Modelling and analysis of rotary airborne wind energy systems : a tensile rotary power transmission design

Airborne wind energy is a novel form of wind power. Through the use of lightweight wings and tethers it aims to access locations out of reach to current wind harvesting devices, at a lower cost and with a lower impact on the environment. There are multiple airborne wind energy systems currently under development, one group of these, referred to as rotary systems, use multiple wings networked together to form rotors. This thesis presents an analysis on the design and operation of rotary systems, with a particular focus on the power transmission from the airborne components down to the ground. There are various power transmission methods used for rotary systems, among them tensile rotary power transmission uses multiple networked tethers held apart by a small number of rigid components to transfer torque from a flying rotor down to a ground station. The aim of this research is to improve the design and operation of rotary airborne wind energy systems that incorporate tensile rotary power transmission, and to assess system performance based on mathematical modelling and test data. It focuses on the Daisy Kite system design, a rotary system, being developed by Windswept and Interesting. Included in this thesis work is the development of three mathematical representations to support systematic analysis and design improvement. The first representation, a steady state model, is used to analyse rotary system design. The second and third models are dynamic representations of varying complexity. Also included is an experimental campaign conducted on the Daisy Kite in collaboration with Windswept and Interesting. Field tests are carried out on nine different Daisy Kite prototypes at their test site on the Isle of Lewis, Scotland. Measured data is collected for the various prototype designs under different operating conditions. The measured data is used to assess the reliability of the three mathematical representations. This allows the models to be validated and compared to one another in terms of their accuracy and computational efficiency. During the experimental campaign several design and operational improvements are made that increase the power output and lead to more reliable operation. The mathematical representations are used to identify key design factors and to optimise rotary system design. Improved understanding and design of the rotary airborne wind energy system has been achieved through this holistic investigation.Airborne wind energy is a novel form of wind power. Through the use of lightweight wings and tethers it aims to access locations out of reach to current wind harvesting devices, at a lower cost and with a lower impact on the environment. There are multiple airborne wind energy systems currently under development, one group of these, referred to as rotary systems, use multiple wings networked together to form rotors. This thesis presents an analysis on the design and operation of rotary systems, with a particular focus on the power transmission from the airborne components down to the ground. There are various power transmission methods used for rotary systems, among them tensile rotary power transmission uses multiple networked tethers held apart by a small number of rigid components to transfer torque from a flying rotor down to a ground station. The aim of this research is to improve the design and operation of rotary airborne wind energy systems that incorporate tensile rotary power transmission, and to assess system performance based on mathematical modelling and test data. It focuses on the Daisy Kite system design, a rotary system, being developed by Windswept and Interesting. Included in this thesis work is the development of three mathematical representations to support systematic analysis and design improvement. The first representation, a steady state model, is used to analyse rotary system design. The second and third models are dynamic representations of varying complexity. Also included is an experimental campaign conducted on the Daisy Kite in collaboration with Windswept and Interesting. Field tests are carried out on nine different Daisy Kite prototypes at their test site on the Isle of Lewis, Scotland. Measured data is collected for the various prototype designs under different operating conditions. The measured data is used to assess the reliability of the three mathematical representations. This allows the models to be validated and compared to one another in terms of their accuracy and computational efficiency. During the experimental campaign several design and operational improvements are made that increase the power output and lead to more reliable operation. The mathematical representations are used to identify key design factors and to optimise rotary system design. Improved understanding and design of the rotary airborne wind energy system has been achieved through this holistic investigation

Development of Safe and Efficient Operation for an Airborne Wind Energy (AWE) System - A Rotary Design

This report details the work that has been done in the 2nd year of a 3 year research PhD. A brief background into the motivation behind this work is given along with an introduction to Airborne Wind Energy. The novelty of this work is described and the aims and objectives of this research are set out. A short literature review is then given highlighting the prior research on the modelling of airborne wind energy systems with a particular focus on rotary system. Following this rotary systems are defined and the existing prototypes are introduced. A test campaign run on the Daisy Kite design is then described with the results collected so far shown. Finally a mathematical model is introduced. The model is used to simulate the Daisy Kite and its results are compared to the experimental data collected during the test campaign. It is shown the model is able to accurately predicted the Daisy Kites power output. This report is concluded by highlighting the future work that will initially focus on the development of a dynamic model of the tensile rotary power transmission used within the Daisy Kite

Assessing species’ habitat associations from occurrence records, standardised monitoring data and expert opinion: a test with British butterflies

Accurate knowledge of species’ habitat associations is important for conservation planning and policy. Assessing habitat associations is a vital precursor to selecting appropriate indicator species for prioritising sites for conservation or assessing trends in habitat quality. However, much existing knowledge is based on qualitative expert opinion or local scale studies, and may not remain accurate across different spatial scales or geographic locations. Data from biological recording schemes have the potential to provide objective measures of habitat association, with the ability to account for spatial variation. We used data on 50 British butterfly species as a test case to investigate the correspondence of data-derived measures of habitat association with expert opinion, from two different butterfly recording schemes. One scheme collected large quantities of occurrence data (c. 3 million records) and the other, lower quantities of standardised monitoring data (c. 1400 sites). We used general linear mixed effects models to derive scores of association with broad-leaf woodland for both datasets and compared them with scores canvassed from experts. Scores derived from occurrence and abundance data both showed strongly positive correlations with expert opinion. However, only for occurrence data did these fell within the range of correlations between experts. Data-derived scores showed regional spatial variation in the strength of butterfly associations with broad-leaf woodland, with a significant latitudinal trend in 26% of species. Sub-sampling of the data suggested a mean sample size of 5000 occurrence records per species to gain an accurate estimation of habitat association, although habitat specialists are likely to be readily detected using several hundred records. Occurrence data from recording schemes can thus provide easily obtained, objective, quantitative measures of habitat association

Potential landscape-scale pollinator networks across Great Britain: structure, stability and influence of agricultural land cover

Understanding spatial variation in the structure and stability of plant-pollinator networks, and their relationship with anthropogenic drivers, is key to maintaining pollination services and mitigating declines. Constructing sufficient networks to examine patterns over large spatial scales remains challenging. Using biological records (citizen science), we constructed potential plant-pollinator networks at 10km resolution across Great Britain, comprising all potential interactions inferred from recorded floral visitation and species co-occurrence. We calculated network metrics (species richness, connectance, pollinator and plant generality) and adapted existing methods to assess robustness to sequences of simulated plant extinctions across multiple networks. We found positive relationships between agricultural land cover and both pollinator generality and robustness to extinctions under several extinction scenarios. Increased robustness was attributable to changes in plant community composition (fewer extinction-prone species) and network structure (increased pollinator generality). Thus, traits enabling persistence in highly agricultural landscapes can confer robustness to potential future perturbations on plant-pollinator networks

Direct Estimate of Lateral Eddy Diffusivity Upstream of Drake Passage

The first direct estimate of the rate at which geostrophic turbulence mixes tracers across the Antarctic Circumpolar Current is presented. The estimate is computed from the spreading of a tracer released upstream of Drake Passage as part of the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES). The meridional eddy diffusivity, a measure of the rate at which the area of the tracer spreads along an isopycnal across the Antarctic Circumpolar Current, is 710 ± 260 m[superscript 2] s[superscript −1] at 1500-m depth. The estimate is based on an extrapolation of the tracer-based diffusivity using output from numerical tracers released in a one-twentieth of a degree model simulation of the circulation and turbulence in the Drake Passage region. The model is shown to reproduce the observed spreading rate of the DIMES tracer and suggests that the meridional eddy diffusivity is weak in the upper kilometer of the water column with values below 500 m[superscript 2] s[superscript −1] and peaks at the steering level, near 2 km, where the eddy phase speed is equal to the mean flow speed. These vertical variations are not captured by ocean models presently used for climate studies, but they significantly affect the ventilation of different water masses.National Science Foundation (U.S.) (Award OCE-1233832)National Science Foundation (U.S.) (Award OCE-1232962)National Science Foundation (U.S.) (Award OCE-1048926

Determinants of impact : towards a better understanding of encounters with the arts

The article argues that current methods for assessing the impact of the arts are largely based on a fragmented and incomplete understanding of the cognitive, psychological and socio-cultural dynamics that govern the aesthetic experience. It postulates that a better grasp of the interaction between the individual and the work of art is the necessary foundation for a genuine understanding of how the arts can affect people. Through a critique of philosophical and empirical attempts to capture the main features of the aesthetic encounter, the article draws attention to the gaps in our current understanding of the responses to art. It proposes a classification and exploration of the factors—social, cultural and psychological—that contribute to shaping the aesthetic experience, thus determining the possibility of impact. The ‘determinants of impact’ identified are distinguished into three groups: those that are inherent to the individual who interacts with the artwork; those that are inherent to the artwork; and ‘environmental factors’, which are extrinsic to both the individual and the artwork. The article concludes that any meaningful attempt to assess the impact of the arts would need to take these ‘determinants of impact’ into account, in order to capture the multidimensional and subjective nature of the aesthetic experience

The Biological Records Centre: a pioneer of citizen science

People have been recording wildlife for centuries and the resulting datasets lead to important scientific research. The Biological Records Centre (BRC), established in 1964, is a national focus for terrestrial and freshwater species recording in the United Kingdom (UK). BRC works with the voluntary recording community (i.e. a mutualistic symbiosis) through support of national recording schemes (i.e. ‘citizen science’, but unlike most citizen science it is volunteer led) and adds value to the data through analysis and reporting. Biological recording represents a diverse range of activities, involving an estimated 70 000 people annually in the UK, from expert volunteers undertaking systematic monitoring to mass participation recording. It is an invaluable monitoring tool because the datasets are long term, have large geographic extent and are taxonomically diverse (85 taxonomic groups). It supports a diverse range of outputs, e.g. atlases showing national distributions (12 127 species from over 40 taxonomic groups) and quantified trends (1636 species). BRC pioneers the use of technology for data capture (online portals and smartphone apps) and verification (including automated verification) through customisable, inter-operable database systems to facilitate efficient data flow. We are confident that biological recording has a bright future with benefits for people, science, and nature