Wind energy is commonly considered to be a clean and environmentally friendly renewable energy resource, as they do not pollute our atmosphere with greenhouse gas, nor do they cause any radioactive problems compared to nuclear energy. However, there are still some environmental impacts due to the installation and operation of the wind turbines that cannot be ignored, such as noise, visual and climatic impact. Especially, the observed local climate change in some wind farm areas has attracted general concern in recent years. Experts suspected that long time operation of wind turbines in an area can cause changes to local precipitation, evaporation of the water on earth surface, and even affect the frequency of drought happening. Nevertheless, we still cannot figure out whether these changes would be caused by wind turbines or not. The target of this study is to investigate the potential local impact of an operating wind turbine by numerical simulation. Because of the big geometric size of commercial wind turbines, experimental method is very limited in this type of study. Numerical simulation using CFD is considered to be a suitable approach and commercial software “FLUENT” is utilized in this study. Firstly, an accurate 3-D numerical wind turbine model was established and the frozen blade method was used to realize the rotation of the wind blades. Before further simulation, a wind-tunnel test has been undertaken by using a scaled physical wind turbine model for validation purpose. The experimental results show good agreement with those predicted by the numerical simulation. This suggested that the computation results were validated and the computational model can be used for further study. In this research, three wind turbine cases, with different typical ambient temperature and surface temperature, were simulated. Characters like wake structure, turbulence intensity and local temperature change was collected and analyzed in each simulated case. The results show that the operating wind turbine can bring obvious velocity deficit in the wake and a strong turbulence intensity enhancement was observed at the top tip because of the rotation. Also, local temperature change was found in the near wake region. The investigation of the local impact of the operating wind turbine is very significant. This study provides a valuable insight into the potential impacts of wind farms on local meteorology, which is rarely studied before. Meanwhile, a more comprehensive study on the effect of a wind farm on the environment is highly recommended. / published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

Small scale wind turbines operating in an urban environment produce dismal amounts of power when compared to their expected output [1-4]. This is largely due to the gusty wind conditions found in an urban environment, coupled with the fact that the wind turbines are not designed for these conditions. A new concept of a Segmented Variable Pitch (SVP) wind turbine has been proposed, which has a strong possibility to perform well in gusty and variable wind conditions. This dissertation explains the concept of a SVP wind turbine in more detail and shows analytical and experimental results relating to this concept. Also, the potential benefits of the proposed concept are mentioned. The results from this dissertation show that this concept has potential with promising results on possible turbine blade aerofoil configurations. Scaled model tests were completed and although further design optimisation is required, the tests showed good potential for the SVP concept. Lastly a proof-of-concept full scale model was manufactured and tested to prove scalability to full size from concept models. Along with the proof-of-concept full scale model, a wireless control system (to control the blade segments) was developed and tested.

Global wind power generation has grown rapidly in response to targets to reduce greenhouse gas emissions as part of efforts to mitigate climate change, and to increase energy security. While much of the focus in wind energy technology to date has been on wind farms, a relatively recent development is the expansion of the micro-wind sector (turbines generating < 100 kW), and there are now over 870,000 small wind turbines (SWTs) installed globally. However, official planning guidance for SWTs in the UK and elsewhere is lacking. This may be a barrier to SWT installations if there is confusion over the requirements to gain planning permission. One reason for the lack of planning guidance is that our understanding of the wildlife impacts of SWTs is limited and therefore it is difficult to make recommendations for their mitigation. There are a range of potential negative effects wind power can exert on wildlife, in particular on birds and bats, yet to date, there has been very little published research into the wildlife impacts of SWTs. Mortality rates of wildlife at SWTs appear to be relatively low, but disturbance of bats, highly protected species, near SWTs has been previously demonstrated. However, the extent (if any) of this disturbance at habitat features of known importance was unclear. Therefore this thesis used acoustic surveys of bat activity to quantify disturbance of use of linear features (e.g. hedgerows, treelines), habitat important to bats for commuting and foraging, caused by SWTs. Firstly, bat activity did decline after experimental installation of SWTs 5m away from linear features. This decline was species-specific with Pipistrellus pygmaeus showing declines in activity in close proximity to the SWT associated with SWT operation, while P. pipistrellus activity declined in response to installation both at the SWT site and 30m away. Secondly, bat use of linear features is lower when SWTs are located nearby. In particular, P. pygmaeus activity at linear features is lower the closer a SWT is to the feature, and at high wind speeds Myotis spp. use of linear features is similarly lower where SWTs are located nearby. This disturbance did not dissipate along the linear features away from the SWT for at least 60m. This is much further than previously documented disturbance of bats by SWTs, which appeared fairly localised, and may be due to the importance of linear features specifically for commuting between habitat fragments. If so, the cumulative impacts of such disturbance will be important in areas where suitable foraging and roosting habitats is limited and fragmented, and linear features suitable for commuting between habitat fragments are already rare. These results offer support for recommendations that SWTs should be subject to siting restrictions that create a buffer distance between them and important bat habitats such as linear features. Specifically, this thesis recommends that in landscapes with few alternative commuting routes or where particularly rare bat species are present SWT installations require buffer distances to ensure they are a minimum of 60m away from linear features. There has also been a lack of research into public attitudes towards SWTs, despite local attitudes towards wind farm developments having been linked to planning outcomes, implying attitudes can be a barrier to installations. This thesis presents the results of the first survey of public attitudes specifically towards SWTs. Generally attitudes towards SWTs were positive, with over half of respondents rating SWTs as acceptable across a range of landscape settings. However, as for wind power where public attitudes in general are positive but local wind farm developments may still face opposition, only 35% of respondents were in favour of having a SWT installed in sight of their home. A key finding of this survey was that acceptance of SWTs significantly differed between landscape settings, with those in hedgerows and gardens being less well accepted compared to those on road signs, buildings and fields. Respondent comments highlighted visual impacts, efficient use of technology, noise impacts, wildlife impacts and educational value as important factors in their decisions regarding SWT acceptability. Public concern about wildlife impacts appears to be responsive to context, being important to the lower acceptance of SWTs in hedgerows, which were perceived to be particularly risky for wildlife. Potential SWT owners are also shown to be concerned about wildlife impacts from SWTs. Using a choice experiment methodology, an economics technique that allows valuation of non-market goods, farmers (a group most likely to own SWTs in the UK) were found to be willing-to-pay, through loss of SWT earnings from electricity generation, to avoid disturbance of birds and bats or collision mortality of bats. These findings also support the recommendation of the use of buffer distances for SWTs. Buffer distances between SWTs and linear features will help to alleviate public and SWT owner concerns about wildlife impacts, and also increase public acceptance of SWTs by encouraging their installation away from some of the least accepted landscape settings such as hedgerows. Further, potential SWT owners were also found to have no significant preference for avoiding siting restrictions of SWT installations, suggesting they are open to the use of buffer distances, although the suggested distances were substantially smaller than those this thesis ultimately recommends. The findings presented in this thesis have implications for planning guidance, policy makers and developers, but also raise many questions that will require further study. A list of planning guidance recommendations and a list of recommendations for future SWT research are presented in the final section.

The Altamont Pass Wind Resource Area (Altamont) near Livermore, California is the oldest and largest wind farm in the United States. It is known as a location of high avian mortality, especially for diurnal raptors such as the Golden Eagle (Aquila chrysaetos). Using the avian monitoring data collected at Altamont for over thirteen years (1998-2003, 2005- 2011), records were analyzed of 134 golden eagle deaths caused by wind turbine collisions. All wind turbines present during the same temporal range were characterized according to turbine variables, and geographic placement characteristics. Values of turbines that killed golden eagles were compared to values of turbnes that did not. It was discovered that turbines that have killed golden eagles (kill turbines) share characteristics that are significantly different from those that have not. Kill turbines are more often situated on lattice structure towers, have larger rotor blade-swept areas, placed in less dense turbine arrays, are further away from the next nearest turbine and are less often placed on top of ridgelines compared to nonkill turbines. Finally, kill turbines are more often situated at the end of a turbine row than are nonkill turbines. The differences between kill and nonkill turbine model, hill slope, tower height, generating capacity, array diversity, row count of turbines and placement in a hill saddle were found to be not significant. These findings support in part, earlier turbine studies at Altamont, but do not concur with all previous findings. The methods used in this study can be applied to any bird species at Altamont and at any wind resource area throughout the world. As the wind industry continues to grow, techniques used in studies such as this are an important tool that can be used to direct wildlife conservation policies.