The field of solar energy conversion has experienced resurgence in recent years due to mounting concerns related to fossil fuel consumption. The sheer quantity of available solar energy and corresponding opportunity for technological improvement has motivated extensive study of novel light-absorbing semiconductors for solar energy conversion. Often, these studies have focused on new ways of synthesizing and altering thin film semiconductor materials with unique compositions and morphologies in order to optimize them for higher conversion efficiencies. In this dissertation, we discuss the synthesis and electrochemical characterization of a variety of candidate semiconductor materials exhibiting promising characteristics for photoelectrochemical solar energy conversion. Three specific methods of thin film deposition are detailed. The first is a physical vapor deposition technique used to independently tune the morphology and composition of hematite (α-Fe2O3) based materials. Because of hematite’s poor electronic properties, these modifications were able to significantly improve its performance as a photoanode for water oxidation. The second technique is electrodeposition, which was employed to deposit the novel ternary metal oxide, CuBi2O4. The study of these films, along with those prepared by physical vapor deposition, provided insight into the factors limiting the ability of this photo-active material to function as a photocathode for hydrogen evolution from water. The third technique is chemical spray pyrolysis, which was employed to deposit and optimize films of the bismuth chalco-halides BiOI and BiSI. These studies were used to obtain previously unknown properties of these materials relevant to their utilization in photoelectrochemical cells. The manipulation of deposition temperature had significant effects on these properties and dictated the films’ overall photoconversion performance. / text

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

Many public and private entities have heavily invested in efficiency measures and renewable sources to generate energy savings and reduce fossil fuel consumption. Private utilities have invested over $4 billion in energy efficiency with 56% of these investments directed towards consumer incentives. However, the magnitude of the expected savings and the effectiveness of the technological measures remain uncertain. Multiple studies attribute the reasons driving these uncertainties to behavioral phenomena such as “the rebound effect.” This work provides insights on the uncertainties generating potential differences between expected and observed performances of demand-side measures (DSM) and distributed generation strategies, using mixed methods that employ both empirical analyses and engineering economics. This study also provides guidelines to stakeholders to effectively use the benefits from DSM strategies towards asset preservation for affordable multifamily houses. Section 2 describes how joint efficiency gains compare to similar singular efficiency gains for single-family households and discusses the implications of these differences. This work provides empirical models of marginal technical change for multiple residential electricity end-uses, including space conditioning technologies, appliances, devices, and electric vehicles. Results indicate that the relative household level of technological sophistication significantly influences the performance of demand-side measures, particularly the presence of a programmable thermostat. As to space conditioning, results demonstrate that sufficient consistent technical improvement leads to net energy savings, which could be due to technical factors or to a declining marginal rebound effect. Section 3 empirically evaluates the performance of distributed residential photovoltaic (PV) solar panels and identifies the technological and demographic factors influencing PV performance and adoption choice. Results show that modeling PV adoption choice significantly impacts the household energy demand, suggesting that the differences in the actual evaluated behavioral responses and the self-reported changes in electricity consumption are more complex than assumed by other studies. The analysis indicates that electricity use decreases marginally for PV adopters if sufficient efficiency improvements in space conditioning are made. Results further imply that households that adopt solar panels might “take back” roughly 24% of the annual electricity production for PV technologies. Section 4 describes replicable engineering economic models for estimating conventional rehabilitation, energy, and water retrofit costs for low-income multi-family housing units. The purpose of this study is to prioritize policy interventions aimed at maintaining property location and use, and to identify the capital investment needs that could be partially provided by local and state housing authorities. Section 5 synthesizes the work, describes the future work, provides guidelines for local and state efficiency program administrators, and insights on prioritizing and designing efficiency interventions. / text

My dissertation seeks to analyze environmental policy using theoretical, computational, and empirical methods. In the first chapter I develop a Bayesian learning framework for damage functions in integrated assessment models that mimics how modelers have historically updated damage functions. To allow for the model to be solved in a reasonable timeframe I must use sparse grid methods for dynamic programming which are new to climate economics. I also use robust control techniques from the macroeconomics literature to capture concerns that there are errors in integrated assessment models that we will not be able to resolve in a timely fashion. Using these methodological advances, I demonstrate that the convention of updating the calibration of damage functions while maintaining a fixed functional form can backfire and reduce ex-post welfare if the damage function is misspecified like many economists believe. Moreover, accounting for misspecification concerns with robust control can exacerbate the backfire and further reduce ex-post welfare. In my second chapter I analyze the impacts of credit trading under renewable portfolio standards. Specifically, I look at how a change in one state's renewable portfolio standard can propagate through this credit channel and result in reductions in fossil fuel usage in another state. I find that a 1 MWh increase in extra-jurisdictional demand for renewable energy credits leads to a reduction in energy production derived from coal usage by 2 mmbtus and a reduction in CO₂ emissions by 0.285 metric tons. In my last chapter I develop an analytic model for renewable energy credit trading to investigate why states have peculiar trading rules for the credits. I find that, counter to conventional economic wisdom, states may actually not want to engage in credit trading. Credit trading may in fact worsen in state pollution to an extent that completely offsets any gains from trade.

Σκοπός της παρούσας εργασίας είναι η πειραματική μελέτη διατάξεων μετατροπής αιολικής και ηλιακής ενέργειας σε ηλεκτρική. Αρχικά, στην εργασία αναλύονται οι κυριότερες ανανεώσιμες πηγές ενέργειας (Α.Π.Ε.), με μικρές αναφορές στο κάθε σύστημα ξεχωριστά. Στη συνέχεια της εργασία, εξηγείται το φαινόμενο της δημιουργίας ανέμων στην ατμόσφαιρα, τονίζεται ο σημαντικός ρόλος που έπαιζε ο άνεμος από τα αρχαία χρόνια, παρατίθεται μια σύντομη ιστορική αναδρομή, αναλύονται τα μέρη της ανεμογεννήτριας, επισημαίνονται τα πλεονεκτήματα και τα μειονεκτήματα της ενέργειας που παράγεται από τον άνεμο. Τέλος αναφέρονται κάποιες αποθηκευτικές διατάξεις και στη συνέχεια αναλύονται περιληπτικά οι συσσωρευτές, αφού στο σύστημα μας υπάρχει χρήση συσσωρευτών. Επιπλέον, αναφέρουμε τα βασικά στοιχειά για ένα μετεωρολογικό σταθμό, τον οποίο και δημιουργήσαμε για το σκοπό της παρούσας διπλωματικής εργασίας. Στη συνέχεια έχουμε την επεξήγηση του τρόπου εγκατάστασης της ανεμογεννήτριας την οποία απέκτησε το εργαστήριο για σκοπούς μελέτης. Επιπλέον επεξηγείται η κατασκευή ορισμένων κυκλωματικών διατάξεων, μέσω των οποίων γίνεται δυνατός ο έλεγχος της ανεμογεννήτριας όπως επίσης και η μέτρηση, καταγραφή, αποθήκευση τεσσάρων βασικών στοιχειών (ταχύτητα ανέμου, διεύθυνση ανέμου, τάση και ρεύμα στο φορτίο) τα οποία θα μας βοηθήσουν στη συνέχεια της διπλωματικής ώστε να δημιουργήσουμε ανεμολογικά δεδομένα για την περιοχή του Πανεπιστημίου Πατρών, όπως επίσης και για την κατασκευή της καμπύλης φόρτισης της ανεμογεννήτριας του Εργαστηρίου Η.Μ.Ε. Ταυτοχρόνως με τις ίδιες κυκλωματικές διατάξεις έχουμε τη δυνατότητα να λαμβάνουμε δεδομένα από τα οποία μετά από επεξεργασία μπορούμε να λάβουμε την παραγόμενη ενέργεια από το κάθε σύστημα, ενώ παρουσιάζονται οι πειραματικές καμπύλες οι οποίες έχουν εξαχθεί από τα πειραματικά δεδομένα της διπλωματικής. Το επόμενο μέρος της διπλωματικής μου εργασίας αναφέρετε στα ηλιακά ΦΒ-συστήματα, αναφέροντας τα βασικότερα μεγέθη τα οποία επηρεάζουν την απόδοση τους. Επίσης αναφέρονται οι βασικότεροι τύποι υλικών κατασκευές ΦΒ-στοιχειών για τα οποία αναφέρουμε τις βασικότερες παραμέτρους τους. Αναφέρουμε επίσης κάποια πειραματικά συστήματα τα οποία προσπαθούν να αυξήσουν την παραγωγή ενέργειας από τα ΦΒ. Μετά ακολουθούν οι γραφικές παραστάσεις των πειραματικών αποτελεσμάτων τα οποία έχουμε πάρει από τις πειραματικές μας διατάξεις. Τέλος, γίνεται μια προσπάθεια να αναπτύξουμε ένα μαθηματικό μοντέλο με τα οποίο προσπαθούμε να δώσουν απάντηση στο ερώτημα, αν συμφέρει η όχι από οικονομικής άποψης, το θέμα της επένδυσης χρημάτων σε ΦΒ-σταθμούς. / -

Torrefaction is a thermo-chemical pre-treatment of biomass within a narrow temperature range from 200°C to 300°C, where mostly the hemicellulose components of a biomass depolymerise. This treatment is carried out under atmospheric conditions in a non-oxidizing environment at low heating rates (< 50°C/min) and for a relatively long reactor residence time. Torrefaction increases the energy density of a biomass and reduces its O/C and H/C ratio, so its properties approach to that of coal. Biomass is usually referred to as lignocellulose, as its major mass constituents are cellulose, hemicelluloses and lignin. Research on torrefaction carried out to date deals solely with lignocellulose biomasses, and their degradation mechanism is explained primarily in terms of hemicellulose. However, there are biomasses which are non-lignocellulosic, have a small fraction of fibres in them or could possibly benefit from torrefaction. These include municipal solid waste, sewage sludge, animal waste, etc. Experiments were conducted on three non-cellulose biomasses (poultry waste, digested sludge, and undigested sludge) along with three typical lignocellulose biomasses (wood pellet and switchgrass and an agricultural waste – coffee bean husks). Results showed that non-lignocellulose biomasses torrefy similarly to their lignocellulose counterparts. Due to the immense potential of the torrefaction process, numerous manufacturers have developed their own patented technology for torrefying. Nevertheless, choosing the right torrefaction technology has become exceptionally difficult because of a near absence of a comparative assessment of different types of reactors. An experimental work was conducted to review the major generic types of reactors such as rotating drum, convective bed, fluidized bed and microwave, delineating the essential features of generic types of reactors. According to the results of this study, biomass torrefaction in a rotating drum gave the highest energy dense product, followed by fluidized bed and convective bed; the microwave reactor showed over-torrefaction at the core, while leaving the exterior green. To help effective design of a torrefier, several systematic experiments were conducted to investigate the effects of some of the more important operating parameters, such as torrefaction temperature, residence time and biomass particles size on the torrefaction yield. Although the mass yield decreased with the torrefaction temperature, energy density increased with it. Moreover, torrefaction yield varied for different biomass particle sizes depending on the type of reactor used, but the particle size did not have any clear effect on the energy density of the torrefied product.

The grid connected PV plants comprising of the PV cells and the power electronic inverters are a widely used technology in distributed power generation systems based on renewable energy sources. Microinverters form an extensive part of the ongoing research in this field. This thesis focuses on the inverter section of the microinverter. The cost and efficiency of the grid connected inverter is a chief contributing factor in the overall system price. The MOSFETs used in the DC/AC inverter are usually hard switched causing a lot of EMI noise and losses in the inverter. This is true for both, single and three phase inverters. A low switching frequency is desirable to increase the efficiency, which in turn imposes a large compromise in designing the output filter. In this thesis, switching losses have been minimized by incorporating zero voltage switching at switch turn on and variable dead-time control at switch turn off. The soft switching technique is based on control algorithms and involves no use of any auxiliary circuit. Also, the size of the output filter is reduced without increasing the switching frequency, by employing multiple paralleled inverters. The interleaving technique that is usually used in dc/dc converters is extended for dc/ac inverters and is well employed to maintain the quality of the current fed into the utility grid. In this way, at low switching frequency, high efficiency and reduced cost and sizes are achieved. The study is validated through simulation and lab experiments. The novel control circuit was first implemented using analog circuitry. After assessing the performance of the analog version of the proposed controller, it was then digitally implemented through the Field Programmable Gate Array (FPGA) technique. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2012-04-30 15:06:26.071

京都大学 / 新制・課程博士 / 博士(地球環境学) / 甲第24063号 / 地環博第226号 / 新制||地環||43(附属図書館) / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)教授 宇佐美 誠, 教授 小林 広英, 准教授 TRENCHER Gregory / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DGAM

In Bangladesh, as elsewhere in the world, energy both commercial and noncommercial, serves as a major vehicle for development. In the last three decades, lopsided development efforts, without proper concern for the environment and productivity level of natural resources have created significant problems for development sustainability in Bangladesh. The energy sector faces deep crisis in meeting increasing energy demands for development of agriculture, industry, transportation and other sectors of economy. The country is heavily dependent on import of commercial fossil fuel energy, petroleum, petroleum products and coal. Such dependency makes Bangladesh economy more vulnerable to external price shocks in the international energy market. Non-commercial energy plays a dominant role in overall energy consumption in Bangladesh. Use of non commercial energy constitutes about two-thirds of the country’s total energy balance and is almost entirely supplied from the already overstressed biomass resources of the country. The population size and the vast majority living in rural areas have created immense pressure on the country’s biomass resources resulting in massive deforestation, decline of soil fertility and reduced productivity of agriculture. Desperate access to resources, particularly in rural areas is also causing uneven development of the rural population in Bangladesh. The development of the energy sector is a time bound issue and demands proper and timely attention. For Bangladesh, substitution of current biomass energy use with iv sustainable energy sources and their effective management is therefore critically important to sustain its overall development. There is ample scope for introducing energy efficient technologies and energy conservation measures in commercial and non-commercial energy use in Bangladesh. Effective and realistic energy planning and policy formulation is therefore crucially important for sustainable development in Bangladesh. The thesis explores the possibility of introducing an alternate approach to rural energy development through a series of case studies on selected technologies viz. biogas and improved efficiency cook stoves technology projects in the public sector and Grameen Shakti’s renewable energy programme in the private sector. Application of village energy supply system based on renewable energy technologies utilising abundantly available renewable resources of the country and already well in place technologies such as solar PV, bio digesters and energy storage batteries will be trailed within a framework that works with the participation of the (rural/village) community in running and managing energy supply in the villages. Introduction of a community based energy supply system Rural Energy Cooperative (REC) has been examined as a model for rural energy development, targeting economic, environmental and community development at the same time, which forms together the necessary foundation for sustainable development in (rural) Bangladesh, as well as in other parts of the developing world.

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on January 8, 2008) Includes bibliographical references.