/library/oar/handle/123456789/144534 Thu, 28 May 2026 12:37:13 GMT 2026-05-28T12:37:13Z /library/oar/handle/123456789/146869 Title: Comparing photoluminescence imaging and microwave detected photoconductivity for measuring recombination lifetimes of silicon wafers Abstract: This study investigates the correlation between recombination lifetime and photoluminescence (PL) in silicon solar cells, aiming to evaluate the reliability of Photoluminescence Imaging (PLI) as compared to the well-established Microwave Detected Photoconductivity (MDP) technique. Recombination lifetime is a critical parameter influencing solar cell efficiency, as it determines how long charge carriers persist before recombining. Using both MDP and PLI tools, the recombination lifetimes and corresponding PL grey values of monocrystalline silicon wafers were measured under various thermal and contamination conditions. Heat treatments at 800°C and 950°C, along with deliberate contamination using a copper coin and latex gloves, were employed to produce a wide range of recombination activity across the samples. Data were analysed using ImageJ to correlate PL grey values with MDP-measured lifetimes. A linear relationship of the form Y = 0.0090X, where Y is the recombination lifetime and X is the grey value, was established through regression analysis. Results revealed a consistent relationship between the two measurement techniques, validating the potential of PLI as a rapid and non- destructive proxy for lifetime assessment. The findings support the development of cost-effective and efficient quality control methods in photovoltaic manufacturing by leveraging the complementary strengths of both PLI and MDP. Description: M.Sc.(Melit.) Wed, 01 Jan 2025 00:00:00 GMT /library/oar/handle/123456789/146869 2025-01-01T00:00:00Z /library/oar/handle/123456789/146070 Title: Shared micro-mobility services : a sustainability assessment of their use in Malta Abstract: Shared micro-mobility services in Malta, such as bicycles, e-bikes and e-scooters, were analysed in this dissertation. Literature shows that shared micro-modes of transport pose several benefits, such as reduced traffic congestion and the promotion of an active alternative mode of commuting, posing cost-effective, health and social benefits. They are ideal for last mile trips and work extremely well when properly integrated with the transport system, particularly the road infrastructure and public transport systems. Shared micro-mobility services reduce the energy demand and have the potential of reducing carbon and greenhouse gas (GHG) emissions on local roads. Although in 2016 shared micro-mobility services were introduced in Malta, these abruptly halted their services. Thus, the aim of this thesis was formulated as follows: To perform a sustainability assessment on shared micro-mobility services in Malta, to understand their sustainability advantage, the reasons why they stopped operating, and to make recommendations for their inclusion in sustainable transport locally. The methodology to gather data was semi-structured interviews with 18 key stakeholders of transport in Malta. A simplified sustainability assessment and policy review were also conducted. Results show that the majority of participants perceived them as sustainable and that there needs to be a competitive advantage over other modes of transport (particularly the private car), the provision of safe infrastructure and better enforcement. Participants also claimed that the main reasons why they left was due to abuse, chaos, no discipline (especially amongst e-scooter users), vandalism and lack of safety towards pedestrians and other road users; with 40% of the respondents agreeing with these services halting operations. The Maltese government is looking towards the future, providing incentives for the use of personalised e-bikes and e-scooters. However, sharing services are still not being pushed to reintroduce them. Although private micro-vehicles may reduce the abuse, irregularities and dangers to self or pedestrians, they do not eliminate them. Shared services still have the potential to provide a cheap, flexible and convenient alternative to commuting, and its potential (considering Malta’s size) should not be ignored. Key concluding recommendations include the need for pilot projects, an enhanced regulatory framework and enforcement, more awareness and acceptance, improved public transport (bus/ferry) and integration, and the provision of safe infrastructure. Description: M.Sc.(Melit.) Sust.Energy Wed, 01 Jan 2025 00:00:00 GMT /library/oar/handle/123456789/146070 2025-01-01T00:00:00Z /library/oar/handle/123456789/144597 Title: A study on the effect of thin object shading on the performance of photovoltaic modules Abstract: This study investigates a specific and underexplored aspect of partial shading of photovoltaic (PV) systems that is caused by thin horizontal objects. Following a review of both fundamental principles and current state-of-the-art, the primary aims were to examine differences in shadow formation and associated power loss between laboratory and outdoor environments, quantify shadow formation characteristics, and to assess the scientific validity of commonly used simplifications in representing penumbra shadows. This study presents a comparative analysis of thin object shadows under laboratory environment conditions using a solar simulator, and under outdoor environmental conditions. Using a 156.0 × 156.0 mm solar cell, 56 thin object shading cases were compared using thin objects of thicknesses of ⌀2.0 mm - ⌀20.0 mm at distances between 10 cm – 40 cm in 5 cm increments. The solar cell placed in outdoor conditions produced higher power losses in the range of 0.34 W - 0.67 W, equivalent to 8.18% to 16.13% power loss respectively, when converted to standard test conditions (STC). This observation was validated by producing a quantitative factor which incorporated both the size and intensity of the overall shadow at equal weight where clearly the outdoor environment produced stronger shadow formation. Moreover, the image capture of all 56 cases found evidence of the laboratory environment producing fringed shadow patterns caused by Fresnel diffraction on the thin objects, most evidently in the shadows of the smallest thin object (⌀2 mm). This thesis also implemented a novel methodology to quantify the shadow formation and the power loss of 104 thin object shading cases, using custom made image analysis tool named ThinShadePV. This tool utilises image analysis and Random Forest machine learning to determine the size and intensity of umbra and penumbra shadow regions from captured shadow images and predict the associated power losses. Validation through 15 real-world thin shadow cases demonstrated strong agreement between predicted and actual power loss values, with a mean deviation of just 0.48% and an accuracy range of –3.68% to +2.71%. Moreover, Spearman correlation and sensitivity analyses revealed that penumbra intensity is the most influential factor for smaller objects (⌀2.8–⌀8.0 mm thick), while the size of the umbra shadow dominates in larger objects (⌀10–⌀16.0 mm) thick. The study also assessed the validity of approximating varying-intensity penumbra shadows with constant-intensity penumbra representations using neutral density (ND) filters. While constant-intensity shadows closely replicated the relationship profile, they consistently overestimated power loss, despite matching the size and average varying intensity shadows. A large effect size (Cohen’s d = –0.893) confirmed a significant discrepancy, indicating that varying-intensity penumbra shadows should not be simplified to constant-intensity models in analytical or simulation contexts. One of the key contributions of this study lies in its significant advancement of current knowledge by empirically quantifying the effects of horizontal thin object shading on PV performance and establishing key relationships between shading parameters and power loss. The development of ThinShadePV, a purpose-built image analysis tool, enables quantitative measurement of shadow characteristics and power loss prediction. Moreover, ThinShadePV holds strong potential for integration into commercial PV simulation software, enhancing the accuracy of performance forecasts under real-world shading conditions. Description: Ph.D.(Melit.) Wed, 01 Jan 2025 00:00:00 GMT /library/oar/handle/123456789/144597 2025-01-01T00:00:00Z