/library/oar/handle/123456789/94057 2025-11-08T20:26:44Z /library/oar/handle/123456789/94316 Title: Thermal analysis of cisterns/wells for air conditioning and heat pump Abstract: The ever-increasing price of energy is driving improvements in the efficiency of many systems. Air-conditioning is one of the major sources of energy consumption in buildings. Several countries utilize the stability of ground temperature to improve the efficiency of air-conditioning systems. This idea can be transferred to using well water to exchange heat with the air-conditioning system. The success of such system depends on the thermal conductivity of the surrounding rock which is needed to extract or supply heat to the water. A numerical model was developed to find the thermal conductivity of a well, constructed from concrete bricks in an excavated pit in limestone rock. The model uses the energy change in water as the input for the numerical model. The same model was used to find the thermal conductivity by imposing the water temperature on the surface nodes. To validate the results a three-dimensional computational model was also developed. The results of these models were compared to analytical solutions available in textbooks for semi-infinite solids with different boundary conditions. The thermal conductivity of the well in consideration was found to be 1.4 W/mK when utilizing the numerical model. For the three-dimensional computation model, the thermal conductivity was found to be 2 W/mK when assuming an energy input caused by the change in water temperature, or 1.05 W/mK when the water temperature was imposed on the surface nodes. The results are comparable to handbook values for limestone and concrete. The analytical solution for exponential heat flux for a semi-infinite solid verified the numerical model. It was noted however, that the assumption of having linear flow of heat or one-dimensional flow of heat is not accurate since it overestimates the thermal conductivity of rock for the energy method. A work around to this problem was to assume an ever-increasing heat transfer area with increasing depth from the surface nodes. This improved the result considerably. Using the thermal conductivity found in this dissertation an example scenario was created to analyse if using well water as the source or sink of heat is beneficial when compared to using air. It was assumed that an air-conditioner of peak load 2.5 kW operated for 6 hours a day dumps heat into a well having a capacity of 45 m3 . In this scenario the improvement is minimal over the summer period, given the rate at which water temperature increases and does not justify the added capital cost of the system. The thermal conductivity of rock has to be higher to justify such a system. Description: M.SC.ENG. 2020-01-01T00:00:00Z /library/oar/handle/123456789/94283 Title: Feasibility study on combined heat and power systems for hotels in the Maltese Islands Abstract: The services sector in the Maltese Islands consumes around 29% of the total energy to satisfy the heating and cooling demands. Although several measures have been implemented to achieve the desired energy reduction, this has not been achieved yet. In the study being presented in this dissertation an investigation was carried out on the feasibility of Combined Heat and Power (CHP) and Combined Cooling, Heating and Power (CCHP) systems for the hospitality sector in Malta. The research presented makes use of a software package, RETscreen to create strategic models of a whole spectrum of hotels with different energy demands, rather than focusing on only one type of hotel. Through the use of this software different scenarios were captured using a number of different variables, including size related and financial aspects. For comparative purposes, data was normalised for all the hotels. Six hotels were chosen, two of the hotels had a 5-star rating, two had a 4-star rating and another two had a 3-star rating. All the hotels had a different footprint and different electrical and heating demands. While creating simulations with these six hotels five different variables were considered and analysed, these were CHP size, financial grants, electricity tariffs, feed-in tariffs and fuel prices. All the prices and tariffs investigated included the current price point, a higher price point and a lower price point to determine which variables had the most impact on the feasibility of working with such systems. The CHP systems were primarily sized to match the hotels’ heating demand, although models were then simulated with both oversized and undersized systems. The main outcome of this dissertation was to obtain the financial and environmental impact that a CHP and a CCHP system has on the hotels energy characteristics. The study was able to identify the key variables which have the highest impact on such projects, which were the financial incentives, the electricity prices and the size of the system. In this study the financial results were analysed, using the simple payback period, the net present value, the internal rate of return and the operating profit. The study showed that the 4-star hotels considered would benefit most from having such projects implemented, and even with minor changes in electricity tariffs it would still be financially feasible to install a CHP system for these hotels. The CCHP system which was simulated for the 4-star hotels, had an additional absorption cooling system. In this case having a CCHP system with the current initial capital investment and the current electricity prices resulted in the system not being feasible. Description: M.SC.ENG. 2020-01-01T00:00:00Z /library/oar/handle/123456789/94281 Title: Energy certification in buildings a review of the EPC software for non-dwellings in Malta Abstract: Malta joined the European Union in 2004. It was only five years later, in 2009 that the Energy Performance Certification for buildings started to be locally enforced, in line with the Energy Performance Building Directive (EPBD) (Directive 2002/91/EC and its recast 2010/31/EU). The scope of this dissertation is to assess the software being used to issue Energy Performance Certificates (EPC’s) for Commercial Buildings in Malta. Given that the current software was based on the iSBEM-uk model which has been adopted and upgraded to investigate and energy evaluate buildings in Malta, this dissertation analyses the calculation methodology which has been adopted to achieve the energy performance rating. In order to understand the fundamentals behind the compilation of the software, various legislation, standards, and EU directives were examined. One of the main documents which sets a benchmark within the local software is the Technical Guidance Document, Part F of the Maltese Building Regulations issued by the BICC. This document lists all the minimum requirements for Energy Conservation, Fuel Conservation, and the use of Natural Resources in Buildings in Malta. For the scope of this exercise, this document was analysed in detail. Several points and suggestions have been found, one of which was that it was not clear under which category of commercial buildings do industrial buildings fall part of. The study then goes through a step by step procedure within the iSBEM-mt software which an assessor should go through in order to issue an EPC. From this study, several points were identified how the final EPC may represent a more accurate illustration of the real energy profile and performance of the building. One such example was the fixed efficacy values for different lamp types where LED’s are not listed as the most efficient. This is in contrast to the best available technology found today. In addition to the above, an assessment of a sample building was made using the iSBEM-mt software. The final energy ratings were compared to several improvements in the building fabric and Mechanical and Electrical Building ¸£ÀûÔÚÏßÃâ·Ñ. These were used to identify the cost effectiveness of increasing the minimum requirements stipulated in the Technical Guide F. The above study was then substantiated with a number of questionnaires which were directed to a number of professionals in the field. Such professionals include EPC assessors, Architects, Engineers and Real estate Agents. Description: M.SC.ENG. 2020-01-01T00:00:00Z /library/oar/handle/123456789/94275 Title: Wind analysis over a building roof in the presence of photovoltaics Abstract: Solar power generation using photovoltaic (PV) panels is one of the most common sources of alternative energy. Compared to pitched roofs, the installation of building integrated PV panels on flat roofs offers the possibility to incline and orient the photovoltaic array in such a way as to maximize diurnal insolation hence achieving better system performance and higher energy output. Apart from their main function of generating electrical energy from solar radiation, PV panels create secondary effects to the building structure. PV panels offer cooling effects to the top-most surface of a building through shading, and also through the effects on the thermal convective heat transfer coefficient (CHTC) which results from the interference of the wind velocity profile. The latter has seldom been addressed in the literature. This main focus of this project is to test the hypothesis of whether the CHTC between roofs with PV panels and those without cause any significant difference in building energy performance. This quantity is known to have an impact on the thermal transmittance coefficient (U-value) of roof structures which has a direct impact on the energy consumption of heating, ventilation, and air conditioning (HVAC) equipment which is used to maintain the building envelope in suitable thermal comfort. For the purpose of this study, several wind tunnel experiments were performed. These experiments consisted of studying the behaviour of flow and CHTC on a flat plate surface. The influence of inclined panels on flow and CHTC was analysed. These observations were also compared to numerical analysis using computational fluid dynamics (CFD). Building energy simulation tools were used to model a building envelope and perform simulations using CHTC results obtained from CFD simulations. The main scope of the building energy simulations was to quantify the energy demand of a building without PV panels and compare it to that of a building with PV panels. From these results, the effects of PV panels on building energy performance due to external CHTC could be quantified. It was found out that the presences of PV panels force the flow of air to accelerate and reach higher velocity beneath the panels. Higher velocity resulted in improving the CHTC of localized areas of the building roof. Using building energy simulations, the increase of CHTC in buildings with PV panels resulted in a reduction of approximately 2% in the total energy consumption for heating and cooling of the topmost floor of a building. This study was limited to a constant wind velocity and energy consumption results were based on this wind velocity. The obtained results offer a research direction for future studies. Future work should include the analysis of wind transient effects to investigate whether or not similar results are obtained. Description: M.SC.ENG. 2020-01-01T00:00:00Z