Search

Electricity generation from renewable sources has increased greatly in recent years. The use of photovoltaic (PV) solar modules is constantly studied and improved. Silicon (Si) solar cells dominate the current market share, because Si is abundant, non-toxic, stable and has benefited from developments in the semiconductor industry. However, the PV single-junction solar cell limiting energy conversion efficiency is approximately 30% (depending on specific assumptions). Tandem technology is based in multiple solar cells that are each optimized for a part of the spectrum and can achieve higher efficiencies compared to single junction solar cells. Considering a Si bottom cell, there are also a few enhancements that can be made to achieve even higher efficiencies for tandem solar cells. Especially for crystalline Si (c-Si) wafer solar cells, there are many variations in the existing production processes to improve module performance, such as the passivated emitter and rear cell (PERC) technology, which is replacing the recently-dominant screen-printed aluminium back surface field (Al-BSF) technology in the future.Environmental analysis should complement the development of new PV technologies. Life cycle assessment (LCA) is a methodology that assesses environmental impacts through the inputs and outputs associated with all the stages of a product's life cycle, from the raw material extraction to the end of life. A significant quantity of inventory data is necessary to build a model as close as possible to reality to perform a realistic LCA and the availability of relevant and recent data is the greatest challenge for all LCA practitioners, independently of methodological approaches. The goal of this research is to undertake a comparison of several environmental impacts of different Si-tandem solar module technologies through the LCA method. Besides that, this research aims to partially address the inventory gap issue by developing life cycle inventory (LCI) data of some PV

Odours from wastewater treatment facilities can cause nuisance impacts in the community and erode public acceptance, while odorous emissions from biosolids can limit opportunities for their beneficial reuse via land application. The aim of this research was to understand how odour emissions throughout wastewater treatment plants are affected by the configuration and operation of biosolids processing. Odour emissions can be more effectively managed if reasons for the presence of different types of odorants and their sensorial impacts are known.Odorants in emissions throughout the biosolids processing at eight wastewater treatment plants were quantified using methods specifically targeting volatile sulfur compounds (VSCs), which are thought to be key odorants in wastewater treatment. In addition, a range of volatile organic compounds (VOCs) and their sensorial properties were studied using gas chromatography coupled with an odour detection port (GC-MS/O). Intra and inter site variations in emissions were compared to the different biosolids processing operations over the eight sites.VSCs such as hydrogen sulfide, methyl mercaptan and dimethyl sulfide were identified as dominant odorants due to their high concentrations and low odour detection thresholds. In addition, certain VOCs such as p-cresol, trimethylamine and volatile fatty acids were detected at sensorially perceptible levels. Anaerobic digestion and dewatering were studied to determine their influence on nuisance emissions from the biosolids product. Temporal variations in biosolids emissions were studied over an eight week period at one WWTP showing significant variations in biosolids iron, aluminium and sulfur content which appeared to be related to certain emissions. Optimisation of a full scale dewatering centrifuge showed weir plate height and feed flow affected emissions of ammonia and dimethyl sulfide as the biosolids aged.GC-MS/O analysis was used to identify odorants based on their sensorial propertie

Water treatment chemicals are pervasive across conventional and modern technologies for water and wastewater treatment operations around the world. While their technical performance has been extensively studied to fulfil a particular purpose (e.g. disinfection or coagulation) their environmental performance has received less attention. The environmental performance of the supply chains for these chemicals can be quantified using life cycle assessment (LCA) in order to understand the potential environmental impacts on decisions associated with operational improvements, new designs or potential future upgrades of water and wastewater infrastructure. However, the methodological challenges associated with developing the life cycle inventory (LCI) data required for robust LCAs can be complex. Challenges which increase the uncertainty of LCA results include multifunctionality, truncated system boundaries and indirect effects depending on the typology of the LCA study undertaken.This research aims to develop relevant, recent and local data which enable the assessment of the environmental performance of water treatment chemicals under several LCA methodologies used by decision makers. This is achieved through a comprehensive development of process, hybrid and consequential models including assessment of the most important sources of methodological uncertainty associated with them. Firstly, this study investigates chemical consumption trends in the Australian water industry with the objective of identifying the most important chemicals and targets them for assessment. Secondly, this research develops a comprehensive set of process-based LCI models for the prioritised water treatment chemicals, applies different techniques for solving multifunctionality and demonstrates the potential consequences of methodological choices. Thirdly, this thesis develops and demonstrates an input-output model which is subsequently developed into a tiered hybrid model specifically tailored to th