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Dielectric elastomers are highly promising as functional materials for the rapidly developing field of flexible actuator and generator technology. They offer a unique combination of low densities and large reversible deformations of up to more than 100% in area, and consequently have great potential for many new types of application. However, implementation has been impeded by the lack of specialized materials. The elastomers that have so far been investigated suffer from a number of disadvantages, including the need for very high activation voltages and limited service lifetimes. This thesis describes an investigation of the use of elastomeric composites as dielectric elastomers with the aim of optimizing and improving their performance in actuators. The influence of materials properties on actuation was first analyzed on the basis of a simple physical model and materials properties derived from standard test methods. The implications for the actuation performance of three conventional dielectric elastomers were then considered in detail. A preliminary conclusion was that the actuation performance could be improved if the permittivity of the elastomers were to be increased by modification with ceramic or conductive fillers. However, actuation performance was shown to depend not only on the permittivity, but also on the elastic modulus, the electrical breakdown strength, and strain hardening. Thus, although significant increases in permittivity were achieved by this approach, actuation performance was compromised by an increase in modulus in the case of the ceramic fillers, and a dramatic drop in electrical breakdown strength, in the case of the conducting fillers. A more promising approach was therefore suggested to be the use of an organic conducting filler encapsulated in an insulating matrix. It was demonstrated that it is indeed possible to increase the permittivity of a given elastomer while maintaining a high electrical breakdown strength. Different processing routes were investigated in order to control the dispersion of the filler and tailor performance. The optimum filler concentration, i.e. that providing the best compromise between permittivity and stiffness, was determined to be approximately 16 vol%, resulting in an improvement by a factor of 2 in actuation strain for a given applied voltage over that obtained with the unmodified matrix. Higher filler concentrations were also argued to have considerable potential for use in generators, given that the observed increased permittivity was also associated with high electrical breakdown strengths and increased strains at break. A threefold increase in converted energy per working cycle was predicted for a composite containing 25.5 vol% fillers based on a simplified model for a dielectric elastomer generator. Whilst these results are extremely encouraging, it is concluded that the composite approach has, in general, only limited potential as a means of obtaining further increases in actuation performance. The major difficulty remains that the use of a relatively rigid second phase to increase dielectric performance will inevitably also increase the elastic modulus beyond a certain filler concentration. As argued in the final part of the thesis, the way forward may therefore ultimately depend on the development of new types of synthetic elastomeric matrix materials that combine intrinsic improvements in electrical response with reduced moduli.

The search for affordable high performance electrode materials in photoelectrochemical hydrogen production by solar water splitting is an ongoing quest. Hematite is a photoanode material with an electronic band gap suitable for efficient absorption of visible light in a photoelectrochemical cell (PEC). Although its poor electronic structure makes hematite a controversial candidate for PEC, it remains promising because it is an earth abundant, chemically stable and low cost material – necessary prerequisites for PEC to become a competitive cost-efficient solar fuel economy. In addition to reviewing some recent PEC research on hematite and its relevant physical and chemical characteristics, we show how hematite obtained by a low cost synthesis can be refined by hydrothermal treatment and further functionalized by coating with phycocyanin, a light harvesting protein known for photosynthesis in blue-green algae.

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.

Wood biomass is turned into industrial fuel through chipping. The efficiency of chipping depends on many factors, including chipper knife wear. Chipper knife wear was determined through a long-term follow-up study, conducted at a waste wood recycling yard. Knife wear determined a sharp drop of productivity (>20%) and a severe decay in product quality. Dry sharpening with a grinder mitigated this effect, but it could not replace proper wet sharpening. Increasing the frequency of wet sharpening sessions determined a moderate increase of knife depreciation cost, but it could drastically enhance machine performance and reduce biomass processing cost. Since benefits largely exceed costs, increasing the frequency of wet sharpening sessions may be an effective measure for reducing overall chipping cost. If the main goal of a chipper operator is to increase productivity and/or decrease fuel consumption, then managing knife wear should be a primary target. (C) 2014 Elsevier Ltd. All rights reserved.

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 [...]

A water-soluble organic redox couple (TT−/DTT) and new organic dyes (D45 and D51) have been developed for aqueous dye-sensitized solar cells (DSCs). An optimal efficiency of 3.5% was obtained using the D51 dye and an optimized electrolyte composition. The highest IPCE value obtained was 68% at 460 nm.

The oleaginous alga Chlorella protothecoides accumulates lipid in its biomass when grown in nitrogen-restricted conditions. To assess the relationship between nitrogen provision and lipid accumulation and to determine the contribution of photosynthesis in mixotrophic growth, C. protothecoides was grown in mixo- and heterotrophic nitrogen-limited continuous flow cultures. Lipid content increased with decreasing C/N, while biomass yield on glucose was not affected. Continuous production of high lipid levels (57% of biomass) was possible at high C/N (87-94). However, the lipid production rate (2.48 g L(-1) d(-1)) was higher at D=0.84 d(-1) with C/N 37 than at D=0.44 d(-1) and C/N 87 even though the lipid content of the biomass was lower (38%). Photosynthesis contributed to biomass and lipid production in mixotrophic conditions, resulting in 13-38% reduction in CO2 production compared with heterotrophic cultures, demonstrating that photo- and heterotrophic growth occurred simultaneously in the same population.

We report the properties of a shape-persistent tetra-terpyridine ligand whose coordination to transition metal ions guides its three-dimensional self-assembly in two steps: at first, nanoscale objects form, which with time, self-assemble into micrometer structures. This work highlights the potential for control of the molecular self-assembly of molecules on the nanoscale, and the successive self-assembly of the formed supramolecular nanosystems to yield mesoscopic objects.