This thesis concerns the design, implementation and operation of a hydrogen energy storage facility that has been added to an existing renewable energy system at West Beacon Farm, Leicestershire, UK. The hydrogen system consists of an electrolyser, a pressurised gas store and fuel cells. At times of surplus electrical supply, the electrolyser converts electrical energy into chemical energy in the form of hydrogen. This hydrogen is stored until there is a shortage of electrical energy to power the loads on the system, at which point it is reconverted back to electricity by the process of reverse-electrolysis that takes place within a fuel cell. The renewable energy sources, supplying electrical power to domestic and office loads at the site, are photovoltaic, wind and micro-hydroelectric. This work is being carried out through a project, conceived and overseen by the author, known as the Hydrogen and Renewables Integration (HARI) project. The purpose of this study is to demonstrate and gain experience in the integration of hydrogen energy storage with renewable energy systems and, most importantly, to develop software models that could be used for the design of future systems of this type in a range of applications. Effective models have been created and verified against the real-world operation of the system. These models have been largely completed, although some minor details remain unfinished as the are dependant upon studies linked to this one which are yet to be concluded. Subject to some fine tuning that this would entail, then, the models can be used to design a stand-alone, integrated hydrogen and renewable energy system, where only the load profile and weather conditions of a site are known. Significant practical experience has been gained through the design, installation and two years' of operation of the system. Many important insights have been obtained in relation to the integration of the system and the design and operation of its components.

Dans le contexte de la transition énergétique, les grandes technologies de stockage d’énergie à grande échelle sont considérées comme l’une des options qui peut faciliter une pénétration élevée des sources d’énergie renouvelables. La thèse est concentrée sur l’évaluation de la mise en œuvre le Power-to-Gas sur le marché énergétique roumain, qui a enregistré une croissance significative des énergies renouvelables et les enjeux auxquels devra faire face. Après avoir établi l’approche générale, les deux voies techniques du Power-to-Gas, l’Hydrogène et SNG, sont techniquement dimensionnés et économiquement évalués du point de vue des investisseurs dans deux scénarios temporels (2015 et 2030), afin d’évaluer la situation économique actuelle et les prix appliqués pour atteindre une rentabilité positive. Les résultats indiquent que des facteurs de grande capacité sont nécessaires afin de compenser les coûts d’investissement élevés, mais même dans cette situation un prix élevé est nécessaire pour la faisabilité économique, 68,1 Euro / MWh pour la voie Hydrogène et 112 Euro/MWh pour Power-to Gas SNG. Le marché d’équilibrage est également étudié comme un marché à haute valeur ajoutée dans le contexte français, avec des résultats indiquant une amélioration de 4% de la NPV, mais soulignant également les limites dans le cadre de l’analyse. Un avantage significatif, en termes d’impact GWP et utilisation de l’énergie fossile, a été identifié dans l’évaluation du cycle de vie de base de plusieurs scénarios d’alimentation au gaz, qui a également révélé l’importance de la source d’électricité utilisée pour la compression d’hydrogène. / In the energy transition context, large scale energy storage technologies are considered as one of the options that can facilitate a high penetration of renewable energy sources. The Thesis focuses on evaluating the implementation of Power-to-Gas in the Romanian energy market that recorded a significant growth in the share of renewables and will potentially face the related issues. After establishing a general approach, the two technical pathways of Power-to-Gas, Hydrogen and SNG, are technically sized and economically evaluated from an investor’s point of view in two temporal scenarios (2015 and 2030), in order to assess the current economic feasibility and the required price premiums that have to be put in place in order to reach a positive business case. Results indicate that high capacity factors are needed to compensate for the high capital costs, but even in this situation price premiums are required for economic feasibility, 68.1 Euro/MWh for the Hydrogen pathway and 112 Euro/MWh for Power-to-Gas SNG. The balancing market is also investigated as a high-value market in the French context, with results indicating a 4% improvement in NPV, but also highlighting the limitations of the proposed analysis framework. A significant benefit in terms of GWP impact and fossil energy use has been identified in. the basic life cycle assessment of multiple Power-to-Gas scenarios that also revealed the importance of the source of electricity used for hydrogen compression.

With the objectives of designing a solar cooling system with cold storage unit for the Iraqi climate, solar energy resources were assessed and methods were proposed to enhance harvesting the solar energy in the Iraqi climate. Where the results showed that adopting monthly average optimal tilt angles led to an increase in the amount of useful solar energy gained nearly 9%. A methodology of multi objective optimisation of solar absorption cooling system was then developed and demonstrated by applying it in a domestic application in Baghdad. Maximising the system performance in exergy, economic and environment were the objectives of the project. A decision-making tool was then implemented to select the most suitable design. The optimal proposed system has exergy efficiency of 56%, total cost rate of 4.19US$/hr, annual CO2 emission of 32199kg and payback period of 18.7years. After analysing the optimal configuration of the system, a cold thermal energy storage unit with the solar absorption cooling system was suggested in order to store the cold energy produced by the system at times when the solar energy is available (at daytime) and use (discharge) it at times when there is no solar energy available (at night). Next, a new control strategy was developed and applied in the system to make it more cost effective. Five scenarios were considered to manage the quantity of charging of the cold storage tank according to the splitting rate of the mass of the supplied chilled water by the chiller to the cold storage tank and the building. Finally, the chosen optimal system that uses an efficient controlled cold thermal energy storage, has exergy efficiency of 69.4%, total cost rate of 4.25US$/hr and total avoided annual CO2 emissions of 33.9% less than system without cold storage tank. Additionally, without any government incentive, the payback was recorded 9.3years, which was 50% less than the system without cold storage tank.

Les supercondensateurs ou Condensateurs à Double-Couche Electrochimique sont des systèmes novateurs et prometteurs pour le stockage de l'énergie. La modélisation par la simulation numérique est l'outil principalement utilisé dans cette thèse pour étudier les supercondensateurs. La modélisation est complémentaire aux expériences, et les deux méthodologies sont autant que possible mises en regard. Dans un premier temps, une méthode permettant de calculer la capacité des électrodes poreuses modélisées à l'équilibre a été mise au point, afin de mesurer les performances des systèmes étudiés. Puis, des cycles de charge et de décharge, processus dynamiques correspondant à des situations hors-équilibre, ont été réalisés, sur des systèmes modèles variés : différentes structures d'électrodes nanoporeuses de carbone, en contact avec des électrolytes purs ou avec solvant, soumis à des différences de potentiel plus ou moins élevées. À partir des données obtenues, le mécanisme de charge des supercondensateurs a été identifié et décomposé en plusieurs étapes. L'influence de la structure du matériau, du solvant et de la valeur du potentiel a été analysée. Enfin, des simulations à l'équilibre ont permis d'étudier le transport des espèces de l'électrolyte dans les milieux poreux particuliers que sont les électrodes de carbone. Ce travail propose par conséquent une étude complète et cohérente des processus dynamiques dans les supercondensateurs / Supercapacitors or Electrical Double Layer Capacitors (EDLC) are an innovative and promising technology in the field of energy storage. Modeling via computer simulation is the main technique used in this work to study supercapacitors. This methodology is complementary to experiments, and comparisons are made. Firstly, a methodology allowing the calculation of capacitance for the modeled systems with porous electrodes has been developed. This enabled performance to be measured for these complex systems. Secondly, cycles of charging and discharging (out-of-equilibrium processes) have been realised on various model systems composed of different structures of carbon electrodes, in contact with either pure electrolytes or solvated ionic liquids, submitted to raised or lowered potential differences. From the data obtained, the charging mechanism of supercapacitors has been elucidated and decomposed in different steps. Furthermore, the influence of the structure of the material, the solvation, and the value of the potential has been analysed. Finally, equilibrium simulations were performed. This enabled the study of electrolyte species transport inside the porous carbon electrodes media. This work consequently provides a complete and consistent study of the dynamic processes in supercapacitors.

Demand-side resources are taking an increasingly prominent role in providing essential grid services once provided by thermal power plants. This thesis considers the economic feasibility and environmental effects of integrating demand-side resources into the electric grid with consideration given to the diversity of market and environmental conditions that can affect their behavior. Chapter 2 explores the private economics and system-level carbon dioxide reduction when using demand response for spinning reserve. Steady end uses like lighting are more than twice as profitable as seasonal end uses because spinning reserve is needed year-round. Avoided carbon emission damages from using demand response instead of fossil fuel generation for spinning reserve are sufficient to justify incentives for demand response resources. Chapter 3 quantifies the system-level net emissions rate and private economics of behind-the-meter energy storage. Net emission rates are lower than marginal emission rates for power plants and in-line with estimates of net emission rates from grid-level storage. The economics are favorable for many buildings in regions with high demand charges like California and New York, even without subsidies. Future penetration into regions with average charges like Pennsylvania will depend greatly on installation cost reductions and wholesale prices for ancillary services. Chapter 4 outlines a novel econometric model to quantify potential revenues from energy storage that reduces demand charges. The model is based on a novel predictive metric that is derived from the building’s load profile. Normalized revenue estimates are independent of the power capacity of the battery holding other performance characteristics equal, which can be used to calculate the profit-maximizing storage size. Chapter 5 analyzes the economic feasibility of flow batteries in the commercial and industrial market. Flow batteries at a 4-hour duration must be less expensive on a dollar per installed kWh basis, often by 20-30%, to break even with shorter duration li-ion or lead-acid despite allowing for deeper depth of discharge and superior cycle life. These results are robust to assumptions of tariff rates, battery round-trip efficiencies, amount of solar generation and whether the battery can participate in the wholesale energy and ancillary services markets.

Master of Science / Department of Mechanical and Nuclear Engineering / Hitesh Bindra / Storing excess thermal energy in a storage media that can later be extracted during peak-load times is one of the better economical options for nuclear power in future. Thermal energy storage integration with light water-cooled and advanced nuclear power plants is analyzed to assess technical feasibility of different storage media options. Various choices are considered in this study; molten salts, synthetic heat transfer fluids, and packed beds of solid rocks or ceramics. In-depth quantitative assessment of these integration possibilities are then analyzed using exergy analysis and energy density models. The exergy efficiency of thermal energy storage systems is quantified based on second law thermodynamics. The packed bed of solid rocks is identified as one of the only options which can be integrated with upcoming small modular reactors. Directly storing thermal energy from saturated steam into packed bed of rocks is a very complex physical process due to phase transformation, two phase flow in irregular geometries and percolating irregular condensate flow. In order to examine the integrated physical aspects of this process, the energy transport during direct steam injection and condensation in the dry cold randomly packed bed of spherical alumina particles was experimentally and theoretically studied. This experimental setup ensures controlled condensation process without introducing significant changes in the thermal state or material characteristics of heat sink. Steam fronts at different flow rates were introduced in a cylindrical packed bed and thermal response of the media was observed. The governing heat transfer modes in the media are completely dependent upon the rate of steam injection into the system. A distinct differentiation between the effects of heat conduction and advection in the bed were observed with slower steam injection rates. A phenomenological semi-analytical model is developed for predicting quantitative thermal behavior of the packed bed and understanding physics. The semi-analytical model results are compared with the experimental data for the validation purposes. The steam condensation process in packed beds is very stable under all circumstances and there is no effect of flow fluctuations on thermal stratification in packed beds. With these experimental and analytical studies, it can be concluded that packed beds have potential for thermal storage applications with steam as heat transfer fluid. The stable stratification and condensation process in packed beds led to design of a novel passive safety heat removal system for advanced boiling water reactors.

The aerospace industry is currently looking at options for fulfilling the technological development targets set for the next aircraft generations. Conventional engines and aircraft architectures are now at a maturity level which makes the realisation of these targets extremely problematic. Radical solutions seem to be necessary and Electric Distributed Propulsion is the most promising concept for future aviation. Several studies showed that the viability of this novel concept depends on the implementation of a superconducting power network. The particularities of a superconducting power network are described in this study where novel components and new design conditions of these networks are highlighted. Simulink models to estimate the weight of fully superconducting machines have been developed in this research work producing a relatively conservative prediction model compared to the NASA figures which are the only reference available in the literature. A conceptual aircraft design architecture implementing a superconducting secondary electrical power system is also proposed. Depending on the size of the aircraft, and hence the electric load demand, the proposed superconducting architecture proved to be up to three times lighter than the current more electric configurations. The selection of such a configuration will also align with the general tendency towards a superconducting network for the proposed electric distributed propulsion concept. In addition, the hybrid nature of these configurations has also been explored and the potential enhanced role of energy storage mechanisms has been further investigated leading to almost weight neutral but far more flexible aircraft solutions. For the forecast timeframe battery technology seems the only viable choice in terms of energy storage options. The anticipated weight of the Lithium sulphur technology is the most promising for the proposed architectures and for the timeframe under investigation. The whole study is based on products and technologies which are expected to be available on the 2035 timeframe. However, future radical changes in energy storage technologies may be possible but the approach used in this study can be readily adapted to meet such changes.

The power sector needs to be decarbonised by 2050 to meet the global target for greenhouse gas emission reduction and prevent climate change. With fossil fuels expected to play a vital role in the future energy portfolio and high efficiency penalties related to mature CO2 capture technologies, this research aimed at evaluating the efficiency improvements and alternate operating modes of the coal-fired power plants (CFPP) retrofitted with post-combustion CO2 capture. To meet this aim, process models of the CFPPs, chilled ammonia process (CAP) and calcium looping (CaL) were developed in Aspen Plus® and benchmarked against data available in the literature. Also, the process model of chemical solvent scrubbing using monoethanolamine (MEA) was adapted from previous studies. Base-load analysis of the 580 MWel CFPP retrofits revealed that if novel CAP retrofit configurations were employed, in which a new auxiliary steam turbine was coupled with the boiler feedwater pump for extracted steam pressure control, the net efficiency penalty was 8.7–8.8% points. This was close to the 9.5% points in the MEA retrofit scenario. Conversely, CaL retrofit resulted in a net efficiency penalty of 6.7–7.9% points, depending on the fuel used in the calciner. Importantly, when the optimised supercritical CO2 cycle was used instead of the steam cycle for heat recovery, this figure was reduced to 5.8% points. Considering part-load operation of the 660 MWel CFPP and uncertainty in the process model inputs, the most probable net efficiency penalties of the CaL and MEA retrofits were 9.5% and 11.5% points, respectively. Importantly, in the CaL retrofit scenarios, the net power output was found to be around 40% higher than that of the CFPP without CO2 capture and double than that for the MEA retrofit scenario. Such performance of the CaL retrofit scenario led to higher profit than that of the 660 MWel CFPP without CO2 capture, especially if its inherent energy storage capability was utilised. Hence, this study revealed that CaL has the potential to significantly reduce the efficiency and economic penalties associated with mature CO2 capture technologies.

This research investigates the energy, financial and environmental performance of an innovative integrated gasification fuel cell combined cycle fuelled by municipal solid waste that includes hydrogen storage and electrolysis. The suitability for fuel cells to run on synthesis gas coming from the gasification of waste is determined by the sensitivity of the fuel cell to run on contaminated fuel. Out of the available fuel cell technologies solid oxide fuel cells (SOFCs), because of their ceramic construction and high operating temperatures, are best suited for syngas operation. Their high operating temperature ( > 650°C) and the presence of nickel at the anode means that it is possible to reform hydrocarbons to provide further hydrogen. A major contaminant to be considered in gasification systems is tar which can foul pipework and cause substantial performance losses to the plant. Experimental research on the effects of tar on a SOFC at varying concentrations and operating conditions show; that some carbon deposition serves to improve the performance of the fuel cell by reducing the ohmic resistance, and there is a tendency for the tar to reform which improves overall performance. These improvements are seen at moderate tar concentrations but at higher concentrations carbon deposition causes substantial performance degradation. Numerical simulations representing all aspects of the proposed system have been developed to understand the energy performance of the system as a whole as well as the financial and environmental benefits. Taking into account variations in the waste composition, and the wholesale electricity price the proposed system, scaled to process 100,000 tonnes of waste per year (40,000 removed for recycling), has a simple payback period of 7.2 years whilst providing CO2 savings of 13%. Over the year the proposed system will provide enough electricity to supply more than 23,000 homes and enough heat for more than 5,800 homes (supplying 25% of the electrically supplied homes).

The increasing use of electrical technologies within on-board (aircraft, road vehicle, train and ship) power systems is resulting in complex and highly dynamic networks in which energy storage devices have an important role to play, for example to resolve the instantaneous mismatch between load demand and power availability or to provide the flexibility to optimise overall performance. In this thesis, a multi-level controller for a super-capacitor based energy storage system (ESS) is designed, simulated, emulated and validated experimentally to show its effectiveness in smoothing load and managing state-of-charge of the energy storage system. This thesis first investigates the low level control of the dual-interleaved converter, particularly at light load where seven discontinuous conduction modes (DCMs) appear. A thorough analysis of these operating modes is given and validated by simulations and experiments. Based on the analysis, an inverse-model-based feed-forward current controller is implemented, offering a low level converter control interface which serves the high level supervisory controller within the energy storage system. Two supervisory control methods have been proposed in this thesis, both producing a super-capacitor current reference for the low level controller. The first supervisory control not only manages the energy within the ESS but also shields the primary power source from rapid load transients , which has been examined through an emulated ESS in the Intelligent Electrical Power Network Evaluation Facility (IEPNEF). A more advanced supervisory controller is then proposed which in addition to the benefits of the first control, regulates the rate-of-change in power that is drawn from the primary power source in the system. The proposed second control method is implemented within a real super-capacitor energy storage system in IEPNEF, with both simulation and experimental results successfully demonstrating and validating its operation.