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Estimating the yield of micro wind turbines in an urban environment: A methodology
Abstract
Micro wind turbines currently have the majority share of micro (electricity) generation installations in Ireland. These technologies are being installed predominantly in rural environments, and current applications to the Distribution Services Operator (DSO) for connection of all types of micro generator stand at less than 500. Poor market dissemination of information and research findings compounded with poor options for spill payment - as well as onerous planning restrictions do not - it appears - create a platform conducive to encouraging development in this market. This paper outlines the complexities associated with evaluating the wind resource within an urban environment and investigates the means to `estimate' wind regimes in an urban environment based on an extrapolation of a reference wind speed from a rural environment into the urban area. Methodologies for estimating the wind speed in such circumstances are considered with modeled wind data - benchmarked against wind data acquired from a site in the city centre - being applied to a set of commercially available wind turbines.
... The influence of the buildings on the wind wind turbines distinguished between the wind energy conversion in rural and urban areas [4]. However, Wind resource in the urban environment is complicated where the resource is proportionate to the surface topography, temperature influences and the dynamic nature of the urban environment [5]. Because of the high roughness length of the environment and the presence of obstacles characterized by different shapes and porousness along the flow stream path, the wind profile in urban areas is entirely not quite the same as the classical log-law based profile with the zero-speed elevation shifted up to a peculiar value (displacement, d) which is a function of the average height of the neighboring buildings ( Figure 1) [6]. ...
The prospect of harnessing wind energy in urban areas is not promising owing to low wind speeds and the turbulence caused by surrounding obstacles. However, these challenges can be overcome through an improved design of wind turbine that can operate efficiently in an urban environment. This paper presents a novel design of a building integrated cross axis wind turbine (CAWT) that can operate under dual wind direction, i.e., horizontal wind and vertical wind from the bottom of the turbine. The CAWT consists of six horizontal blades and three vertical blades for enhancing its self-starting behavior and overall performance. The study employed a mock-up building model with gable rooftop where both of the developed CAWT and the conventional straight-bladed vertical axis wind turbine (VAWT) are mounted and tested on the rooftop. The height of the CAWT and the VAWT above the rooftop was varied from 100 to 250 mm under the same experimental conditions. The results obtained from the experimental study showed that there is significant improvement in the coefficient of power (Cp) and self-starting behavior of the building integrated CAWT compared to the straight-bladed VAWT. At 100 mm height, the Cp,max value of the CAWT increased by 266%, i.e., from 0.0345 to 0.1263, at tip speed ratio (TSR) (λ) of 1.1 and at wind speed of 4.5 m/s. Similar improvements in performance are also observed for all condition of CAWT heights above the rooftop where the CAWT outperformed the straight-bladed VAWT by 196%, 136% and 71% at TSR of 1.16, 1.08, and 1.12 for Y = 150, 200, and 250 mm, respectively. Moreover, the CAWT performs better at 10° pitch angle of the horizontal blade compared to other pitch angles.
... For instance, the wind speed is much more variable at low altitude due to the influence of the rough surface of the earth and obstructions in the vicinity (e.g. buildings or trees) [2], [3]. Also, for a small wind turbine, the cost of certain components or mechanisms becomes unacceptable in relation to the total investment cost. ...
Grid-connected small wind turbines are a promising technology to further increase the share of renewables in the energy supply. Although their impact on the environment is proven to be advantageous, the cost effectiveness needs to increase to favor a market breakthrough. This can be achieved with technological improvements, driven by research. The most obvious improvements can be found in the optimization of each component. However, the combination of highly efficient components does not necessarily result in an efficient system. The interactions between the subcomponents also play an important role in the total system efficiency. Therefore, the interaction between the converter and the generator will be the focus of this research. The impact of the control strategy of the converter on the generator efficiency will be explained in this paper.
The paper provides an analysis of small wind turbines with less than 10 kW of installed power. Power curves are compared and analyzed for a number of different wind turbines. Furthermore, the possible electricity production is assessed for all of them with their different power curves, same pole heights and wind characteristics using a multiannual array of data measured at a location in Croatia. The impact of the shape of the power curve, together with the turbine rated power relative to its swept area, on the total electricity production and generated income is analyzed and discussed. Results indicate much larger ranges of both potential electricity production and the cost of electricity than expected.
Building sector represents one the highest percentages in global energy consumption. The current financial situation in Europe, and especially in Spain, is encouraging companies of this sector to study solutions to decrease this percentage. In addition, neighborhoods and cities are promoting smart buildings with nearly zero consumption in consonance with the European climate and energy policies for 2020 (the 20–20–20 targets). The savings provided by the use of renewable energy resources can be analyzed with the help of ICT and numerical simulation. In this paper a numerical analysis of the wind potential of a new district in the city of Gijón (“Nuevo Roces” neighborhood) is studied. A numerical model of this district is developed by using CFD techniques and experimental data of the direction and speed of the wind. The best locations for the different wind generators are studied. Results allow the selection of technological solutions taking into account the environmental impact, the selection of the best locations for these technologies.
The purpose of this study is to analyse the implications of atmospheric turbulence within the urban environment on the generation capability of a micro-wind turbine. In the interests of determining an empirical relationship regarding the influence of ambient turbulence on the generation of a micro-wind turbine, wind resource data from a number of sites has been considered in accordance with corresponding measured power data for a micro-wind generator. The results of this study illustrate that atmospheric turbulence has a considerable impact on the power generation of a micro-wind turbine, but that this effect differs depending on the region of the power curve considered. However, as turbulence has been found to only considerably affect power generation at wind speeds that are doubtful to occur in the urban environment due to its high roughness, it could be interpreted, that with specific regard to urban wind energy, the level of turbulence at a particular site might not be such a critical factor in potential energy generation after all.
Small scale wind turbines installed within the built environment is classified as micro generation technology. This paper reports the investigation results of wind power application in buildings. First, general information is given for common type of wind turbines are used on buildings. Second, the wind aerodynamics and wind flows over the buildings are investigated based on local meteorological data and local building characteristics. However, to receive the highest potential wind energy resource and avoid turbulent areas, the tool of Computational Fluid Dynamics (CFD) has to be used to model the annual wind flows over buildings to help analyze, locate, and design wind turbines on and around buildings. Three different sample models for buildings and rural residential areas are explained with CFD models.
The wind profile in the urban boundary layer is described as following a logarithmic curve above the mean building height and an exponential curve below it. By considering the urban landscape to be an array of cubes, a method is described for calculating the surface roughness length and displacement height of this profile. Firstly, a computational fluid dynamics (CFD) model employing a k-ε turbulence model is used to simulate the flow around a cube. The results of this simulation are compared with wind tunnel measurements in order to validate the code. Then, the CFD model is used to simulate the wind flow around a simple pitched-roof building, using a semi-logarithmic inflow profile. An array of similar pitched-roof houses is modelled using CFD to determine the flow characteristics within an urban area. Mean wind speeds at potential turbine mounting points are studied, and optimum mounting points are identified for different prevailing wind directions. A methodology is proposed for estimating the energy yield of a building-mounted turbine from simple information such as wind atlas wind speed and building density. The energy yield of a small turbine on a hypothetical house in west London is estimated. The energy yield is shown to be very low, particularly if the turbine is mounted below rooftop height. It should be stressed that the complexity of modelling such urban environments using such a computational model has limitations and results can only be considered approximate, but nonetheless, gives an indication of expected yields within the built environment.
Several methods to determine the aerodynamic characteristics of a site through analysis of its surface form (morphometry) are considered in relation to cities. The measures discussed include zero-plane displacement length (zd), roughness length (z0), depth of the roughness sublayer, and aerodynamic conductance. A sensitivity analysis is conducted on seven formulas to estimate zd and nine to estimate z0, covering a wide range of probable urban roughness densities. Geographic information systems developed for 11 sites in 7 North American cities are used to characterize their morphometry - the height, shape, three-dimensional area, and spatial distribution of their roughness elements (buildings and trees). Most of the sites are in residential suburbs, but one is industrial and two are near city centers. This descriptive survey of urban geometric form is used, together with the morphometric formulas, to derive the apparent aerodynamic characteristics of the sites. The resulting estimates of zd and z0 are compared with values obtained from analysis of wind and turbulence observations. The latter are obtained from a survey of approximately 60 field studies and 14 laboratory studies of real and scale model cities. Despite the comprehensive nature of the survey, very few studies are found to be acceptable and their scatter is large, hence they do not provide a standard against which to test the morphometric algorithms. Further, the data show only weak relations between measured zd and z0 and roughness density. The relative merits of morphometric and wind-based estimates of aerodynamic parameters are discussed. Recommendations are made concerning the choice of method to estimate zd and z0 in urban areas and their most likely magnitude.
The outcome of COST 715 is reviewed from the viewpoint of a potential user who is required to consider urban meteorology within an air pollution assessment. It is shown that descriptive concepts are helpful for understanding the complex structure of the urban boundary layer, but that they only apply under a limited number of conditions. However such concepts are necessary to gain insight into both simple and complex air pollution models. It is argued that wider considerations are needed when considering routine air quality assessments involving an air quality model's formulation and pedigree. Moreover there appears to be a reluctance from model developers to move away from familiar concepts of the atmospheric boundary layer even if they are not appropriate to urban areas. An example is given from COST 715 as to how routine urban meteorological measurements of wind speed may be used and adapted for air quality assessments. Reference to the full COST 715 study is made which provides further details.
on the promotion of the use of energy from renewable sources [2] SEAIRenewable Energy in Ireland 2010 UpdateIrish Government White Paper: Delivering a Sustainable Energy Future for IrelandThe energy yield of roof mounted wind turbines
- Ec Of
- The European
- Parliament
- Of
- A Council B
- M Best
- P Clark
- D Hollis
- D Middleton
- G Rooney
- D Thomson
- C Wilson
[1]
"DIRECTIVE 2009/28/EC OF THE EUROPEAN
PARLIAMENT AND OF THE COUNCIL on the
promotion of the use of energy from renewable sources,"
ed, 2009.
[2]
SEAI, "Renewable Energy in Ireland 2010 Update," 2010.
[3]
DCMNR, "Irish Government White Paper: Delivering a
Sustainable Energy Future for Ireland, March 2007," 2007.
[4]
B. A. Best M., Clark P., Hollis D., Middleton D., Rooney
G., Thomson D., Wilson C., "Small-scale wind energy
Technical Report," Met Office2008.
[5]
S. Mertens, "The energy yield of roof mounted wind
turbines," Wind Engineering vol. 27, pp. 507-518, 2003.
[6]
Modelling the mean velocity profile in the urban canopy layerMeteorology Applied ti Urban Air Pollution Problems
- R Macdonald
- B E A Fisher
- S Joffre
- J Kukkonen
- M Piringer
R. MacDonald, "Modelling the mean velocity profile in
the urban canopy layer," Boundary-Layer Meteorology,
vol. 97, pp. 24-45, 2000.
[10]
B. E. A. Fisher, Joffre, S., Kukkonen, J., Piringer, M.,
Rotach, M., Schatzmann, M, "Meteorology Applied ti
Urban Air Pollution Problems. Final Report of COST
Action 715," ed: Demetra Ltd. Publishers, 2005, p. 276.
[11]