The impact of refrigeration systems on the environment can be reduced by the use of alternative reffigerants which are less harmful to the atmosphere and the optimisation of systems and control strategies to deliver increased levels of energy efficiency. Mathematical modelling offers the opportunity to test the performance of systems under different operating conditions and with alternative refrigerants. Dynamic models allow comparison of both transient and steady-state behaviour and this is of particular importance for liquid chillers, since these systems can operate under transient conditions for long periods. This thesis details the development of a general dynamic model for the simulation of liquid chillers. Mathematical models of the reciprocating compressor, expansion valve, evaporator and condenser are presented. The models are integrated to form the overall system model by passing conditions from one component to another. A series of steady-state and transient experimental tests were carried out on a liquid chiller and the model was used to simulate these tests. Validation was carried out by comparison of these measured results to those predicted by the simulation for both the steady-state and transient tests. Once validated, the model was used to investigate the steady-state and dynamic performance of liquid chillers operating with various refrigerants. The effect of the mass of the system refrigerant charge was examined for a number of refrigerants. The steady-state performance for a range of evaporator and condenser coolant temperatures was also investigated. Finally, the effect of different system refrigerants on start-up transients was examined and the losses in cooling capacity due to cycling quantified. The effect of the expansion valve's initial superheat spring setting on the dynamic response and transient losses was also investigated.

Climate change is emerging as a significant challenge in terms of the response needed to mitigate or adapt to the predicted global changes. Severe impacts due to rising sea-level, seasonal shifts, increased frequency and intensity of extreme weather events such as storms, floods or droughts have become accepted by the scientific community as a real and present threat to civilisation. The most significant impacts are expected in the Arctic, the Asian mega-deltas, Small Island Developing States (SIDS) and sub-Saharan Africa (IPCC 2007). There are two approaches to global climate change either mitigation or adaptation. This dissertation aims to provide the initial design concepts for a system to mitigate methane, a significant Greenhouse Gas (GHG), emitted from coalmines by ventilation air circulated through the underground workings. The VamTurBurner©, a Ventilation Air Methane (VAM) gas turbine based methane burning system, is proposed as a method of extracting the thermal energy from the VAM. A key aspect of the problem responsible for the difficulty in extracting the energy from VAM is the low concentration of methane in the high volume ventilation airflow. This approach recasts the concepts of combustion dynamics of a premixed fuel flow to that expected for VAM to ascertain the conditions conducive to combustion or oxidation of the methane in the ventilation air. A numerical model using Large Eddy Simulation (LES) to study the combustion dynamics revealed that the temperature of the incoming ventilation air is a key variable related to the concentration of the VAM. Computational Fluid Dynamics modeling was used to study the design features needed to engineer a system capable of providing the required temperature of the incoming ventilation air. Applications for the available thermal energy are discussed in terms of the potential to generate electricity with steam turbines, provide space heating, produce hot water for many uses, and use the heat for industrial drying or as desired. The efficiency of the energy system is enhanced when the output from the amount of natural gas or electricity purchased is compared to the output enhanced by the addition of methane, considered as free. The VamTurBurner© concept, as described in this dissertation, appears to be a viable method of mitigating atmospheric methane in the pursuit greenhouse gas reduction.

No description available.

The Royal Botanic Gardens (RGB) is used as an umbrella name for the institution that runs Kew and Wakehurst Place gardens in Sussex The RBG has a large number of glasshouses at Kew and Wakehurst sites that consume lots of heating energy which is a major concern and the group is looking for an alternative heating system that will be more efficient and sustainable to save energy, cost and reduce CO2 emissions. Glasshouse due to greenhouse effect trap solar energy in the space with the slightest solar gains but the energy trapped in the space most often is vented through the roof wasted to keep the space temperature to the required level. An environmental measurement was carried out in twenty one zones of the glasshouse to establish the temperature and humidity profiles in the zones for at least three weeks. The investigation established that large amount of heat energy is vented to the atmosphere wasted and therefore need a heating system that could absorb and store the waste thermal energy. Phase change material (PCM) thermal energy storage technique was selected to be the best options compared to the others. It has been established that active and passive solar systems could provide enough thermal energy to meet the glasshouse heating requirements. PCM filled heating pipes will be installed to absorb the heat energy trapped in the glasshouse and use it when needed. The research analysis established that 204 MWh of the trapped energy wasted could be saved. The space temperature of the glasshouse could be maintained through melting and freezing of the PCM filled in the heating pipes. The site CHP waste heat could be useful. The research results have shown that nearly zero CO2 emission heating system could be achieved and the project is technically, economically and environmentally viable.

Ongoing modification and change is core to how domestic and built environments function. Thus occupants domestication and development of home heating practices around low-carbon technologies is likely to exceed what building engineering sciences have the ability to plan ahead for. Yet, environmental policies and low -carbon industry approaches to sustainable energy consumption are characterised by a high degree of technological determinism. Disciplinary approaches to sustainable energy consumption tend to separate home heating into stable, routine interaction with control points, environmental factors and socio-demographic drivers. Framing low-carbon technical change in isolation from domestic environments often leads to a gap between intended and actual use of technologies. By focusing on TRVs (thermostatic radiators valve) and radiators, this thesis takes an interdisciplinary turn to jointly examine the social and environmental elements of households energy use. A turn to sensory ethnography and practice-place relationships offers a way to better understand how people use energy for space heating in relation to the buildings they live in and how improvisatory uses of technologies emerge from flows of material, domestic, sensory and physical contingencies of the home. Combining home video tours with building energy monitoring in eight homes, the thesis demonstrates that home heating is a place-event of the home because heating systems and energy consumption are woven into the fabric of everyday life. Environmental elements show that the social and technical are inseparable in energy used for space heating and individual elements imply that the domestication of technologies is highly unpredictable. The thesis synthesises findings into a taxonomy table of irregular radiator and TRV use. On the one hand, irregularities indicate that improvisatory uses of technologies are productive sources of sustainable change because they can be potential sites for co-design. On the other hand, the interwoven character of the social and technical in households energy use critically challenges how environmental policy, low-carbon industry and disciplinary approaches frame intervention into sustainable energy consumption. The thesis argues for the value of logic of intervention and sustainable change that is collaborative, system-focused and gradually uncovers interrelationships.

This thesis presents the design and implementation of control strategies for building energy management systems (BEMS). The controllers considered include the multi PI-loop controllers, state-space designs, constrained input and output MIMO adaptive controllers, fuzzy logic solutions and genetic algorithm techniques. The control performances of the designs developed using the various methods based on aspects such as regulation errors squared, energy consumptions and the settling periods are investigated for different designs. The aim of the control strategy is to regulate the room temperature and the humidity to required comfort levels. In this study the building system under study is a 3 input/ 2 output system subject to external disturbances/effects. The three inputs are heating, cooling and humidification, and the 2 outputs are room air temperature and relative humidity. The external disturbances consist of climatic effects and other stochastic influences. The study is carried out within a simulation environment using the mathematical model of the test room at Loughborough University and the designed control solutions are verified through experimental trials using the full-scale BMS facility at the University of Bradford.

Bei einem thermischen Energieversorgungssystem, insbesondere einer Warmwasserheizungsanlage, spielen die in Wärmeträgermedium (Wasser) gelösten Gase (Sauerstoff und Stickstoff) für einen einwandfreien Betreib eine große Rolle, weil einerseits der im Wasser gelöste Sauerstoff zu einer Korrosionsreaktion an metallischen Anlagenbauteilen führt, was wiederum eine Reihe von negativen Konsequenzen, wie Verschleiß der Bauteile, Verstopfung der Rohrleitungen oder Durchrostung, hat. Andererseits kann der im Wasser gelöste Stickstoff aufgrund seiner reaktionsträgen Eigenschaft zu einer Gasblasenbildung führen, die wiederum eine Zirkulationsstörung im Wasserkreislauf bzw. eine Beeinträchtigung der Wärmeversorgung der Heizkörper bewirkt. Die Folgen dieser Systemstörungen sind hohe Wartungs- und Reparaturkosten sowie Reklamationen bei Planern, Anlagenherstellern und Kunden. Erkennt man die Ursachen für das Vorhandensein der Gase in der Heizungsanlage, so können Gegenmaßnahmen rechtzeitig ergriffen werden. Dadurch kann das Problem zum Teil behoben oder zumindest das Schadensausmaß begrenzt werden. Ziel dieser Arbeit ist es, das Gasproblem aufgrund der Gaspermeation in Heizungsanlagen quantitativ zu beurteilen und anschließend anhand der daraus gewonnenen Erkenntnisse mögliche Lösungsansätze zur Reduzierung bzw. Beseitigung des Gasproblems vorzuschlagen.

L'efficacité énergétique du bâtiment occupe une place importante dans les projets de construction. La façade, intermédiaire entre l'environnement et l'intérieur, joue un rôle clé pour déterminer les performances énergétiques du bâtiment. Les systèmes de fenestration complexes sont généralement utilisés pour améliorer son efficacité. L'étude des performances de la façade inclut généralement la consommation d'énergie, l'éclairage naturel et les aspects de confort visuel et thermique. Les efforts récents s'orientent vers l'utilisation de modèles intelligents tels que le Building Information Modeling. CFS pourraient être facilement comparées dans la phase de conception du bâtiment afin d'optimiser ses performances. Nous présentons une méthodologie pour transformer le modèle architectural du BIM en modèle énergétique ainsi que des modèles optique et thermique du CFS compatibles avec le BIM. Ces modèles sont validés par une comparaison avec des données expérimentales et les normes actuelles. / The energy efficiency of the building occupies an important place in construction projects. The facade plays a key role in determining the performance of the building. Complex fenestration systems (CFS) are therefore generally used to improve its efficiency. The facade's performance evaluation usually includes energy consumption, natural lighting, visual and thermal comfort aspects in order to choose the optimal CFS. Recent efforts have focused on using rich models such as Building Information Modeling (BIM). These models provide an opportunity for automation and cost savings. Several CFS models could easily be compared to optimize the building's performance. In this thesis, we present a methodology to transform the architectural model of the BIM into a Building Energy Model compatible with several simulation software. We also present optical and thermal models compatible with BIM. These models are validated by comparison with experimental data and current standards.

Les systèmes de stockage de chaleur par sorption (SSCS) ouvrent de nouvelles perspectives dans l'exploitation de l'énergie solaire pour le chauffage des bâtiments résidentiels. En effet, ces systèmes sont très prometteurs dans la mesure où ils permettent un stockage de chaleur sur de longues périodes (le stockage est réalisé sous forme de potentiel chimique) et offrent des densités énergétiques importantes (jusqu'à 230 kWh/m3 de matériau en moyenne) en comparaison aux systèmes classiques comme le stockage par chaleur sensible (qui, pour le cas de l'eau, dispose d'une densité énergétique moyenne d'environ 81 kWh/m3 de matériau pour une variation de 70°C) et le stockage par chaleur latente (qui atteint des densités énergétiques de 90 kWh/m3 de matériau).La présente thèse vise à étudier les performances d'un système de stockage de chaleur par sorption à base de zéolithe 13X intégré à un bâtiment type basse consommation. Des modèles mathématiques de transferts couplés de masse et de chaleur des différents composants du système sont développés et validés par le biais de l'expérimentation. La simulation numérique dynamique, comme outil de dimensionnement, permet, à partir des résultats d'analyses de sensibilité paramétrique sur les différents composants du système, l'étude de son fonctionnement et les critères de sa faisabilité. / Sorption heat storage systems (SHSS) open new perspectives for solar heating of residential buildings. These systems allow long term heat storage (storage is done in the form of chemical potential) and offer high energy densities (up to 230 kWh/m3 of material on average) compared to conventional heat storage systems such as sensible heat storage (which, for the case of water, has an average energy density of approximately 81 kWh/m3 of material for a temperature change of 70 °C) and latent heat storage (nearly reaching energy densities of 90 kWh/m3 of material on average).This thesis aims to study the performance of a sorption solar heat storage system on zeolite 13X, integrated to low-energy building. Mathematical models of coupled heat and mass transfer of various components of the system are developed and validated through experimentation. Numerical dynamic simulations allow to study the functioning of the SHSS in specific conditions, and its design with the results from the parametric sensitivity analysis on its components.

The UK government’s Carbon Plan-2011 aims for 80% carbon emission reduction by 2050, and the 2009 UK National Renewable Energy Action Plan has set a target of delivering 15% of total energy demand by renewable energy sources by 2020. Ground Source Heat Pump (GSHP) systems can play a critical role in reaching these goals within the building sector. Achieving such benefits relies on proper design, integration, installation, commissioning, and operation of these systems. This work seeks to provide evidence to improve the practices in design, installation and operations of large GSHP systems. This evidence has been based on collection and analysis of data from an operational large-scale GSHP system providing heating and cooling to a university building. The data set is of significance in that it is collected from a large-scale system incorporating fifty-six borehole heat exchangers and four heat pumps. The data has been collected at high frequency since the start of operation and for a period of three years. The borehole heat exchanger data is intended to form a reference data set for use by other workers in model validation studies. The ground thermal properties at the site have been estimated using a novel combination of numerical model and parameter estimation methods. The utility of the reference data set has been demonstrated through application in a validation study of a numerical borehole heat exchanger model. The system heat balances and power consumption data have firstly been analysed to derive a range of performance metrics such as Seasonal Performance Factors. Analysis has been carried out at the system and individual heat pump level. Annual performance has been found satisfactory overall. A series of analyses have been carried out to investigate the roles of circulating pump energy, control system operation and dynamic behaviour. Monitoring data from one of the heat pumps has also been analysed in further detail to make comparisons with manufacturer’s steady-state performance data and with consideration to variations in fluid properties. Some modest degradation from stated performance has been identified. The most significant operational factors accounting for degradation of overall system performance have been excessive pump energy demands and short cycling behaviour. Some faults in operation of the system during the monitoring period have also been identified. A series of recommendations are made as to ways to improve the design and operation of large-scale GSHP systems based on this evidence. These recommendations are chiefly concerned with better design for part-load operation, reduction in pump energy demands and more robust control systems.