21684 research outputs found
Sort by
Modelling and simulation of a multi-valve heat pump integrating a heat storage for flexible operating modes
Get PDFTo address the urgent need to reduce global warming, it is essential to transition to low emission technologies in the heating sector. In this context, heat pumps are expected to play a major role. The UK government has set ambitious targets for heat pump adoption, with air-source heat pumps seen as a promising alternative to gas boilers for individual households due to their affordability and flexibility. However, research shows two main challenges with air-source heat pumps that can significantly affect performance in a UK setting: lack of flexibility and high operating costs when supplying hot water at high temperatures; frosting issues in cold and humid conditions. These challenges could reduce the economic appeal of heat pumps compared to gas boilers. This raises the question: What modifications or improvements could be made to the heat pump cycle to address both the need for cost-efficient operation at a 60 °C supply temperature and effective defrosting in the UK climate, without making the system overly complex or costly, while still allowing for flexible operation?
This thesis addresses this question by establishing a theoretical foundation through a benchmark numerical study of a multi-valve heat pump concept with integrated heat storage for flexible operation. The study analyses this system’s potential to address these challenges and deliver efficient, cost-competitive performance in the UK. The flexible heat pump’s four operating modes and thermodynamic benefits are evaluated relative to a conventional heat pump cycle in different scenarios. Economic and environmental impacts are also assessed against an A-rated gas boiler and a conventional air-source heat pump water heater, forming a basis for future experimental validation, model improvements, and commercial applications.
The defrosting process is examined under ideal conditions, comparing the thermodynamic behaviour and performance of the flexible heat pump to that of a standard reverse cycle defrosting system. By using latent heat storage as the evaporating unit during defrosting, the flexible heat pump can effectively defrost the evaporator while maintaining continuous heating capacity, saving power, and achieving a COP increase from 8.9 % to 13.2 % at maximum improvement storage temperature, depending on refrigerant choice. Key parameters, including storage temperature and defrost duration, are examined in detail. An exergy analysis highlights the main sources of losses in the cycle, identifying the compressor and heat exchangers as major contributors due to the deviation from isentropic compression and temperature differentials. The latent heat storage also affects these losses during discharging/defrosting, especially if the temperature difference between the storage and the refrigerant is not minimised. System exergy efficiency is notably higher in discharging/defrosting mode than in heating/charging mode due to the lower compression ratio.
In addition to thermodynamic performance, the economic and environmental assessments highlight the flexible heat pump’s potential as a viable UK alternative to gas boilers and conventional air-source heat pumps. The system’s power-saving mode demonstrated a lower total annual cost rate than a conventional air-source heat pump water heater, with an average payback period of about four years. Additionally, it showed potential operating cost savings compared to an A-rated gas boiler. The Total Equivalent Warming Impact of the flexible heat pump was also lower than that of a conventional air-source heat pump, supporting its environmental benefits. With rising energy costs and the UK’s commitment to Net Zero Emissions, these findings suggest that the flexible heat pump system could be an economically attractive option for sustainable heating.
The thesis also explores a dedicated charging mode to store heat during periods when heating is not required, which could take advantage of off-peak electricity rates. Both latent and sensible heat storage configurations are evaluated, and results indicate that this mode still improves performance compared to a conventional heat pump cycle. Analyses of extended parameters, such as thermal storage losses and temperature variations in the water storage tank, provide further insights into how to increase cycle efficiency. A roadmap for selecting the best refrigerants across the flexible heat pump’s operating modes is also provided.
Overall, this thesis shows that the flexible heat pump with integrated heat storage has strong potential for residential applications in the UK and could play an important role in reducing carbon emissions in the heating sector. Further research is encouraged to support the development and deployment of practical flexible heat pump systems
Interactions of Wolbachia with insect-specific viruses and effects on arboviruses in Aedes mosquitoes
No full textAbstract not currently available
The free port risk: the consequences for art and cultural heritage in the long history of free ports established for economic stimulation
No full textAbstract not currently available
Odhrm Ruadh: Maraiche an-Iar is an-Ear Le Meòrachadh air an Eadar-theangachadh na Chois
Get PDFNo abstract available
Understanding parental challenges in the neonatal intensive care unit: psychological support and decision making
Get PDFAbstract available at each chapter
The role of IL15 in Angiotensin II-mediated cardiac remodelling
No full textAbstract not currently available
Towards fiscal justice: Adopting a socio-legal approach to explore the potential of and for human rights budgeting in Scotland
Get PDFThe Scottish Government has committed to addressing the ongoing accountability gap for human rights in Scotland by introducing new legislation to domestically enshrine a range of international human rights currently unrecognised and unprotected in national law. This includes economic, social, and cultural rights, which have historically been misconceived as merely programmatic or aspirational. This legislative move represents a significant advancement for Scotland, reaffirming its commitment to the rights articulated by the Universal Declaration of Human Rights. However, the true impact of this legislative change on the lives of people in Scotland will hinge not only on their legal entrenchment but also on the resources made available for their implementation. The realisation of economic, social, and cultural human rights has long been recognised as contingent upon the resources available to the state. Consequently, a state's public budget emerges as a crucial instrument in effectuating these rights. In recent years, the relationship between human rights and public budgets has garnered renewed attention from the international human rights community. Over the past decade, new contributions have emerged in literature and practice, emphasising the importance of human rights budgeting and budget analysis. This thesis leverages these developments to advocate for using human rights budgeting as a vital tool for assessing the progressive realisation of economic, social, and cultural rights and for shaping budgetary practices and processes in Scotland. The thesis adopts a socio-legal approach to explore the challenges to and potential for economic, social and cultural rights to begin shaping budgetary processes in Scotland. The thesis provides a deep dive into the potential of the minimum core doctrine to set national priorities and incorporates insights from practitioners in fiscal practices and human rights organisations. By integrating new empirical perspectives into the existing discourse on human rights budgeting, this thesis proposes a more pragmatic and actionable framework for Scotland. It argues for clearer, minimum core priorities to be set for fiscal decision-makers, longer-term planning through multi-year budgets, a focus upon rights outcomes over policy inputs and for a more progressive approach to resource mobilisation. Finally, the thesis concludes with thirty recommendations which aim to guide decision-making processes toward the development of human rights-compatible budgets, thereby facilitating the effective realisation of economic, social, and cultural rights within the Scottish context
Delineating the role of inflammatory CC chemokine receptors 1, 2, 3 and 5 in atherosclerosis
No full textAbstract not currently available
Severe infection in ANCA-associated vasculitis: Incidence, prognostic factors and prediction
Get PDFIntroduction
Individuals with ANCA-associated vasculitis (AAV) are at high risk of severe infections. Using prognosis research methodology, this thesis will explore the incidence of severe infection, examine glucocorticoid exposure as a prognostic marker for severe infection and will develop prognostic models to predict severe infection events: the occurrence of first severe infection after diagnosis and early mortality following a severe infection event. Subsequent chapters will examine Covid-19 in AAV patients including prognostic factors for severe disease and the impact of SARS-CoV-2 vaccination in AAV patients treated with rituximab.
Methods
Diverse datasets were utilised to address the thesis aims. Novel semantic web technology was deployed to federate multiple European AAV registries to determine severe infection incidence. Data linkage was used to develop a large AAV dataset using national Scottish routinely-collected health data for the severe infection prognostic marker and prognostic modelling studies. A binational cohort of AAV patients with Covid-19 was developed through the contribution of vasculitis clinicians throughout the UK and Ireland. SARS-CoV-2 vaccination data was derived from the AAV sub-group of the UK-wide multicentre multi-disease OCTAVE study of immunosuppressed individuals. For the prognostic modelling studies, modern prediction methodologies were applied.
Results
Severe infection incidence was high, especially in the first year after diagnosis. Glucocorticoid exposure thresholds above 10 mg daily all had a substantial positive association with severe infection. Multivariable models were developed with good predictive ability for both severe infection events and early mortality following severe infection. Prognostic factors for severe Covid-19 included immunosuppressive agents. The humoral immune response to SARS-CoV-2 vaccination was severely attenuated in AAV patients compared to controls.
Discussion
Through applying prognosis research methodology, this thesis quantified the incidence of severe infection, identified prognostic factors and developed prognostic models for severe infection in individuals with AAV. Prognostic factors relating to Covid-19 were determined
Data sources:
Access Repository Dashboard
Do you manage Open Research Online? Become a CORE Member to access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard! 👇