A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> The aim of this work is the investigation of the wind environment around a large airport terminal building. The study addresses the less understood, yet important, effects of turbulence generated by a dominant flow obstacle on the wind field of a nearby runway. The flow is fully turbulent, isothermal (neutral atmospheric conditions are assumed) and incompressible. Three-dimensional Computational Fluid Dynamics (CFD) simulations have been performed based on the Reynolds Averaged Navier-Stokes (RANS) equations. Wind tunnel data are available for the mean and turbulence velocities over the runway in the wake of the terminal building to assist in defining boundary and initial conditions and for comparison with the simulations. Qualitative and quantitative treatment of the results is carried out indicating the extent of the influence of the building on the wind field patterns. Particular attention is paid to the study of the effects of the building on the in flight conditions over the nearby runway. <s> BIB001 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> Building mounted micro-wind turbines and photovoltaics have the potential to provide widely applicable carbon free electricity generation at the building level. Photovoltaic systems are well understood and it is easy to predict performance using software tools or widely accepted yield estimates. Micro-wind, however, is far more complex and in comparison poorly understood. This paper presents the key findings of the building mounted ( <s> BIB002 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> This paper describes the concept development and work to date, of an innovative ‘true’ building integrated wind turbine. The context for this is the role of small-scale renewable energy in addressing climate change. In the UK a number of small wind turbines have reached the market, however, in almost all cases, these are existing HAWT or VAWT tower mounted systems. Due to their inherent design qualities, and issues such as planning requirements, these have much reduced output due to their form and siting and are unable to take advantage of augmented airflow around buildings. ::: The Crossflex proposal is a radical new development of a Darrieus turbine form. As well as having a technically innovative flexible blade system, it also utilises a lightweight cowling system that can provide both augmented airflow and improved visual integration into new and existing building forms. It is a modular form that can be sited on ridges and corners of buildings to provide useful levels of generation. <s> BIB003 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> In this paper, a review is presented of academic literature regarding urban wind speeds for building mounted wind turbines. Site measurement of wind speed requires time and money that often are not available for small micro-generation projects. Research into wind speed estimation for the urban environment has shown that street canyons affect urban wind flow, that wind speed up over the roof ridge is only evident for isolated single buildings, that the wind resource “seen” by a building mounted wind turbine is affected by positioning (height above roof ridge and position relative to the prevailing wind direction), that urban terrain roughness is high, and that adjacent buildings can cause wind shadow. This multiplicity of factors makes it difficult to generalise a wind resource estimation methodology for the urban environment. Scaling factors may prove to be a practical solution, provided the accuracy of their use is well understood. <s> BIB004 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> Building-integrated micro-wind turbines are promising low-cost renewable energy devices. However, the take-up of micro-wind turbines in high density suburban environments is still very limited due to issues such as: a) low wind speeds; b) high turbulence intensity; and c) the perception of potentially high levels of aerodynamic noise generated by the turbines. The wind flow field above the roof of buildings in this environment is different to that over flat terrain or around isolated buildings. The effect of the local suburban topology on the wind speed and turbulence intensity fields in a given locality is therefore an important determinant of the optimal location of micro-wind turbines. This paper presents a numerical study of above roof wind flow characteristics in three suburban landscapes characterized by houses with different roof profiles, namely: pitched roofs, pyramidal roofs and flat roofs. Computational Fluid Dynamic (CFD) technique has been used to simulate the wind flow in such environments and to find the optimum turbine mounting locations. Results show how the wind flow characteristics are strongly dependent on the profile of the roofs. It is found that turbines mounted on flat roofs are likely to yield higher and more consistent power for the same turbine hub elevation than the other roof profiles. <s> BIB005 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> The renewed interest that is being paid by architects, project developers and local governments to small-size wind turbines is mainly connected to the attractive prospects of future applications in the urban environment; the delocalized power production of these systems could indeed provide an effective answer to both the growing demand for renewable energy and the increased attention in buildings with a sustainable and low-energy design. In particular, Darrieus vertical-axis wind turbines (VAWTs) are being considered as one of the most attractive solutions due to their low visual impact, the reduced acoustic emissions and their better response to a turbulent and skewed oncoming flow. The feasibility of this scenario has, however, to be proved yet; in particular, doubts are still connected to the real producibility in a complex terrain like the urban one and to the compatibility of microeolic machines with a densely populated area. On these assumptions, the aim of this work is to critically evaluate the energetic suitability of a Darrieus VAWT installation in the rooftop of a building in a reference European city. With this goal in mind, a numerical CFD analysis was carried out to characterize the flow field in the rooftop area of buildings with different shapes and geometrical proportions: the flow velocity modulus and direction were calculated for different oncoming wind profiles and the results were projected into a net available wind distribution in the rooftop of each building. As a second step, in order to provide a reliable estimation of the real functioning of the turbine in the investigated environment, a specific numerical model has been developed to account for the effects of a skewed flow on the power performance of the Darrieus rotor. The results of these analyses were finally combined and synthesized in an energy-oriented study to evaluate the feasibility of a rooftop installation. <s> BIB006 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> Generic proposals for an effective integration of renewable energy sources in the urban environment are frequently carried out by project developers, local governments and media, although an in-depth knowledge of the technical and energetic limitations is often missing. In particular, the installation of small wind turbines on the rooftops of tall buildings is considered to represent an attractive solution thanks to the supposed possibility of exploiting local flow accelerations induced by the building facades. The real feasibility of this scenario has, however, yet to be proved, both in terms of real energy harvesting and of compatibility of the machines with a densely populated area. <s> BIB007 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> Abstract The velocity of wind in an urban location is comparatively lower than in rural or semirural locations. This paper deals with the study of a new methodology to increase the wind speed and power output of small turbines located in urban areas. The new methodology is adopted based on TRIZ (Theory of Solving Inventive Problems) principles. This idea was obtained from the different shapes adopted for the Roof Tops of Buildings at various locations. The methodology used here studies the impact of monoslide roof shape on wind speed using CFD. Majority of buildings in India have Flat Roofs. So, the paper suggests the use of adjustable roof so that the roofs could be tilted at various angles. The present study gives a diagrammatical representation of the new method and an analysis using CFD. Measuring the velocity of wind at an urban location at various altitudes and at various locations of the buildings is a complex task. Computational Fluid Dynamics (CFD) is already a necessary tool for modelling the wind over complex urban terrains. This study underlines a system to reduce the passiveness and idle time of wind turbines located in buildings. That could make the urban wind turbine more agile and active for higher power generation and resource utilization. <s> BIB008 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> The increasing interest among architects and planners in designing environmentally friendly buildings has led to a desire to explore and integrate renewable sources of energy. Roof mounted wind turbines is a technology that presents a high potential for integration within the built environment. However, there is a state of uncertainty regarding the feasibility of these wind turbines. This paper argues that part of this uncertainty is attributed to uninformed decisions about positioning and locating urban wind turbines. This is underpinned by lack of consideration to the accelerating effect of different roof shapes, buildings' heights and surrounding urban configurations. This paper aims to present the results of Computational Fluid Dynamics (CFD) simulations for the purpose of identifying the effect of different roof shapes on the energy yield and positioning of roof mounted wind turbines covering different buildings' heights within different urban configurations under different wind directions. Results from this investigation suggest that an increase in energy yield could be achieved which can reach 56.1% more electricity in the case of a vaulted roof if an informed wind assessment above buildings' roofs is carried out. <s> BIB009 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> The growth of the world energy demand, the limited fossil fuel reserves and the increasing greenhouse gas emissions require improvements in energy-generation technologies. Specifically, urban wind energy is a source with great potential that is currently being wasted. <s> BIB010 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> The urban terrain and the associated morphological complexities therein, present significant challenges for the deployment of small wind turbines. In particular, a considerable amount of uncertainty is attributable to the lack of understanding concerning how turbulence within urban environments affects turbine productivity. Current wind turbine power output measurements (particularly for small/micro wind turbines) are based on an average wind speed over an observation period; with limited accountability of the variability of wind speed within the observation time frame. This paper however, presents two models that can instead accurately consider such wind speed variation and how it affects the turbine, based solely on the observed mean wind speed and standard deviation within successive (10 min) time intervals. These models are predicated on an appreciation of the industry standard metric, turbulence intensity (TI), in conjunction with the power curve of a 2.5 kW wind turbine. Simple ‘look-up’ tables collating how the turbine's power curve is affected by varying TI are used so that a novel methodology for estimating the turbine's electrical performance is achievable. Ultimately, the two models presented afford an opportunity to provide an indicative real-world wind speed distribution based on the two standard measurements. The first approach is an adaptation of a model originally derived to quantify the degradation of power performance of wind farm turbines, using a Gaussian probability distribution to simulate turbulence (and more specifically, turbulence intensity (TI)). Such Gaussian modelling has potential however, for disproportionately high and asymptotic TI, associated, for example, with gusting within low mean wind speed observation windows. Furthermore, the approach requires an accurate turbine power curve. The second approach overcomes these limitations through the novel application of the Weibull Distribution, a widely accepted means to probabilistically describe wind speed. Both models are tested at an urban and suburban location in Dublin City, Ireland, where sonic anemometry is positioned at approximately 1.5 times the average height of buildings at the respective locations. Both observation sites represent two distinct urban landscapes. The instrumentation is positioned specific to their surrounding locations and, record the three dimensional wind vectors at a temporal resolution of 10 Hz. The hypotheses presented here consider an idealised electrical performance of the turbine, with results suggesting that both approaches can replicate very accurately this idealised basis. <s> BIB011 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> Abstract Wind power is generating interest in many countries as a way to produce inexpensive and sustainable electrical power. Building integrated wind turbines (BIWTs) are an interesting option in this respect. BIWTs are low cost renewable sources of energy. Since the power in wind is proportional to the cubic power of the wind velocity approaching the wind turbine, a small amount of wind speed acceleration leads to a large increase in energy output. To augment free wind speed streams, the open area between two buildings can be used as diffuser by taking advantage of the Venturi effect. A system where two buildings are used to increase the winds kinetic energy is called building augmented wind turbine (BAWT). This article shows that the shape of buildings can be changed to maximize the power generated by wind and power augmentation. To estimate building power augmentation using a simplified turbine model, this paper constructed a process that simulated the augmented power and wind velocity in regard to different building geometries using an adaptive neuro-fuzzy (ANFIS) method. This intelligent estimator was implemented using MATLAB/Simulink. The simulation results presented in this paper demonstrated the effectiveness of the method developed in this study. <s> BIB012 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> A numerical investigation was carried out to determine the impact of structural morphology on the power generation capacity of building-integrated wind turbines. The performance of the turbines was analysed using the specifications of the Bahrain Trade Centre which was taken as the benchmark model, the results of which were compared against triangular, square and circular cross-sections of the same building. The three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations along with the momentum and continuity equations were solved for obtaining the velocity and pressure field. Simulating a reference wind speed of 6 m/s, the findings from the study quantified an estimate power generation of 6.4 kW indicating a capacity factor of 2.9 % for the benchmark model. The square and circular configurations however determined greater capacity factors of 12.2 % and 19.9 %, recording an estimated power production capability of 26.9 kW and 35.1 kW and confirming the largest extraction of the incoming wind stream. The optimum cross-sectional configuration for installing wind turbines in high-rise buildings was the circular orientation as the average wind speed at the wind turbines was accelerated by 0.3 m/s resulting in an overall augmentation of 5 %. The results from this study therefore highlighted that circular building morphology is the most viable building orientation, particularly suited to regions with a dominant prevailing wind direction. <s> BIB013 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> The installation of small and medium-size wind turbines on the rooftops of high buildings has been often suggested by architects and project developers as a potential solution for achieving sustainable energy in building design. In such locations, however, because of the presence of buildings and other adjacent obstructions, wind is normally turbulent, unstable and weak, in terms of direction and speed. The use of wind turbines in the built environment poses challenges to overcome, including energy yield reduction due to lower mean wind speeds in urban areas, and environmental impacts because of their close vicinity to people and property. <s> BIB014 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> Abstract To maximize uptake of micro renewable-energy generation, specifically small wind-turbines, it is crucial to permit for tower heights which allow maximum utilization of the available wind resource. Within New Zealand, municipal governments have authority to place limitations on the height of built structures in rural areas, including wind turbines. Numerical simulations using Computational Fluid Dynamics (CFD) are used to examine the effects of simple house shapes and heights on the characteristics of the air flow reaching wind turbines. Within New Zealand, municipal governments have authority to place limitations on the height of built structures in rural areas, including wind turbines. However at present they have insufficient information to understand which height limitations may decrease wind-resource utilisation by small wind-turbines installed in these areas. This research finds that current permitted structure heights are not sufficiently high, necessitating either lengthy planning consent processes or acceptance of sub-optimal turbine output. Municipal councils in New Zealand could reduce barriers to small wind-turbine installations by considering taller towers, in the 15–20 m range, acceptable. This 15–20 m range is transferrable to all rural areas, in other developed or developing countries, where a lone small turbine or small number of small wind-turbines are being considered for installation near dwellings. <s> BIB015 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> Wind energy continues to stand out as a more established and mature technology to offset a large proportion of power. Efforts aimed at improving wind energy use to meet the energy demand in turbulent urban wind environment have been the main technical focus. In previous studies on wind resource and behavior in urban environment, different designs of horizontal axis wind turbines (HAWTs) and vertical axis wind turbines (VAWTs) have been reviewed. This paper vividly captures the fact that wind resource has a great potential to be fully explored and developed in the urban environment. Varying ways of application and application techniques being applied for electrical generation, ventilation and pollution dispersion, onshore cooling and dehumidification of coastal urban cities, and economics and environmental benefits of applying wind energy in urban environments are summarized. Although many new ideas and solutions that factor technical, economical and environmental sustainability in urban areas are coming up every day, challenges in design are gradually being solved to take advantage of urban low and turbulent wind speed characteristics, installation space challenges, vibration and noise reduction, among others. Some of the unique solutions that have been and are being developed in the applications of wind energy technology in urban environments are also reported in this paper. <s> BIB016 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> The effect of wind distribution on the architectural domain of the Bahrain Trade Centre was numerically analysed using computational fluid dynamics (CFD). Using the numerical data, the power generation potential of the building-integrated wind turbines was determined in response to the prevailing wind direction. The three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations along with the momentum and continuity equations were solved for obtaining the velocity and pressure field. Simulating a reference wind speed of 6m/s, the findings from the study quantified an estimate power generation of 6.4kW indicating a capacity factor of 2.9% for the benchmark model. At the windward side of the building, it was observed that the layers of turbulence intensified in inverse proportion to the height of the building with an average value of 0.45 J/kg.The air velocity was found to gradually increase in direct proportion to the elevation with the turbine located at higher altitude receiving maximum exposure to incoming wind. This work highlighted the potential of using advanced computational fluid dynamics in order to factor wind into the design of any architectural environment. <s> BIB017 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> Abstract Wind energy development in a built up environment will be an important subject for future sustainable cities. Maturing CFD technology is making more wind flow simulation experiments available, which can be validated by in situ and wind tunnel measurements. Starting from research on wind accumulation by the Venturi effect in built environment, this paper tries to establish the relationship between wind energy potential and the configuration of two perpendicular buildings by performing parametric CFD wind tests. Two reference buildings (width × length × height = 6 m × 15 m × 10 m) forming a symmetrical corner are chosen and different building lengths, widths, heights, corner separation distances, angles of inlet and altitudes of assessment are considered. Results show that, in converging inlet mode, wind energy potential over the roof generally increases sensibly as the corner separation becomes larger, while in diverging inlet mode it decreases rather slowly with corner enlargement. Meanwhile, compared with a single, isolated reference building, most of the corner configuration cases studied here show greater wind energy density over the roof. <s> BIB018 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> The analysis of the wind flow around buildings has a great interest from the point of view of the wind energy assessment, pollutant dispersion control, natural ventilation and pedestrians wind comfort and safety. Since LES turbulence models are computationally time consuming when applied to real geometries, RANS models are still widely used. However, RANS models are very sensitive to the chosen turbulence parametrisation and the results can vary according to the application. In this investigation, the simulation of the wind flow around an isolated building is performed using various types of RANS turbulence models in the open source code OpenFOAM, and the results are compared with benchmark experimental data. In order to confirm the numerical accuracy of the simulations, a grid dependency analysis is performed and the convergence index and rate are calculated. Hit rates are calculated for all the cases and the models that successfully pass a validation criterion are analysed at different regions of the building roof, and the most accurate RANS models for the modelling of the flow at each region are identified. The characteristics of the wind flow at each region are also analysed from the point of view of the wind energy generation, and the most adequate wind turbine model for the wind energy exploitation at each region of the building roof is chosen. <s> BIB019 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> The analysis of the wind flow around buildings is of great interest in the field of renewable energies. This work presents an investigation of the effects of roof-mounted solar panels on the wind flow on building roofs, from the point of view of the wind energy exploitation. CFD simulations of the wind flow around an isolated building are performed with OpenFOAM. The simulations are compared with two wind tunnel experiments for validation: an isolated building and an array of solar panels. The wind flow on an empty roof is compared with roof-mounted solar panels cases. The solar panels are tested with tilt angles of 10° and 30°, the most adequate inclination for solar panels in the Mediterranean region. The analysis is carried out both quantitatively and qualitatively. The full-scale building results are compared with a reduced-scale model and scaling issues are reported. The most adequate wind turbine for each roof region is suggested. <s> BIB020 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> In response to the gradual degradation of the natural environment, there is a growing interest to advance the development of sustainable buildings, in which renewable energy technologies are often incorporated to strategically minimize the carbon footprint of buildings. Pearl River Tower, a 71-storey tall building in Guangzhou, China, was designed to be the most energy efficient tall building in the world. In addition to a series of energy-efficient measures, the most eye-catching innovation in the design of Pearl River Tower is the deployment of four wind turbines installed in four openings in the tall building for power generation. This study aims to provide a performance assessment of these tall building-integrated wind turbines. At the first step, a 1:150 scaled wind tunnel testing is carried out to experimentally assess the wind speed amplification effects inside the four openings. Comparative analysis and discussions corresponding to four different cases are presented. At the second step, the results from the wind tunnel testing, in conjunction with the statistical analysis results of long-term meteorological wind data recorded in Guangzhou, are applied for the performance assessment of these wind turbines for power generation. The outcomes of this study are expected to provide useful information for architects and engineers involved in the design of sustainable tall buildings. <s> BIB021 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> Abstract Building augmented wind turbine (BAWT) has been studied numerically. BAWT is a new technology trend to combine wind turbine with building and it has several advantages compared with the conventional stand-alone wind turbine such as minimization of electrical transmission loss and construction cost for the distributed power source and by using existing building. In this paper, a 110 kW horizontal axis wind turbine blade is designed and CFD analysis is carried out with various reference wind speed and flow angle for the 110 kW BAWT. The results show that aerodynamic power output of 110 kW BAWT is higher than that of 110 kW stand-alone wind turbine due to the concentration effect caused by the wind speed acceleration between buildings. Also this kind of advantage appeared in flow angle between −30 ° and 15 °. Due to the fixed rotational direction of the wind turbine, the effect of flow angle shows asymmetric nature. It is also shown that to exceed Betz limit of 0.593 is possible by the effect of buildings similar to the ducts and shrouds. The results of this study can be applied to the research and development of various BAWT and enhancement of energy efficiency of wind turbine. <s> BIB022 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> From the viewpoint of installing small wind turbines (SWTs) on rooftops, this study investigated the effects of wind direction and horizontal aspect ratio (HAR = width/length) of a high-rise cuboid building on wind conditions above the roof by conducting large eddy simulations (LESs). The LES results confirmed that as HAR decreases (i.e., as the building width decreases), the variation in wind velocity over the roof tends to decrease. This tendency is more prominent as the angle between the wind direction and the normal vector of the building’s leeward face with longer roof edge increases. Moreover, at windward corners of the roof, wind conditions are generally favorable at relatively low heights. In contrast, at the midpoint of the roof's windward edge, wind conditions are generally not favorable at relatively low heights. At leeward representative locations of the roof, the bottoms of the height range of favorable wind conditions are typically higher than those at the windward representative locations, but the favorable wind conditions are much better at the leeward representative locations. When there is no prevailing wind direction, the center of the roof is more favorable for installing SWTs than the corners or the edge midpoints of the roof. <s> BIB023 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> There is great potential in the use of urban wind energy to form electricity generation modules over a distribution network to maximize wind power production in densely urbanized areas. The objective of this study is to therefore develop computational fluid dynamics (CFD)-based evaluation procedures to determine potential mounting sites of wind turbines and obtain estimates of wind power by taking into consideration the details of the local urban topography and boundary conditions of micro-environments. The predictions, including those of the wind velocity and direction as well as turbulence intensity, are compared with field measurements via ultrasonic anemometers and thermal flow velocity probes at 10 monitored sites over five different floors inside an objective building to validate the computational model as well as attain a better understanding of the interaction of the wind with buildings in a complex terrain. The predicted power density and turbulence intensity profiles are then used to analyze the power density, turbulence intensity and lowest mounting height for optimizing the potential mounting sites and estimates of wind power. The suggested deployment solution of using CFD for wind turbines on the studied site is clearly different from those suggested in the literature and their deficiency in providing optimum mounting sites in micro-environments. Moreover, an improved roof design with a rounded shape is proposed for the enhancement of wind power density with relatively lower turbulence intensity. <s> BIB024 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> In recent years, wind farm optimization has received much attention in the literature. The aim of wind farm design is to maximize energy production while minimizing costs. The wind farm layout optimization (WFLO) problem on uniform terrains has been tackled by a number of approaches; however, optimizing wind farm layouts on complex terrains is challenging due to the lack of accurate, computationally tractable wake models to evaluate wind farm layouts. This paper proposes an algorithm that couples computational fluid dynamics (CFD) with mixed-integer programming (MIP) to optimize layouts on complex terrains. CFD simulations are used to iteratively improve the accuracy of wake deficit predictions while MIP is used for the optimization process. The ability of MIP solvers to find optimal solutions is critical for capturing the effects of improved wake deficit predictions on the quality of wind farm layout solutions. The proposed algorithm was applied on a wind farm domain in Carleton-sur-Mer, Quebec, Canada. Results show that the proposed algorithm is capable of producing excellent layouts in complex terrains. <s> BIB025 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> Abstract The next decades will be a golden period for the utilization of wind power in buildings. This paper assesses the wind power resource for constructing a thousand-meter scale megatall building in China. Considering there is no existing documentation of more detailed sources for upper level wind data, we elaborated on using the mesoscale meteorological model Weather Research and Forecasting Model (WRFv3.4) to investigate the wind characteristics at different levels within the thousand-meter scale megatall building's height. At the first step, the WRF model is validated through the comparisons between the simulated wind data and meteorological observations, including the ground-based observatory data and radiosonde data. At the second step, the results from the WRF model are used in the assessment of directional wind power densities, based on which the directional electric powers at the corresponding heights of the platforms are estimated as well. The results indicate that the maximum wind power density and electric power occur at 300 and 200 m above the ground, respectively. Additionally, both the wind power density and electric power from the north and south are significantly larger than those from the other two directions. <s> BIB026 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> Low-powered devices are ubiquitous in this modern age especially their application in the urban and built environment. The myriad of low-energy applications extend from wireless sensors, data loggers, transmitters and other small-scale electronics. These devices which operate in the microWatt to milliWatt power range and will play a significant role in the future of smart cities providing power for extended operation with little or no battery dependence. Low energy harvesters such as the aero-elastic belt are suitable for integration with wireless sensors and other small-scale electronic devices and therefore there is a need for studying its optimal installation conditions. In this work, a case study presenting the Computational Fluid Dynamics modelling of a building integrated with aero-elastic belts (electromagnetic transduction type) was presented. The simulation used a gable-roof type building model with a 27° pitch obtained from the literature. The atmospheric boundary layer flow was employed for the simulation of the incident wind. The work investigates the effect of various wind speeds and aero-elastic belt locations on the performance of the device giving insight on the potential for integration of the harvester into the built environment. ::: ::: The apex of the roof of the building yielded the highest power output for the aero-elastic belt due to flow speed-up maximisation in this region. This location produced the largest power output under the 45° angle of approach, generating an estimated 62.4 mW of power under accelerated wind in belt position of up to 6.2 m/s. For wind velocity of 10 m/s, wind in this position accelerated up to approximately 14.4 m/s which is a 37.5% speed-up at the particular height. This occurred for an oncoming wind 30° relative to the building facade. For velocity equal to 4.7 m/s under 0° wind direction, airflows in facade edges were the fastest at 5.4 m/s indicating a 15% speed-up along the edges of the building. <s> BIB027 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> Extracting energy from wind by placing wind turbines over tall buildings is an emerging idea for "greener" cities. This paper discusses the best location for placing wind turbines based on numerical simulations. Different building geometries are considered by varying the dimension and number of buildings. Here real atmospheric boundary layer profiles are created with the help of the Weather Research and Forecasting model and also compared with the theoretical profiles from power law equation. Outputs from the simulations show the location where wind velocity is maximum and the possibility of placing wind turbines on the top as well as in the gap between the buildings. The paper also describes the significance of using realistic profiles instead of theoretical profiles. <s> BIB028 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> The standard k–e turbulence model is well known to perform poorly in the stagnation regions in front of buildings where it over-predicts the turbulent kinetic energy, k. It is less well known that this error is compounded by an excess decay of the turbulence over and behind a building so that k is eventually under-estimated in the building wake. A new formulation of the eddy viscosity in the standard k–e turbulence model was developed and compared with previous modifications designed for stagnation regions. The new formulation provides more accurate values of k and it showed similar results for streamwise mean velocity predicted by the shear stress transport turbulence model. A blend between the new model and the standard eddy viscosity model provides the best overall prediction of the mean velocities and turbulence. <s> BIB029 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> Abstract Wind energy development in the built environment can help to realise a sustainable city. In this paper, the wind energy over roof of a building with canopy roof was discussed. The method of evaluating wind potential over a building with canopy roof was presented. CFD parameter study was undertaken and validated by wind tunnel experiment before launch of the simulation. Several verification methods were discussed to help adjust parameter choice and to evaluate the simulation results. We studied the capacity of wind concentration over roof of a reference building with different heights, overhangs and pitch angles of the canopy roof. A proposition of wind turbine position for maximum wind potential was then given for the chosen model building. The results show that, under the flat canopy there is hardly any wind energy amplification effect. Adding an overhang to a flat canopy in the upstream can have a slight improvement of wind concentration under the canopy but no concentration above it. The trough canopy models show wind potential advantage mainly under the canopy and the gable canopy models mainly above the canopy. The double-pitched canopy with a pitch angle of 20° was found to be the best one in wind concentration. <s> BIB030 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> Abstract As a renewable energy source, wind power has received growing attentions, but mostly been utilized in wind power farms or high-rise buildings where the wind with high speed is available. Few studies focus on the micro-wind utilization in low-rise buildings due to the bottleneck that the wind speed cannot meet the minimal speed requirement of small wind turbines. This paper aims to identify the optimal building design which could enable the harvesting of the maximal micro-wind power around low-rise residential buildings. Based on the comparison among different building shapes and the computational fluid dynamics (CFD) analysis via software Phoenics , this paper identified that the building shape of “composite prism” could enable the harvesting of the most micro-wind power. The identified building shape was then tested in a simulated environment of a residential community in Pingtan Island, China. The local wind conditions, long-term community planning, and the requirement of comfort level were all considered in the simulation model. The result shows that the potential of utilizing wind energy in low-rise residential buildings is huge by adopting the proposed building shape of “composite prism”. The finding has significant implications for renewable energy utilization in built environment. <s> BIB031 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> Abstract Efficient wind energy harvesting by utilizing small-scale wind turbines in the urban environment requires techniques to enhance the desirable flow characteristics, including velocity magnitude and uniformity, and diminish the unfavorable characteristics, including high turbulence and intermittence. This study proposed a Double-Skin Facade (DSF) system with strategic openings to harvest wind energy in the built environment. A series of wind tunnel tests and CFD simulations have been conducted to investigate the characteristics and related mechanisms of flow within the cavity of DSF integrated with a tall building model at different incident wind angles. The discrepancy between numerical and experimental results generally remains within an acceptable range of 15% which validates the capability and accuracy of the developed CFD simulations in predicting the flow characteristics. It was found that the flow becomes more uniform while the turbulence progressively decays as flow progresses through the cavity for all wind directions. Hence the regions in the middle of both the leading and trailing sides of the cavity are favorable locations for installing small-scale, building-mounted wind turbines. Overall, the DSF system with a strategic opening can effectively enhance the flow within the cavity for a wide range of incident wind angles and can be adapted for wind energy harvesting purposes. <s> BIB032 </s> A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment <s> Building Scale <s> Abstract Roof mounting wind turbine (RMWT) is a promising form of wind energy utilization in urban environment. According to the International Energy Agency wind task 27, a recommended practice on micrositing of small wind turbines in the areas of high turbulence needs to be formulated. A computational fluid dynamics (CFD) study on the wind turbulence characteristics over the Engineering and Technology Building (ETB) on campus based on the urban atmospheric boundary layer (UABL) inflow condition is conducted, and the results are validated by wind lidar measurements. The micrositing method of RMWT is developed based on the CFD simulations, which contains preliminary and accurate micrositings. Results from this investigation suggest that the optimum installation height ranges from 1.51 to 1.79 times the height of building and the best locations are at the forefront where the wind acceleration reaches the maximum, as the wind direction varies. The methods developed in this paper can provide a feasible scheme for micrositing of RMWTs in urban environment and the results can also serve as a recommendation to this topic. <s> BIB033
There has been renewed interest by architects, built environment engineers, developers and governments regarding the installation of wind turbines into urban or built environments due to their capability to provide delocalised power which could provide a solution to the increasing urbanisation and renewable energy demand and interest in low energy and sustainable buildings BIB021 BIB026 . Wind turbines positioned at the rooftop of a tall building to extract wind energy, in theory, could take advantage of a higher area of the wind velocity profile (see Figure 11 ) which is not significantly affected by the surface roughness BIB006 BIB004 . Prominent examples include, the World Trade Centre in Bahrain, Strata Tower in London, and Pearl River Tower in Guangzhou which have building-integrated wind turbines BIB001 . Computation 2017, 5, x FOR PEER REVIEW 14 of 37 There has been renewed interest by architects, built environment engineers, developers and governments regarding the installation of wind turbines into urban or built environments due to their capability to provide delocalised power which could provide a solution to the increasing urbanisation and renewable energy demand and interest in low energy and sustainable buildings BIB021 BIB026 . Wind turbines positioned at the rooftop of a tall building to extract wind energy, in theory, could take advantage of a higher area of the wind velocity profile (see Figure 11 ) which is not significantly affected by the surface roughness BIB006 BIB004 . Prominent examples include, the World Trade Centre in Bahrain, Strata Tower in London, and Pearl River Tower in Guangzhou which have buildingintegrated wind turbines BIB001 . Currently, there are several challenges to installing wind turbines in urban areas, particularly turbines near an urban environment. The main challenge is the availability of adequate wind resource in these environments. The wind conditions in urban areas are highly complex due to surface roughness and the presence of obstacles, i.e., buildings and structures, characterised by low wind speed and high turbulence which are not desirable regarding power production by WTs BIB017  . Furthermore, the wind turbines in buildings also raise other concerns such as aesthetic dissatisfaction, vibration and aerodynamic noise BIB002 . Several researchers have employed CFD modelling to establish the feasibility of building integrated turbines. CFD can investigate how the wind flows over a building, the effect of the speed, direction and turbulence of flow and the interference effects of surrounding buildings or structures. It is important to carefully assess the position of the WT on a building so that the great volume of power can be gathered. Figure 12 illustrates examples of the incorporation of large scale wind turbines (roof, between buildings, within the structure) and small-scale wind turbines into buildings. Ayhan and Sağlam BIB027 conducted an investigation of wind turbine installations in buildings using CFD modelling. The wind flows and aerodynamics were examined according to the local meteorological data and local buildings features. To achieve the greatest potential resource of wind energy and prevent turbulent places, CFD was used to simulate the annual wind flows with buildings to assist in locating, analysing, and designing wind turbines around and on buildings. The work highlighted that the height of mounted WT was essential as wind can be extremely strong at rooftop height. Moreover, smaller VAWTs are more advisable to use in urban areas. The typical Darrieus WT was not suitable because it was observed to be too noisy, while the Savonious rotor has the drawback of low power levels. Through improvement of the initial design of Darrieus by decreasing the TSR, the noise can be minimised. Currently, there are several challenges to installing wind turbines in urban areas, particularly turbines near an urban environment. The main challenge is the availability of adequate wind resource in these environments. The wind conditions in urban areas are highly complex due to surface roughness and the presence of obstacles, i.e., buildings and structures, characterised by low wind speed and high turbulence which are not desirable regarding power production by WTs BIB017  . Furthermore, the wind turbines in buildings also raise other concerns such as aesthetic dissatisfaction, vibration and aerodynamic noise BIB002 . Several researchers have employed CFD modelling to establish the feasibility of building integrated turbines. CFD can investigate how the wind flows over a building, the effect of the speed, direction and turbulence of flow and the interference effects of surrounding buildings or structures. It is important to carefully assess the position of the WT on a building so that the great volume of power can be gathered. Figure 12 illustrates examples of the incorporation of large scale wind turbines (roof, between buildings, within the structure) and small-scale wind turbines into buildings. Ayhan and Saglam BIB027 conducted an investigation of wind turbine installations in buildings using CFD modelling. The wind flows and aerodynamics were examined according to the local meteorological data and local buildings features. To achieve the greatest potential resource of wind energy and prevent turbulent places, CFD was used to simulate the annual wind flows with buildings to assist in locating, analysing, and designing wind turbines around and on buildings. The work highlighted that the height of mounted WT was essential as wind can be extremely strong at rooftop height. Moreover, smaller VAWTs are more advisable to use in urban areas. The typical Darrieus WT was not suitable because it was observed to be too noisy, while the Savonious rotor has the drawback of low power levels. Through improvement of the initial design of Darrieus by decreasing the TSR, the noise can be minimised. The size of WTs for building integration is constrained by the available space. To highlight this issue, a number of studies have tried to increase power by forcing air through a duct with a turbine which accelerates velocity and increases the kinetic energy of the air. This acceleration can also be attained by locating the wind turbine between two buildings. These increases in wind velocity occurring between two buildings are also known as the Venturi effects BIB003 or building augmented wind turbine (BAWT) BIB012 . Heo et al. BIB022 conducted CFD analysis of a 110-kW BAWT with different reference wind speed and flow angles. Figure 13 shows the structure of the wind turbine and sky bridge on the buildings. The turbulence model used was the RANS-SST. Results showed that aerodynamic power production of 110 kW BAWT was more compared to 110 kW stand-alone WT because of the concentration effect produced by the wind acceleration among buildings when flow angle is between −30 and 15°. Because of the steady rotational direction of the WT, the impact of flow angle showed unsymmetrical nature. The size of WTs for building integration is constrained by the available space. To highlight this issue, a number of studies have tried to increase power by forcing air through a duct with a turbine which accelerates velocity and increases the kinetic energy of the air. This acceleration can also be attained by locating the wind turbine between two buildings. These increases in wind velocity occurring between two buildings are also known as the Venturi effects BIB003 or building augmented wind turbine (BAWT) BIB012 . Heo et al. BIB022 conducted CFD analysis of a 110-kW BAWT with different reference wind speed and flow angles. Figure 13 shows the structure of the wind turbine and sky bridge on the buildings. The turbulence model used was the RANS-SST. Results showed that aerodynamic power production of 110 kW BAWT was more compared to 110 kW stand-alone WT because of the concentration effect produced by the wind acceleration among buildings when flow angle is between −30 and 15 • . Because of the steady rotational direction of the WT, the impact of flow angle showed unsymmetrical nature. The size of WTs for building integration is constrained by the available space. To highlight this issue, a number of studies have tried to increase power by forcing air through a duct with a turbine which accelerates velocity and increases the kinetic energy of the air. This acceleration can also be attained by locating the wind turbine between two buildings. These increases in wind velocity occurring between two buildings are also known as the Venturi effects BIB003 or building augmented wind turbine (BAWT) BIB012 . Heo et al. BIB022 conducted CFD analysis of a 110-kW BAWT with different reference wind speed and flow angles. Figure 13 shows the structure of the wind turbine and sky bridge on the buildings. The turbulence model used was the RANS-SST. Results showed that aerodynamic power production of 110 kW BAWT was more compared to 110 kW stand-alone WT because of the concentration effect produced by the wind acceleration among buildings when flow angle is between −30 and 15°. Because of the steady rotational direction of the WT, the impact of flow angle showed unsymmetrical nature. A similar study by Chaudhry et al. BIB013 also used CFD to analyse the efficiency of BAWT but focused on the shape or structural morphology of the building. The performance of the turbines integrated into buildings with triangular, square and circular cross-sections (see Figure 14) was analysed and compared with a benchmark model which was based on the Bahrain Trade Centre. Based on the simulated conditions, the results showed that the circular building shape was the most effective orientation, particularly in the areas with a dominant wind direction. Wang et al. BIB018 established the relationship between potential of wind energy and two perpendicular building configurations (converging and diverging) by conducting CFD analysis. The results showed that, in a converging configuration, the wind energy potential at the rooftop normally increased when the corner separation became bigger, while in a separating configuration, it decreased gradually with corner enlargement. Veena et al. BIB028 conducted research on the optimal sitting of wind turbines with high rise buildings using CFD simulations. Two configurations were compared: wind turbines in between twin towers and building with roof top wind turbines. The use of realistic wind profiles gathered from a weather projection model was the focus of the study. Results have shown that for a standalone high-rise building, there was a substantial fraction on which winds were enough to be used in wind power production. In the case of twin buildings, WTs wind can be positioned also in between the buildings and not only at the roof top. The velocity of 2 m/s can be achieved for a separation distance of fraction 0.2 and 2-2.8 m/s for 0.5. A similar study by Chaudhry et al. BIB013 also used CFD to analyse the efficiency of BAWT but focused on the shape or structural morphology of the building. The performance of the turbines integrated into buildings with triangular, square and circular cross-sections (see Figure 14) was analysed and compared with a benchmark model which was based on the Bahrain Trade Centre. Based on the simulated conditions, the results showed that the circular building shape was the most effective orientation, particularly in the areas with a dominant wind direction. Wang et al. BIB018 established the relationship between potential of wind energy and two perpendicular building configurations (converging and diverging) by conducting CFD analysis. The results showed that, in a converging configuration, the wind energy potential at the rooftop normally increased when the corner separation became bigger, while in a separating configuration, it decreased gradually with corner enlargement. Veena et al. BIB028 conducted research on the optimal sitting of wind turbines with high rise buildings using CFD simulations. Two configurations were compared: wind turbines in between twin towers and building with roof top wind turbines. The use of realistic wind profiles gathered from a weather projection model was the focus of the study. Results have shown that for a standalone high-rise building, there was a substantial fraction on which winds were enough to be used in wind power production. In the case of twin buildings, WTs wind can be positioned also in between the buildings and not only at the roof top. The velocity of 2 m/s can be achieved for a separation distance of fraction 0.2 and 2-2.8 m/s for 0.5. Locating a roof-mounted wind turbines where there is a significant separated zone will subject the WT to low wind velocity and positioning it where there is high turbulence intensity could cause early blade failure. Hence, CFD simulation of the wind flow around the building rooftop with wind turbines could help mitigate the issues during the early stages of the design. Ledo et al. BIB005 studied the wind flow characteristics around three typical suburban roof profiles including flat, pyramidal, pitched roofs. The wind flow in such areas was simulated using CFD based on SST k-ω turbulence model and to search the most effective and efficient turbine place of installation. Findings showed that power outputs of WT installed on flat roofs were more consistent and with higher power as compared to some roof profiles. The work of Balduzzi et al. BIB006 BIB007 presented a comprehensive CFD analysis of the suitability of rooftop installation of Darrieus wind. The effects of geometric proportion, roof shape, and building height on the performance were evaluated. Padmanabhan BIB008 used CFD to investigate the feasibility of wind turbines on an adjustable roof to increase power production and wind velocity of small WTs positioned in urban environments. Locating a roof-mounted wind turbines where there is a significant separated zone will subject the WT to low wind velocity and positioning it where there is high turbulence intensity could cause early blade failure. Hence, CFD simulation of the wind flow around the building rooftop with wind turbines could help mitigate the issues during the early stages of the design. Ledo et al. BIB005 studied the wind flow characteristics around three typical suburban roof profiles including flat, pyramidal, pitched roofs. The wind flow in such areas was simulated using CFD based on SST k-ω turbulence model and to search the most effective and efficient turbine place of installation. Findings showed that power outputs of WT installed on flat roofs were more consistent and with higher power as compared to some roof profiles. The work of Balduzzi et al. BIB006 BIB007 presented a comprehensive CFD analysis of the suitability of rooftop installation of Darrieus wind. The effects of geometric proportion, roof shape, and building height on the performance were evaluated. Padmanabhan BIB008 used CFD to investigate the feasibility of wind turbines on an adjustable roof to increase power production and wind velocity of small WTs positioned in urban environments. A CFD study was conducted by Abohela et al. BIB009  to investigate wind flow on top of six different roof shapes including vaulted, flat, gabled, wedged, domed, and pyramidal roofs, to identify the most efficient location of the WT and the most efficient roof shape for installing WTs, as shown in Figure 15 . Results showed that the vaulted roof was the most effective roof shape as the WT generated 56% more electricity compared to a stand-alone WT at the exact place with similar flow settings. In contrary, the wedged roof showed the least accelerating effect on wind on top of it. The Tabrizi et al. BIB014 study also investigated the performance of a WT installation on a rooftop of a warehouse using CFD. The analysis also included the surrounding buildings to a radius of 200 m. Although many studies BIB019 BIB029 BIB023 BIB020 have shown that Large Eddy Simulation (LES) presents better agreement with experiments than RANS in particular when predicting the behaviour of the separated flows around buildings, its computational cost for modelling full scale geometries is very high. Hence RANS models are still widely used. Toja-Silva et al. BIB019 performed CFD simulations based on several RANS turbulence models of the airflow around different types of roof-mounted wind turbines (HAWT, VAWT and ducted). The focus was to replicate actual measurements data for both airflow velocity and turbulence kinetic energy around the roof of a building. The work provided guidelines on the optimum positioning of wind turbines on top of an isolated building model. Mohamed and Wood BIB029 modified the standard k-ε model by developing new formulation of the eddy viscosity and compared with previous modifications designed for stagnation regions around buildings. The results showed that the developed model provided more accurate k values and displayed comparable results for stream-wise mean velocity predicted by the SST model. Furthermore, combination of the developed model and eddy viscosity model provided the most accurate estimation of the velocities and turbulence. Many of the RANS models showed substantial over estimation of the k or normal stresses at the windward side of the building while other RANS models that accurately reproduced the windward side k or normal stresses showed significant under estimation of the k or normal stresses above the centre or leeward side of the building BIB023 . Toja-Silva et al. BIB020 expanded their work by studying the impact of roof solar panels on wind turbines. The solar panels were simulated with tilt angles of 10-30 • . The study highlighted that the recirculation vortex among the upstream edge of the roof and the first array of solar panel had the highest velocity and the study recommended to position the Vertical Axis Wind Turbine in a horizontal position inside this vortex. A CFD study was conducted by Abohela et al. BIB009  to investigate wind flow on top of six different roof shapes including vaulted, flat, gabled, wedged, domed, and pyramidal roofs, to identify the most efficient location of the WT and the most efficient roof shape for installing WTs, as shown in Figure 15 . Results showed that the vaulted roof was the most effective roof shape as the WT generated 56% more electricity compared to a stand-alone WT at the exact place with similar flow settings. In contrary, the wedged roof showed the least accelerating effect on wind on top of it. The Tabrizi et al. BIB014 study also investigated the performance of a WT installation on a rooftop of a warehouse using CFD. The analysis also included the surrounding buildings to a radius of 200 m. Although many studies BIB019 BIB029 BIB023 BIB020 have shown that Large Eddy Simulation (LES) presents better agreement with experiments than RANS in particular when predicting the behaviour of the separated flows around buildings, its computational cost for modelling full scale geometries is very high. Hence RANS models are still widely used. Toja-Silva et al. BIB019 performed CFD simulations based on several RANS turbulence models of the airflow around different types of roof-mounted wind turbines (HAWT, VAWT and ducted). The focus was to replicate actual measurements data for both airflow velocity and turbulence kinetic energy around the roof of a building. The work provided guidelines on the optimum positioning of wind turbines on top of an isolated building model. Mohamed and Wood BIB029 modified the standard k-ε model by developing new formulation of the eddy viscosity and compared with previous modifications designed for stagnation regions around buildings. The results showed that the developed model provided more accurate k values and displayed comparable results for stream-wise mean velocity predicted by the SST model. Furthermore, combination of the developed model and eddy viscosity model provided the most accurate estimation of the velocities and turbulence. Many of the RANS models showed substantial over estimation of the k or normal stresses at the windward side of the building while other RANS models that accurately reproduced the windward side k or normal stresses showed significant under estimation of the k or normal stresses above the centre or leeward side of the building BIB023 . Toja-Silva et al. BIB020 expanded their work by studying the impact of roof solar panels on wind turbines. The solar panels were simulated with tilt angles of 10-30°. The study highlighted that the recirculation vortex among the upstream edge of the roof and the first array of solar panel had the highest velocity and the study recommended to position the Vertical Axis Wind Turbine in a horizontal position inside this vortex. Wang et al. BIB030 studied the effect of different forms (flat, trough, double-pitched, gable) of a canopy roof on the airflow over the roof and the potential wind energy generation using CFD simulation. The results showed that under the flat type canopy there is minimal amplification of wind energy amplification. The addition of an overhang to the upstream of the flat canopy slightly improved the wind concentration under the canopy, however, it was disadvantageous for the region Wang et al. BIB030 studied the effect of different forms (flat, trough, double-pitched, gable) of a canopy roof on the airflow over the roof and the potential wind energy generation using CFD simulation. The results showed that under the flat type canopy there is minimal amplification of wind energy amplification. The addition of an overhang to the upstream of the flat canopy slightly improved the wind concentration under the canopy, however, it was disadvantageous for the region above it (no concentration of wind). The trough configuration showed improved wind concentration compared to the flat type mainly under its canopy while the gable configuration mainly above its canopy. The double pitched type with a 20 • pitch angle was found to be the best in terms of wind concentration. CFD was used to evaluate the impacts of heights and simple house shapes on the air flow reaching wind turbines in the study of White and Wakes BIB015 . Municipal governments in New Zealand have authority to impose height of the building constraint in rural areas, including the WTs. Currently, there is no sufficient information to understand which height limitations may reduce wind resource use by small WTs placed in these areas. The study found that permitted structure height is not high, forcing either acceptance of sub-optimal turbine output or length planning consent process. Municipal governments can minimise the barriers to small wind turbine installation through taking taller towers into account, in the range of 15-20 m. This range is transferrable to all rural area, where a small number of small turbines are recognised for installation near dwellings. Several studies focused on the impact of surrounding buildings on the performance of BIWT BIB010 BIB016 BIB033 BIB024  . Zhou et al. BIB031 focused on finding the most efficient and effective design that could accelerate the speed of wind flow for wind turbines in low-rise residential buildings. Figure 16 shows an example of the wind amplification effect of the designed building shape in a sample building. According to the assessment between different building shapes and CFD assessment using Phoenics software, the building shape of composite prism can enable the harvesting of most of the wind power. The tested building shape was later tested in a simulated environment of a residential area in China. The long-term community system, local wind conditions, and the comfort level needed were all considered in the simulation model. The result of the study showed that using wind energy harvesting in low rise residential buildings by adopting the proposed building composite prism shape has a great potential. above it (no concentration of wind). The trough configuration showed improved wind concentration compared to the flat type mainly under its canopy while the gable configuration mainly above its canopy. The double pitched type with a 20° pitch angle was found to be the best in terms of wind concentration. CFD was used to evaluate the impacts of heights and simple house shapes on the air flow reaching wind turbines in the study of White and Wakes BIB015 . Municipal governments in New Zealand have authority to impose height of the building constraint in rural areas, including the WTs. Currently, there is no sufficient information to understand which height limitations may reduce wind resource use by small WTs placed in these areas. The study found that permitted structure height is not high, forcing either acceptance of sub-optimal turbine output or length planning consent process. Municipal governments can minimise the barriers to small wind turbine installation through taking taller towers into account, in the range of 15-20 m. This range is transferrable to all rural area, where a small number of small turbines are recognised for installation near dwellings. Several studies focused on the impact of surrounding buildings on the performance of BIWT BIB010 BIB016 BIB033 BIB024  . Zhou et al. BIB031 focused on finding the most efficient and effective design that could accelerate the speed of wind flow for wind turbines in low-rise residential buildings. Figure 16 shows an example of the wind amplification effect of the designed building shape in a sample building. According to the assessment between different building shapes and CFD assessment using Phoenics software, the building shape of composite prism can enable the harvesting of most of the wind power. The tested building shape was later tested in a simulated environment of a residential area in China. The long-term community system, local wind conditions, and the comfort level needed were all considered in the simulation model. The result of the study showed that using wind energy harvesting in low rise residential buildings by adopting the proposed building composite prism shape has a great potential. Figure 16 . Wind amplification effect of the designed building shape in sample building(s) BIB031 . Micro sitting of wind turbines installed at the rooftop in an urban environment was investigated in Wang et al. BIB024 study using CFD simulation to analysed the wind turbulence behaviours on the Engineering and Technology Building (ETB) on campus according to the urban ABL inflow, and the outcomes were validated by lidar measurements. The micrositing method of roof mounted WT was developed based on the CFD simulations that contains accurate and preliminary micrositings. The results suggested that the optimum installation height was 1.51-1.70 times theheight range of building and the best locations were at the front position where the acceleration of the wind reaches the maximum, as the wind direction changes. The methods proposed in this study could offer a viable schem for micrositing of WT installed at the rooftop in urban areas. Micro sitting of wind turbines installed at the rooftop in an urban environment was investigated in Wang et al. BIB024 study using CFD simulation to analysed the wind turbulence behaviours on the Engineering and Technology Building (ETB) on campus according to the urban ABL inflow, and the outcomes were validated by lidar measurements. The micrositing method of roof mounted WT was developed based on the CFD simulations that contains accurate and preliminary micrositings. The results suggested that the optimum installation height was 1.51-1.70 times theheight range of building and the best locations were at the front position where the acceleration of the wind reaches the maximum, as the wind direction changes. The methods proposed in this study could offer a viable schem for micrositing of WT installed at the rooftop in urban areas. Sunderland et al. BIB011 presented two models which can consider issues such as wind velocity variation and how it affects the turbine and wind velocity variation which are entirely based on the standard deviation within successive 10-min time intervals and observed mean wind speed. These approaches were based on turbulence intensity, appreciation of the standards metric, and in conjunction with the power curve of a 2.5-kW WT. The first method was an adaptation of a model based on the initial results to measure the loss of power performance of turbines with the use of Gaussian probability distribution to stimulate turbulence. The second method overcomes these barriers by the novel application of the Weibull Distribution. The first and second models were assessed at suburban and urban locations in Ireland, where sonic anemometry was installed at around 1.5 times the standard height of the buildings at particular areas. According to the results of the investigation, it was suggested that both methods can replicate this. Yang et al.  developed an assessment methodology based on CFD to identify the potential mounting locations of WTs and calculate the generation while considering the impact of the local terrain. The CFD model was validated with field experiments and the results of the realisable k-ε model agreed well with the experimental data. The authors highlighted the difference between the method they proposed and those recommended in the literature which had flaws in offering optimum mounting locations in small-scale environments. Several authors BIB032 BIB025 explored the potential of unconventional methods of incorporation of wind energy systems into the built environment. Park et al. BIB032 proposed and assessed a BIWT systems incorporated into the building façade which combines a series of guide vanes to re-direct and accelerate the wind into a rotor. The work used CFD to simulate and optimise the system configuration which was also validated by scaled experiments. The results showed that the system can accelerate the wind velocity to satisfactory levels and, therefore, increases power production. Hassanli et al. BIB025 used CFD modelling to assess the characteristics of the flow in a Double-Skin Façade (DSF) system with openings for harvesting wind energy in high rise buildings. The model was assessed with wind tunnel experiments and a good agreement was found between the results (15% discrepancy). The results showed that the uniformity of the flow improved while the turbulence progressively decays as the flow progressed through the DSF cavity. Table 2 summarises the different CFD studies on building integrated wind turbines in urban areas. The studies highlighted the complex wind conditions in urban areas which presents major challenges for the installation of WTs. The wind conditions in urban locations are very complex due to surface roughness and the presence of obstacles, i.e., buildings and structures, characterised with low wind speed and high turbulence which are not desirable with regards to power generation by wind turbines. Also, there is uncertainty and limited understanding regarding how the turbulence within urban areas affects the WT effectiveness. Several researchers have employed CFD modelling to establish the feasibility of roof-or building-integrated turbines. CFD was utilised to study how the wind flows on a building or a roof, the effect of the speed, direction and turbulence of flow and the interference effects of surrounding buildings or structures on the wind turbine. Many studies used CFD simulation on WTs integrated in a building to understand the wind flow around the building and use the result to optimise the positioning of the wind turbines and maximise the power generation. Similar to the small-scale wind turbines, many of the CFD studies used low order models and few investigations used models such as LES and Reynolds Stress Transport models. The results demonstrated that in converging inlet mode, wind energy potential on the roof rises reasonably as the corner separation becomes larger, whereas in diverging inlet mode it reduces gradually with corner enlargement. When compared with isolated building, most of the corner configurations investigated demonstrated more wind energy density over the roof.