Leveraging the Opportunities of Wind for Cities through Urban Planning and Design: A PRISMA Review

Abstract

Wind has been utilized for passive ventilation and mechanical power since antiquity. As an abundant renewable resource, today, wind is increasingly seen as a critical resource to help tackle issues associated with rapid urbanization and climate adaptation and mitigation, such as improving thermal comfort, providing clean energy, improving air quality, and reducing carbon emissions. Despite the growing importance of wind as an invaluable resource for cities, wind in the context of urban planning and design is a relatively understudied area of research. This study aims to explore the means by which cities that can benefit from wind and ways urban planning and design can help deliver these benefits. The study adopts a systematic literature review methodological approach. The findings disclosed that: (a) improving urban wind environment via sound urban planning and design may enhance urban ventilation and energy performance; (b) better urban ventilation and energy performance enable cities to become climate positive or net zero and relieve the urgent climate crisis; (c) wind sensitive urban design is an emerging research area critical to harvest the benefits of wind for cities. This study offers a novel conceptual framework and research directions for wind sensitive urban design and informs urban planning, design policy and practices.

1. Introduction

The world’s urban population is experiencing exponential growth. Current estimates anticipate that the global population will expand by 25% by 2050, with an extra 2.5 billion people moving to cities in the following three decades [1]. As climate change and other stressors increase, the need for a more sustainable and resilient built environment becomes increasingly important [2,3,4] Cities need to be designed to support strategic resource management by integrating sustainable resource utilization to meet contemporary pressures of accelerating urbanization, limited resource availability, and changing climate—particularly by benefiting from the technology offerings and their sustainable practices [5,6,7].

The notion of harnessing the kinetic energy of wind and transforming it into usable mechanical labor was first envisioned in antiquity, and wind energy is the earliest source of energy that has been used by humans [8]. Furthermore, wind also serves as a natural resource that ventilates buildings and provides a cooling effect [9]. Yet, to increase the applicability of wind research to practical solutions for a sustainable and resilient city, there needs to be a translation of the technical and quantitative information in a way that can inform urban development strategies. However, past efforts have either been scattered across different areas or did not consider detailed urban implications [10]. Further research is needed to advance the translation of wind engineering research into urban design and planning processes.

In terms of the background and significance of such need, a systematic literature review can provide insights into current research on leveraging and managing the potential of wind in cities. So far, several different systematic reviews on urban wind applications have been published in various academic disciplines over time. For instance, Blocken and Carmeliet [11] examined pedestrians’ wind comfort from a building physics perspective and illustrated this with four practical examples. However, the study considers wind as a potential hazard rather than useful asset. The widespread interests in urban sustainability and energy transition have produced an increasing number of academic papers on leveraging the potential of wind. Likewise, Stathopoulos et al. [12] reviewed developments in urban wind energy. Their review highlighted engineering and technical issues associated with urban wind turbine technologies, and the difficulties of assessing urban wind energy potentials. Palusci and Cecere [13] produced a systematic review on the topic of urban ventilation in compact cities, where they stressed the importance of embedding a multidisciplinary methodology into urban management and planning processes.

In terms of problem definition, despite the growing attempts at utilizing renewable resources—that also includes wind—for making our cities more sustainable and livable, there is limited and scattered knowledge on effective and efficient ways to leverage the opportunities of wind for cities through urban planning and design mechanisms [14]. Given the presumption that urban planning and design can effectively integrate renewable sources in the urban environment, there is a critical need to develop a comprehensive conceptual framework in our existing and future cities. In recent years a new planning and design concept has emerged, i.e., wind sensitive urban design (WiSUD) [15]. However, a review of the literature and practice shows that the current practice of WiSUD is highly limited.

In terms of motivation and objectives, against the above backdrop, the aim of this study is to investigate how cities may benefit from wind and how urban planning and design can aid in achieving these advantages. To achieve this, the paper adopts a systematic literature review methodological approach. The findings offer conceptual framework and prospective research directions for wind sensitive urban design and informs urban planning, design policy, and practices. The main objective is to synthesize different aspects of urban wind research and propose a conceptual framework that can actuate the benefits of wind in organizing, planning, and designing our cities.

Following this background, the rest of the paper is structured as follows. Section 2 details the methodological approach. Section 3 presents the results of the study. Section 4 discusses the findings, proposes a conceptual framework, and puts forward prospective research directions. Section 5 concludes the paper.

2. Materials and Methods

This study utilizes a systematic literature review method by employing the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) technique, consisting of four primary phases as explained by Moher et al. [16] and Cortese et al. [17]. This method includes identifying the relevant articles, screening, determining eligibility, and finally inclusion. A search of the literature was carried out in the first step, which was identification, using the two databases with the most peer-reviewed articles, i.e., Web of Science (WoS) and Scopus. The goal was to generate new insights into the current state of knowledge of wind as a useful resource in the urban context.

The research acknowledges the complexity and multidisciplinary nature of urban wind research, which includes fields such as computer science, engineering, and natural sciences. The research focus is on wind research with connection to urban development strategy. Therefore, the area of study concentrated on urban studies and social science to shortlist the records included in the dataset for analysis. Technical articles in the fields of engineering and natural sciences frequently provide novel methodologies and instruments for realizing the use of wind in urban environments. The literature in these subjects, on the other hand, tends to be rather theoretical and seldom addresses the topic’s applicability within actual urban environments. In contrast, literature produced in the domains of urban studies and social science offers a more holistic perspective, including novel knowledge from empirical observation to detailed implications on city operations.

Criteria to identify relevant sources included: (a) journal papers that were peer-reviewed; (b) readily available online; and (c) written in English. The publishing date was purposefully kept open so that it considered the earliest documents that were accessible. The search was conducted with the following query string in May 2022: “wind OR gust OR breeze” AND “urban OR city OR cities” AND “planning OR design”. By limiting the field of studies, Scopus and WoS provided 617 and 179 records, respectively. Following the elimination of duplicate records, the total number became 767.

The second stage consisted of focusing on the advantageous characteristics of wind that may be harnessed with urban development strategies. Papers that were completely unrelated to the goal of the study, as well as articles that covered the mitigation measures for the negative aspects of wind, such as wind hazards, were not included in the analysis.

Table 1. Exclusion and inclusion criteria.

Primary Criteria		Secondary Criteria
Inclusionary	Exclusionary	Inclusionary	Exclusionary
Academic journal	Duplicate records	Wind research relating to urban development strategies	Technical papers in engineering and natural sciences
Peer-reviewed	Books, chapters, conference papers	Relevance to research objective	Irrelevant to research objective
Full-text online	Industry/government reports
Published in English

summarizes the inclusionary and exclusionary criteria for the screening stage.

For the third and fourth stages, to establish whether the selected records were relevant to the overall scope of the study, abstracts and titles of the sources were checked. Then, the number of articles was reduced to 101. Those articles were then read in full text. A further 31 articles were excluded from the pool. A supplementary document search in Google Scholar was also conducted because research shows WoS and Scopus tend to have a strong bias towards natural sciences and engineering in their content [18]. The search engine returned 35 additional articles, bringing the total number of articles to 105 (Figure 1). The full list of the selected articles is presented in Appendix A. Records were then processed and labelled following the guideline by Degirmenci et al. [19]. The documents were screened in Excel and were sorted into a concept matrix according to the subject matter, the research relevance, geographic scale, methodologies, and regions.

3. Results

3.1. General Observations

This review encompasses 105 different articles. The publication distribution by year and regions are illustrated in Figure 2 and Figure 3. The earliest article was released in 2003; the number of sources has steadily increased since 2015, demonstrating researchers’ growing interest in urban wind. About 70% of the articles are from the recent five years. This indicates that the findings are relatively current. Europe and East Asia are the leading study regions in terms of the number of publications, with 20 and 54, respectively. This demonstrates that academic institutions and researchers in these two locations have a significant interest in wind research. Due to the threat posed by climate change and the concerns surrounding the unpredictability of energy supply, it is probable that the issue of the importance of comprehending the urban wind environment is gaining a rising amount of attention in academic circles, mainly throughout East Asia and Europe.

On the other hand, it is important to highlight the fact that wind research coming out of East Asia is gaining more and more prominence. From the 31 papers originating from East Asia, 28 were published by authors from this region after 2015. Researchers from East Asian countries such as China, Japan, and South Korea contributed the most, which is probably because the region has the highest urban development intensity compared to other regions of the world [20]. A possible justification for this occurrence is that East Asian cities, particularly Chinese cities, are increasingly confronted not only with difficulties related to energy sustainability, but also with the deterioration in the urban environment because of the rapid urbanization that has occurred over the course of the previous decade [21]. There is also an increasing number of relevant publications from regions other than Europe and East Asia. Papers from the Middle East (n = 7), Oceania (n = 6), and Southeast Asia (n = 2) were all published after 2015, which demonstrated the ubiquitous necessity of incorporating wind into urban development strategies. To tackle this complication, a simple keyword search was performed to identify the terms that appeared most frequently in the list of selected articles. The most common search terms returned were “ventilation” and “wind turbine”, and the results may be divided into three broad categories: “Wind in the Context of Urban Ventilation”, “Wind in the Context of Urban Energy”, and “Wind in the Context of Urban Planning and Design”. Based on the review, a mind map of urban wind research was created and is illustrated in Figure 4.

3.2. Wind in the Context of Urban Ventilation

In comparison to rural regions, urban areas have a less favorable wind condition (He et al., 2019). Air pollution and excessive heating are two primary problems that may result from inadequate wind movement [22]. The negative consequences of unfavorable wind conditions can be alleviated by good ventilation. Urban ventilation is referred to as the capacity of cities to introduce fresh air inside its tissues while also dispersing pollutants and heat within their canyons [23]. According to the literature review findings, urban ventilation can contribute to the satisfaction of requirements for thermal comfort, the conservation of building energy, and the promotion of health and wellbeing among urban dwellers. The results acquired in one location cannot be immediately applicable to other locations with different climates; for instance, high wind penetration is less desirable in cooler climates but more favorable in warm climates. This section of the review is not intended to be exhaustive on the quantitative details of various climatical parameters such as wind speed, temperature, and radiation intensity. Rather, the objective of this part is to provide a succinct summary of the rationale and considerations of optimizing ventilation in the contemporary urban context. The articles in this section provided extensive evidence and inference regarding the purported benefits.

3.2.1. Thermal Comfort

Urban ventilation’s capacity to lower the urban heat island (UHI) effect is the most frequently cited benefit [14,24,25]. The impacts of UHI may have a detrimental influence on the thermal comfort of outdoor activities due to the increased temperature [26]. Better ventilation and wind penetration are especially significant in cities located in regions with warmer climates because they enhance outdoor thermal comfort by accelerating heat exchange between the population and the environment [27]. Empirical research indicates that UHI occurrences can be greatly mitigated when wind speeds are beyond a particular threshold [28]. Consequently, ventilation effectiveness is frequently evaluated based on wind velocity and the resulting change in the external temperature environment [6,29,30].

Other specific aspects must also be addressed when enhancing thermal comfort through urban ventilation, according to studies. For example, in addition to wind speed, relative humidity also impacts thermal comfort [26,31]. This is especially pertinent in coastal regions that often receive a sea breeze. As a sea breeze brings moisture, multiple studies have documented a sea breeze’s ability to reduce the impacts of UHI to various extents [15,32]. Wind flow direction characteristics are as significant as wind velocity when developing an effective ventilation system for cities [33,34]. It is imperative that structures do not obstruct the prevailing wind, since it has been observed that in coastal cities, waterfront development significantly reduces the cooling effect of sea breeze, hence exacerbating the urban heat island effect in inland regions [35].

Even though many studies emphasize the need of optimizing ventilation to mitigate the impacts of the UHI effect, it is necessary to keep in mind that thermal comfort is also significant in a variety of contexts. Higher wind speed is certainly desirable in summer but can cause discomfort in winter [34,36]. A greater wind speed may be required if a pedestrian is partially shaded, while a lower wind speed may be preferred if the air temperature is cooler [37]. Therefore, it is necessary to comprehensively evaluate the wind’s effect on the thermal environment according to different climate contexts, activities, and needs [38]. Additionally, thermal comfort is a subjective matter. It is difficult to extrapolate with precision for an individual’s subjective thermal comfort from meteorological and climatological measures alone. Due to psychological, sociological, and cultural factors, inhabitants of different locations experience distinct thermal experiences in comparable temperature conditions [26]. As a result, in addition to quantitative measurements, qualitative methods have been employed to assess residents’ perceptions of thermal comfort [39].

3.2.2. Energy Conservation

The benefits of wind in terms of energy conservation are evaluated at the building level, as buildings require energy to supply occupants with adequate thermal conditions. According to studies, interior and outdoor ventilation performance have variable effects on the energy efficiency of buildings [40]. As a result, incorporating natural ventilation features in individual building is becoming a more popular design option since it offers a desirable thermal environment while also offering the potential for significant energy savings and emission reduction [41]. In conjunction with other techniques, empirical research demonstrates the effect of natural ventilation that changes indoor temperatures and influences the building’s overall energy efficiency [42,43,44]. However, temperature is not the only element that impacts the energy usage of a building. Noise and pollution can influence the energy-saving potential of natural ventilation. As both air quality and noise levels are significant determinants for whether a building’s occupants choose to open windows, both factors can have a significant impact [45].

Studies have found that at the city level, the loss of annual cooling energy due to noise is comparable to that due to air pollution [46]. Further studies have highlighted the importance to expand the scale of building energy evaluation. The building scale energy analysis was unable to predict the impact of tall buildings built in a low-lying urban area, which limited passive ventilation potential and energy efficiency by impeding wind flow [47]. A study in metropolitan regions with a high population density during the summer revealed that outdoor thermal settings had a significant influence on urban energy consumption [48].

Different climate contexts must also be accounted for in terms of the energy conservation features for urban ventilation. Large-scale temporal simulations of building energy consumption reveal that wind speed has the greatest effect on building energy consumption [49]. A study conducted in colder areas revealed that winter household power usage is substantially correlated with the adoption of windbreaks that limit incoming wind speed [50]. The effect of ventilation on energy consumption was found to be greatest in cities with the largest seasonal climatic variations. In these locations, cities with efficient ventilation decrease summer energy use but increase winter energy demand [51].

3.2.3. Health and Wellbeing

One of the biggest threats to the health and wellbeing of urban residents is poor air flow and resulting poor ventilation [52]. In addition to thermal comfort, the most significant function that urban ventilation has on health and wellbeing is the dispersion of air pollution. Indeed, air pollution is a major health problem across the globe, especially in cities in developing countries that are experiencing a rapid pace of urbanization [53].

Addressing air pollution through ventilation necessitates viewing cities as living entities that breathe, delivering clean and fresh air into their tissues, and therefore diluting pollutants trapped in urban canyons. This is a simile to the biology discipline. Consequently, interdisciplinary terminologies, such as breathability, were previously utilized to define the pollutant dispersion capacity of urban areas [54,55]. While wind speed is vital for the dispersion of air pollutants, the wind direction pattern is more important, according to Krüger et al. [56], since wind not only disperses urban air pollution, but may also move pollutants from industrial to residential areas [57].

As such, the term ventilation corridor was widely used [23,58,59]. The premise is that the air outside cities is relatively clean, and that wind may bring this cleaner external air into the urban area while also removing contaminants. As a result of the interaction between the entering atmospheric flow and the building blocks, this capability is directly linked to the patterns of air flow that occur inside the urban canopy [60,61]. Water bodies, green fields, and road networks can function as ventilation corridors which direct airflow through the urban canyons and have shown a substantial effect on improving urban air quality [25].

Depending on the scope and approaches of the study, both thermal comfort and the dispersion of urban pollutants are being studied at various geographical scales. Airflow within urban regions is typically categorized into four geographical scales, i.e., street, precinct, city, and region [54]. Airflow within the urban canyon is explicitly addressed in the preceding three microscales. At theses scales, the quality of urban air relies on the features of the street, precinct, and city [54]. Cities are handled as a larger roughness feature in regional scale studies to provide boundary conditions for smaller-scale analyses, and often incorporated within city-scale assessments for pollution dispersion [57].

3.3. Wind in the Context of Urban Energy

Wind energy has emerged as one of the most rapidly developing renewable energy sources. Nonetheless, most of the developed and committed developments were for huge onshore and offshore projects located far from cities. The premise is that rural wind flow is generally faster, steadier, and more predictable compared to that in urban areas [62]. Nonetheless, there is substantial potential for wind energy exploitation in urban environments, and there are numerous developments worldwide [63,64,65]. The establishment of an effective wind energy system closer to the point of use may satisfy the local power demand while minimizing the usage of fossil fuel-based energy generation, and therefore substantially reduce greenhouse gas emissions. According to the findings of the literature review, if appropriately utilized and integrated into the current energy grid, wind energy is a viable renewable energy alternative. It has the potential to be incorporated into low-emission building designs, and technology developments have led to an increase in the number of urban wind turbine installations that are more efficient and less expensive. This review acknowledged the complexities of urban aerodynamics and its connection to wind energy outputs. To reconcile this complexity, this portion of the study attempts to highlight the important developments of wind energy research in urban settings, with a focus on their significance to the future urban planning and design process.

3.3.1. Renewable Energy and Grid Integration

One of the major premises of renewable energy development within city boundaries is that most supplied energy is generated by distant, large power plants that are connected to a high-voltage transmission network. Using low-voltage distribution networks, energy will be transferred and subsequently delivered to end-users [66]. This centralized model has yielded economies of scale and reliability, but it has considerable disadvantages. A portion of the energy may be lost during transmission and distribution, and large centralized power plants necessitate substantial capital investments [67]. Thus, the notion of microgeneration or decentralized or distributed energy generation has emerged [63,68].

Distributed generation often involves the installation of small, grid-connected devices that capture renewable energy sources near the customer. As one of the most established and mature renewable resources, much work has been devoted to exploiting wind energy and enhancing its applicability in urban areas. Due to the turbulent and unpredictable wind profile in cities and the overall volatility of urban wind speed, a small variance in expected wind speed can result in a significant difference in possible wind power outputs [69,70]. Consequently, a substantial amount of study has been dedicated to the evaluation of wind patterns, such as seasonal variations in wind speeds and directions, at probable turbine installation sites [68,71,72].

Theoretically, urban wind energy harvesting is optimal in relatively flat and open locations, such as urban peripheries, where there is less surface drag that would cause turbulence [71]. However, low-density locations with relatively smooth surfaces were regarded unsuitable for the construction of large-scale urban wind turbines due to the low average wind speed near the surface [72]. Certain urban locations with the most complex wind conditions, such as dense urban centers, are considered as potential sites for the installation of urban wind turbines [71,73]. It was recommended that urban wind turbines be installed on or around tall structures where wind speeds can reach peak values [74,75]. However, tall buildings in places with a high building density may not always result in significant wind energy potential, as they may obstruct the prevailing wind [76]. The proper assessment and installation of wind turbines in these windy locations thus become the key to increase distributed wind energy output.

Conducted studies have shown that urban wind energy harvesting is more effective when combined with other urban renewable energy sources such as solar or biomass [77]. Urban wind energy alone is not only inefficient in terms of cost, but also insufficient to meet the overall urban energy demand, much alone the requirement for thermal heating [78,79]. The same concept applies to photovoltaic systems, which are a more popular alternative to urban wind turbines [80]. A hybrid renewable energy system that combines solar, wind, and other sources can be more cost-effective than a single form renewable energy generation [81]. Given the huge cost and efficiency benefits, wind energy harvesting is frequently mentioned in studies on distributed generation with a hybrid system [80,81,82].

According to empirical research, the combination of solar and wind can potentially meet the energy needs of large buildings [83]. In other instances, if the performance of wind energy is inadequate, the outputs might be used to assist the operation of other renewable energy devices [77]. In addition, the hybrid energy system must be carefully assessed and well-managed to minimize conflicting outcomes, such as choosing the correct mix of renewable energy and related infrastructure [77,78].

3.3.2. Emission Reduction

Since urban wind energy harvesting has shown the possibility of integrating into the existing energy grid and contributing to the fulfilment of urban energy demands, new concepts for urban development have evolved, such as “net zero buildings” and “positive energy buildings” [43,44,79]. The net zero buildings focus on producing as much renewable energy as they consume, whereas the positive energy buildings produce more than they consume. Although distinct in definition and scope, they share a common concept and set of strategies: mitigating the environmental effects of greenhouse emissions by integrating renewable energy into the built environment. A number of studies discovered that urban wind turbines save more carbon emissions than other renewable energy sources at a lower cost, if put in places with abundant wind resources [62]. The whole life cycle of a wind turbine, which includes carbon-intensive processes such as manufacturing, transport, and recycling, must be accounted for in emission calculations [63].

As stated in Section 3.2.2, building energy analysis should not be restricted to the building level. Net zero buildings or positive energy buildings are fundamentally focused on energy performance on-site, with most of the attention placed on the building level [43,74]. For a more precise estimate of emission reduction, it is necessary to include both the interdependence of buildings and the urban area in which they reside [47]. Studies have sought to broaden their focus beyond specific structures. Larger city size spatial analysis greatly increases the level of complexity by combining a larger number of influencing variables and interdependencies; therefore, city size special analysis may produce less reliable findings. [68,71]. An intermediate scale, such as a neighborhood, appears to be an appropriate scale for going beyond the boundaries of a single structure without losing its robustness and, at the same time, is capable of addressing tangible solutions to a collection of buildings [69,79,84].

3.3.3. Technology as an Enabler

The expansion of earlier niche urban wind energy development has been made possible by technological advancements, particularly in turbine technology. The two foci of urban wind turbine research are on the design and positioning of turbines. Horizontal-axis wind turbine (HAWT) and vertical-axis wind turbine (VAWT) are the two common types of wind turbine designs [85]. Due to the technical maturity of HAWTs, the majority of large-scale wind farm and early urban wind turbine designs are primarily based on them, leading to lower costs and greater generation capacity [65]. However, HAWTs are highly sensitive to wind direction and do not function effectively in turbulent airflow [65]. As a result, urban HAWT installations have experienced underperformance relative to manufacturer data [66,86,87].

In the often slow and unsteady urban wind environment, the performance of these HAWT turbines degrades significantly. As manufacturers publish power generation curves, only ideal sites and uniform wind conditions have been considered [86]. Thus, research suggests that performance criteria for wind turbines should not only be based just on wind speed, but also on turbulence or gust intensity, which is the sudden rise in wind speed. If forecasts are accurate and turbine adjustments are made appropriately utilizing sophisticated monitoring systems, energy outputs may be improved [88].

VAWT is a relatively recent idea in turbine design, and its use is restricted to satisfy modest energy demands [67]. Two kinds of VAWT exist: Darrieus and Savonius. The Darrieus VAWT is the most researched type and is viewed as a viable alternative to HAWTs for urban applications due to its comparable generation capacity, whilst the Savonius VAWT has a lower generation capacity but is less expensive and easier to construct [67]. Both types of VAWT are deemed suitable for urban applications due to their ability to function effectively in turbulent wind conditions. In addition, VAWT is quieter, produces less vibration, and is relatively more aesthetically pleasant than HAWT [65,67]. However, VAWT designs are still considered immature and suffer from a lack of comprehensive and dependable long-term performance data, resulting in poor market acceptability. If costs, performance, and reliability reach a particular level, novel turbine designs and dependable testing results may result in greater urban VAWT deployment [67].

Urban wind turbine installation location falls into three categories: standalone, rooftop installation, or architecturally integrated into buildings [85]. The architecturally integrated approach is referred as a building integrated wind turbine (BIWT) [85]. A stand-alone wind turbine away from buildings has a few advantages, including the fact that the turbine is located away from buildings and their occupants, minimizing the influence of the turbine’s noise and vibration [85].

Alternatively, rooftop or architecturally integrated wind turbines can harvest more energy by taking advantage of stronger wind speeds at a greater height [65,89]. Consequently, most large-scale urban wind turbines are BIWTs. Due to the restricted number of available building spaces, BIWTs may only meet a small fraction of the energy demand. Innovative designs that combine turbines with cooling towers, water harvesters, and solar panels may help circumvent this issue [83].

As turbine technology continues to progress, studies have highlighted the need of adopting updated wind assessment guidelines based on empirical data [67,85]. Real-world operation of urban wind turbines has shown multiple instances of zero outputs and inconsistencies, suggesting that actual performance may differ from modeling and testing results, as was proven in field studies [86]. Therefore, it becomes crucial that urban wind turbine performance is validated by not only turbine designs and positioning, but also by factoring the impacts of urban aerodynamics [85]. As a result, the methods of measuring urban aerodynamics in connection to ventilation and energy are constantly undergoing development, and state-of-the-art methodologies, such as machine learning and artificial intelligence, have been included in the process [90,91]. In addition, the proliferation of sensors and real-time monitoring technology may reduce the level of uncertainty associated with wind forecasting in urban areas, which formerly relied on weather stations situated far from the installation site [77].

3.4. Wind in the Context of Urban Planning and Design

A great portion of academic discussion on the implication of urban wind environment has focused on the topic of wind hazards and many countries have codes and design guidelines for urban planning and design in relation to gust and strong wind problems [37]. Based on the above discussion, good wind urban environment can greatly benefit the sustainable development of a city. As such, there has been growing attention to the question of “how urban areas and its wind environment can be optimized that leads to better ventilation and energy production?” [28,92]. Because urban geometries and configurations have a substantial impact on the urban wind environment, urban aerodynamics and wind engineering become the quintessential research subject that must be understood in depth. Considerable progresses have been documented in the past years to comprehend the aerodynamics of urban environments, and the urban wind flows continue to be extensively investigated with a variety of novel methodologies and techniques [90,93].

The challenge that arises next is the incorporation of urban wind engineering knowledge into urban planning and design practices. A substantial number of studies have been devoted to bridging this gap by identifying morphological parameters that affect the urban aerodynamics response and provide relevant design guidelines [22,92]. The morphological studies, albeit essential, are subject-specific, focusing on either ventilation or energy production. To reconcile this issue, this section presents a brief overview of the pertinent parameters and indices derived from empirical research. Then, the common themes between ventilation and energy production are provided. The primary objective of this section is to give a qualitative review that synthesizes findings from selected wind ventilation or energy production studies and highlights relevant suggestions that may be translated into improved urban planning and design practices to maximize wind’s benefits in cities.

3.4.1. Urban Morphology

The term urban morphology, as used here, refers to a three-dimensional urban spatial structure created by a collection of buildings and open areas, beyond building features. Relevant morphological parameters and indices that impact the wind environment may be determined from the urban spatial structure analysis. Studies have included a range of quantifiable urban morphological parameters and indices that influences urban aerodynamics, for example, surface roughness [71,94,95], sky view factors [56,96,97], frontal area density and index [14,32,51], plan area density [13,22,75], building coverage ratio [98], building height and height variance [25], and height-to-width ratio [99]. These morphological parameters are analyzed alongside quantifiable ventilation and energy performance indicators such as temperature changes [14,24,100], age of air [99], air exchange velocity [101], pollutant concentration [59,60,102], energy density [73,103], and turbine capacity factor [71]. Noting that multiple indices are reported in feature articles, individual indices should not be considered as exhaustive representations of either ventilation or energy production.

Urban density is a fundamental concept that frequently appears in featured articles. The term is highly ambiguous, context-dependent, and utilized differently across study areas. Density can be based on individual parameters or their combination relating to street layouts, building types, space arrangements, and landscape element [104,105,106]. Density is also scale-dependent, and the quantifiable results can be blurred by enlarging study resolution, as mentioned in Section 3.2.3. Despite its ambiguity, a common theme can be found, which is the discourse on the notion of “high-density” or “compact” development impacts on urban wind environment [30,107,108].

High density or compact development is a blanket term used to describe areas with higher building volume and height, lower distance between buildings, and narrower streets [51,107]. It is often viewed as advantageous during urban sustainability initiatives due to its potential to enable higher usage of public transportation and the preservation of land resources [30]. Conversely, high density or compact development can lead to a decrease in urban wind speed, while also suffering from UHI intensity and severe air pollution [61,109]. High density or compact developments also present a unique opportunity for energy production. As noted by several studies, wind energy production is better suited at higher altitude above the surface [65,73]. Vertical, high-rise developments characterized by high floor density could host a few wind turbines either on the roof or between buildings to harness the above-average wind speed and utilize the larger space in these locations [70,76,92]. However, high density environments can also lead to turbulence and unwanted gusts that hamper energy production [73].

Given ventilation and energy production potential is highly dependent on wind condition, high density urban development could consider increasing its wind penetration within its urban canyon. There are several specific areas of improvements.

First, the development of breezeway and wind corridors by the use of coarse and dense alleyways, roadways, and interconnecting open areas might ensure deep penetration of prevailing winds into cities [36,42,105]. Second, lowering building coverage and plot area density to provide proper spacing between buildings increases urban porosity and decreases wind blocking at the pedestrian level [39,94,99]. Thirdly, rather than a constant building height in the prevailing wind direction, a specific building height variation is required so as not to impede wind flow [54,91]. Fourthly, urban tree planting must be monitored carefully to avoid obstructing wind flow in locations such as waterfront and downwind areas [110,111]. Large building frontal surface areas should be oriented away from the prevailing wind direction to minimize wind obstruction and building arrays should be oriented towards the prevailing wind to allow cross-ventilation [32,51,102,112].

Nonetheless, it is possible that qualitative description may not systematically capture the effect of wind on overall ventilation or energy performance. For instance, street orientation may not be as important as building configuration in high-rise precincts [28,40,58]. Research indicates that the influence of wind on thermal environment in high density areas may not be as significant as that of shade, since solar radiation impacts the thermal environments more [29]. Even though wind exerts less effect than solar radiation, another study found that the wind’s capacity to cool was greater in larger open regions. However, if the background temperature is higher, the influence on cooling is greater than that of solar radiation [106]. This again emphasizes the need for design guidelines to properly reference the site environment.

3.4.2. Building Typology

The prior section focuses on spatial elements such as lot, streets and building configuration. This section focuses on the fundamental building design features covered in the selected articles. Building parameters that impact the urban wind environment include building height [25,89,92], building permeability [94,98,113], façade features [101], corner characteristics [75,92], and roof shapes and types [75,99,114].

Other building level features may include plot size and building plot coverage attributes, which were addressed in the preceding section. Plot size is frequently determined by a building’s setback. Consequently, lot sizes can have a substantial effect on the width of an urban canyon, which impacts wind conditions [37]. Studies conclude that the impact of building typology such as building height on urban wind conditions is not as substantial as that of morphological factors such as building density [22]. The rationale is that the localized building wind environment is a by-product of the urban wind environment [107].

Urban morphology relates to the general aerodynamics of cities, which has implications for both ventilation and energy production. Building typologies are more topic-specific and narrowly focused. Building permeability and façade features are frequently used in the analysis of the natural ventilation potential of a building [94]. Building permeability is a quantifiable measurement of airflow through a structure’s envelope, including windows, doors, and void spaces [99,113]. Building openings contribute to the pressure differential across building facades, allowing air to be channeled through the structure [37]. Thus, studies have often advocated for greater permeability to promote better-ventilated buildings [43].

However, this can result in conflicts between designs based on appearances and designs based on empirical evidence. Street roofs and building arcades, for instance, can potentially impede wind flow if not designed appropriately; therefore, it is recommended that roofs and arcades be semi-open to allow for more permeability [55,99]. Common façade elements, such as balconies, can also affect the ventilation potential; in particular, windward balconies can change the wind patterns in street canyons. Windward balconies hinder airflow from entering deeply into the canyon, hence limiting wind speed at street level, and increasing the concentration of pollutants [101].

In contrast, investigations have indicated that roof shapes and corner shapes are prevalent factors in wind energy production studies. Wind energy production is extremely sensitive to wind speed and turbulence, as previously stated. Turbulence formation is localized and substantially influenced by the roof and corner geometry of buildings, which significantly modifies the pattern of incoming airflow [75,92]. Round and smooth corners may lead to more energy generation and have lower turbulence intensities over downstream structures than sharp corners [75,92].

In terms of roof design, research has found that dome or vaulted-shaped roofs with a curved geometry are optimal for turbine installation due to their reduced turbulence [75,89,114]. Additionally, wind turbines may be installed on building facades. In contrast to roof wind turbines, research indicates that extending the radius of a building’s duct opening has a negligible effect on wind speed, whereas a sharp edge enhances wind speed. Combining a greater radius with a sharp ducted edge increases the potential energy production [103].

3.4.3. Governance as an Enabler

Urban governance is crucial for transforming the scientific findings of the urban wind research into tangible, functional, and practical outcomes. As early as the 1980s, European towns such as Stuttgart and Graz considered the influence of wind on thermal and air quality in the context of urban ventilation [36]. To improve ventilation, land use and building performance targets were established to maximize wind access. The city administrations of high-density East Asian cities, such as Tokyo and Hong Kong, embraced European cities’ relevant expertise and knowledge, and developed their own planning and design practices [37]. Emerging cities in China have implemented a series of wind related planning and design directives to combat the significant degradation of their urban wind environment due to rapid urbanization [23].

Indeed, considerable macro-level contributions from governments are a crucial component of a functional urban ventilation system [39]. Although the consideration of urban ventilation is widely accepted, the corresponding practices continue to be extremely context-dependent. In regions where the climate is hot and arid, for instance, large-scale use of vegetation or water bodies may be prohibitively expensive. In circumstances where altering the geometry of outdoor space has been shown to be the most effective passive cooling strategy, the degree to which outdoor space geometry may be adjusted in real projects is frequently constrained [115]. A better wind environment for ventilation can be achieved by lowering building heights and decreasing site coverage by increasing setbacks; however, these measures are often at odds with the pursuit of economic goals [116].

Feature articles on governance in the context of urban wind energy generation tend to focus mostly on the socioeconomic impact of wind turbines. The two most important considerations in wind turbine governance are economic viability and public acceptance. Wind turbines, as discussed in Section 3.3.1 and Section 3.3.3, may be unviable and inefficient due to their high financial cost and poor energy-generating capacity in some circumstances, as well as because they generate nuisances such as noise and vibrance. Regarding wind turbine design and energy system optimization, appropriate urban policies must be in place before they can be enabled. A financial incentive known as a “feed-in tariff” is commonly offered by governments or utilities to encourage more renewable energy generation, in this case, utilizing wind power [64,68,117].

Early adoption of this strategy in the UK appears to have increased the incentive for user installation, but it was regarded a gross economic loss, primarily due to low energy capacity and higher operation costs [64]. Consequently, research suggests that providing a discount on energy bills is more effective than offsetting the initial capital committed by households to counter their high operational expenses [117,118]. In terms of social acceptability, it appears that the public’s attitude towards the installation of urban wind turbines deviates from the previous assumption of “not in my backyard (NIMBY)” due to nuisance, and includes other layers of concerns, such as the distrust of technology, businesses, and public institutions [119]. Local public opposition and distrust towards wind turbines may result in significant project deficiencies, such as a reduction in the scope of adoption [120].

By comparison, creating greater public acceptance not only increases local community members’ receptivity to the presence of wind turbines, but also increases self-investment intentions and “wind-energy enthusiasts” [121]. Various urban planning methods have been recommended to boost their responsiveness to wind turbines. The small wind turbine development in Dundee, Scotland, was used to illustrate how planning systems may serve as a mediator between the state, the energy market, and the community. The findings indicate that well-considered strategy planning must incorporate the perspectives of all relevant stakeholders. According to the logic, the objective of planning was to promote democratic conversation over the most effective means of serving the public interest [122].

Exploratory research was conducted to examine how different planning systems responded to the introduction of new technologies. The results indicate that there is no best practice, and that convergence of practices is unlikely until further implementations are created. There are two ways to enhance land control for tiny wind turbines: strategically and experimentally. Initiatives involving wind turbines require a comprehensive set of adaptable policy guidelines as part of their overall strategy. In an experimental strategy, ad hoc approaches may serve to strike a balance between the mobility of technical niches and the rigidity of land use regulations [123].

Ventilation and wind energy production both require the optimization of the existing urban fabric to enable a better wind environment in cities. This requires expert knowledge from a wide range of disciplines, including urban physics, climatology, mechanical and wind engineering of wind turbines, and planning and design practices. Government, developers, and academics from a variety of fields need to collaborate and synthesize their knowledge into effective solutions based on clear communication on an easily understandable platform [23,84].

4. Findings and Discussion

4.1. Conceptual Framework of Wind Sensitive Urban Design

Existing studies concentrate on maximizing the advantages of urban wind in two main areas. These are ventilation and energy generation. Improved thermal comfort, reduced energy consumption, and enhanced health and wellbeing have all been related to adequate ventilation in urban areas. Urban wind energy generation, on the other hand, is a niche area that has the potential to greatly reduce urban carbon emissions, if properly integrated with other renewable energy sources. However, significant technological deficiencies still exist for urban wind energy generation in terms of turbine design, meteorological forecasting, and urban aerodynamics. Ventilation and wind energy generation efficiency are coupled with urban forms, which significantly modify the urban wind environment. As such, urban climatologists and building scientists have used state-of-the-art models and simulation to analyze the influence of urban form parameters on either ventilation or energy generation performance. A number of cities worldwide have included wind accessibility into urban planning and design standards. On the other hand, research has identified obstacles to the inclusion of urban wind energy in cities, in addition to emphasizing the importance of transdisciplinary collaborations.

In recent years, a related new term was coined by several scholars, namely, wind sensitive urban design (WiSUD) [14,15,124]. According to the literature, because urban tissue has a strong link with wind condition and affects thermal environment and air quality, urban planning and design as an intervention tool must consider the influence of wind on these aspects. Nonetheless, the studies neither explored the influence of wind from the viewpoint of wind energy generation, nor comprehensively elaborated the term or offered a conceptual framework.

Building on the findings of the systematic literature review, a conceptual framework for WiSUD was developed with the identified key domains and sub-categories (Figure 5). The framework is organized in the four domains: (a) passive wind measures; (b) active wind measures; (c) governance; (d) planning and design.

The passive wind measures domain includes indicators for measuring ventilation quality, which contains the sub-categories of: (a) energy conservation; (b) thermal comfort; and (c) health and wellbeing. This domain aims to measure the quality of WiSUD and its actual impact. Urban ventilation and energy generation can be improved by WiSUD. Energy conservation is to be achieved using urban wind as an active component to flush out unwanted heat and pollutants. Another outcome of the process is that the overall health status of occupants can be measured to quantify the positive impact of WiSUD on the community. Furthermore, a positive wind environment potentially enables wind energy harvesting infrastructure in the built environment.

The active wind measures domain highlights the urban wind generation component of WiSUD, articulated in the sub-categories of: (a) grid integration; (b) technological innovation; and (c) emission reduction. This domain deals with turbine selection and placement, and integration with the existing grid and other renewable resources. The technology innovation demonstrates the needs to improve computational methods and sensors for accurate wind resource prediction, as well as innovative turbine designs.

The governance domain has three sub-categories as strategic enablers for urban wind. The reviewed literature in this area highlights the need for: (a) regulation capacity, in the form of planning frameworks and design guidelines, where regulatory capacity regards the necessary legislative framework and guidance to foster a positive understanding and uptake of the advantages of WiSUD; (b) cost and payback, which summarize the economic aspects of WiSUD, which in turn need to consider direct and indirect costs of application of either passive or active wind measures, as well as benefits; and (c) public acceptance, which entails public education and knowledge sharing, for example, data visualization and platform design, and community engagement to disseminate WiSUD at a granular scale.

The planning and design domain deals with the physicality of WiSUD in three sub-categories that can also be considered as scales: (a) city-scale; (b) precinct-scale; and (c) building-scale. The city scale summarizes the principles of the urban tissues that can capitalize on urban wind, and it encompasses variables such as urban density, green spaces, and waterways. The precinct scale includes variables such as street layout, vegetation planting and building arrangements. The building scale supports the optimal design of plot size, building heights, and building envelopes that allows greater wind permeability.

4.2. Research Directions

Concerns about the detrimental consequences of urbanization and climate change have grown since the 1990s. Industrialized countries have subsequently developed a variety of urban development initiatives to remodel and restructure their cities to achieve environmental protection and energy conservation [125]. From the earliest eco-city in the 1990s to smart cities in the 2000s, there have been evolutionary efforts to make cities more ecologically friendly, socially equitable, and economically competitive [126,127]. More recently, the urgency of the climate crisis has led many global cities to pledge to become “net zero” or, even better, “climate positive” within a certain timeframe. Although different guidelines, strategies, and protocols have been developed to achieve this objective, one notion is common, i.e., a rapid and major transition towards decarbonization requires cities to maximize renewable resources usage [128].

The incorporation of wind power into the model of urban development presents a major opportunity. As noted, wind may contribute to the fulfilment of needs for thermal comfort, both indoors and outdoors, as well as for air quality. Integration of wind turbines into the urban environment enables users to harvest energy from nearby wind assets and reduces their vulnerability to external energy price volatility and supply restrictions. Hence, the WiSUD concept framework developed by this study highlights that wind resources within urban areas are an environmental and economic asset that should be leveraged. To sufficiently actuate the WiSUD concept, further research works are required to fill the following key knowledge and research gaps:

• Integration of wind energy with other sources of renewable energy has advanced over the years [129,130]. While urban wind energy is a niche market due to high costs and low payback in urban settings, urban wind energy generation is still worth investigating owing to its potential in a hybrid energy system that would achieve urban carbon neutrality or positivity.
• Exploring the synergy and interplay between ventilation and wind energy research beyond the building scale: There is clearly a lack of synergy between ventilation and wind energy harvesting studies, particular beyond the building scale. Multiple studies have addressed the design of a net zero building or a climate positive building that uses ventilation and wind energy generation strategies to achieve high energy efficiency or energy independence, and high livability [43,74,130]. Still, these simulations tend to neglect the effects of the surrounding urban form on the wind environment of the building structure. The effect of urban morphology on the performance of renewable energy is frequently ignored, and this shortcoming has been emphasized by numerous studies [131,132].
• Developing comprehensive urban wind resource assessment approaches beyond the building scale: Addressing the design issue beyond the building scale comes at a cost. The most common wind assessment tools identified in the review, such as laboratory wind tunnel experiments and computational fluid dynamics (CFD) analysis can provide very accurate information regarding the wind flow around a building. However, these methods become much more time-consuming and inaccurate for large datasets [124]. To overcome this deficiency, studies have used a mix of simplistic GIS modeling and more sophisticated CFD modeling [110]. The state-of-the-art techniques such as advance sensing, artificial intelligence, machining learning, and deep learning models may facilitate the process utilizing fewer predictor variables. The transferability and applicability of these models, however, require further testing [93].
• In-depth understanding of local context: The literature reveals the integration of climate knowledge into urban decision making is a complex process that requires consideration of historical interaction with scientists, long-term socio-cultural settings of the city, and prior political and policy actions at all levels of government [133]. On the other hand, there are several additional aspects to consider, such as the local climatic condition, the long-term economic and demographic outlook, and technological advancement. To facilitate the planning phase of WiSUD design, the associated factors must be investigated and recorded. Therefore, additional development of WiSUD models for subcategories based on the local context is critical.
• Developing WiSUD guidelines to inform policy and practice: To make our cities carbon neutral or climate positive, the research’s lead on also developing straightforward WiSUD guidelines is important. Prospective research is needed to translate urban/wind modeling results into locally tailored policy directions and guiding principles. In this way, urban authorities will be able to develop the needed policy and regulations, and the urban development or construction industry will be able to implement the WiSUD guidelines. Along with this, in-depth studies of the motivations and barriers to adopting WiSUD at an institutional level are highly desired.
• Exploring pathways for knowledge exchange and collaboration: Communication of results is a key factor for success, and it is also important that relevant climate analysis meets planning’s demand-driven needs by providing suitable methods and tools. It is imperative to develop a simplistic, open, and transparent platform, so that the government, developers, and academics from a range of sectors can work together to synthesize their expertise into practical solutions [23,84]. In addition, scholars have identified the need to improve the earlier institutional deficiencies of transferring urban climate knowledge into sensible planning and designing processes and practices [134].

Lastly, we advocate that WiSUD should be understood in the context of other nature-based urban design approaches, notably water sensitive urban design (WSUD) and biophilic sensitive urban design (BUSD) (Figure 6). Water, wind, and flora have been the fundamental elements of nature-based design since time immemorial. However, with industrialization, technology-based systems have dominated design thinking and these fundamental elements have until recent decades been relegated to the periphery of design thinking in industrialized urban countries. More recently, WSUD and BSUD thinking has come to the fore, while WiSUD is still to be fully understood by the urban design industry as a key nature-based design approach. The benefits of nature-based urban design approaches are that they can be effective from an operational cost and environmental perspective in lessening the energy and pollution loads on complex mechanical, electrical, and material engineered systems, as well as providing an incalculable human-nature-oriented design benefit.

4.3. Study Limitations

This paper placed literature on wind and the city under the microscope of a systematic review and conceptual analysis to address the issue of leveraging the opportunities of wind for cities through urban planning and design. The findings generated insights and formed a conceptual framework of WiSUD. Although the research team minimized the limitations of the study as much as possible, the following possible restrictions should be noted when interpreting the results: (a) identified search keywords and target databases may not cover all articles relevant to the research objective; (b) only peer-reviewed journal articles that were available in full-text were included in the analysis; that is, information from book chapters, conference proceedings, and white papers are omitted; (c) similarly, grey literature such as government policy documents, and industry reports and websites, were not considered; (d) the results might have been influenced by unintentional biases of the authors; and (e) the methodological approach is limited to a manually handled review technique; further analytical techniques could be considered, such as bibliometric, scientometrics, content analysis, cognitive mapping, and concept clustering techniques. These limitations will be addressed in our prospective studies.

5. Conclusions

Even though it is one of the oldest known forms of renewable energy that may be harnessed for ventilating cities and generating energy, urban wind has not yet been substantially integrated into the planning and design of sustainable and resilient cities. The current study evidenced the importance of future research for leveraging the opportunities of wind for cities through urban planning and design. Moreover, this study expands the term WiSUD by developing a novel conceptual framework that aims to establish wind as a useful renewable asset and provide pathways to integrate wind into the urban planning and design process. In turn, this will help our cities become carbon positive.

The overall findings of the study revealed that: (a) improving the urban wind environment via sound urban planning and design may enhance urban ventilation and energy performance; (b) better urban ventilation and energy performance enable cities to become climate positive or net zero and relieve the urgent climate crisis; and (c) WiSUD is an emerging research area that is critical to harvest the benefits of wind for cities.

The specific findings of the systematic literature review unveiled that: (a) optimizing the urban wind environment may improve the thermal environment and air quality, resulting in reduced energy use and improved health outcomes; (b) leveraging urban wind to generate energy at a given site alongside other renewable energy sources may significantly reduce urban carbon footprints; (c) turbine and wind assessment technology needs to be further improved for efficient urban wind energy generation; (d) WiSUD requires comprehensive understanding of the local urban context, including urban form, governance, and socioeconomic conditions; and (e) currently, urban ventilation, urban wind energy generation, and urban planning and design studies are disconnected.

This study contributes to worldwide research efforts to combat the climate crisis by incorporating renewable energy into the urban planning and design process by proposing the WiSUD conceptual framework. From an academic standpoint, this study underscores the need for increased attention to be devoted to the study of urban wind environment and its implications for urban sustainability and resilience. From a professional practice perspective, the WiSUD framework has value during urban development planning and implementation for the assessment of the impact of urban wind, and prospective ventilation and energy performance enhancements. We also underline the critical need for future research to inform urban policy formation and diffusion for better urban and environmental performance [135]. Our prospective research will focus on advancing the conceptual framework into an operational assessment framework and undertaking empirical WiSUD modeling studies.