Micro wind turbine performance under real weather conditions in urban environment

Abstract

The aim of this article is to evaluate the performance of micro wind turbines in a built-up environment. For this purpose, five independent micro wind turbine systems, consisting of two distinctly different models, were tested and evaluated under real life conditions over a period of 12 months. This article provides an overview of the experimental set-up used to test the two different micro wind turbines and then goes on to present the basic background theory for horizontal axis micro wind turbines and the variation of coefficient of performance with wind speed. The wind potentials at the test site were assessed to determine the theoretical outputs of the turbines which were compared with the measured outputs over a year. The measured outputs were disappointingly low. One reason for this is turbulence, for which directional turbulence (lateral turbulence) has been shown to be a key indicator, better than the standard wind speed (longitudinal) turbulence. Another factor is the inverter efficiency and power consumption, which is not negligible. Finally the theoretical paybacks under the 2010 Feed-in Tariffs were calculated along with estimated carbon savings. Practical application: Renewables such as wind turbines are increasingly being designed and installed to help achieve lower carbon buildings. The output of micro turbines, however, can be disappointing due to lateral turbulence and inverter consumptions. These factors are explained so that designers can be aware and assess the likely outputs more accurately. Symbols¼ air density (kg/ms À1 ) A ¼ swept area of turbine (m 2 ) U 0 ¼ air speed (m/s) P 0 ¼ power contained by wind (W) P T ¼ power generated by turbine (W)

The cost of energy associated with micro wind generation: International case studies of rural and urban installations

“…For a typical wind turbine, Muljadi et al suggest a C p -λ of around 42% [20]. When this is considered in conjunction with typical generator efficiencies of around 90% [21] and converter losses of 5% [22], wind turbines can have overall efficiencies in the order of 30% [23].…”

The impact of urban atmospheric turbulence on the generation capability of a micro-wind generator

“…From the available literature considering urban wind energy, it is obvious that there are two established metrics within the industry that characterise the urban wind regime and its limited energy exploitation; a lower annual mean wind speed caused by the roughness of the environment, and a more turbulent flow created by the associated complex topography [6,7]. Many studies [2][3][4][5][6][7][8][9][10] have illustrated that the urban environment can significantly decrease productivity of a wind turbine installation in comparison to areas boasting more laminar wind profiles, with some studies demonstrating turbine capacity factors as low as 1% for urban installations, in comparison to typical factors of 30-40% for turbines in isolated areas [4]. It has even been shown that due to the high roughness of the urban environment and subsequent lower wind speeds compared to a typical rural climate, micro-wind turbines can actually become net consumers of energy [5].…”

“…Micro/small-wind turbines are being installed predominantly in rural environments. There are studies where the performance of these technologies has been analysed in more urban environments [2][3][4][5]; however, there is still a lot of confusion relating to the performance and generating capability of these technologies in such areas due to variations in surface topography, temperature influences and the dynamic nature of such environments leading to the development of turbulent air masses. In the context of this paper, atmospheric turbulence can be considered as the small-scale, irregular air motions characterised by winds that randomly vary in both speed and direction, as that often indicated by lulls and gusts in the wind.…”

Evaluation of the Microlocal Wind Power Potential for the Operation of a University Wind Turbine

“…In the same year, a research work related to the performance of wind micro-turbine, in an urban environment, under real climatic conditions was also published [3]. The method used to estimate the wind potential was to record, using a Davis Vantage Pro2 plus weather station, data on wind speed, wind direction, atmospheric pressure, and humidity.…”