Wind conditions in the built environment are complex in nature and characterized by lower wind speeds and higher turbulence due to the presence of obstructions. A growing body of literature and research/testing activities related to performance evaluation of small wind turbines (SWTs) in urban wind conditions have inferred that urban installed SWTs are subjected to higher level of turbulence and face dynamic loading that impedes their performance, and reduces fatigue life. This paper reviews the diverse studies conducted on the application of SWT technology in the built environment to understand the characteristics of inflowing wind, their performance and identify the gaps in the knowledge. This review paper also investigates the extent to which the international design standard for SWTs, IEC 41400-2, is valid for urban installations. The findings from this review show that the wind models incorporated in IEC 61400-2 is not suitable for installation of SWTs in the built environment. The authors recommend a thorough study through measured data and characterization of urban wind to make current standard inclusive of wind classes that characterize urban wind conditions. Thus, SWT design can be made more consistent with urban wind conditions and their performance and reliability can be assured.

Introduction

With rapid growth in population, the global energy consumption is projected to increase by 56% between 2010 and 2040 [1]. In 2015, fossil fuel (coal, petroleum and natural gas) accounted for 78.4% of global final energy consumption, with the share of renewables (modern and traditional) and nuclear power at 19.3% and 2.3% respectively[2]. Worldwide, the share of renewable energy will increase to address global climate change by 2030. Modern renewable energy is being used increasingly in four distinct markets: power generation, heating and cooling, transport fuels, and rural/off-grid energy services [3]. In recent years, progress has been made in increasing the renewable energy share in the power 103 sector particularly in the wind, solar photovoltaic (PV) and hydropower sectors [4]. In 2014, 104 the total renewable power capacity was 712 GW out of which 370 GW was from wind energy through utility scale wind turbines [5]. The total global capacity of wind energy reached 432 106 GW at the end of 2015, representing a cumulative growth of 17%. Although large-scale generation using wind energy has taken shape, there are some problems for their sustainable development. For example, the main barriers of large scale on-shore wind farm are available sites, impact of grid power quality, public acceptability and losses in transmission and distribution of electricity to the consumers [6]. One alternative that reduces some of these barriers is the application of small wind turbine (SWT) technology.