Local Wind Climate Research Articles

Research Optimizing Building Ventilation Performance through the Application of Trombe Walls in Regions with Hot Summers and Cold Winters: A Case Study in China

The hot-summer and cold-winter climate zone spans a large latitude, where the passive means of retrofitting the Trombe wall (TW) can be utilized to effectively improve the indoor wind environment and thermal comfort. In this study, a public building in Wenzhou, China, was selected as the object, and CFD numerical simulations and the wind environment data in spring, summer, and fall were collected through field experimental measurements. Comparative analyses were carried out to explore the adaptive strategy and effectiveness of the application of the Trombe wall on the local wind environment and climate and to quantify the improvement effect of the application of the Trombe wall on the Indoor environment. The results showed that the application of the Trombe wall in spring and fall in hot-summer and cold-winter regions could obviously increase the average indoor wind speed and the wind speed at the building outlet by 0.2–0.8 m/s and 0.9–3.6 m/s, respectively. This further effectively prolongs the indoor thermal comfort hours in spring and fall, which is a relatively applicable season, while the ventilation performance in summer is poor compared to spring and fall seasons.

Genetic Fuzzy Learning of local wind conditions

The wind climate measured in a point could be described as the regional wind climate of the zone forced by local effects derived from topography, roughness and obstacles in the surrounding area. This paper presents a method that allows to find fuzzy relations between the local wind climate in a location and the physical geography of the area. The fuzzy sets used in this work will connect relief elements with a probability relationed with the chances of flow over the concerned element. Thus, evaluating the heights and slopes of the terrain around the selected point, each fuzzy system will generate a possible local wind climate, which will be compared with the real one. In order to obtain the best agreement, a population of these fuzzy systems will be improved using Genetic Algorithms.

Impact of solar power plant design parameters on snowdrift accumulation and energy yield

Solar power plants designed in accordance with established design principles are influenced by snowdrift accumulation in Polar climates. A strategy to avoid snowdrifts in the plant is to adapt the design of the plant itself. To provide a background for the adaptation of solar power plants to Polar climates, the effect of performing parameter adjustments on the snow accumulation conditions as well as the plant yield should be quantified. This study uses Computational Fluid Dynamic (CFD) and energy yield simulations, validated with field measurements, to investigate the sensitivity of snowdrift accumulation and energy yield to solar power plant design parameters. The investigated parameters include the panel tilt, the row spacing, the gap-to-ground, the system scale and the azimuth/wind direction. Here it is shown that the investigated design parameters exhibit a large variation in sensitivity and that only two parameter adjustments which reduce the risk of snowdrift accumulation increase or have an insignificant impact on the energy yield, namely increasing the gap-to-ground and the system scale. Tilt, pitch and azimuth adjustments can reduce the risk of snowdrift accumulation but for a trade-off in energy yield. As the snowdrift accumulation conditions depend on the local snow and wind climate and PV system characteristics such as plant size, the design adjustments should be performed for the specific design scenario. This study provides a background for adjusting the design of the plant to the local climate to increase the snowdrift resilience while minimizing adverse effects on the system yield.

The Destructive Static Tree-Pulling Test Provides Reliable Estimates of the Soil–Root Plate of Eastern Baltic Silver Birch (Betula pendula Roth.)

Under the intensifying cyclonic activity, the wind resistance of European forests could be increased through science-based adaptive forest management, which requires the quantification of tree stability. In this regard, the dimensions of the soil–root plate can be directly attributed to tree wind resistance; however, naturally uprooted trees might be a biased source of information for the evaluation of adaptive measures due to uncontrolled conditions and uneven sample size. Therefore, the dimensions of the soil–root plates of naturally windthrown silver birch trees (Betula pendula Roth.) are compared to artificially overturned trees under a static tree-pulling test in Eastern Baltic region. The application of static tree-pulling overestimated the dimensions of the soil–root plates of silver birch compared to windthrown trees. The overestimation of soil–root plate dimensions was consistent spatially and across soil types, which is likely a regional adaptation to local wind climate. This implies that static tree-pulling is representative of the assessment of the effects of adaptive management on tree stability via the dimensions of the soil–root plates.

Multi-fidelity shape optimization methodology for pedestrian-level wind environment

In this study, a multi-fidelity shape optimization framework is proposed for the pedestrian-level wind environment (PLWE). In the proposed framework, low-fidelity computational fluid dynamics (CFD) models based on steady Reynolds-averaged Navier–Stokes equations (RANS) models and high-fidelity CFD models based on large-eddy simulation (LES) are efficiently integrated into the optimization process to improve the optimization reliability while maintaining its computational speed in an affordable range for practical engineering applications. The optimization solver is coupled with an approximation model generated by low-fidelity CFD samples obtained using a design of experiments (DOE) technique. The optimal candidates are then evaluated according to the degree of improvement of the objective function compared to the reference case. If the degree of improvement shows significant deviations between the low-fidelity and high-fidelity models, suitable corrections and modifications are applied to improve the reliability of the optimization process. The applicability of the proposed method was investigated in terms of minimizing the high-wind-speed area, as the optimization objective, around a high-rise building considering (a) uniform urban blocks and (b) real urban blocks with different frequency distributions of wind directions associated with two different local wind climates. In summary, a significant reduction in the critical strong-wind area around the target building was realized using the proposed optimization framework. Furthermore, the application of the proposed multi-fidelity optimization framework highlighted the importance of considering the local wind climate in architectural design.

A Refined Study of Atmospheric Wind Properties in the Beijing Urban Area Based on a 325 m Meteorological Tower

The urban atmospheric boundary layer (UABL) is complex due to the heterogeneous underlying city surface. The nine anemometers installed at different heights along the 325 m meteorological tower provide an opportunity to carry out a refined study of wind properties in the UABL in central Beijing, China. Based on the recent 5-year high-resolution measured data, in total, 229,488 10-min length segments of wind records related to each anemometer are reliable for further analyses. Accordingly, the statistical properties of the wind speed and direction are first analyzed to present the local wind climate in a comprehensive way. Moreover, the pattern of the wind profiles related to two typical synoptic intense events are illustrated in order to give a preliminary perspective, then the statistical properties corresponding to a series of intense windstorms are described. Here, the deviations in the wind direction occur between 200 m and 280 m of the atmosphere, which might be due to the existence of an Ekman spiral; besides this, the laws of wind profiles based on open terrain are not suitable for the UABL, and the aerodynamic characteristic parameters of the UABL based on vertical stratified structures have to be considered. The results contribute to the establishment of revised models for the wind profile and are useful for the further understanding of the structure of UABL wind.

An Integrated Approach to Predict Wind Resource Energy from an Urban Wind Turbine in a Complex Built Environment

Introducing an urban wind turbine in the crowded and complex City of North Sydney built environment can provide a significant opportunity to generate onsite wind energy and reduce electric demand and utility costs. Elevated turbulent conditions present a number of well-known challenges to urban wind turbines and as a result the energy production may reduce due to changes in wind speeds and directions. This current case study presents a procedure to optimize urban wind turbine energy production comprising key steps which include the project site potential for the installation of wind turbines, the estimation of the annual wind power available and the cost estimate for installation and maintenance. The wind potential for the project site was initially determined from statistical wind data cross-referenced with typical weather data for the Sydney region. Computational Fluid Dynamics (CFD) simulations of principal wind directions were then used to adjust the local wind climate data and establish a suitable wind turbine position. Finally, the annual energy production for a number of 10-20 kW commercially available wind turbines was estimated taking into account the wind turbine power curve and technical specifications. The CFD simulations in the current study accounted for the complex site topography and incorporated the shielding impact of nearby trees and other vegetation in order to find the least turbulent area for a successful installation. This study assessed all the parameters that have impact on the accuracy of the numerical model including, computational domain, mesh distribution, numerical scheme and CFD results integration with the localized weather data for the project site.

Time-cost ‘‘trade-off’’ analysis for wind-induced inhabitability of tall buildings equipped with tuned mass dampers

One of the major concerns for tall buildings is the extreme accelerations induced by wind loads and perceived by their occupants. Normally, tuned-mass dampers (TMD) are installed on tall buildings to suppress vibration. However, an established procedure to evaluate the impact of the TMD system from the standpoint of financial profit/deficit is not readily available. This study proposes a framework that integrates local wind climate, wind-induced vibration and TMD performance analysis in terms of monetary outcomes. The proposed framework is composed of three parts: 1) evaluation of wind speed probability distribution at the building site; 2) calculation of wind-induced structural acceleration and its mitigation by TMD with variable mass ratio; 3) lifetime ‘‘net profit’’ assessment, based on the annual normalized inhabitable floor area. A feasibility study suggests that, for super-tall buildings, the TMD is financially effective in reducing wind-induced vibration and inhabitable floor area. Furthermore, large TMD is unnecessary and can lead to a financial deficit. Finally, a simulated mid-rise building does not require a TMD since the financial benefit is marginal.

Wind field generation for performance-based structural design of transmission lines in a mountainous area

The first step of performance-based design for transmission lines is the determination of wind fields as well as wind loads, which are largely depending on local wind climate and the surrounding terrain. Wind fields in a mountainous area are very different with that in a flat terrain. This paper firstly investigated both mean and fluctuating wind characteristics of a typical mountainous wind field by wind tunnel tests and computational fluid dynamics (CFD). The speedup effects of mean wind and specific turbulence properties, i.e., turbulence intensity, power spectral density (PSD) and coherence function, are highlighted. Then a hybrid simulation framework for generating three dimensional (3D) wind velocity field in the mountainous area was proposed by combining the CFD and proper orthogonal decomposition (POD) method given the properties of the target turbulence field. Finally, a practical 220 kV transmission line was employed to demonstrate the effectiveness of the proposed wind field generation framework and its role in the performance-based design. It was found that the terrain-induce turbulence effects dominate the performance-based structural design of transmission lines running through the mountainous area.

Better Natural Ventilation Design for Single Sided Apartments Utilising Computational Fluid Dynamics

Wind-driven natural cross ventilation to many single-aspect apartments can be achieved via building indentations and façade articulation. The ventilation rate of these apartments will rely on pressures differences between openings caused by approaching wind pressure, local wind climate and interaction with the surrounding built environment and external pressure gradients on the building indentations or any other facades articulation and their potential driving force on natural ventilation. Detailed simulation methods are therefore required to consider all above mentioned parameters and provide internal and external airflow information to the design team to allow for design modifications or refinement where required to provide robust natural cross ventilation for such apartments. This study assesses the above parameters for a proposed development, designed with recesses and slots to enhance natural cross ventilation in single-sided apartments, and presents a reliable procedure to advise on compliance with national and/or international design guidelines utilising an advanced combined outdoor-indoor Computational Fluid Flow (CFD) analysis integrated with localized weather data for the project site.

Extreme wave events recorded in sedimentary archives of the Geropotamos River (north-central Crete, Greece)

Recent tsunami events have shown that tsunamis may propagate far inland by entering rivers mouths and may cause massive damage along the river banks. However, so far, only a few studies have been conducted such a search for studying tsunami signals in incised valley systems along the Mediterranean coasts although the tsunami hazard is high. The island of Crete is known to have been affected several times by strong tsunamis, e. g., by the AD 365 and the Late Bronze Age (LBA) Santorini tsunamis. The narrow Geropotamos River valley, distinctly incised into local bedrock and located at the northern coast of Crete and fully exposed to the Cretan Sea, was selected as a promising natural setting to search for palaeotsunami signatures in fluvial sedimentary archives. Based on a multi-electrode geoelectrical survey and a set of sediment cores, we investigated the event-geochronostratigraphic record of both the Geropotamos River mouth area and the river valley ca. 1 km upstream by means of sedimentological, geo-chemical, geochronological, geomorphological, and micropalaeontological methods. The sedimentary environment towards the present-day river mouth is dominated by (fluvio-)lagoonal muds since the mid- Holocene. These lagoonal sediments are intersected by six coarse-grained sand layers each representing an extreme wave event (EWE). EWE layers are up to several decimetres thick and are characterized by an allochthonous foraminiferal assemblage comprising shallow marine to open marine species. Also ca. 1 km further upstream, the sedimentary record revealed grain size and microfossil evidence of two high-energy events showing a clear marine imprint. Based on this, we suggest inundation from the seaside that reached minimum 1 km inland and left EWE signatures in a presently inactive external bank position of the Geropotamos River. Considering the sedimentary characteristics, the local wind and wave climate of the Cretan Sea, and the overall geomorphological setting, we interpret these EWE layers as tsunami- related. A major hiatus identified in the Geropotamos River mouth sediments seems to be related to the LBA Santorini tsunami as can be inferred based on local age-depth relations. The LBA tsunami is known to have severely hit the northern coast of Crete. However, the hiatus may also reflect changes in the subsidence rate and the local accommodation space architecture. The youngest EWE signal in the Geropotamos River archive appears to have been caused by the AD 365 tsunami event. Candidate deposits for both tsunami deposits were identified ca. 1 km further inland. Evidence of EWE impact documents channelling and acceleration effects of intruding water masses caused by the narrow and steeply incised Geropotamos River valley in an upstream direction. Further geochronological studies based on OSL dating are necessary for a reliable age control of these EWE candidate layers.

Wave Climate from Spectra and Its Connections with Local and Remote Wind Climate

AbstractWind-generated waves can propagate over large distances. Therefore, wave spectra from a fixed point can record information about air–sea interactions in distant areas. In this study, the spectral wave climate for a point in the tropical eastern Pacific Ocean is computed. Several well-defined wave climate systems are observed in the mean wave spectrum. Significant seasonal cycling, long-term trends, and correlations with the Southern Oscillation, the Arctic Oscillation, and the Antarctic Oscillation are observed in the local wave spectra, showing abundant climatic information. Projections of wind vectors on the directions pointing to the target location are used to connect the spectral wave climate and basin-scale wind climate, because significant correlations are observed between the wave spectra and the wind projections of both local and remote wind systems. The origins of all the identified wave climate systems, including the westerlies and the trade winds in both hemispheres, are clearly shown in wind projection maps. Some of these origins are thousands of kilometers away from the target point, demonstrating the validity of this connection. Comparisons are made between wave spectra and the corresponding local and remote wind fields with respect to seasonal and interannual variability and long-term trends. The results show that each frequency and direction of ocean wave spectra at a certain location can be approximately linked to the wind field for a geographical area, implying that it is feasible to reconstruct spectral wave climates from observational wind field data and monitor wind climates from observational wave spectra geographically far away.

Probabilistic serviceability-performance assessment of tall mass-timber buildings subjected to stochastic wind loads: Part II - structural reliability analysis

In this paper, the second of two companion papers, the serviceability-performance of a tall mass-timber building is evaluated probabilistically. For the assessment, the Alan G. Davenport Wind Loading Chain is adapted to a probabilistic Performance-Based Wind Engineering (PBWE) framework. The framework allows incorporation of uncertainties at each step of the wind loading chain, i.e., local wind climate and exposure, aerodynamics, dynamic effects, and criteria. As a case study, the framework is applied to quantify the serviceability-performance of a 102-m tall mass-timber building. Initially, parametric analyses are carried out to study the influence of critical damping ratio, wind direction, and local turbulence intensity on the response of the case study tall mass-timber building. Results showed the dependence of story level structural responses on the studied parameters and hence the need to consider the role of uncertainties. Therefore, uncertainties in various parts of the Wind Load Chain are explicitly modeled using fifteen random variables. Structural reliability analysis using Monte Carlo sampling is performed to propagate the uncertainties through the Wind Loading Chain. The results from reliability analysis are used to develop fragility curves for wind vulnerability estimations. Based on the results, design recommendations based on building functionality are forwarded.

Extreme wind speed distribution in a mixed wind climate

The meteorological services of mid-latitude countries record wind speeds averaged over 10 min or 1 h periods and peak wind speeds for the same averaging period or a full day. Design wind speeds based on the statistical analysis of this data in a mixed wind climate may prove to be imprecise and unsafe due to the occurrence of intense, small and rapid extreme wind events such as thunderstorm outflows. Considering the 6 year continuous high-frequency records registered in two Port areas of the Upper Tyrrhenian Sea, a preliminary but representative analysis of the extreme wind speed distribution has been carried out in a mixed wind climate area frequently struck by thunderstorms. Results show that wind speeds with a high return period are always related to thunderstorm outflows. The mixed extreme distribution asymptotically overlaps with that for thunderstorms for high return periods and always provides the highest wind speeds. Gathering the ensemble of all extreme values into a single set leads to underestimating of the extreme wind speed. The Italian code provides conservative estimates of the extreme wind speed that protect designers from thunderstorms as well. However, refined analyses of the local wind climate that ignore thunderstorm events may lead to severe underestimations of the design wind velocity.

A unified framework for performance-based wind engineering of tall buildings in hurricane-prone regions based on lifetime intervention-cost estimation

Accurate evaluation of structural performance is necessary in modern tall building design. In wind engineering, the current approach employed by researchers is the Monte-Carlo sampling method. Structural failure probability is calculated by combining structural fragility curves with the random variability of wind speed and direction, depending on local wind climate. In the hurricane-prone regions of the USA, wind climate and its effects on building response require accurate assessment of wind-induced structural performance.This paper proposes a simulation framework for tall buildings that combines fragility analysis with local wind climate information to evaluate structural vulnerability. Hurricane wind climate information directly considers maximum wind speed, wind direction along with their correlation at hurricane landfall. Consequently, structural fragility surfaces will be generated, conditional on these two variables. This result will be used to examine lifetime intervention cost accumulation, associated with nonstructural damage on the building façade, and to determine an “optimal” wind-direction-dependent building orientation.

Observations and predictions of wind damage to Larix kaempferi trees following thinning at an early growth stage

It is important to find effective forest management strategies to reduce wind damage risk, which is expected to increase due to climate change and increasing areas of planted forests. Thinning is one of the most important forest management activities, but it initially increases tree vulnerability due to an increase in wind penetration into the forest. In this paper, we analysed the damage to trees remaining after the thinning of Larix kaempferi (Lamb.) Carr. at an early growth stage in order: (1) to find the critical factors related to wind damage using statistical models and (2) to calculate the critical wind speeds for damage using a modified version of the mechanistic model GALES. Tree damage caused by a storm in 2006 was examined in plots of different stem densities (300, 500 and 1000 stem ha(-1)), which were thinned at a young age in a replicated silvicultural trial. Subsequently, tree-pulling experiments were conducted to obtain the parameters required in the GALES model. The logistic regression models based on the observations indicated that a longer crown length and a faster annual increase in crown width were significantly related to a reduction in damage occurrence. Estimation of wind damage to trees using GALES did not agree with the observed damage, probably due to the model not accounting for the influence of neighbouring trees and the degree of tree acclimation to the local wind climate after thinning. However, our research is based on only one example of tree damage in stands with different stem densities. Furthermore, our assessment might be biased because we used the trees remaining after the storm to derive parameters for the GALES model, and these trees might on average be more resistant than the storm damaged trees.

The influence of angular configuration of two buildings on the local wind climate

Understanding flows in urban areas is important for a wide range of research areas. In this study the influence of different angular configurations of two buildings on the local wind climate is analysed. PIV (particle image velocimetry) measurements are conducted in an atmospheric boundary layer wind tunnel. Blocken et al. (2008a) showed that, counterintuitively, the wind speeds in the passage of diverging configurations is higher compared to converging configurations. Blocken et al. focused on the wind climate at pedestrian level. The results of this new study show that from the ground to the roof level the wind speeds in the passage are increasing with increasing angles between the buildings for the converging cases, while they are decreasing for the diverging cases. For all cases the highest turbulent kinetic energies can be found downstream of the passage. For the converging cases these regions are located downstream of the buildings and mostly above the pedestrian level, while for diverging cases these regions are located between the buildings at the pedestrian level, where the probability that pedestrians are present is higher.

Wind Power Integration to the Transmission Grid: The Egyptian Perspective

The Government of Egypt has recognized that the availability of reliable power supply is essential for economic and social prosperity and human development as well as for attracting private sector investments in the country. Egyptian Economic reform and growth have triggered a rapid increase in electricity demand. Peak load growth rate averaged 7 % p.a. in 2005–2008 and reached as high as 12% in 2008/09. In response to the rapid growth in demand, the supply capacity has expanded through an ambitious power sector investment program that has been under implementation since 2002. The Government's new energy strategy is aiming to increase the share of renewable energy to 20 % by the year 2020. 12% of this value, i.e 7200 MW, is from wind resources. The complexity of the interconnection of wind farms to the power grid stems from the fact that wind energy is rather unstable and available only during certain hours of the day. By its nature the wind power generation may drop suddenly. To keep the grid operation stable, there is a need to ensure that other power generation sources are available to compensate for the drop. Another common characteristic of the wind farms is that they are located somewhat remote from the power grid. Therefore, the utility has to ensure the sufficiency of power transmission capacity. A rather unique feature of wind power in Egypt is that most of the wind resources are concentrated in the Gulf of Suez and Eastern and Western bank of Nile River areas. This raises the additional issue of the impact on the system when large amount of wind power are interconnected at certain points of the network and not distributed over along the country. The effects of having 3000 MW in Gulf of Suez and 4200 MW at Western Nile River areas depend very much on the local wind climate and the typical hour-to-hour load curve (electricity demand). Some important issues needed to be considered are therefore: how should wind farms be expected to behave and perform, and which requirements should be imposed in order to expect wind farms to support the system? Is it realistic to expect wind turbines and wind farms to behave as any other power plant? What is the Impact on thermal loading of lines/transformers? What are the Power Quality Aspects should be mitigated? What is the behaviour during grid faults/Fault ride through? Reactive power compensation and voltage control…..etc. Grid codes are set up to specify the relevant requirements which have to be met in order to integrate wind turbines into the grid. This paper will focus on The Egyptian approach to integrate wind power to the Egyptian Power System and the important issues related to system operation, stability, protection and the associated technical issues. Grid code requirements for large scale integration of wind power will also be illustrated.

Wind-Climate Estimation Based on Mesoscale and Microscale Modeling: Statistical–Dynamical Downscaling for Wind Energy Applications

AbstractThis paper demonstrates that a statistical–dynamical method can be used to accurately estimate the wind climate at a wind farm site. In particular, postprocessing of mesoscale model output allows an efficient calculation of the local wind climate required for wind resource estimation at a wind turbine site. The method is divided into two parts: 1) preprocessing, in which the configurations for the mesoscale model simulations are determined, and 2) postprocessing, in which the data from the mesoscale simulations are prepared for wind energy application. Results from idealized mesoscale modeling experiments for a challenging wind farm site in northern Spain are presented to support the preprocessing method. Comparisons of modeling results with measurements from the same wind farm site are presented to support the postprocessing method. The crucial element in postprocessing is the bridging of mesoscale modeling data to microscale modeling input data, via a so-called generalization method. With this method, very high-resolution wind resource mapping can be achieved.

Generation of an Annual Typical Meteorological Wind Speed for Armidale NSW,Australia

-The most common data for describing the local wind climate is through what is called Typical Meteorological Year data (TMY). Typical wind speed data is very important for the calculations of many wind applications. In this study, Typical Wind Speed year for Armidale town in New South Wales in Australia are generated from the daily and monthly wind speed data measured at ten meter height from ground level and collected for 20 years during the period 1994 to 2013, utilising the Finkelstein-Schafer statistical method. The study outcome is expected to show how wind speed is potential in Armidale NSW and would be a real help for wind energy generation systems’ designers in this region for all building applications varying between residential, educational, administrative and commercial for sizing and maximising efficiency of such systems by using the tabular TYR outcome for the each day of the year.