15 research outputs found
Superconducting wireless power transfer for electric vehicles
Electric vehicles (EVs) are an important pillar for the transition towards a cleaner and more
sustainable future as renewable energy can penetrate into the transportation section and act as
energy storage to cope with the intermittent supply of such energy sources. EVs have recently
been significantly developed in terms of both performance and drive range. Various models are
already commercially available, and the number of EVs on roads increases rapidly. Rather than
being limited by physical cable connections, the wireless (inductive) link creates the opportunity
of dynamic charging – charging while driving. Once realised, EVs will no longer be limited by
their achievable range and the requirement for battery capacity will be greatly reduced. However,
wireless charging systems are limited in their transfer distance and power density. Such drawbacks
can be alleviated through high-temperature superconductors (HTS) and their increased current
carrying capacity, which can substitute conventionally used copper coils in the charging pads.
This thesis investigates the effectiveness of wireless power transfer (WPT) systems as a whole
and when HTS coils are used as well as HTS performance at operating frequencies commonly
used in WPT-systems. Initially, the fundamentals of superconductivity are outlined to give some
background on how such conductors can help tackle problems occurring in WPT-systems and how
their behaviour can be simulated. Subsequently, key technical components of wireless charging
are summarised and compared, such as compensation topologies, coil design and communication.
In addition, health and safety concerns regarding wireless charging are addressed, as well as their
relevant standards. Economically, the costs of a wide range of wireless charging systems has also
been summarised and compared.
To explore the benefits of WPT-system for EVs, a force-based vehicle model is coupled with an
extended battery model to simulate the impact of wireless charging on the state of charge of the
accumulator sub-system. In total, three different scenarios, i.e. urban, highway and combined
driving are presented. The trade-off between having a standalone charging option versus combined
dynamic (or on-road charging) and quasi-dynamic (stationary charging in a dynamic environment)
wireless charging is outlined and minimum system requirements, such as charging power levels
and road coverage, for unlimited range are established. Furthermore, the effects of external factors
such as ambient temperature, battery age and wireless transfer efficiency are investigated. It is
shown that employing combined charging at medium power levels is sufficient to achieve
unlimited range compared to high power requirements for standalone charging.
HTS coils show great potential to enhance the WPT-system performance with high current-carrying capability and extremely low losses under certain conditions. However, HTS coils exhibit
highly nonlinear loss characteristics, especially at high frequencies (above 1 kHz), which
negatively influence the overall system performance. To investigate the improvements, copper,
HTS and hybrid wireless charging systems in the frequency range of 11-85 kHz are experimentally
tested. Results are compared with finite element analysis (FEA) simulations, which have been
combined with electrical circuit models for performance analysis. The measurements and
modelling results show good agreement for the WPT-system and HTS charging systems have a
much higher transfer efficiency than copper at frequencies below 50 kHz. As the operating
frequency increases towards 100 kHz, the performance of HTS systems deteriorates and becomes
comparable to copper systems. Similar results are obtained from hybrid systems with a mixture of
HTS and copper coils, either as transmitting or receiving coils. Nevertheless, it has been
demonstrated that HTS significantly improves the transfer efficiency of wireless charging within
a certain range of frequencies.
The AC losses occurring in HTS coils, particularly transport current loss, magnetisation loss and
combined loss, at high frequencies are studied further. A multilayer 2D axisymmetric coil model
based on H-formulation is proposed and validated by experimental results as the HTS film layer
is inapplicable at such frequencies. Three of the most commonly employed coil configurations,
namely: double pancake, solenoid and circular spiral are examined. While spiral coils experience
the highest transport current loss, solenoid coils are subject to the highest magnetisation loss due
to the overall distribution of the turns. Furthermore, a transition frequency is defined for each coil
when losses in the copper layer exceed the HTS losses. It is much lower for coils due to the
interactions between the different turns compared to single HTS tapes. At higher frequencies, the
range of magnetic field densities, causing a shift where the highest losses occur, decreases until
losses in the copper stabilisers always dominate. In addition, case studies investigating the
suitability of HTS-WPT are proposed.
Lastly, methods to reduce AC losses of HTS coils are investigated with particular focus on flux
diverters, which have been used for low frequency superconducting applications but their
effectiveness at high frequencies is unexplored. Therefore, the impact of flux diverters on HTS
double pancake coils operating at high frequencies up to 85 kHz is researched. Various geometric
characteristics of the flux diverter are investigated such as air gap between diverter and coil, width
and thickness. An FEA-model was used to examine the coil and diverter losses at such frequencies
and different load factors between 0.1 and 0.8. It is demonstrated that flux diverters are a viable
option to reduce the coil losses even at high frequencies and the width of the coil has the biggest
impact on the loss reduction. In general, flux diverters are more suitable for applications using
high load factors. Lastly, the impact of the diverter in terms of magnetic field distribution above
the coil and overall loss distribution in the HTS coil was examined
Transition Metal Complexes with 1-Adamantoyl Hydrazones - Cytotoxic Copper(II) Complexes of Tri- and Tetradentate Pyridine Chelators Containing an Adamantane Ring System
Five pentacoordinate copper(II) complexes with 2-acetylpyridine or di(2-pyridyl) ketone 1-adamantoyl hydrazone ligands (Adpy and Addpy, respectively) of the formulae [CuCl2(Adpy)] (1), [Cu-2(-Cl)(2)(Adpy-H)(2)] (2), [Cu(NCS)(2)(Adpy)] (3), [Cu-2(-Cl)(2)(Addpy-H)(2)] (4), and [Cu-2(NCS)(2)(-Addpy-H)(2)] (5) were synthesized and characterized by spectral, electrochemical, and X-ray structural analysis. Flow cytometry and morphological analysis confirmed that the copper(II) complexes 2 and 5 induced accumulation of a sub-G1 phase population, and fluorescence microscopy indicated the presence of large cells in apoptosis. The interaction of the copper(II) complexes with calf thymus DNA (CT-DNA) was monitored by changes in their UV/Vis spectra. The observed intrinsic binding constants for 2 and 5 (K-b = 1.77x10(6) and 3.58x10(6) M-1, respectively) together with ethidium displacement fluorescence experiments indicate intercalative binding. Complexes 2 and 5 showed nuclease activity against pUC19 plasmid DNA