Tidal current power generation offers a prospect of renewable energy which is predictable, and has lower CO2 emissions than traditional energy generation sources. It also has the potential to fulfil a significant part of the energy requirements of the UK and the rest of the world. The horizontal axis tidal turbine (HATT) acts as one of the means to convert the kinetic energy available in seawater into mechanical energy, and this research explores the hydrodynamics and the Computational Fluid Analysis (CFD) based design study of this. The first aim of this research was to develop a novel HATT blade shape through bio-mimicking a curved caudal fin shape to produce improved power coefficient. A second aim was to compare two different turbulence modelling techniques to enable the comparison of the power coefficients with the standard HATT models in tidal turbine blade literature. There were two types of numerical approaches used: The SST model and a more complex mathematical model, LES-Smagorinsky, to perform steady state and transient CFD analysis respectively on the designed blades using ANSYS CFX. The initial default HATT was designed, parameterised, and represented as a straight blade following to the standard HATT literature. The airfoil centres of the straight blade are built around the centreline, where the centreline acts as the master, and a novel third order polynomial function was integrated on the centreline to model the Blue Marlin fish caudal fin look-alike target shape. This approach was used to model the further 3 sets of curved blade shapes in percentage wise chord lengths. The CFD analysis of the two dimensional airfoils was conducted using ANSYS CFX, and compared against the literature. A further comparative analysis was performed with different mesh settings, and using the SST turbulence model. The comparative analysis formed an integral part of the CFD analysis to define the boundary conditions and the verification of the three dimensional CFD based HATT design study. The design strategy to move the curved blade backwards to the straight blade was also developed. The results obtained from the three dimensional comparative CFD analysis show good agreement between the two different turbulence modelling techniques used also producing an improved curved blade shape achieving the power coefficient of 0.5073% for SST simulations and 0.5178% for the LES-Smagorinsky CFD simulations. It is seen that LES-Smagorinsky CFD results produce slightly greater efficiency than the SST simulations, but the computational overhead required is massive. Finally, after comparing the improved efficiency of the bio-mimicked curved blade with the standard HATT models in the literature, it can proved that bio-mimicking the caudal fin look-alike blade produces a higher power coefficient than the standard HATT blade.

Electromagnetic interference has become an important topic of research as more and more radios are getting integrated around us. One of the well-known techniques to lower the EMI from integrated circuits is to use spread spectrum techniques [1]. Traditionally, phase locked loops (PLL) have been utilized to generate SSC clocks. The PLL’s consist of a high power voltage controlled oscillator. This is undesirable in scenarios wherein the low power operation is required such as medical implants. In addition, the PLL loop band width impacts the intentional jitter. The current work introduces a non-PLL (Phase Locked Loops) modulator to enable low power operation. A chaotic modulation profile has been proposed to efficiently spread the frequency spectrum. Since there is no feedback loop, the input deterministic jitter is passed to the output. One of the proposed applications is biomedical telemetry. With the advent of more and more implantable and non-implantable devices for monitoring various physiological paramete s, the operating frequency band will become more and more clouded. Hence, there is a need to lower the EM signature of the transmitter. In addition, the transmitters need to be able to shift the operating frequency as per the MAC protocols [2] [3] to be able to operate in a channel with least interference. Also, the transmitter needs to be low power to conserve power. The interference path from the transmitter lies within the body and outside the body. The in body path to the adjacent transmitter depends upon the operating frequency and the distance from source [4]. The proposed architecture is able to integrate within DOSS (dynamic open spectrum sharing) protocol and is able to adjust the frequency of operation based on the communication from the MAC controller [5]. A system level model has been built to simulate an implanted transmitter and tested with a 10s sleep signal obtained through Physionet [6]. Another proposed application is generation of on die clocks. The ever increasing speed of clocks and higher data rates leads to increased radiated coupling. Traditionally PLL’s have been utilized for generating the dithered clock on die [7]. Multi clock domains from the same PLL clock source [8] require different amount of spreading. The proposed frequency modulator could be used in such scenarios to allow the clock domains to be independently controlled from the source PLL. The frequency modulator and a chaotic generator have been fabricated on AMS 6 metal layer 0.18µm technology. The frequency modulator was fabricated, characterized and measurements have been presented. The current work achieves a low power through circuit techniues by proposing a non-PLL based topology thus excluding the use of high power consuming VCO. Low emission is achieved using a variety of modulation profiles (periodic and chaotic) for spreading the bandwidth of the modulated spectrum. The current work was supported by European Research Council and Intel Research Labs through various grants.

Lead has long been a ubiquitous material within the energy industry, with use in the classic lead acid batteries (PbO2 and PbSO4), lead telluride thermoelectrics, and the emerging class of lead perovskite photovoltaics. Photoactive films of highly (110) orientated alpha-PbO have been synthesised through the electrochemical oxidation of Pb foil. Using a combination of electrochemical growth and x-ray diffraction the growth of these films has been understood as developing from beta-PbO through to highly (110) orientated alpha-PbO as the growth time progresses. This orientation has further been understood as only developing in an out-of-plane manner, with no preferred in-plane orientation observed. PbO2 films have been electroplated onto transparent conducting oxides. A thermal reduction method has been used to reduce these films to Pb3O4, beta-PbO and alpha-PbO. The thermal reduction of PbO2 has been studied in situ using high pressure photoelectron spectroscopy (HiPPES). HiPPES measurements of PbO2 have also yielded results suggesting oxygen vacancy healing in the material. Deep eutectic solvents (DES) have demonstrated excellent application to the recycling of lead-based energy materials. By dissolving the spent material in a DES, the toxic Pb can be selectively electrodeposited out. The technique shows a means for environmentally friendly recycling of lead acid batteries and for lead perovskite solar cells, overcoming one of the main prohibitive steps preventing their marketplace integration. The electronic structure of PbTe has been studied through a combination of hard x-ray photoelectron spectroscopy (HAXPES), soft x-ray photoelectron spectroscopy (SXPS) and density function theory calculations. The results have yielded a thorough understanding of the electronic structure of the PbTe valence band due to the high resolution of the photoelectron spectra and the calculated partial density of states. Using the varying probing depths of HAXPES and SXPS an upward surface band-bending of 0.26 eV has been observed, closely matching theoretical predictions.

The performance of solution processed solar cells such as organic bulk heterojunction (OPV) devices is limited by strong recombination. However, the mechanisms are still unclear. In this thesis, I develop a toolbox using steady-state spectroscopy measurements to explore the recombination mechanisms in a range of solution-processed solar cells. In the first results chapter, I use the reciprocity relation between light absorption and light emission to explore theoretical and practical performance limits for solar cells based on organic semiconductors and perovskites and compare the results with data for state-of-the-art photovoltaic cells made from GaAs, c-Si, and CIGS. In OPV systems, I show that the energetic losses due to the mismatch of the bandgap have been significantly reduced through optimisation of the donor polymer, but the non-radiative recombination losses remain the same and become the major barrier to higher performance. In the next two chapters, I use light intensity dependence of open-circuit voltage measurement (suns-VOC) and electroluminescence – injection current measurement (EL-J) to disentangle recombination mechanisms in OPV and perovskite cells, respectively. First, I identify the present of Shockley-Read-Hall recombination and surface recombination in OPV devices. I intentionally control the sample geometry to modulate the amount of surface recombination and demonstrate that surface recombination can significantly affect the device performance. In the following chapter, I analyse time dependent suns-VOC and EL-J measurements on perovskite cells with different architectures and pre-conditioning regimes used. I identify the changes in recombination mechanisms with delay time and pre-conditions. The effects of ion migration are used to interpret the results. In the final chapter, I apply luminescence spectroscopy techniques to investigate the degree of fullerene crystallinity in polymer:fullerene blends. Charge-transfer state emission is used to probe the onset of the crystallisation of fullerenes in an amorphous polymer. I relate the CT peak shift directly to the change in microstructure of a blend film.

Energy technology innovation is critical to transitioning to a sustainable energy system. The energy R&D expenditure worldwide has increased recently to combat the challenges of climate change, energy security and energy affordability. Emerging economies play an increasingly important role in energy technology innovation. As the largest energy producer and consumer, China’s energy technology innovation has an influential impact on the global energy system. China has emerged as the largest investor and user of renewable energy technology. The country accounts for 33% of the global wind power capacity, far ahead of the USA (17%) and Germany (11%). Among the world’s ten largest wind turbine producers, half of them are Chinese enterprises. China’s rapid development of wind technology attracted wide interest. The two key questions are a) how does China compare with leading countries in wind technology innovation, and b) what factors have been responsible for China’s successes and failures. This thesis draws upon innovation systems theory and innovation metrics to answer these two questions. It is found that China has caught up fast in inputs and certain outputs but significantly lags the leading countries in other aspects especially outcomes. The relative weakness in invention capability represents China’s most obvious bottlenecks. It demonstrates that the country’s system performance is highly related to the fulfilment of the system functions which are affected by the presence and capability of the structural elements. The thesis is offered as a comprehensive study on China’s wind energy innovation system. It presents useful lessons on facilitating the generation, adoption and diffusion of renewable energy technology as well as the challenges that need to be addressed to smooth the energy transition globally. The research makes methodological, empirical and theoretical contributions to the innovation systems literature.

Northern Powergrid (NPG) is an electrical distribution network operator in the UK servicing Yorkshire and the Northeast of England. Currently they produce long-term eight year forecasts for each substation on the network with an emphasis on an annual maximum demand (MD) figure. The current method used by NPG is thought to oversimplify the problem and does not give enough insight into changes in substation demand. In order to inform their current forecast, the novel CL-ANFIS method uses a combination of machine learning techniques for both forecasting and general insight to the drivers of demand. Also introduced here are novel techniques for determination of MD at NPG and methods for handling load transfer periods. In order to address a problem of this size, a twofold approach is taken. One is to address the drivers of demand such as weather, economic or demographic data sets through the use of statistics and machine learning techniques. The other is to address the long-term forecasting problem with a transparent technique that can aid in explaining the drivers of demand on any given substation. Techniques used include cluster analysis on demographic data sets in addition to ANFIS as a forecasting method. The results of the novel CL-ANFIS method are compared against the current NPG forecast and show how more insight into substation demand profiles can drive the decision-making process. This is done through a combination of using a tailored customer database for NPG and leveraging the information provided by the membership functions of ANFIS.

This thesis develops and implements computationally efficient and accurate wind farm coordinated control strategies increasing energy per area by mitigating wake losses. Simulations with data from the Brazos, Le Sole de Moulin Vieux (SMV) and Lillgrund wind farms show an increase of up to 8% in farm production and up to 6% in efficiency. A live field implementation of coordinated control strategies show that curtailing upstream turbine by up to 17% in full or near-full wake conditions can increase downstream turbine’s production by up to 11%. To the best knowledge of the author, this is the first practical implementation of Light Detection And Ranging (LiDAR) based coordinated control strategies in an operating wind farm. With coordinated control, upstream turbines are curtailed using coefficient of power or yaw offsets in such a way that the decrease in upstream turbines’ production is less than the increase in downstream turbines’ production resulting in net gain. This optimum curtailment is achieved with on-line coordinated control which requires an accurate and fast processing wind deficit model and an optimiser which achieves the desired results with high processing speed using minimum overheads. Performance evaluation of carefully selected optimisers was undertaken using an objective function developed for increasing farm production based on coordinated control. This evaluation concluded that Particle Swarm Optimisation (PSO) is the most suitable optimiser for on-line coordinated control due to its high processing speed, computational efficiency and solution quality. The standard Jensen model was used as a starting point for developing a fast processing and accurate wind deficit model referred to as the Turbulence Intensity based Jensen Model (TI-JM), taking wake added turbulence intensity and deep array effect into consideration. The TI-JM uses free-stream and wake-added turbulence intensities for predicting effective values of wake decay coefficients deep inside the farm. This model is validated using WindPRO and data from three wind farms case studies as benchmarks. A methodology for assessing the impact of wakes on farm production is developed. This methodology visualises wake effects (in 360°) by calculating power production using data from the wind farms (case-studies). The wake affected wind conditions are further analysed by calculating relative efficiency. The innovative coordinated control strategies are evaluated using data from the wind farms case studies and WindPRO as benchmarks. A live field implementation of coordinated control strategies demonstrated that the production of downstream turbines can be increased by curtailing upstream turbines. This field setup consisted of two operating wind turbines equipped with modern LiDAR. Analyses of the high frequency real time data were performed comparing field results with simulations. It was found that simulations are in good agreement (within a range of 1.5%) with field results.

This thesis describes the development of a charge-extraction layer for perovskite solar cells based on a network of polymer-functionalized single-walled carbon nanotubes (SWNTs). The starting point is the addition of SWNTs as additives to improve the charge trans- port characteristics of a solid-state hole-transporting material - 2,2,7,7-tetrakis-(N,N-di-p- methoxyphenylamine)9,9-spirobifluorene (spiro-OMeTAD). In a double-layer structure this is shown to perform comparably well to devices in which the charge transport of spiro-OMeTAD is enhanced by conventional doping. By means of photo-induced absorption spectroscopy, it could be shown that a significant fraction of photogenerated charges are transferred to the SWNTs. This finding demonstrates that the nanotubes act as charge selective contacts in their own right without requiring the presence of dedicated hole transporter material. In- stead, they can be embedded in a matrix of an inert polymer, which can be chosen according to characteristics related to stability rather than their electronic properties. Such an SWNT- PMMA composite structure is shown to outperform conventional hole-transporter systems during and after thermal stressing cycles. Finally, the issue of hysteresis is addressed. The additive 4-tert-butylpyridine (tBP) is shown to significantly improve the steady-state performance of devices with the SWNT-PMMA composite structure. In order to understand the mechanism and underlying interactions of the additive, the possible interaction interfaces are investigated one by one, leading to the conclusion that a direct interaction between tBP and the perovskite absorber must be responsible for the observed effect. The work in this thesis opens the avenue for SWNT-based hole transporter systems which provide a chemically stable and mechanically resilient charge-selective contact, and show particular promise for improving the overall stability of perovskite devices.

This thesis focuses on several approaches for the development of high charge/discharge rate lithium-ion batteries and electrochemical capacitors. The general background of lithium-ion batteries and electrochemical capacitors, and experimental techniques and methods are presented in the Chapter 1 and Chapter 2. The Chapter 3 in this thesis discusses the development of nanostructured cathodes for lithium-ion battery by introducing graphene or base washed graphene oxide as conductive additive. The carbon black is the most used conductivity enhancing additive in today’s lithium-ion batteries, nevertheless, makes it difficult for carbon black particles to form a wide-ranging “point-to-point” conductive network. Essentially, higher amounts of carbon black should be added in the electrodes to achieve percolation, leading to a lowering of the gravimetric capacity of the battery. Chapter 3 will detail the conditions used to investigate the optimal electrode composition containing different ratios and particle sizes of intercalation material and conductive additives (graphene and carbon black) in order to improve connectivity and conductivity leading to superior performance of a lithium-ion cathode material, Li(Ni1/3Mn1/3Co1/3)O2 at high charge/discharge rates. The second part of this work is focuses on electrochemical capacitors based on transition metal oxide. Manganese oxide (MnO2) is recognised as promising pseudocapacitive material, however poor ionic and electronic conductivity is the major limiting factor for its practical application. Chapter 4 discuss that through a straightforward and scalable synthesis it is possible to develop a bulk MnO2 material with randomly isolated layers. The synthesis conditions promote the formation of disordered material that allow ion transfer throughout the material that is not limited by solid state diffusion. Relatively low temperatures and inclusion of Na+ disrupt the formation of a highly crystalline material with a large domains size leading to a capacitance of ~200 F g-1 which was maintained at extremely high rates (1000 mV s-1 and 200 A g-1) for disordered Na0.35MnO2 nanosheets. In Chapter 5, an aqueous asymmetric electrochemical capacitor was assembled with Na0.35MnO2 pseudocapacitive electrode material as the positive electrode and activated carbon (AC) as the negative electrode. The optimisation charge balance between positive and negative electrodes, and modification of 0.5 M Na2SO4 aqueous electrolyte with addition of small amount of NaHCO3, is possible to suppress manganese oxide dissolution and hydrogen evolution, leading to long-term cycling at extended cell voltage of 2.4 V. In Chapter 6 following the promising results with Na0.35MnO2 within Chapter 4, other alkali metal intercalated MnO2 were investigated. Results show that the inclusion of the larger non-hydrated K+ (ionic radius = 1.52 Å) is key in the phase-controlled synthesis, where alkaline ion can serve as a template in the formation of layered structures of MnO2. Moreover, inclusion of small non-hydrated Li+ (ionic radius = 0.9 Å) was unable to prevent from forming α-MnO2 phase leading to relatively poor electrochemical performance.

The secure and economic operation of the future power system is facing major challenges. These challenges are driven by the increase of the penetration of converter connected and distributed renewable generation and electrified demand. In this thesis, a new smart energy management paradigm, i.e. a Virtual Energy Storage System (VESS), to address these challenges was studied. A VESS aggregates energy storage and flexible demand units into a single entity which performs similarly to a large-capacity conventional energy storage system. A VESS mitigates the uncertainty of the response from flexible demand through coordination with a minimum capacity of costly energy storage systems. Mathematical models of four components of a VESS were developed. Specifically, models of two types of energy storage, i.e. flywheel energy storage and battery energy storage, were developed. Thermodynamic models of two types of flexible demand units, i.e. domestic refrigerators and industrial bitumen tanks, were developed. These models were validated against the performance of similar equipment from the literature. Aggregated models, representing a population of units, for each of flywheels, batteries, refrigerators and bitumen tanks were developed. These aggregated models represent a randomly diversified population of units. These aggregated models were used to establish the frequency and the voltage control schemes of a VESS. A frequency control scheme of the VESS was designed. The control scheme provides low, high and continuous frequency response services to the system operator. The centralised control scheme coordinates models of refrigerators and units of the flywheel energy storage system. Following frequency deviations, the local frequency controllers of refrigerators changed their power consumption. The local frequency controllers of the flywheel units cover the power mismatch between the change in refrigerators power consumption and the required response from the VESS. The required response from the VESS is determined by a droop control. Case studies were conducted to evaluate the frequency control scheme by connecting the VESS to a simplified GB power system. Results showed that the response from the frequency control scheme of the VESS was similar to that of only flywheel energy storage. Based on an economic evaluation, the VESS is estimated to obtain approximately 50% higher return compared with the case II that only uses flywheel energy storage system. These revenues are based on providing frequency response services to the system operator. A voltage control scheme of the VESS was also designed. The control scheme facilitates the integration of distributed renewable energy generation by enhancing the voltage control of the distribution network. The control scheme coordinates models of bitumen tanks and battery energy storage system through different time delay settings of their voltage controllers. The local voltage controllers of bitumen tanks alter their power consumption following significant voltage deviations. If voltage violations continue, the distributed voltage controller of the battery energy storage system charges or discharges the battery using a droop setting obtained from voltage sensitivity factors. A case study was undertaken to assess the voltage control scheme by connecting the VESS, solar panels and wind farms to a UK Generic Distribution System (UKGDS) network. Results showed that the voltage control scheme made a significant improvement in the voltage and reduced tap changing actions of the on-load tap changing transformer and the voltage regulator by approximately 30 % compared with the base case where no VESS was used. Based on an economic evaluation, The VESS is an efficient solution to accommodate distributed renewable energy generation compared with network reinforcement.