https://www.um.edu.mt/library/oar/handle/123456789/26979 Mon, 06 Apr 2026 07:36:57 GMT 2026-04-06T07:36:57Z https://www.um.edu.mt/library/oar/handle/123456789/31575 Title: Analysis of the operation and performance of a solar cooling system Abstract: Significant research is being carried out in the field of renewable energy to develop and improve current technology to reduce or eliminate the dependence on fossil fuels. Such developments include the use of solar cooling systems to provide process or space cooling in diverse industrial processes. A solar cooling system was funded through the Italia-Malta Interreg program. It consists of an ammonia-water vapour absorption chiller and evacuated tube collectors was installed at the Buskett Research centre for Viticulture and Oenology to provide chilled water for wine temperature control during fermentation. The solar collectors generate the required thermal energy for the chiller to operate. One of the objectives was to evaluate the performance and observe the operational characteristics of this solar powered cooling system. These were collected through extensive experimentation sessions both prior and during the fermentation period. Moreover, an extensive literature review was carried out on steady-state and transient modes of operation and its application across the wine industry to determine those factors that have a direct impact on the operational performance of such systems. From the review, it resulted that several configurations and control strategies can be applied to achieve the optimal performance for the various ambient conditions. During the first experimental runs, the solar cooling system could not operate in high solar radiation conditions. The evacuated tube collectors generated thermal energy beyond the required yield causing over-heating of the working fluid, which for this system is water. In this scenario, the system had to be switched off to allow the water to change phase back to liquid and the pressure to return to the nominal value. The solar collector arrays were significantly upgraded to improve the overall performance of the solar cooling system. The system was then tested rigorously across the summer months. Data measured during two distinct experimentation sessions is presented in this dissertation. In the initial runs, the system was unable to operate in high solar radiation conditions which impeded the wine fermentation process. After the experimentation, the system can operate uninterrupted while being remotely monitored, positively impacting the process. Description: M.SC.SUS.ENERGY Sun, 01 Jan 2017 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/31575 2017-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/28083 Title: Feasibility analysis of underwater pumped-hydro energy storage in Maltese waters Abstract: The dissertation focused on Underwater Pumped Hydro Storage (UPHS) Systems and their feasibility in the local scenario. In order to better understand such systems, an extensive literature review was carried out on energy storage technologies, namely batteries, flywheels, compressed air, underwater compressed air, thermal and pumped hydro storage. A comparison was carried out between a number of these storage types and it was found that Underwater Compressed Air Energy Storage (UWCAES) and PHS (which includes UPHS) were two leading technologies due to high power rating and a long discharge times. The objectives of this study were to : 1. Generate an analytical tool to analyse a UPH System at the local scenario and to determine the revenue and feasibility of the system ; 2. Obtain reliable data and cost estimates of componenets and parts to use in the system analysis for economic viability 3. Determine the revenues and feasibility of a UPHS system at the local level ; 4. Determine what conditions must be met in order to make such a system economically feasible Throughout this dissertation, the UPHS Systems that were considered for case studies were the MIT Energy Strage Spheres and Fraunhofer’s StEnSea Unit. These Units were described in detail and costs, expenses and the in-life cycle of a system were determined. A Microsoft Excel tool named the SubSea Analytical Tool was developed to work out the costings necessary to commission a System and to determine the profitability of such a System. The results showed that for the Systems presented, neither one was feasible to commission in a local scenario. The revenue generated after selling the energy stored as electricity was toolow compared to the capital and running costs. In the discussion, a sensitivity analysis was conducted to show he impact of modifying each variable with the Levelised System Profits over the System’s lifetime, and the critical cost-drivers were successfully identified. The cost drivers were identified to be the electricity price margin, concrete costs, pump-turbine costs and the semi-submergible barge costs. The electrical interface only had an impact with a low number of Units in a System. Note that the term “Unit” refers to either a StEnSea Unit or an Energy Storage Sphere. Cost-cutting ideas were generated and applied to both Systems, and once these improvements were applied, both Systems turned to be economically viable. The set of conditions to have a feasible System were successfully determined as part of the conclusions to this study. Description: M.SC.SUS.ENERGY Sun, 01 Jan 2017 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/28083 2017-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/28082 Title: Monitoring and analysing the performance of a shallow ground geothermal heat pump system for space conditioning of buildings Abstract: The aim of this dissertation is to monitor and analyse the performance of a shallow ground geothermal heat pump (GSHP) system. The GSHP system was installed at the premises of the Institute for Sustainable Energy situated in Marsaxlokk, Malta. The GSHP system is composed of horizontal ground heat exchangers (GHE) buried at 2m and 3m depths, connected to a reversible geothermal heat pump, which is connected to a fan coil unit system installed in a test room. An air source heat pump (ASHP) system installed in the same test room was also monitored and the heating and cooling performance of both the GSHP and ASHP systems were experimentally determined and compared based on the accumulated data. This dissertation is divided into six main chapters. In the first chapter a brief introduction of the overall aim and objective of this dissertation is given. Chapter 2 focuses on providing a description, summary and evaluation of the studies already conducted related to GSHP systems. From this chapter it was shown that parameters affecting the performance of a GSHP system included flow rate, depth of buried pipes, length of pipes and site location amongst others. In addition to this, upon comparing the performance of a GSHP system to an ASHP system, the values obtained in terms of COP were higher for the GSHP than the ASHP. Chapter 3 describes the design and installation of the GSHP system and also the type of experimental investigation that has been undertaken in order to analyse its performance. In Chapter 4, several equations related to the analysis of the performance of both the GSHP system and the AC unit were listed and described. Chapter 5 deals with analysing the performance of both the GSHP and ASHP systems by using the recorded data obtained from the calibrated equipment installed together with the equations stated in Chapter 4. In this chapter, a comparison between the results obtained for both systems was conducted and the results showed that the GSHP system obtained higher performance rating values than the ASHP system when operating in both heating and cooling modes. The last chapter of this dissertation, Chapter 6, contains a summary of all the results obtained alongside a brief conclusion which includes also some recommendations for future works as well as some areas for improvement. The first findings of this study showed that the coefficient of performance (COP) of the GSHP system reached 8.3 in the heating mode, while the energy efficiency ratio (EER) reached 5.9 in the cooling mode. On the other hand, the COP and EER achieved by the ASHP system achieved reached 3.14 and 3.33 respectively. These results show that the GSHP system can prove to be a potential alternative to the ASHP system, since the performance values obtained for the GSHP system are significantly higher than those obtained for the ASHP system in both operating modes. The ground temperature profile at 2 and 3 metres indicated that there is good thermal potential in order to operate efficiently the GSHP system in both operating modes. Description: M.SC.SUS.ENERGY Sun, 01 Jan 2017 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/28082 2017-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/28078 Title: Investigation of the technical aspects of a solar assisted reversible heat pump system for space conditioning Abstract: This study considers the potential of solar assisted heat pumps for a small island nation like Malta for energy savings and investigates the impact that such technology can have. For this purpose, testing was carried out to quantify the potential energy savings this renewable technology can introduce to the country, which could contribute to the country’s target of improving energy efficiency by 27% by 2020. This dissertation is divided into six chapters. Chapter 1 provides a background, the scope of the research and the approach taken. Chapter 2 gives a literature review dealing with aspects concerning the subject matter and Chapter 3 outlines the theoretical elements. Chapter 4 provides a description of the instruments used and the experimental setup. This is followed by an analysis of the results obtained and a discussion in Chapter 5. Finally, Chapter 6 delivers the conclusions that were drawn from this research. Results indicate that the integration of a solar collector for space heating and cooling is not viable for small-scale use. The ambient temperature and solar radiation were identified as the main influential factors for inconsistency throughout the experiments. This dissertation also compared the potential energy savings of solar water heaters to a hypothetical 30% energy savings of solar assisted heat pumps on a nationwide level. It concludes that if Malta is to meet the 2020 targets, solar water heaters should be given priority since the potential savings are greater with this technology. Description: M.SC.SUS.ENERGY Sun, 01 Jan 2017 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/28078 2017-01-01T00:00:00Z