Urban Wind Turbines Research Articles

Analytical Review of Wind Assessment Tools for Urban Wind Turbine Applications

Analytical Review of Wind Assessment Tools for Urban Wind Turbine Applications

A Study on the Effect of Turbulence Intensity on Dual Vertical-Axis Wind Turbine Aerodynamic Performance

Examining dual vertical-axis wind turbines (VAWTs) across various turbulence scenarios is crucial for advancing the efficiency of urban energy generation and promoting sustainable development. This study introduces a novel approach by employing two-dimensional numerical analysis through computational fluid dynamics (CFD) software to investigate the performance of VAWTs under varying turbulence intensity conditions, a topic that has been relatively unexplored in existing research. The analysis focuses on the self-starting capabilities and the effective utilization of wind energy, which are key factors in urban wind turbine deployment. The results reveal that while the impact of increased turbulence intensity on the self-starting performance of VAWTs is modest, there is a significant improvement in wind energy utilization within a specific turbulence range, leading to an average power increase of 1.41%. This phenomenon is attributed to the more complex flow field induced by heightened turbulence intensity, which delays the onset of dynamic stall through non-uniform aerodynamic excitation of the blade boundary layer. Additionally, the inherent interaction among VAWTs contributes to enhanced turbine output power. However, this study also highlights the trade-off between increased power and the potential for significant fatigue issues in the turbine rotor. These findings provide new insights into the optimal deployment of VAWTs in urban environments, offering practical recommendations for maximizing energy efficiency while mitigating fatigue-related risks.

Dataset on SCADA Data of an Urban Small Wind Turbine Operation in São Paulo, Brazil

Small wind turbines (SWTs) represent an opportunity to promote energy generation technologies from low-carbon renewable sources in cities. Tall buildings are inherently suitable for placing SWTs in urban environments. Thus, the Institute of Energy and Environment of the University of São Paulo (IEE-USP) has installed an SWT in an existing high-height High Voltage Laboratory building on its campus in São Paulo, Brazil. The dataset file contains data regarding the actual electrical and mechanical operational quantities and control parameters obtained and recorded by the internal inverter of a Skystream 3.7 SWT, with 1.8 kW rated power, from 2017 to 2022. The main electrical parameters are the generated energy, voltages, currents, and power frequency in the connection grid point. Rotation, referential wind speed, and temperatures measured in some points at the inverter and in the nacelle are also recorded. Several other parameters concerning the SWT inverter operation, including alarms and status codes, are also presented. This dataset can be helpful for reanalysis, to access information, such as capacity factor, and can also be used as overall input data of actual SWT operation quantities.

Implantation, Operation Data and Performance Assessment of An Urban Area Grid-Connected Small Wind Turbine

Over the last few decades, and more prominently currently, many countries have launched and reinforced campaigns to reduce CO2 emissions from all human activities and, in the area of energy, promote energy generating technologies from low carbon, renewable sources, especially wind and solar. In recent years, this promotion of renewables can be seen in statistics as well as an extraordinary increase in plants using renewable sources. There is more activity surrounding the use of small devices installed close to consumers, such as small wind turbines (SWT). In cities, the best places to install SWT are tall buildings. The Institute of Energy and Environment (IEE-USP) has installed a 1.8 kW SWT on the University of São Paulo campus in São Paulo, Brazil. Even with low-magnitude winds at the site, the SWT installation was carried out to serve as a didactic apparatus and demonstration initiative of wind energy generation connected directly to the University’s electric grid, which already has other embedded renewable sources installed, namely photovoltaic and biogas plants. The turbine was placed on the roof of the existing High Voltage Laboratory building, leading to an operating height of 35 m. This paper presents previous local wind data measurements using a Lidar system, annual energy yield estimation calculations, and measurements, also bringing all implementation details. It reports and analyzes the operation and energy production data from three full operational years, from 2018 to 2020, discussing and concluding with further improvements of SWT from technical and economic aspects.

Experts versus the Public: Perceptions of Siting Wind Turbines and Performance Concerns

Experiences of wind turbines (WT) shape public perception and acceptance of the technology, influencing government policy, deployment, and land-use policies of wind turbines. This paper attempts to find changes in public perceptions over the last three decades and differences between experts and the public over different land-use options. A semi-structured questionnaire that integrates a visual survey of 10 images of WT technology in different urban, landscape and seascape settings was presented to both groups. The perceptions of siting, proximity, landscape type, and maturity of urban wind turbines’ technology in renewable energy generation were contrasted. The results revealed that both the public and experts alike significantly preferred images of WT inclusion in seascape and landscape settings and responded negatively to images of WT as an addition to buildings in urban contexts. Images of wind turbines around transport settings were ranked in the second set of acceptances, after landscape settings, indicating that closer proximity to WT is acceptable, but for a short duration. The analysis also highlighted a preference by the public for aesthetically engaging WT, even if they resulted in lower energy yields, but were less accepted by the experts who based their judgment on technical performance.

Savonius Wind Turbine Numerical Parametric Analysis Using Space-Filling Design and Gaussian Stochastic Process

Wind energy is an alternative source of clean energy to address the growing energy demand and provide pollution-free electricity. With the rapid development of urban areas, high wind energy resources such as high-rise building rooftops are excellent locations for urban wind turbine installation. One of the practical and simple urban wind turbines is the Savonius design. It has a simple design, easy to maintain, and is very affordable. This work focuses on the design evaluation of a Savonius wind turbine (SWT) by varying the rotor diameter, rotor height, and twist angle for urban applications. A transient computational fluid dynamics (CFD) approach is applied to assess the various design treatments using a space-filling design of experiments. To address the spaces in the hypercube statistical design, a sphere packing design method was adopted which suited the evaluation of computational simulations results such as that of the CFD. The Gaussian stochastic process model was applied to establish the trend of the parametric performance of the optimized SWT design through the model fitting. The results have shown that optimized SWT performs well with its self-starting capability compared to the traditional Savonius design. In addition, the optimized SWT has shown a better peak power coefficient compared with the results of previous works on the design of SWT.

ZASOBY WIETRZNE W STRUKTURZE MIEJSKIEJ – ANALIZA NUMERYCZNA CFD. MOŻLIWOŚCI WYKORZYSTANIA ENERGII WIATRU NA PRZYKŁADZIE OSIEDLA SŁONECZNEGO W SZCZECINIE

The issue of wind in an urbanized structure, considered in the context of benefits, forces to undertake activities across multiple disciplines. The lack of understanding of the aerodynamic phenomena in heterogeneous space may lead to failures in implemented projects. The article presents the general scope of issues related to the urban wind turbine and the numerical CFD simulation of air flows in the Słoneczne housing estate in Szczecin, together with the conclusions drawn from it.

Qualitative and quantitative assessments of an Archimedes Spiral Wind Turbine performance augmented by A concentrator

Wind power is one of the fastest developing alternative energy technologies. Continuous improvement of the performance of urban wind turbines has become essential to achieving sustainability for developing countries to reduce dependence on fossil fuel. However, conventional wind turbines are designed with wind speeds higher than 5 m/s. This value limits the choice of wind turbines that can be implemented. A new type of horizontal axis wind turbine, namely, Archimedes spiral wind turbine (ASWT) is designed for urban utilization. It is characterized as a lift-drag type wind turbine. In the present work, the aerodynamic characteristics of the ASWT and its performance were investigated using 3D numerical analysis. Furthermore, a concentrator has been augmented to the ASWT to improve the turbine performance. The maximum power coefficient, CP, obtained from the analysis was 0.311 at tip speed ratio, TSR, equals 2. This maximum CP for ASWT augmented by a concentrator is increased by 33.48% compared with bare ASWT. The best configuration of the concentrator is at a position of 0.1 of the rotor diameter, concentrator angle of 20°, and tip clearance of 0.05 of the rotor diameter, and concentrator length of 0.6 of the rotor diameter.

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

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

CFD Design of Urban Wind Turbines: A Review and Critical Analysis

The Urban Wind Turbines (UWTs) industry has experienced diverse results with some positive outcomes and various negative ones. Regarding negative outcomes, designers have often overestimated performances of UWTs. Differences of 20% or less between actual energy produced and energy originally estimated were found in literature. These differences would have been caused by the incorrect location of UWTs. Notice that determining the optimal locations of UWTs is a complex task due to unforeseen wind behaviour found in urban environments. To cope with this complex task, Computational Fluid Dynamics (CFD) approach is presented as a suitable alternative. Thus, this paper aimed to develop a review to introduce recent advancements in the field of CFD design of UWTs, and to perform a critical analysis of these advancements. Accordingly, a Systematic Literature Review associated with the topic was performed to obtain suitable information (primary studies) for the critical analyses. The results showed that the maximum velocity amplification factor, power coefficient and torque coefficient found in the primary studies were 1.8, 0.4627 and 0.4195, respectively. Notices that these values were obtained using novel UWTs and wind amplification devices. Regarding CFD modelling, standard k–? was the most used turbulence model (42% of studies).

CFD-Based Wind Assessment for Suburban Buildings. The Case Study of Aarhus University, Herning Campus

The development in the field of wind turbines is continuously growing. However, most of the times, the energy of wind is exploited by using huge wind-power plants, while wind energy installations in urban and suburban areas, as space and available land, are a lot more limited, is something relatively new, with great potential though. The major challenge regarding small urban wind turbines can be summarized as a lack of understanding of the wind resource in the built environment, with a combination of missing measurements in this field that needed to be addressed. Aarhus University Campus Herning, located in the suburban area of Herning, is looking for a suitable place to install one small wind turbine (SWT). This study attempts to provide a comprehensive framework for SWTs and the characteristics of urban wind flow. The analysis helped in identifying the two most appropriate sites for SWTs installation sites in the AU Herning building.

Three-Dimensional Wind Field Construction and Wind Turbine Siting in an Urban Environment

Three-dimensional urban wind field construction plays an important role not only in the analysis of pedestrian levels of comfort but also in the effectiveness of harnessing wind energy in an urban environment. However, it is challenging to accurately simulate urban wind flow due to the complex land use in urban environments. In this study, a three-dimensional numerical model was developed for urban wind flow construction. To obtain an accurate urban wind field, various turbulence models, including the Reynolds stress model (RSM), k-ω shear stress transport (SST), realizable k-ε, and (Re-Normalisation Group (RNG) k-ε models were tested. Simulation results were compared with experimental data in the literature. The RSM model showed promising potential in simulating urban wind flow. The model was then adopted to simulate urban wind flow for Purdue University Northwest, which is located in the Northwest Indiana urban region. Based on the simulation results, the optimal location was identified for urban wind turbine siting.

On the Wind Energy Resource above High-Rise Buildings

One of the main challenges of urban wind energy harvesting is the understanding of the flow characteristics where urban wind turbines are to be installed. Among viable locations within the urban environment, high-rise buildings are particularly promising due to the elevated height and relatively undisturbed wind conditions. Most research studies on high-rise buildings deal with the calculation of the wind loads in terms of surface pressure. In the present paper, flow pattern characteristics are investigated for a typical high-rise building in a variety of configurations and wind directions in wind tunnel tests. The aim is to improve the understanding of the wind energy resource in the built environment and give designers meaningful data on the positioning strategy of wind turbines to improve performance. In addition, the study provides suitable and realistic turbulence characteristics to be reproduced in physical or numerical simulations of urban wind turbines for several locations above the roof region of the building. The study showed that at a height of 10 m from the roof surface, the flow resembles atmospheric turbulence with an enhanced turbulence intensity above 10% combined with large length scales of about 200 m. Results also showed that high-rise buildings in clusters might provide a very suitable configuration for the installation of urban wind turbines, although there is a strong difference between the performance of a wind turbine installed at the centre of the roof and one installed on the leeward and windward corners or edges, depending on the wind direction.

Financial Innovation for Energy Innovation

The move to catalyze a global energy transition is underpinned by the collective need to limit the most severe impacts from climate change as well as fostering more sustainable economic growth. Floating photovoltaic power stations on Chinese lakes, integrated carbon capture technology on large-scale power plants in Canada, and decentralized urban wind turbines on Singaporean rooftops, are just a few examples of how the global energy transition is being fueled by radical innovation in the clean energy technology landscape (WEF 2017, Natural Resources Canada 2013, Karthikeya et. al. 2016). Bringing cutting-edge technology from the lab to the global energy market requires a supportive ecosystem: innovation must be matched by enabling technological development, market readiness to adopt disruptive technologies, local capacities to scale up new energy projects, energy policies with climate objectives, as well as sufficient and “aligned” investment capital. This article focuses specifically on the latter requirement; the characteristics of investment capital needed to support clean energy innovation. Investors are key players in the future of energy, as they must drive innovation in the financial system in order to meet the scale of capital needed to transform the energy industry. Important technological leaps in sustainable energy have been hindered by a lack of or a misalignment of investment capital (WEF 2018, Bloomberg Finance New Energy Finance 2010, Monk et al. 2015). One evident example is the severe financing shortage in commercializing novel sustainable energy technologies. This so-called “valley of death” between early-stage cleantech and full-sized deployment is the result of many causes, but a common thread among them is increasing financial risks in the energy industry, as well as opacity within the energy ecosystem (In and Monk 2018). We approach this funding shortage and widening valley of death in the energy sector from a newer perspective. We investigate underlying structural and organizational barriers in today’s capital markets, and discuss how to innovate the financial industry. Our discussion attempts to move the focus of current energy finance and investment research from a deal-by-deal perspective to a continuous process that involves asset owners, asset managers and entrepreneurs. This shift in perspective is important because “investors are often presented with a ‘deal’ rather than a historical understanding of a company, while entrepreneurs themselves are often faced with countless types of investors, from pensions and sovereigns to tax-equity providers” (In and Monk 2018, page 26). In our view, long-termism has been continuously undervalued as a key success factor, despite its strong potential to align various players in the ecosystem. Instead, asset owners and managers are often forced to rely on short-term and costly financial products and services to fund the long-term global project of energy transformation. The financial innovations described in this article thus focus on how to foster long-termism and catalyze patient and smart long-term investment capital to support energy innovation, by innovating governance, management and operations of investors via new collaboration and cooperation among asset owners and managers.

Urban Wind Harvesting Using Flow-Induced Vibrations

The growing global interest in sustainable energy has paved the way to the rapid development of large-scale wind farms, consisting of dozens to hundreds of wind turbines. Although these large wind farms can generate enormous amount of power, they are also costly and require large areas of land or water, and thus are not suitable for urban environments. Smaller urban wind turbines have been developed for urban environments, but there are significant challenges to their widespread deployment. One of these challenges are their urban wind flows as they are strongly affected by complex building structures, producing highly turbulent flows. Any urban wind turbine would need to be designed to function efficiently and safely under these flow conditions; however, these unpredictable and turbulent winds can induce undesirable vibrations and cause early failures. Recently, bladeless wind turbines are gaining interest due to their reduced costs compared with conventional wind turbines such as the vertical-axis wind turbine and horizontal-axis wind turbine. These bladeless turbines convert flow wind energy into vibration energy, then converts the vibration energy into electricity. This paper examines the effects of force-induced vibrations on a cantilever beam system through wind tunnel experimentation. When fluid flows around a bluff body, periodic shedding of vortices may occur under the right conditions. The vortex shedding process creates an asymmetric pressure distribution on the body which causes the body to oscillate, known as vortex-induced vibrations. The purpose of the paper is to understand the factors affecting flow-induced vibrations and to improve wind energy harvesting from these vibrations. The first part of the paper focuses on wind tunnel experiments, by utilizing a cantilever beam configuration, conceptualized by previous research. Then, the experimental model was tested in different configurations, to determine the best setup for maximizing vibrations induced on the model. The long-term goal of the project was utilizing the model to optimize the system to improve efficiency of wind energy harvesting. The experimental results showed that the presence of an upstream cylinder will significantly improve the amplitude of vibration for energy harvesting, furthermore, the experiments showed that spacing in different directions also affect the amplitude of the vibrations. A two tandem cylinder system was used in this work, including a fixed rigid upstream cylinder and a downstream cylinder supported by a cantilever beam. Various configurations of these two cylinders in terms of spanwise and streamwise separation distances were studied and their maximum and root mean square displacements are reported for different wind speeds. Results showed that the presence of an upstream cylinder will significantly improve the amplitude of vibrations. This work verified that a wind energy harvester needs to consider the effects of wind speed and separation configuration of the cylinders in order to maximize the harvester’s performance in urban environments. KEYWORDS: Sustainable Energy; Energy Harvesting; Urban Environments; Bladeless Wind Turbines; Flow-Induced Vibrations; Cantilever Beam System; Wind Tunnel; Wake

A Study of Power Production and Noise Generation of a Small Wind Turbine for an Urban Environment

Wind energy has had a major impact on the generation of renewable energy. While most research and development focuses on large, utility-scale wind turbines, a new application is in the field of small wind turbines for the urban environment. A major design challenge for urban wind turbines is the noise generated during operation. This study examines the power production and the noise generated by two small-scale wind turbines tested in a small wind tunnel. Both rotors were designed using the blade-element momentum theory using either the NREL S823 or the Eppler 216 airfoils. Point noise measurements were taken using a microphone at three locations downstream of the turbine: 16% of the diameter (two chord lengths), 50% of the diameter, and 75% of the diameter. At each location downstream of the turbine, a vertical traverse was performed to analyze the sound pressure level (SPL) from the tip of the turbine blades down to the hub. The rotor designed with the Eppler 216 airfoil showed a 9% increase in power production and decrease of up to 7 dB(A).

Numerical Investigations of the Effects of the Rotating Shaft and Optimization of Urban Vertical Axis Wind Turbines

The central shaft is an important and indispensable part of a small scale urban vertical axis wind turbines (VAWTs). Normally, it is often operated at the same angular velocity as the wind turbine. The shedding vortices released by the rotating shaft have a negative effect on the blades passing the wake of the wind shaft. The objective of this study is to explore the influence of the wake of rotating shaft on the performance of the VAWT under different operational and physical parameters. The results show that when the ratio of the shaft diameter to the wind turbine diameter (α) is 9%, the power loss of the wind turbine in one revolution increases from 0% to 25% relative to that of no-shaft wind turbine (this is a numerical experiment for which the shaft of the VAWT is removed in order to study the interactions between the shaft and blade). When the downstream blades pass through the wake of the shaft, the pressure gradient of the suction side and pressure side is changed, and an adverse effect is also exerted on the lift generation in the blades. In addition, α = 5% is a critical value for the rotating shaft wind turbine (the lift-drag ratio trend of the shaft changes differently). In order to figure out the impacts of four factors; namely, tip speed ratios (TSRs), α, turbulence intensity (TI), and the relative surface roughness value (ks/ds) on the performance of a VAWT system, the Taguchi method is employed in this study. The influence strength order of these factors is featured by TSRs > ks/ds > α > TI. Furthermore, within the range we have analyzed in this study, the optimal power coefficient (Cp) occurred under the condition of TSR = 4, α = 5%, ks/ds = 1 × 10−2, and TI = 8%.

Numerical investigations of the effect of rotating and non-rotating shaft on aerodynamic performance of small scale urban vertical axis wind turbines

The shaft is a very important part of small scale vertical axis wind turbines (VAWTs) being used in urban environments. The shedding vortices will be formed as wind passes around the shaft, the shedding vortices released by the shaft have a negative effect on the aerodynamic performance of the blades passing the wake of the wind shaft, and this will lead to lower power output of the wind turbine. The objective of this study is to explore the differences of the effect of the rotating and non-rotating shafts of VAWTs on the aerodynamic performance of small scale urban VAWTs. In addition, the effect of surface roughness on the performance of the rotating and non-rotating shaft wind turbines is also investigated. The dynamic analysis of the VAWT is carried out by the method of Computational Fluid Dynamics. The aerodynamic loads in the study are obtained by solving the two-dimensional (2D) unsteady Navier-Stokes equations with the Transition SST turbulence model. The results are validated with experimental results. The results show that when the ratio of the shaft diameter to the wind turbine diameter (α) is 3.9%, the power coefficient (Cp) of the rotating shaft wind turbine is 2.2% higher than that of the non-rotating shaft wind turbine. Increasing the shaft diameter-based Reynolds number (Res) will increase the Cp of rotating and non-rotating shaft wind turbines, when Res is 2.6 × 104 and the Cp of the non-rotating shaft wind turbine is 5.7% higher than that of the rotating shaft wind turbine. The Cp of the non-rotating and rotating shaft wind turbines is reduced by 6.9% and 6.3%, respectively, by increasing the turbulence intensity from 4% to 16%. The optimal power output occurs under the condition of the non-rotating shaft wind turbine, and the relative surface roughness (ks/ds) is 0.005, where it is observed that Cp increased by 2.1% in comparison to that of the smooth shaft wind turbine.

Energy storage coupling in a high efficiency household scenario: A real life experimental application

Distributed renewable energy sources and storage could play a key role in the future energy ecosystems, reducing emissions, strengthening grid resilience and improving energy efficiency. Nowadays, several ongoing pilot projects aim at measuring real-life performances of different coupling criteria between RES generators, storage apparatuses and the final users’ consumption. In such a context, this paper presents an innovative experimental project led by E.ON Sverige AB in the Hållbarheten residential complex, in Malmö (Sweden). In a modern and innovative apartment, 58 passive loads and 2 local generating units – a PV system and an urban wind turbine – have been monitored. Within the project, real users lived in the apartment and a proactive energy behavior was promoted thanks to a special energy tariff (specifically implemented for the experimental project) and to dedicated media, supposed to easily provide information to the users (e.g. iPad app depicting in real-time energy tariff, energy consumption and production, etc.). In a second phase, a numerical analysis has been carried out to evaluate the effectiveness of the integration of an electrochemical energy storage system in the apartment, testing different control laws, evaluating different technologies and, eventually, proposing a techno-economic analysis.

Wind turbine designs for urban applications: A case study of shrouded diffuser casing for turbines

The increased demand for renewable energy and the development of energy independent building designs have motivated significant research into the improvement of wind power technologies that target urban environments. However, the implementation of wind turbines in urban environments is still very limited. There have been some studies analyzing different designs of urban wind turbines either using computational fluid dynamics (CFD), wind tunnel tests or field data for existing or new turbine designs. This paper reviews the state-of-the-art of urban wind energy by examining the various types of urban wind turbine designs, with a view to understand their performance and the synergy between the turbines and the urban environments. It also considers a flanged diffuser shroud mechanism - a fluid machine, mounted on rooftop of buildings used as casing for small wind turbines to improve turbine performance by using mainly CFD. The diffuser shroud mechanism can draw the airflow over buildings utilizing its special features such as, cycloidal curve geometry at the inlet and a vortex generating flange at the outlet, to guide and accelerate the airflow inside. The performance of the fluid machine is optimized parametrically. The mechanism is modeled on a building rooftop in a real test site in Montreal, Canada with real statistical wind data. The CFD result confirms the functionality of the fluid machine to take advantage of the airflow over buildings in complex built-environments for wind power generation.