling with high-resolution gust speed data." Agricultural and Forest Meteorology 268, no. : 23-31.
Molecular diffusion is commonly assumed as main physical process of gas transport in soils. However, non-diffusive gas transport processes like the so-called pressure-pumping effect can affect soil gas transport significantly. The pressure-pumping effect has only been detected indirectly and the underlying mechanisms remain unclear. Using a novel in situ method the soil gas transport at a conifer forest site was monitored over a seven-week period. Airflow and air pressure were simultaneously measured above and below the forest canopy and air pressure was also measured in the soil. During episodes of high above-canopy wind speed, the effective soil gas diffusivity temporarily increased due to pressure-pumping. The enhancement of the gas transport rate in the topsoil reached up to 30%. We found that the best meteorological proxy explaining this effect was related to air pressure fluctuations measured at soil surface and not the mean wind speed directly above ground. While sub-canopy wind speeds continuously decreased from the bottom of the tree crown to the soil surface, amplitudes of the air pressure fluctuations were nearly constant in the whole sub-canopy profile and in the soil. We hypothesize that the air pressure fluctuations responsible for pressure-pumping are related to characteristics of above-canopy airflow rather than to airflow directly above the soil surface.
Thomas Laemmel; Manuel Mohr; Bernard Longdoz; Helmer Schack-Kirchner; Friederike Lang; Dirk Schindler; Martin Maier. From above the forest into the soil – How wind affects soil gas transport through air pressure fluctuations. Agricultural and Forest Meteorology 2018, 265, 424 -434.
AMA StyleThomas Laemmel, Manuel Mohr, Bernard Longdoz, Helmer Schack-Kirchner, Friederike Lang, Dirk Schindler, Martin Maier. From above the forest into the soil – How wind affects soil gas transport through air pressure fluctuations. Agricultural and Forest Meteorology. 2018; 265 ():424-434.
Chicago/Turabian StyleThomas Laemmel; Manuel Mohr; Bernard Longdoz; Helmer Schack-Kirchner; Friederike Lang; Dirk Schindler; Martin Maier. 2018. "From above the forest into the soil – How wind affects soil gas transport through air pressure fluctuations." Agricultural and Forest Meteorology 265, no. : 424-434.
The response of four Scots pine trees to wind excitation was measured and analyzed. We investigated whether wind-induced tree sway in the fundamental mode is affected and enhanced by resonance effects between cyclic wind loading and oscillatory tree response. By combining results from wavelet analysis and analysis of phase-amplitude coupling, we demonstrate that the response in the fundamental mode is an indirect reaction of the trees to displacement from their rest position mainly caused by large organized turbulent structures in the canopy airflow, such as sweeps and ejections. In particular, sweeps caused large tree displacement. It is suggested that sway in the fundamental mode mainly results indirectly from the trees’ elastic energy that is stored in the stem and roots because of wind-induced compression and tension, and the damping that returns them to their rest position. Since no direct excitation of sway in the fundamental mode was found, it is concluded that there is no resonant response of the studied Scots pine trees to wind excitation.
Dirk Schindler; Manuel Mohr. No resonant response of Scots pine trees to wind excitation. Agricultural and Forest Meteorology 2018, 265, 227 -244.
AMA StyleDirk Schindler, Manuel Mohr. No resonant response of Scots pine trees to wind excitation. Agricultural and Forest Meteorology. 2018; 265 ():227-244.
Chicago/Turabian StyleDirk Schindler; Manuel Mohr. 2018. "No resonant response of Scots pine trees to wind excitation." Agricultural and Forest Meteorology 265, no. : 227-244.
Wind-to-hydrogen (WH) is a promising option for reducing greenhouse gas emissions in the transport sector. Therefore, the reduction potential of fossil fuels by WH was estimated taking meteorological, geographical, and technical constraints into account. The wind resource estimation is based on the application of the high-resolution (200 m × 200 m) wind speed-wind shear model (WSWS). Together with the power curves of the six most frequently installed wind turbines in 2017, WSWS was used to assess Germany's technical wind energy potential. The WH and fossil fuel reduction potentials were calculated based on proton exchange membrane electrolysis. Results from the wind resource assessment demonstrate that in addition to the currently realized wind energy (89 TWh/yr in 2017), which is directly used for electricity generation, Germany's technical onshore potential for WH is 780 TWh/yr. This amount of renewable energy available for WH could replace 80.1% of the fossil fuels currently used in the transport sector.
Christopher Jung; Linda Nagel; Dirk Schindler; Leonie Grau. Fossil fuel reduction potential in Germany's transport sector by wind-to-hydrogen. International Journal of Hydrogen Energy 2018, 43, 23161 -23167.
AMA StyleChristopher Jung, Linda Nagel, Dirk Schindler, Leonie Grau. Fossil fuel reduction potential in Germany's transport sector by wind-to-hydrogen. International Journal of Hydrogen Energy. 2018; 43 (52):23161-23167.
Chicago/Turabian StyleChristopher Jung; Linda Nagel; Dirk Schindler; Leonie Grau. 2018. "Fossil fuel reduction potential in Germany's transport sector by wind-to-hydrogen." International Journal of Hydrogen Energy 43, no. 52: 23161-23167.