Comme nombre d'autres Etats aux ressources insuffisantes, le Cameroun, pour satisfaire sa demande croissante en électricité, est à la recherche des solutions novatrices en terme de coûts et de garanties dans l'optique d'assurer le développement durable de son secteur énergétique. Les énergies renouvelables y contribueront certainement étant donné la prise de conscience des impacts négatifs sur l'environnement des systèmes actuels et l'existence d'un potentiel important, équivalent pour les trois filières étudiées (gazéification de la biomasse ligneuse, biométhanisation de la biomasse humide et la microhydroélectricité) au moins à la consommation actuelle prélevée du réseau national. La question de fond est de savoir comment cet accroissement indispensable devrait s'effectuer ?, selon quelles modalités ?, quelles rythmes ?, et suivant quels choix ? La contribution de cette thèse est le développement d'un modèle d'analyse permettant d'intégrer les critères environnementaux et économiques dans le processus de décision lors de la définition des politiques d'électrification. L'application du modèle au secteur électrique camerounais montre en tenant compte de l'évolution de la consommation en électricité (2006-2025) que l'intégration de l'électricité verte améliore le bilan financier du secteur électrique malgré le surcoût d'investissement qu'elle engendre. L'appel de fonds nécessaire à l'investissement peut trouver auprès des organismes financiers une réponse d'autant plus favorable aux énergies renouvelables qu'au delà de l'amélioration du bilan financier, l'effet favorable pour l'environnement peut générer des recettes supplémentaires via les mécanismes de Kyoto et d'autres fonds internationaux en faveur de la protection de l'environnement mondial car ce scénario permet d'éviter environ 6 millions de tonnes de CO2 équivalent sur la période analysée.

Comme nombre d'autres Etats aux ressources insuffisantes, le Cameroun, pour satisfaire sa demande croissante en électricité, est à la recherche des solutions novatrices en terme de coûts et de garanties dans l'optique d'assurer le développement durable de son secteur énergétique. Les énergies renouvelables y contribueront certainement étant donné la prise de conscience des impacts négatifs sur l'environnement des systèmes actuels et l'existence d'un potentiel important, équivalent pour les trois filières étudiées (gazéification de la biomasse ligneuse, biométhanisation de la biomasse humide et la microhydroélectricité) au moins à la consommation actuelle prélevée du réseau national. La question de fond est de savoir comment cet accroissement indispensable devrait s'effectuer ?, selon quelles modalités ?, quelles rythmes ?, et suivant quels choix ? La contribution de cette thèse est le développement d'un modèle d'analyse permettant d'intégrer les critères environnementaux et économiques dans le processus de décision lors de la définition des politiques d'électrification. L'application du modèle au secteur électrique camerounais montre en tenant compte de l'évolution de la consommation en électricité (2006-2025) que l'intégration de l'électricité verte améliore le bilan financier du secteur électrique malgré le surcoût d'investissement qu'elle engendre. L'appel de fonds nécessaire à l'investissement peut trouver auprès des organismes financiers une réponse d'autant plus favorable aux énergies renouvelables qu'au delà de l'amélioration du bilan financier, l'effet favorable pour l'environnement peut générer des recettes supplémentaires via les mécanismes de Kyoto et d'autres fonds internationaux en faveur de la protection de l'environnement mondial car ce scénario permet d'éviter environ 6 millions de tonnes de CO2 équivalent sur la période analysée.

The importance of utilizing different types of energy and their technical application is discussed. Awareness around the globe about the world energy crisis and its critical environmental condition has put more emphasis on the use of renewable energies in every corner of life. It is a well‐known fact that global warming, inefficient use of energy and greenhouse gases are damaging the environment, species and human life drastically. These issues will be discussed in recently conducted research. To address the crucial state of our environment, two simultaneous scenarios are considered. Initially, energy conservation and the switch to a low carbon/no carbon fuel are studied. As for energy conservation in buildings, smart methods in the use of energy in buildings are discussed. Based on different research reported, humans must change their attitude toward the use of resources, and in particular, be conscientious about energy consumption. Next, renewable energy promises a suitable alternative to energy needs in this century, and the best means to overcome the environmental issue and energy crisis is discussed. The practical methods of calculation for solar technology equipment, ground source heat pumps, and wind turbines are explained. In the application part of the study, four buildings are chosen as case studies; two of them from residential sectors, one is a commercial/institutional building, and the fourth is an industrial building. A ground source heat pump for heating and cooling, a solar water heater for heating space or hot water, and a photovoltaic panel for generating electricity are designed for the case studies. Even projects under hybrid systems combined from two technologies are designed. 36 different energy options are calculated for the four case studies. Results show that if a target is reducing CO2 emissions, what systems are the best. In contrast, when decision making is based on budget, what system is the first choice? Not only are technology, environmental protection and cost the main parameters for deciding on renewable technologies, but so are reliability, installation, maintenance and ease of use. Hence, renewable energy systems are categorized based on a broad vision.

El sector energético se está dirigiendo hacia un nuevo paradigma, favoreciendo la aparición de procesos de conversión más eficientes, el uso de las fuentes de energía renovables y la micro-generación. La bioenergía es una solución prometedora para la futura combinación de energías. Los conceptos de ingeniería deben de integrarse junto con los aspectos económicos, ambientales y sociales en el desarrollo de proyectos. Los sistemas de energía centralizados y distribuidos necesitan enfoques a medida para explotar las características de cada posible sistema. Esta tesis investiga el potencial del sector bioenergético, mediante el estudio de la gasificación de biomasa a través de técnicas avanzadas de modelización de procesos y de la incorporación de la gestión de la cadena de suministro, en el marco del diseño conceptual para la toma de decisiones. Los sistemas estudiados son: (i) gasificación integrada con ciclo combinado y con métodos de captura y almacenamiento de CO2 (IGCC-CCS, 285 MWe) para los sistemas de energía centralizados, y (ii) un gasificador de biomasa combinada con un motor de gas (BG-GE, 14 kWe) para los sistemas de energía distribuidos. La superestructura concebida puede ser utilizada en el diseño preliminar de alternativas para los diferentes procesos considerados, para adaptar los ya existentes y para adquirir conocimiento sobre las condiciones de operación de plantas de gasificación. El problema de optimización multi-objetivo considerado evalúa el equilibrio entre los criterios técnico-económicos y ambientales de 25 escenarios, con mezclas de diferentes materias primas y cambios topológicos: mezclas de carbón, coque y biomasa y la generación de electricidad a partir de gas de síntesis, la generación de electricidad a partir de H2 y la producción de H2 puro, considerando o no el uso del gas de purga del PSA en el ciclo combinado. El análisis de Pareto revela que como mejores escenarios el que utiliza coque de petróleo como materia prima para producir H2, con reciclo del gas de purga del PSA y el que utiliza biomasa residual sin reaprovechamiento del gas de purga del PSA. La implementación de la tecnología CCS conlleva una penalización en la eficiencia de un 8,7% en términos de potencia neta, si el H2 se utiliza en el ciclo combinado. La gestión de cadenas de suministro de sistemas centralizados, señalan que España tiene potencial de biomasa residual, invirtiendo en nuevas centrales IGCC-CCS, o para producir electricidad mediante co-combustión en las centrales térmicas de carbón ya existentes. Para el primer caso, el valor actual neto óptimo es 230 millones de € para un periodo considerado de 25 años. Para el segundo caso, se ha calculado que las políticas de subvención en este tipo de proyectos deben de tener en cuenta la sostenibilidad económica, cubriendo en un rango de 5,84% a 20,25% el aumento de los precios de la electricidad. El caso de estudio propuesto y optimizado como ejemplo de un sistema distribuido tiene en cuenta una comunidad de Ghana en el marco de la electrificación rural, a abastecer con peladuras de yuca y mediante sistemas BG-GE. Los resultados revelan una red inviable. De las cadenas de suministro resultantes como óptimas, se puede deducir que cierto nivel de centralización es necesario para que las propuestas sean sostenibles en el tiempo. El sector de la bioenergía cumple ofrece ventajas en términos de impacto ambiental y social. Su implementación es posible con el apoyo de las tecnologías actuales de conversión de energía. Los principales retos están en la mejora de los procesos de pretratamiento de la biomasa y en su almacenamiento. La conversión de la biomasa, junto con los métodos de captura y almacenamiento de CO2, necesitan de incentivos políticos para poder penetrar definitivamente en el mercado, como sería el caso de cualquier otra tecnología alternativa de conversión de energía / The energy sector faces a new energy paradigm, with more efficient conversion processes, renewable sources and micro-generation. Bioenergy is a promising solution. Engineering aspects must be integrated with economic, environmental and social aspects in bioenergy projects. Biomass properties enhancement is crucial. It concerns energy and matter densifications, for stabilisation and easier transport. Tailor-made approaches are needed to account for the characteristics of each potential system, being it centralised or distributed. This thesis has assessed the bioenergy potential using advanced modelling techniques, enlarged with supply chain management strategies, in the framework of conceptual design for decision-making. The studied energy systems are (i) an integrated gasification combined cycle power plant combined with carbon capture and storage (IGCC-CCS, 285 MWe) for centralised energy systems, and (ii) a biomass gasifier with a gas engine (BG-GE, 14 kWe) for distributed energy systems. Process system modelling and optimisation approaches are integrated with supply chain management to analyse co-gasification and co-production of electricity and hydrogen alternatives in IGCC-CCS, and co-combustion of biomass and coal in pulverised coal power plants in the light of economic and environmental considerations. Process modelling is integrated with supply chain management optimisation for rural electrification by BG-GE systems, considering economic, environmental and social issues. The superstructure can be used for the design of process alternatives, retrofit of existing ones and to gain knowledge on operation of IGCC-CCS. The multi-objective optimisation problem evaluates the trade-off between techno-economic and environmental criteria of 25 scenarios. Considerations comprise different coal, petcoke and biomass combinations and electricity generation from syngas, electricity generation from H2 and purified H2 production without and with PSA purge gas use in the combined cycle. The Pareto frontier analyses reveals that the scenario with petcoke as feedstock for H2 production with PSA flue gas profit is the best in terms of techno-economic optimisation. The scenario with residual biomass without PSA flue gas profit is the best in terms of environmental optimisation. CCS technology implementation leads to an efficiency penalty of 8.7% in net power terms if H2 is used in the IGCC. To maintain the same power level than that obtained with the combustion of syngas, the feedstock should be increased by 21% on a mass basis. Supply chain studies highlight, for Spain, a huge biomass waste potential for electricity and H2 production by investing on new IGCC-CCS power plants, or adaptation of existing plants. For the first case, the optimal NPV is around 230M€ for a period of 25 years. The sensitivity of the optimal solutions to changes in prices is demonstrated. For the second case, policy subsidies or alternatively price increases range from 5.84% to 20.25%. The investment is within 549M€ and 1640M€. A supply chain in a specific community from Ghana is proposed for rural electrification using cassava peels. Optimisations considers 9 communities and an overall electricity demand of 118 MWh/yr. The results reveal an unviable network. From the resulting networks, distributed approaches need a certain level of centralisation to be feasible on time. Bioenergy offers decisive advantages in terms of environmental and social impacts. Its deployment is straightforward to support with current energy conversion technologies. Challenges concern the biomass pre-treatment and storage. Despite all the striking advantages, political incentives are needed for definitive market entry, as would be the case for any energy conversion alternative.

This thesis is a statement about a series of paintings based on an invented dollhouse object that conveys the artist’s identity and placement in the world. Through this essay, the artist represents the home as a space that fosters the recovery and rebirth of invisible energy, ki and examines ideas of transience, interconnection, and rebirth in the mysterious flow of ki in the home. Also the artist will explain her own view about being an artist, the methodologies and specific techniques of her paintings, and her artistic direction for the future.

This research has generated interesting findings from the inductive approach and the qualitative methods that were used in the inquiry process. Thanks to the literature review, the semi-structure interviews, a focus group and secondary data it was possible to obtain the necessary information to answer the research question: How do ecological, economic and social sustainability influence employee motivation? In order to answer this question, two sub-questions were considered first, namely What constitutes sustainability in the company-specific context of Wagner & Co Solartechnik? and Does sustainability motivate people? The answer to the latter question has to be yes, as the analysis revealed numerous linkages. From the data gathered, it is apparent that economic sustainability constitutes the most basic level of sustainability at Wagner Solar. Although the influence of money has its clear limitations, an increase in material orientation could be observed compared to previous. At the company level, ecological sustainability manifests itself as ‘striving for the energy turnaround’. The majority of employees show, as their most important source of motivation, an interest in solar technology as well as a concern for increased eco-efficiency. The information gathered has permitted an assessment of whether the company hires people that are already committed to the company’s vision and mission, or whether the company makes an effort to socialise employees. While this does not seem to be the case it is apparent that the company cultivates a communication and information policy that perpetuates its values. Wagner Solar also exhibits a strong and consistent corporate culture. In terms of social sustainability, democratic decision-making appears to exert the greater amount of influence on employee motivation, while the influence of employee ownership is comparatively diminished. The company appears to both attract and seek out employees who value the ability to work autonomously, partially explained by the German nationality but not exclusively. Positive work environment and good collaborations between colleagues were deemed another important motivational factor, both by the interviewees and the intra-company survey. However, working at Wagner Solar is not without its perceived negatives. These are mostly related to the company’s unique decision-making structures, the use of the language, and possible “island” mentality that some departments might suffer. The study also aimed to analyse the influence of different motivators on employees. When contemplating which pillars of sustainability motivate the most, the analysis of the main motivators revealed that the most important pillar is the social one, since most of the participants have one or more main motivators connected to it. Overall, the impression is that the social values of Wagner Solar are the most pervasive, affecting attitudes and behaviours such as autonomy and responsibility, and, therefore, constitute the main motivators for its employees. The ecological pillar also noticeably influences employee motivation, while the economic pillar is the least influential. / MSPME - Masters in Strategic Project Management European

Specific recognition of ligands including metal ions by proteins is the key of many crucial biological functions and systems. Accurate prediction of the binding strength not only sheds light on the mechanism of the molecular recognition but also provides the most important prerequisite of drug discovery. Computational modeling of molecular binding has gained a great deal of attentions in the last few decades since the advancement of computer power and availability of high-resolution crystal structures. However there still exist two major challenges in the field of molecular modeling, i.e. sampling issue and accuracy of the models. In this work, I have dedicated to tackling these two problems with a noval polarizable force field which is believed to produce more accurate description of molecular interactions than classic non-polarizable force fields. We first developed the model for divalent cations Mg²⁺ and Ca²⁺, deriving the parameters from quantum mechanics. To understand the hydration thermodynamics of these ions we have performed molecular dynamics simulations using our AMOEBA force field. Both the water structures around ions and the solvation free energies were in great accordance with experiment data. We have also simulated and calculated the binding free energies of a series of benzamidine-like inhibitors to trypsin using explicit solvent approach by free energy perturbation. The calculated binding free energies are well within the accuracy of experimental measurement and the direction of change is predicted correctly in all cases. Finally, we computed the hydration free energies of a few organic molecules and automated the calculation procedure. / text

In this thesis we collect the study of two problems in the Calculus of Variations and Partial Differential Equations. Our first group of results concern the analysis of minimizers in a variational model describing the shape of liquid drops and crystals under the influence of gravity, resting on a horizontal surface. Making use of anisotropic symmetrization techniques and an analysis of fine properties of minimizers within the class of sets of finite perimeter, we establish existence, convexity and symmetry of minimizers. In the case of smooth surface tensions, we obtain uniqueness of minimizers via an ODE characterization. In the second group of results discussed in this thesis, which is joint work with A. Vasseur, we treat a problem in compressible fluid dynamics, establishing a uniform bound from below on the temperature for a variant of the compressible Navier-Stokes-Fourier system under suitable hypotheses. This system of equations forms a mathematical model of the motion of a compressible fluid subject to heat conduction. Building upon the work of (Mellet, Vasseur 2009), we identify a class of weak solutions satisfying a localized form of the entropy inequality (adapted to measure the set where the temperature becomes small) and use a form of the De Giorgi argument for L[superscript infinity] bounds of solutions to elliptic equations with bounded measurable coefficients. / text

Energetics, charge selectivity and interfacial charge transfer kinetics affect the efficiency of solar electric energy conversion and solar photochemical formation of fuels. The research described herein focuses on understanding and controlling the energetics, charge selectivity, and interfacial charge transfer processes in organic photovoltaics, as well as new generation semiconductor-semiconductor and metal-semiconductor heterostructured nanorods (NRs) as photocatalysts. Waveguide and transmission based spectroelectrochemistries, photoemission spectroscopies, and impedance spectroscopy were used to characterize the frontier orbital energies, charge selectivity and interfacial charge transfer kinetics in heterostructured NRs and organic photovoltaics. CdSe NRs tipped with Au nanoparticles and CdSe seeded CdS NRs tipped with Pt nanoparticles were used to study the effect of compositional asymmetry and catalytic sites on band edge energies of NRs. We used UV photoemission spectroscopy (UPS) and waveguide and transmission-based spectroelectrochemistry of NR monolayers/multilayers on conductive substrates to estimate valence/conduction band energies. Potential-modulated attenuated total reflectance (PM-ATR) spectroscopy was utilized to measure the apparent heterogeneous rate constants of reversible electron injection into NR films on indium tin oxide (ITO). We conclude from these measurements that metal tipping, which is designed to enhance the photocatalytic activity of semiconductor NRs, altered band edge energies and enhanced electronic coupling to conductive substrates, in ways that are predicted to influence their efficiency as photoelectrocatalysts. Monolayers of functionalized phosphonic acid ruthenium phthalocyanines (RuPcPA) tethered to ITO as a model organic photovoltaic donor/electrode interface were studied to understand the aggregation and orientation dependent charge transfer kinetics and energetics of these systems. The effect of surface roughness on the orientation of RuPcPA was theoretically modeled and compared to the experimental results. Electrochemical and spectroelectrochemical studies revealed the presence of only monomeric species on ITO. Impedance spectroscopy (IS) and PM-ATR were used to measure charge transfer rate constants. Further, frontier orbital energies of RuPcPA modified ITO were measured using UPS, and the results indicated favorable energetics for hole collection at the RuPcPA/ITO interface for OPV applications. The effect of "UV-light soaking" on the performance of organic photovoltaic devices employing metal oxide (MO) electron selective interlayers (ESL) was addressed using sputtered zinc oxide (ZnO) ESL films. This study provides a coherent methodology for differentiating between the proposed origins of the s-shaped current-voltage (J-V) responses in the literature for organic photovoltaics using MO ESLs. We use IS and UPS to demonstrate that the energetic barrier for charge extraction at the ZnO/active layer interface leads to the observed s-shape response in OPVs using ZnO ESLs. Furthermore, this study provides clear guidelines for minimizing the s-shaped J-V response and the effect of UV light on the performances of OPV devices using ZnO ESLs. We have developed solution electrochemical protocols to characterize nanometer-scale porosity and electronic properties of both solution-deposited and sputtered ZnO thin films used as interlayers for electron-harvesting contacts in inverted organic solar cells on ITO substrates. These electrochemical experiments were performed in order to evaluate the hole-blocking abilities of these ZnO ESLs as well as their effective "pinhole density," thus demonstrating a strong correlation to their OPV performances. These electrochemical experiments can be used to characterize and optimize ESLs rapidly, before OPV device fabrication.

Since its discovery, the phenomenon of nuclear fission is the object of extensive theoretical and experimental studies. However, we are still far from a complete understanding of the fission process. Nuclear theory can satisfactorily explain the process of neutron-induced fission at thermal neutron energies, but it meets problems at high neutron energies. However, new applications are nowadays developed involving neutron-induced fission in this energy domain. An example of such an application is accelerator-driven systems (ADS) which are dedicated to transmutation of highly radioactive nuclear waste. Conceptual studies of ADS require new nuclear data on neutron-induced reactions within a wide incident energy range. Along with structural, spallation target and other materials, data on neutron-induced fission are especially required for two nuclides, 232Th and 238U. At present, however, there are no published neutron-induced fission yield data for either 232Th or 238U at energies above 20 MeV. In this thesis, I present measurements of fission fragment mass yields at neutron energies from 10 to 60 MeV for 232Th and 238U. The experiment was done at the Louvain-la-Neuve quasi-monoenergetic neutron beam facility. A multi-section Frisch-gridded ionization chamber was used as the fission fragment detector. The fission fragment mass yields were measured at peak neutron energies of 33, 45, and 60 MeV. In addition, data for the neutron-energy intervals 9-11, 16-18, and 24-26 MeV were also extracted from the low-energy tail. The measurement results show that the symmetric fission component increases with incident neutron energy for both uranium and thorium, but it is more enhanced for thorium. The uranium results were compared to the only existing set of experimental data for neutron energies above 20 MeV. Reasonable agreement was found. However, our data show a lower symmetric fission component. For thorium, the present data are the first above 20 MeV. Model calculations with the TALYS code have also been done. This code is based on the multi-modal random neck-rupture model extended for higher excitation energies. We included a phenomenological model into the code and achieved a good description of our experimental results. / Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 723