The first part is concerned with dynamic aggregated modelling of large offshore wind farms and their integration into power systems via VSC-HVDC links. The dynamic aggregated modelling of offshore wind farms including WT-DFIGs and WT-PMSGs are proposed to achieve effective representations of wind farms in terms of computational time and simulation accuracy for transient stability analysis. Modelling and control of VSC-HVDC systems for integration of offshore wind farms are investigated. Comparisons of two control schemes of rectifier-side converter are carried out to evaluate their dynamic performance for integration of these offshore wind farms in terms of transient stability. The second part is to address the advanced transmission systems with innovative HVDC configurations. Feasibility studies of updated schemes of monoplolar CSC-HVDC link with support of monopolar VSC-HVDC link as the hybrid bipolar CSC/I{VDC system is carried out to deal with two key issues of CSC-HVDC. Small-signal modelling of MTDC grids is investigated and parameter optimisation of PI controller of converters in MTDC grids is carried out using PSO method based on small-signal models of the system at multiple operating points to obtain optimised parameters of PI controllers to improve dynamic performance of MTDC grids at multiple operating points.

The work conducted in this thesis examines the potential for emissions of flame retardants (FRs) from a range of treated end-of-life materials during and following disposal. A series of standardised leaching experiments were developed and conducted to study FR leaching from a range of waste flame retarded products, including: textiles, EPS and XPS building insulation foams, cathode-ray tube plastics and polyurethane furniture foams (PUF). The leaching tests were conducted using a range of leaching fluids, with the view of simulating the characteristics of real landfill leachates. A number of different test parameters were examined, such as a variety of dissolved humic matter concentrations, landfill relevant pHs between 5.8 and 8.5, landfill relevant temperatures, the effect of agitation, contact durations and longer term cycles of periodic wetting and draining of waste. It is apparent from these experiments that despite the relatively hydrophobic physicochemical properties of brominated FRs (BFRs), they are able to leach from waste materials at substantial concentrations. Concentrations of ƩPBDEs (polybrominated diphenyl ethers) in the leachate from the leaching experiments in this study ranged from 14,000 – 200,000 ng L-1, while concentrations of ƩHBCDD (hexabromocyclododecane) ranged from 170 ng L-1 – 13,000 ng L-1 in textile leaching experiments and from 13,000 ng L-1 – 4,200,000 ng L-1 in building insulation foam experiments. BFR leaching appears to be a second order process, whereby a period of initially intense dissolution of more labile BFR is followed by a slower stage corresponding to external diffusion of the soluble residue in the material. Tris (chloroisopropyl) phosphate (TCIPP) is more readily soluble in water than the BFRs studied, and leaching of TCIPP from PUF appears to be a first order process. Concentrations of TCIPP in the leachate from the leaching experiments in this study ranged from 13 mg L-1 – 130 mg L-1. In serial batch leaching experiments, >95 % of TCIPP was depleted from the flexible PUF after the sixth batch (168 h total contact). Hence, leaching is potentially a very significant pathway for TCIPP emissions to the environment. A small survey of waste soft furnishings from a variety of UK domestic and office locations was also conducted, to help determine the total FR content entering the UK waste stream as a result of the disposal of soft furnishings. The predominant FR detected was TCIPP. Closed test chamber experiments investigating the effect of temperature on volatilisation of TCIPP from polyurethane foam were conducted. These experiments show volatilisation of TCIPP from PUF to increase exponentially with temperature and to constitute an additional potentially significant pathway for emissions from UK MSW landfills, with TCIPP emissions via volatilisation from landfilled PUF estimated to range between ~200 and ~3,800 tonnes yr-1.

The main aim of this thesis is to verify the suitability of waste animal fat, obtained from animal by-products in a process called rendering, as a fuel for internal combustion engines. This work is an attempt to provide guidance and minimal requirements for animal fat to be utilised as fuel. The properties of tallow were monitored on a weekly basis throughout a period of one year. Some properties, namely acidity, showed significant variability. Possible reasons causing variable and high acidity are given together with a proposal for an acidity removal method. The available laboratory facilities enabled the verification of changes in fat's viscosity, density, surface tension and lubricity in a range of temperatures. The impact of storage temperature on deterioration in tallow quality was investigated over a period of one month. The available emission control systems have been reviewed and a solution choice has been made, based on legal and economic criteria. A summary of two thousand hours operation of the 800 kW generating set using neat fat is provided. The renewable electricity generation subsidising system in the United Kingdom has been reviewed. A basic feasibility study for the installed generating set was prepared and the highest tallow price at which electricity generation is profitable was determined.

The cleaning of food-based soils is highly relevant in domestic and industrial environments due to the costs associated with these operations as well as the significant consumption of time, water, and energy. Understanding the relationship between chemical and mechanical forces required to clean a surface is a critical step towards optimizing these processes. A complex twophase polymerized grease was developed and characterized with respect to its morphology, component distribution, and chemical composition. A thorough evaluation and physicochemical characterization of the cleaning process of this complex soil from a hard substrate was performed at two different length scales. Results showed that surfactants are more effective at weakening the cohesive interactions within the soil matrix and less effective in removing the adhesive bonds at the soil-substrate interface. A statistical model for cleaning efficiency was developed which described cleaning as a function of chemical and mechanical contributions. The effect of the chemistry on hydration and final cleaning performance was investigated through a definitive model screening and correlated to the tribological forces involved in the process. The model was shown to be applicable to several industrially relevant surfactant systems and revealed that hydration is the main factor driving cleaning of this two-phase soil.

In the first part, an economic scheme to smooth short periodic and heavily fluctuating wave power is proposed by controlling the inherent large amount of inertial energy of nearby offshore wind turbine systems (WTSs). The smoothing principle is that these WTSs are controlled to absorb the fluctuations of the wave power or release power opposite to them. The control challenge is that two objectives have to be achieved simultaneously: the rotor speed of a WTS has to be controlled against smoothing requirement whilst controlled to follow changes of wind speed to achieve wind power capture close to the maximum. To resolve this issue, Integrated Compensation Control is developed by adding two supplementary terms into the original maximum power point tracking (MPPT) control. In the second part, a method for short-term wind power smoothing is proposed by controlling wind turbines inertial energy. To achieve this, the designed power reference of a WTS includes two components: one component can approximately recover the original power trajectory of the MPPT control and the other can compensate the fluctuations of the former. In the third part, a new scheme to isolate and suppress forced oscillations is proposed. It controls the inertial energy of wind farms to timely release or absorb power opposite to the forced oscillating power from perturbation areas. Thus, the forced oscillations are prevented from propagating to the rest of power grid - isolated and the oscillating power in the disturbed areas is also reduced - suppressed.

This thesis is an investigation of different strategies for efficient development and optimization of radial-inflow turbines (RIT) for small-scale ORC systems. A novel methodology based on mean-line modelling, multi-level optimization and experimental study was proposed and validated for a small-scale compressed air RIT. Extending the proposed approach to organic fluids necessitated the use of real-gas equations. Deficiencies of constant turbine efficiency assumption that was commonly used in the literature were highlighted. A novel approach for integrated modelling of organic RIT with ORC coupled with genetic algorithm optimization technique was developed to alleviate the errors during fluid selection and cycle analysis and also optimize the ORC performance. A novel dual-stage transonic RIT was developed to further improve the ORC performance. The efficiency of such turbine was improved further using 3-D CFD optimization technique. Such optimization proved to be very efficient as it substantially improved the turbine efficiency of both stages by about 10%. CFD results for the optimized dual-stage turbine at design point showed the turbine efficiency of 87.12% and ORC thermal efficiency of 13.19%. Such results were considerably higher than the reported values in the literature and highlighted the effectiveness of the combined mean-line and CFD optimizations developed in thesis.

With increasing concern on the dwindling of the fossil fuel reserve and climate change, more and more effort has been focused on seeking green fuel to replace fossil fuel and mitigating the emissions of greenhouse gas (GHG). Biodiesel has attracted much attention for its sustainability, lower emissions of HC, PM and CO, and the diverse feedstock. In this study, diesel/diesel-like fuels were experimentally studied in terms of spray and combustion characteristics.

The atmospheric corrosion of 304L and 3 16L austenitic stainless steels was investigated in conditions relevant to the storage of intermediate level nuclear waste (I L W). Thin electrolyte films were created via automated droplet deposition, allowing multiple tests to be conducted in parallel. In-situ monitoring of droplet arrays on stainless steel samples was conducted with the use of a flat-bed document scanner, allowing large-scale, automated monitoring of corrosion processes. The initiation time for individual corrosion processes was established, showing that corrosion was slower to initiate under less aggressive conditions, and allowing 'true corrosion site lifetimes to be recorded, and compared with their depths. The presence of precipitated species within an electrolyte film was shown to affect the corrosion processes within that film. Both NaCl precipitates and glass shards acted as barriers to ion transport. This affected both the propagation of corrosion, and the electrochemical potential within the droplets; a higher precipitate content decreased the average corrosion depth and the extent of corrosion. The presence of nitrate and sulphate salts, both known corrosion inhibitors in full- immersion conditions, was shown to inhibit atmospheric corrosion when the inhibitor:chloride ratio was above a certain value. This was independent of the absolute amounts of salts, but dependent on the exposure humidity of the test.

Exposure to air pollution can cause adverse health effects, may also adversely affect the central nervous system and affect cognitive performance. Epidemiological studies depend on central site monitors as surrogates to assess personal exposure to air pollution, which can be inaccurate because they do not assess personal exposure in a variety of activities and microenvironments. This thesis aims to assess the level of misclassification in data from central site monitors by using portable modern sensors with high temporal resolution to characterize personal inhaled doses of BC, PM2.5, and UFP, and compare the measurements with surrogate exposure metrics. It also seeks to identify contributing activities and sources associated with the highest concentrations of the three pollutants, and to determine the contribution of these activities and microenvironments to personal exposure, and to study the impact of short-term exposure to air pollution on cognitive function. The first finding is that central site monitors are not a good surrogate for personal exposure. Secondly, travelling in vehicles is linked to the highest concentrations of the three pollutants, while other outdoors activities and outdoors commuting are linked to the highest concentrations of BC and PM2.5, cooking is linked to the highest concentrations of UFP, and activities and time spent indoors are the highest contributors to personal exposure. Thirdly, the results provide strong evidence that short-term exposure to PM2.5 from candle burning and commuting has an adverse effect on cognitive performance.

Using carbon adsorbents is the most common method of removing waste organics from water. However, the question remains of what to do with the carbon after adsorption. Landfill or incineration come with the obvious environmental consequences, and thermal regeneration is energetically costly and can be wasteful. The wastewater management company Arvia have developed a process for using electrochemical regeneration as an alternative. This thesis has examined that process in detail, in particular the role of the specific granular activated carbon used (Nyex). Nyex was characterised using a range of microscopic and spectroscopic methods. It is a highly crystalline graphite material which has been intercalated with bisulphate ions and water. It has an accessible surface area of 2.04 m2/g and a classic platy morphology with oxygen surface functionality. Additionally, the intercalation process has not changed the inter-layer distance. It is known that graphite intercalation compounds can expand upon thermal treatment. Upon heating using either an oven or a domestic microwave, Nyex expanded rapidly, resulting in an expanded carbon with a very typical vermiform morphology. The maximum expansion volume recorded for Nyex was 394 mL g 1, for microwave expanded Nyex. Surface area analysis confirmed that this volume expansion had not introduced porosity into the structure. The structure was damaged by the expansion but the overall number of defects has decreased. Analytical electrochemistry has been carried out, using Nyex as a working electrode and four test materials. Phenol can be irreversibly oxidised at a Nyex working electrode, and the build-up of breakdown products on the surface can be prevented by the application of 1.85 V for 7 s between each cyclic voltammogram. The increased surface area of expanded Nyex led currents to flow at an order of magnitude higher (approximately 40 µA compared to 5 µA for unexpanded Nyex) meaning more phenol could be oxidised at the same potentials. Humic acid and hydroquinone both showed no electrochemical activity at Nyex. Additionally, repeated cycling of potentials in hydroquinone led to the build-up of carbonaceous material on the surface of the electrode which passivated it. The industry provided test material, Tellus oil, passivated both Nyex and platinum electrodes. Two extraction methods to analyse the quantity of oil left on the Nyex after the Arvia process were developed. Using supercritical CO2 (scCO2) an extraction efficiency of 63% was achieved using 1 hour of extraction. Using acetone extraction, efficiencies in the region of 80 - 90% could be achieved in 10 min. The scCO2 extraction was complex, and required specialist equipment and training. In contrast the acetone extraction was simple and gave more reproducible results. Samples provided by Arvia from their pilot plant trial were extracted using the acetone extraction method. The concentration of oil on the samples was approximately 50 wt.% and did not decrease after 1100 hours of regeneration. A trial was run at Nottingham using 25 wt.% of oil which also did not decrease after 8 hours of regeneration. In summary, the combination of analytical electrochemistry and solvent extraction has shown Nyex is able to absorb up to 50 wt.% of oil from water, but the Arvia process does not destroy complex oily wastes. It is effective at oxidising phenol from water, with cycles of regeneration ensuring the Nyex surface is not passivated by the build-up of breakdown products. Nyex expanded in either the microwave or an oven is capable of oxidising much higher quantities of phenol because of its higher surface area.