| 1. |
- Nordenström, Malin
(författare)
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Colloidal interactions and arrested dynamics of cellulose nanofibrils
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Over the past decades, concerns for the environment have increased and efforts to achieve a sustainable society have intensified. One particular challenge is to replace fossil-based plastics with biodegradable materials produced from renewable resources. Cellulose nanofibril (CNF)-based materials are strong candidates due to their excellent mechanical properties, nano-dimensions and molecular structure, which is suitable for modification. CNFs can be obtained from wood and are elongated, often charged, particles which are usually handled in aqueous dispersions. The colloidal stability is sensitive, and instability results in aggregation or transition to an arrested state. Since the properties of CNF-based materials rely on dispersion of the CNFs, an understanding of the colloidal behaviour is crucial.This work has focused on the interactions and dynamics of CNFs in different colloidal states. Arrested states of CNFs were studied in detail and it was found that two types of arrested state exist, with different colloidal interactions and mechanisms governing their formation. The dynamics in arrested and dispersed states were studied by tracer diffusion measurements, and it was found that small amounts of CNFs can constitute an excellent stabiliser for other particle dispersions according to a so far unexplored mechanism.The effects of altering the colloidal interactions using different strategies were also evaluated. The counterions of CNFs were exchanged and the impact on the swelling behaviour was measured. Based on the results, different contributions to the counterion-dependent interactions are discussed. Two strategies for using polymers to alter the interactions were furthermore studied. Polyethylene glycol (PEG) was grafted to CNFs in order to increase the arrested state threshold concentration. PEG, carboxymethyl cellulose and lignin, were also used as additives which improved the redispersion of dried CNF, especially in the case of samples containing lignin.
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| 2. |
- Bejnö, Hampus, 1984-
(författare)
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Early intervention and autism : Improving preschool program quality for children with autism spectrum disorder receiving Early Intensive Behavioral Intervention using the Autism Program Environment Rating Scale (APERS)
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The quality of the learning environment in preschool is of significant importance for children with autism spectrum disorder (ASD). However, very limited research has addressed how this environment can be improved. In regard to early intervention, most previous studies have primarily focused on child characteristics, and intervention content and quantity, rather than the broader learning environment in which interventions are delivered. Thus, the overall aim of this thesis was to study the quality of the learning environment for children with ASD. In particular, the focus was on children who receive Early Intensive Behavioral Intervention (EIBI) in community-based Swedish preschools, using the Autism Program Environment Rating Scale (APERS). Within this framework, three studies were conducted.In study 1, we translated, culturally adapted, and systematically assessed the content validity of APERS, a rating scale designed to assess the program quality for children with ASD in educational settings. In the process, the scale was modified to make the instrument as relevant as possible for the Swedish preschool context, and re-named APERS-P-SE. Nine experts rated the clarity and comprehensiveness of the individual items, as well as the relevance of the scale in its entirety. In study 2, we evaluated APERS-P-SE as the foundation for professional development for preschool staff working with children with ASD receiving EIBI, to promote preschool learning environment quality (primary outcome), and outcomes for autistic children, and preschool staff (secondary outcomes). Using a quasi-experimental design, preschool staff either implemented EIBI enriched by in-service training and on-site coaching based on APERS-P-SE assessments (k = 9), or EIBI only (k = 8) during 8 months. A total of 17 children and 35 preschool staff participated, across 17 preschools. In study 3, individual interviews and focus-group interviews were conducted with preschool staff, preschool principals, habilitation supervisors, and parents to children with ASD who had participated in study 2 and received the APERS-P-SE-based intervention. Through these interviews, the different groups of stakeholders provided their thoughts about what they found to be the most important aspects of preschool programs for autistic children who receive EIBI, and their opinions and experiences of participating in study 2. Study 1 demonstrated a high level of content validity for the Swedish version of the APERS. In study 2, the EIBI/APERS-P-SE preschools significantly improved their learning environment, compared to the preschools that received EIBI only. Outcomes for autistic children and preschool staff did not differ significantly between the groups, despite positive descriptive findings. In study 3, four themes were identified as being key aspects of preschool programs with high quality to promote optimal development of children with ASD: (1) staff’s competence, (2) children’s inclusion and participation, (3) collaboration, and (4) learning environment. Overall, the stakeholders described the APERS-P-SE-based model as helpful in improving children’s participation, preschool staff’s engagement with the child, and optimizing child outcomes.Taken together, the results indicate that APERS-P-SE is an instrument with a high level of content validity, and that it can be used in combination with in-service training and on-site coaching to improve preschool program quality for children with ASD.
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| 3. |
- Chang, Liu, 1986-
(författare)
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Ghost in the shell : Studies on subsurface oxygen in oxide-derived copper nanocube catalysts
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the passage of time and the advancement of our industrial civilization, environmental concerns have become more and more recognized since the 1990s. Carbon dioxide reduction reactions are capable of converting carbon dioxide into valuable hydrocarbons and reducing the carbon emission from the combustion of fossil fuels. This is a promising direction for sustainable energy resources given that the scarcity of fossil fuels is becoming more threatening to the survival of mankind. In recent years, oxide-derived metal nanostructures have been synthesized and show unique catalytic features. Recently, Sloan et al. synthesized a novel oxide-derived copper nanocube structure, which showed a high selectivity toward ethylene over methane and low overpotentials. In this work, the presence of subsurface oxygen in the catalyst surface is tested with density functional theory (DFT) calculations, as a complement to experimental x-ray photoelectron spectroscopy. Due to limitations on the scale of modeling with DFT, the results indicate a very low stability of subsurface oxygen, which give rise to a question if subsurface oxygen would be stable with a reasonably large cluster model. Self-consistent charge density functional tight binding (SCC-DFTB) is adopted to investigate a nanocube model. In this model, a manually reduced cuprious oxide nanocube is constructed and investigated. Subsurface oxygen atoms close to facets are found to be more stable inside. A higher degree of disorder is proposed to be the cause of this difference in stabilizing subsurface oxygen atoms between the slab and nanocube models. The presence of subsurface oxygen enhances the adsorption of CO on the Cu(100) surface, increasing the likelihood for adsorbed CO molecules to dimerize, which is the rate determining step for ethylene production on Cu(100) under low-overpotential conditions. With subsurface electronegative atoms such as oxygen or fluorine, it is also found that the d-band scaling relation could be broken.
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| 4. |
- Englund, Hillevi, 1980-
(författare)
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Soluble amyloid-β aggregates in Alzheimer’s disease
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Soluble oligomeric aggregates of the amyloid-β (Aβ) peptide are suggested to initiate Alzheimer's disease (AD), leading to impaired synapse signalling, widespread neuronal death and loss of cognitive functions. These aggregates seem tightly linked to disease progression, and have therefore gained much attention as potential novel disease markers. In this thesis soluble oligomeric Aβ aggregates in general, and the Aβ protofibril species in particular, have been investigated with the aim to quantify and determine their role in AD pathogenesis. Sandwich-ELISAs specifically measuring Aβ42 peptides are widely used both in AD research and as complements for clinical diagnosis. Here it was demonstrated that presence of soluble Aβ aggregates disturbs such analyses, making it difficult to interpret the results. This discovery was made through analyses of samples from cell- and mouse models carrying the AD causing 'Arctic' APP mutation. When analyzed by ELISA, Aβ42 levels were reduced in Arctic samples, in contrast to levels measured by denaturing SDS-PAGE Western blot. The same divergence in Aβ42-levels between analyses was observed in CSF samples from Down syndrome infants. The discrepancy between methods was hypothesized to be due to presence of soluble Aβ aggregates leading to impaired ELISA detection caused by epitope masking. This was confirmed by developing a protofibril specific ELISA, by which samples from Arctic cell- and mouse models were demonstrated to have enhanced Aβ protofibril levels. AD patients have reduced ELISA-measured Aβ42-levels in CSF compared to healthy controls. To test if this reduction was due to oligomeric Aβ species present in AD CSF, Aβ42-levels were analyzed under both denaturing and non-denaturing conditions. These two measures were combined and an Aβ42 oligomer ratio established. Higher ratios were found in AD patients than healthy controls, implying that Aβ oligomers are present in CSF during Alzheimer pathogenesis. The observations from AD patients and young Down syndrome individuals suggest that Aβ42 oligomer formation is an early mechanism of AD pathogenesis, which potentially could be used as a biomarker to monitor disease development.
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| 5. |
- Eriksson, Martin, 1975-
(författare)
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Trafikpolitik och regional omvandling : Beslutsprocesserna om isbrytningen längs Norrlandskusten 1940-1975
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis is to understand the decision-making processes concerning ice-breaking along the coast of Norrland, with the specific aim to analyse the activities of regional interest groups in the Norrland region and government agents at different administrative levels at the key stages of the decision-making processes: initiation, drafting and decision-making. The thesis also explores how institutional factors at different administrative levels affected the agents that were involved at those stages of the decision-making processes. As navigation along the northern Swedish coast must negotiate winter conditions which causes ports to freeze over, the government ice-breaking service functions as an instrument to compensate the export firms in Norrland for these constrains. Year-round navigation in the north Swedish coastal waters was achieved through a series of decision-making processes that took place during the period from 1940 to 1975. These decision-making processes are important to study since ice-breaking was an integrated component of the expanding heavy basic industries in Norrland and thereby for the rapidly growing exports during the 1950s and 1960s. This period is the decisive point in the economic history of the Norrland region regarding how the natural resources should be exploited and how exports should be advanced. This study concludes that the decision-making processes were initiated by government agents at different administrative levels. Official investigatory commissions were set up at several occasions to deal with issues related to the government ice-breaker service by the ministries responsible for ice-breaker policy. It is also demonstrated that the decision-making processes concerning ice-breaker investments were initiated by the government boards that were responsible for the operation of the ice-breaker service. In this respect, the study concludes that the government activities during the initiation stages should not be confused as a sign of regional interest group passivity on these issues. The activities of the interest groups during the initiation stages were primarily intended to draw attention to the problems caused by winter to regional shipping, in order to put the issue on the political agenda. As the decision-making processes proceeded into the drafting stages, the participation from regional interest groups was much more significant as the government offered interest groups forums and procedures for structural consulting through various organisational arrangements. The regional interest groups that participated in those arrangements were industrial firms in the heavy basic industries sector. In those cases other regional interest groups participated, they would promote the interests of those firms. As a result, the final drafts from committees and government bodies included arguments that favoured an expansion of ice-breaking to promote the growth of the heavy basic industries in the Norrland region. The analysis of the decision-making stages suggests that a combination of institutional factors at different administrative levels contributed to the outcome of the decision-making processes. One result is that the general aims of macro policy such as trade policy, growth policy and regional development policy were favourable towards an expansion of the government ice-breaker service, which would benefit the export industries in the Norrland region. Another result is that the sectoral organization within the government maritime bodies contributed significantly to the outcome of the decision-making processes. Large-scale planning and operational experimentation was allowed to take place within the ice-breaker service, which convinced the government that ice-breaking and winter navigation was a feasible transport alternative.
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| 6. |
- Evertsson, Maria
(författare)
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”Så vittna du om min mandom!” : Wilhelm Peterson-Bergers konstfilosofi och könsuppfattning, med särskild hänsyn till åren 1896-1913
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall purpose of this study is to elucidate Wilhelm Peterson-Berger’s perception of gender and how it is manifested in his philosophy of art. His perception of gender also incorporates conceptions of history, music and nationality. The research question is analysed primarily by reviewing Peterson-Berger’s writings from 1896 to 1913. The research is intended to shed new light on a previously overlooked area of research, using gender theory and discourse analysis. Peterson-Berger and his work have not been examined previously from a gender theory perspective. The research shows that Peterson-Berger was influenced in large measure by the prevailing ideals of his time, although he was in some ways more innovative than many of his contemporaries. Around the turn of the 20th century there was a great deal of focus on biology, with a clear distinction drawn between femininity and masculinity[1] . Masculinity was held up as an ideal, in contrast to femininity and effeminacy. Peterson-Berger advocated this distinction, and emphasized the biological distinction between [2] masculinity and femininity. However, a man need not always have all the characteristics that were considered typically masculine for his time, nor was it necessary for a woman to possess all the feminine characteristics typical of the female gender. According to Peterson-Berger, a woman could have a masculine soul, and vice versa. And although he often took a negative view of women, he granted musical recognition to singers who realized music in what was, to him, a masculine way. Moreover, the majority of Peterson-Berger’s close friends were women, and he dedicated many of his works to women.Theories of race and human evolution were circulating at the turn of the century, and clearly influenced Peterson-Berger. This study has shown that he pursued the writings of [3] Chamberlain[4] and Nietzsche. Incorporating elements of old Gothicist theories with ideas from the two aforementioned thinkers, Peterson-Berger constructed his own racial theory. He asserted that all peoples originated from the Nordic region, which he believed to be the birthplace of the entire human race. According to his theory, southern peoples were inferior[5] , with one exception, the Greeks, towards whom he was very positively disposed. This had to do with the ancient music drama, which Peterson-Berger believed had been created by inhabitants from the north who had migrated to Greece.Peterson-Berger’s notions about peoples from the north versus peoples from the south were interwoven with theories of sexuality. He believed that Germanic peoples were more sexually abstemious than southern Europeans, and that peoples who lived in the south were sexually dissolute. To indulge one’s sexuality was, in his view, a character flaw. Conversely, Peterson-Berger viewed asexuality as a masculine ideal, and believed it to be more common in the north. A number of contradictions have emerged in his perceptions of race and sexuality. A number of his perceptions with respect to gender roles, sexuality, nationalism and philosophy[6] are portrayed in his opera Arnljot, as are the contradictions inherent in them. For instance, the character Arnljot has many of the typical masculine characteristics held up as ideal, but nevertheless exhibits both weaknesses and deficiencies. This is reflected in both the music and the opera libretto.
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| 7. |
- González Arcos, Angélica Viviana, 1986-
(författare)
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RhPt and Ni based catalysts for fuel reforming in energy conversion
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Although current trends in global warming are of great concern, energy demand is still increasing, resulting in increasing pollutant emissions. To address this issue, we need reliable renewable energy sources, lowered pollutant emissions, and efficient and profitable processes for energy conversion. We also need to improve the use of the energy, produced by existing infrastructure. Consequently, the work presented in this thesis aims at investigating current scientific and technological challenges in energy conversion through biomass gasification and the alternative use of fossil fuels, such as diesel, in the generation of cleaner electricity through auxiliary power units in the transportsector. Production of chemicals, syngas, and renewable fuels is highly dependent on the development and innovation of catalytic processes within these applications. This thesis focuses on the development and optimization of catalytic technologies in these areas. One of the limitations in the commercialization of the biomass gasification technology is the effective catalytic conversion of tars, formed during gasification. Biomass contains high amounts of alkali impurities, which pass on to the producer gas. Therefore, a new material with alkali tolerance is needed.In the scope of this thesis, a new catalyst support, KxWO3 – ZrO2 with high alkali resistance was developed. The dynamic capability of KxWO3 – ZrO2 to store alkali metals in the crystal structure, enhances the capture of alkali metals "in situ". Alkali metals are also important electronic promoters for the active phase, which usually increases the catalysts activity and selectivity for certain products. Experimental results show that conversion of 1-methylnaphathalene over Ni/KxWO3 – ZrO2 increases in the presence of 2 ppm of gas-phase K (Paper I). This support is considered to contribute to the electronic equilibrium within the metal/support interface, when certain amounts of alkali metals are present. The potential use of this support can be extended to applications in which alkali "storage-release" properties are required, i.e. processes with high alkali content in the process flow, to enhance catalyst lifetime and regeneration.In addition, fundamental studies to understand the adsorption geometry of naphthalene with increasing temperature were performed in a single crystal of Ni(111) by STM analyses. Chapter 9 presents preliminary studies on the adsorption geometry of the molecule, as well as DFT calculations of the adsorption energy. In relation to the use of clean energy for transport applications, hydrogen generation through ATR for FC-APUs is presented in Papers II to V. Two promoted RhPt bimetallic catalysts were selected in a previous bench scale study, supported on La2O3:CeO2/d – Al2O3 and MgO : Y2O3/CeO2 – ZrO2. Catalyst evaluation was performed in a fullscale reformer under real operating conditions. Results showed increased catalyst activity after the second monolithic catalyst due to the effect of steam reforming, WGS reaction, and higher catalyst reducibility of the RhxOy species in the CeO2 – ZrO2 mixed oxide, as a result of the improved redox properties. The influence of sulfur and coke formation on diesel reforming was assessed after 40 h on stream. Sulfur poisoning was evaluated for the intrinsic activity related to the total Rh and Pt area observed after exposure to sulfur. Sulfur concentration in the aged catalyst washcoat was observed to decrease in the axial direction of the reformer. Estimations of the amount of sulfur adsorbed were found to be below the theoretical equilibrated coverage on Rh and Pt, thus showing a partial deactivation due to sulfur poisoning.
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| 8. |
- Liu, Chang, 1986-
(författare)
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Le Fantôme de l’Opéra - Studies on Atoms and Electrons Beneath
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The carbon dioxide reduction reaction is a promising candidate to tackle ecological challenges of our age. This is due to its capability of reducing carbon dioxide emission generated from the combustion of fossil fuels by converting carbon dioxide into valuable hydrocarbons. Oxide-derived metal nanostructures have been found to exhibit unique catalytic characteristics for facilitating the carbon dioxide reduction reaction. In this thesis work, the stability, influence, and effects of subsurface oxygen atoms are investigated by theoretical computations with various levels of theory and models. It is found that subsurface oxygen atoms are stable and that their presence increases the CO adsorption strength and coverage on oxide-derived Cu surface. This is explained by a reduced σ-repulsion and leads to the breaking of scaling relations. Although it does not directly reduce the CO dimerization barrier, the adsorption of H atoms is inhibited thus steering the selectivity. The presence of subsurface oxygen atoms is also concluded from a joint work with experimental and theoretical efforts of X-ray photoelectron spectroscopy. The precursor region of CO desorption from Ru(0001) is studied with the transition potential method. In contrast, for the simulation of the X-ray spectroscopy results on p4g C/Ni(100), which is a surface reconstruction when carbon atoms adsorb on Ni(100), vibrational effects are also needed for understanding the experimental data.
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| 9. |
- Lord, Anna, 1979-
(författare)
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Targeting Early Stages of Alzheimer’s Disease in a Transgenic Model
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Arctic mutation causes early-onset Alzheimer’s disease (AD), and makes amyloid-β (Aβ) peptides more prone to form Aβ protofibrils. The aims of this thesis were to investigate the mechanisms of the Arctic mutation in vivo, and to use transgenic models to determine the role of early intermediates of Aβ aggregation, like protofibrils, in the pathogenesis. In addition, we aimed to evaluate protofibrils as a therapeutic target.Transgenic models with Arctic and Swedish mutations (tg-ArcSwe), and with the Swedish mutation alone (tg-Swe) were created. The Arctic mutation favored amyloidogenic processing of amyloid-β precursor protein (APP) in transgenic mice and cultured cells. The observed shift in the subcellular location and processing of APP led to increased production of intracellular Aβ in vitro, and also partly explained the early accumulation of intraneuronal Aβ in tg-ArcSwe mice. The intraneuronal Aβ in combination with enhanced levels of protofibrils appeared long before extracellular plaques emerged. Elevated protofibril levels were associated with intraneuronal Aβ and linked to spatial learning deficits in young mice, suggesting that protofibrils cause AD-related cognitive deficits. The Arctic mutation also enhanced senile plaque pathology in aged tg-ArcSwe mice, and the accelerated plaque deposition was accompanied by decreased intraneuronal Aβ. This suggests a dynamic equilibrium between the early accumulation of intraneuronal Aβ and the later senile plaque pathology.Aβ protofibrils were evaluated as a therapeutic target in tg-ArcSwe mice with passive immunization using a protofibril-selective antibody. This treatment cleared protofibrils without removing senile plaques. However, plaque formation was prevented if treatment began early, indicating that protofibrils are intermediate species of Aβ fibrillization in vivo. Targeting senile plaques with immunotherapy requires early diagnosis and intervention, whereas protofibrils can be specifically cleared from brain despite substantial AD-like deposition of insoluble Aβ. The early and persistent presence of protofibrils throughout Aβ amyloidosis makes them a promising target for future diagnostic and therapeutic strategies in AD.
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| 10. |
- Mohseni, Farzad, 1981-
(författare)
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Power to gas : Bridging renewable electricity to the transport sector
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Globally, transport accounts for a significant part of the total energy utilization and is heavily dominated by fossil fuels. The main challenge is how the greenhouse gas emissions in road transport can be addressed. Moreover, the use of fossil fuels in road transport makes most countries or regions dependent on those with oil and/or gas assets. With that said, the question arises of what can be done to reduce the levels of greenhouse gas emissions and furthermore reduce dependency on oil? One angle is to study what source of energy is used.Biomass is considered to be an important energy contributor in future transport and has been a reliable energy source for a long time. However, it is commonly known that biomass alone cannot sustain the energy needs in the transport sector by far.This work presents an alternative where renewable electricity could play a significant role in road transport within a relatively short time period. Today the amount of electricity used in road transport is negligible but has a potential to contribute substantially. It is suggested that the electricity should be stored, or “packaged” in a chemical manner, as a way of conserving the electrical energy. One way of doing so is to chemically synthesize fuels. It has been investigated how a fossil free transport system could be designed, to reach high levels of self-sufficiency. According to the studies, renewable electricity could have the single most important role in such a system. Among the synthetic fuels, synthetic methane (also called synthetic biogas) is the main focus of the thesis. Hydrogen is obtained through water electrolysis, driven by electricity (preferable renewable), and reacted with carbon dioxide to produce synthetic methane. The concept of the mentioned process goes under the name Power to Gas. The electricity to fuel efficiency of such a process reaches about 50 %, but if utilizing excess heat produced during the electrolysis and the reaction, the total process efficiency can reach much higher levels.The economics of the process is as important as the technology itself in terms of large scale implementation. The price of electricity and biogas are the most important influences on the economic viability. The minimum “spread” between purchase and selling price can be determined to obtain a general perception of the economic feasibility. In this case biogas must be sold about 2.6 times higher than purchased electricity per kWh.
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