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Distributed power generation and cogeneration of heat and power is an attractive way toward a more rational conversion of fossil and bio fuels. Solid oxide fuel cell (SOFC) – gas turbine (GT) hybrid systems are emerging as the most promising candidates enabling the achievement of a cleaner and more efficient conversion of a large variety of resources across a broad power range covering from small to medium scale applications. This thesis introduces an innovative concept of SOFC-GT hybrid system that allows reaching efficiencies higher than the state of the art while enabling the carbon dioxide separation and avoiding fuel cell pressurisation technical issues. Several hybrid system design alternatives based on this concept are analysed through a thermodynamic optimisation approach combining process modelling, advanced process integration techniques and multi-objective optimisation. A number of optimal hybrid system configurations are determined for different design targets. The results consistently demonstrate the higher energy conversion performance and flexibility enabled with respect to the state of the art. The innovative concept analysis is extended to two applications for which SOFC-GT hybrid cycles are expected to provide the most significant impact toward sustainability: the small scale distributed generation and the conversion of renewable resources. A simplified version of the new hybrid system layout is especially developed for small scale distributed generation, typical of residential building applications (5-10 kWel). Experimental data are used to prove the technical feasibility of the system and to assess the performance potentially achievable with currently feasible technologies. The results of the analysis underline that energy conversion efficiencies higher than traditional centralised power generation can be achieved even at such a small scale. A systematic process integration and optimisation approach is used to assess the energy conversion performance of the original SOFC-GT hybrid cycle fuelled with hydrothermally gasified wet waste biomass. The analysis highlights the considerable potential of the integrated system that allows for converting wet waste biomass into electricity with First Law efficiency higher than 60% while simultaneously enabling the separation of the biogenic carbon dioxide.

The constituent countries of the MENA region---defined in this thesis in conformity with the regional definition of the International Energy Agency and encompassing 17 Muslim countries in North Africa, in the Levant, on the Arabian Peninsula, and Iran---have developed very rapidly over the past decade. Two figures best exemplify the region's tremendous transformation: Total population has expanded by more than 20% and its aggregate economic output has more than doubled. As much as this development is desirable, said development trends have also dramatically reshaped the energy policy environment in the MENA region and began causing problems of their own---affecting the region's large oil exporters and its energy importers alike. Having traditionally enjoyed high energy security and handsome resource rents by virtue of their abundant and cheap fossil fuels, new realities in the domestic energy systems demand a new policy focus on domestic energy issues. Energy challenges have emerged which threaten security of supply, fiscal stability, and environmental integrity. The challenges differ in magnitude from country-to-country and reflect the specific national conditions and circumstances. However, given the similarity in the underlying drivers and the governing energy policies, the energy challenges resemble each other across borders. More specifically, ballooning domestic energy demand consumes a rising share of national energy production and thus increasingly imperils the constant flow of the much needed proceeds from oil and gas exports. In the MENA countries with less abundant hydrocarbon resources, domestic demand growth has heightened energy dependence and, to make matters worse, the tighter supply situation in the energy exporting neighbors may eventually also lead to a discontinuation of the preferential supply agreements which they have benefitted from in the past. As a further corollary of demand growth, massive capital-intensive infrastructure investments are necessary to keep pace with the growth on the demand side. The regional tradition to sell energy commodities domestically at prices non-competitive prices or even below cost, however, limits the national energy sectors' own capability of mustering the required capital. Finally, the universally observable heavily fossil fuel-dominated national energy mixes in the region render the study countries vulnerable to supply shocks. The virtually complete reliance on the regionally available hydrocarbons for meeting energy demand is also a principal contributor to environmental degradation and at the core of the large carbon footprint of energy consumption in MENA countries. Given current policies in combination with the emerging demographic and economic trends, these challenges must be expected to become more severe in the years to come. Rising living standards, especially in the region's expanding urban population, are likely to boost per capita energy consumption. The projected, continued demographic and economic growth will further drive commodity demand. And the supply side cannot be counted on to mitigate the challenges under given policies. On the contrary. Although no reliable production projections are available, it stands to reason that production from the region's most prolific oil and gas fields---some of which have been producing for several decades now---will increasingly require the use of costly secondary and tertiary recovery methods and that some will eventually [...]

Natural gas is defined as a combustible mixture of hydrocarbons coming from ground deposits and it is mainly used as a source of energy for burners and motors. Its consumption is increasing worldwide, as this represents a cheap and abundant source of energy, while releasing less CO2 emissions than other fossil fuels, in addition to low emissions of particulates. The diversification of the supply sources of gas and the increase of international trading through pipelines and liquefied natural gas (LNG) shipments makes the gas quality vary more than before, which is a rising challenge for the natural gas industry, as currently the vast majority of gas appliances and motors are unable to adapt to changes in gas quality. This will even worsen in the upcoming years with the multiplication of biogas sources and power-to-gas systems that will be added to the pipeline networks. In order to accomodate the appliances to changes in gas quality, compact and low cost natural gas quality transducers have to be developped for the natural gas industry. The present Thesis aimed at investigating the existing methods to determine natural gas quality for combustion, focusing on the determination of the Wobbe Index (WI), which is a key parameter to set up the air-fuel ratio of the combustion in burners and motors, and to qualify a new type of dynamic viscosity transducer developped at Laboratoire de Production Microtechnique (LPM) of EPFL for the determination of the combustion properties. Inference transducers are a new kind of transducers that allow determining the combustion parameters of the gas by relating to fundamental thermo-physical parameters, and not through the determination of the concentration of the gas constituents, as in gas chromatographs and spectrometers. Here, the dynamic viscosity is chosen as the most promising thermo-physical property of a natural gas to relate to the WI and the Higher Heating Value (HHV). The viscometer takes measurements proportional to the resistance to flow of a gas through a capillary under the action of pulses of heat, and it can be therefore be described as a thermal pumping gas viscometer. A mathematical model and a finite element model (FEM) are used to predict the behavior of the system and for thermal optimization, which are combined by a thermal characterization of the system. The miniature heater used to generate the heat pulses inside the viscometer is a key element of the transducer, and after reviewing potential technologies, the design choices are reported and the fabrication process is exposed, followed by a mechanical and thermal characterization. In order to determine and validate the conversion of the WI from the dynamic viscosity, theoretical relations are analyzed and empirical characterizations are done with a test and calibration setup allowing to create given mixes of gases. Finally, the degradation of the transducer to contaminants of natural gas is investigated, and the analysis is focused to the characterization of the corrosion by the sulfur compounds of natural gas. Test vehicles are developed to study the effect of sulfur corrosion on metallic parts, electronic substrates, silicone adhesives and wirebonds materials, and experiments are held with the dedicated test setups developed at LPM of EPFL.

Using recycled rubber crumbs as drainage layer in extensive green roofs have high potential to reduce the heating and cooling loads in buildings over traditional materials used as drainage layer, such as pozzolana gravel. However, the environmental impact due to the life cycle should be analyzed to assess its environmental benefit. This paper evaluates the environmental performance of green roofs in which the drainage layer is made of rubber crumbs, a recycled material the use of which is still experimental for this purpose. In this paper Life Cycle Assessment (LCA) is applied to compare the environmental impact of four constructive systems, two extensive green roofs without insulation layer and with different drainage materials, e a recycled material, rubber crumbs, and a conventional one, pozzolana gravel -, in front of two conventional flat roofs, with and without thermal insulation (polyurethane), built in an experimental set-up consisting of four monitored house-like cubicles, located in Mediterranean continental climate (Lleida, Spain). The LCA considered the production, construction, operational, and disposal phases of the roofs, according to UNE-EN 15643-2. The operational phase was carried out using data measured in the experimental set-up, considering heating and cooling energy consumptions in the winter and summer period, respectively.

Abstract This review summarizes and organizes the literature on life cycle assessment (LCA), life cycle energy analysis (LCEA) and life cycle cost analysis (LCCA) studies carried out for environmental evaluation of buildings and building related industry and sector (including construction products, construction systems, buildings, and civil engineering constructions). The review shows that most LCA and LCEA are carried out in what is shown as “exemplary buildings”, that is, buildings that have been designed and constructed as low energy buildings, but there are very few studies on “traditional buildings”, that is, buildings such as those mostly found in our cities. Similarly, most studies are carried out in urban areas, while rural areas are not well represented in the literature. Finally, studies are not equally distributed around the world.

Low temperature sensitive products transport and storage is an issue worldwide due to changes of the lifestyle population increase. Thermal energy storage (TES) is nowadays one of the most feasible solutions in facing the challenge of achieving energy savings. Many researchers have investigated energy efficiency of different cold units by applying TES systems using phase change materials (PCM). This paper provides an overview of the existing Spanish and European potential energy savings and CO2 mitigation by incorporating TES systems to cold storage and transportation systems. Data on energy savings were compiled from different case studies. Results depend on the scenarios studied and the extent of TES systems implementation; in the case of Europe for instance, yearly CO2 emissions may be cut down between 5% and 22% in reference to 2008 CO2 emissions from cold production considering that the proposed implementation of PCM TES in the case studies found in the literature is done.

The growing interest in forest biomass has made chipping increasingly popular all across Europe. Many operators have equipped for the purpose, but the large variety of working conditions found in the European forests makes it difficult to correctly estimate the productivity of each specific operation, leading to uncertainty in crucial decisions, such as: operation scheduling, price setting, machinery selection and acquisition. In 2001, the Italian National Council for Research (CNR) and the University of California (UC) developed a spreadsheet freeware capable of returning reliable estimates of chipping productivity and cost, on the basis of user-defined input data. The model is still available from the CNR website and is the object of frequent downloading and inquiries. Such model contains a set of predictive equations derived from the results of 102 field trials, conducted with 30 different machines, under a range of working conditions. In order to facilitate comparison with other estimates and to achieve methodological transparency, the equations are assembled into a simple Microsoft Excel workbook, and the costs are calculated with standard costing methods currently used in Forest and Agricultural Engineering. Since then CNR has continued to work on the subject, with the goal of updating and refining the model. Such work has included 45 validation tests and a separate study on the delay (idle) time typical for different chipping operation layouts. The study was concluded in 2009 and confirms that the model developed by CNR can provide reliable estimates of chipper productivity under a range of operational conditions. Authors believe that such a model can assist European foresters in keeping ahead with the growing biomass sector, thus helping them to seize an important business opportunity.

This paper provides a synthesis and comparison of methodologies and results obtained in several studies devoted to the impact of climate change on hydropower. By putting into perspective various case studies, we provide a broader context and improved understanding of climate changes on energy production. We also underline the strengths and weaknesses of the approaches used as far as technical, physical and economical aspects are concerned. Although the catchments under investigation are located close to each other in geographic terms (Swiss and Italian Alps), they represent a wide variety of situations which may be affected by differing evolutions for instance in terms of annual runoff. In this study, we also differentiate between run-of-river, storage and pumping-storage power plants. By integrating and comparing various analyses carried out in the framework of the EU-FP7 ACQWA project, this paper discusses the complexity as well as current and future issues of hydropower management in the entire Alpine region.