| 1. |
- Cruz, Igor, 1986-
(author)
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Evaluating the utilisation of industrial excess heat from an energy systems perspective
- 2022
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Licentiate thesis (other academic/artistic)abstract
- Sweden aims to achieve climate neutrality by 2045. The need to immediately reduce greenhouse gas emissions in order to achieve climate targets affects industry directly. The pulp and paper sector is responsible for more than 50% of industrial energy use in Sweden. Increased energy efficiency is expected to contribute significantly to the reduction of primary energy use. The recovery and utilisation of industrial excess heat (IEH) has been identified as an important potential contribution to energy efficiency in industry. Previous research based on top-down studies has estimated the availability of IEH for entire sectors, and bottom-up results for many case studies are available. While top-down studies lack detailed information on the profile of the excess heat available, bottom-up studies have limited coverage. Detailed information about excess heat amounts and temperature levels is required for the assessment of the potential of the various heat recovery technologies that are available. The aim of this thesis is to present, in a series of steps, methods to systematically analyse an industrial process to obtain a detailed profile of the excess heat available under various process conditions, to aggregate results that can be generalised to whole industrial sectors, and to obtain IEH recovery potentials using different technologies. The assessment of the utilisation options for IEH recovery is complemented with an analysis of system aspects that could affect profitability and global greenhouse gas (GHG) emissions. An energy-targeting procedure combined with optimisation has been applied to six case studies of kraft pulp and paper mills in Sweden. This method obtained IEH profiles that were used in a regression analysis to estimate the IEH availability and electricity generation potentials from low and medium temperature IEH using organic Rankine cycles (ORC). A comparison of profitability and global GHG emissions between ORC electricity generation using IEH and small-scale combined heat and electricity (CHP) production is presented for three energy markets.The results show that there is a potential to increase electricity generation from low and medium temperature IEH by 7–9% in the kraft mills in Sweden, depending on the level of process integration considered. The utilisation of low and medium temperature IEH for electricity generation has the potential to reduce global GHG emissions in all the energy-market scenarios considered, but if biomass is considered a limited resource, district heating (DH) deliveries can achieve higher global GHG reductions. ORC electricity generation from low and medium temperature IEH is economically viable and showed overall better profitability and GHG emissions reductions than small-scale CHP using ORCs. The economic feasibility of ORC electricity generation is less affected by external conditions and uncertainties than direct DH deliveries.
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| 2. |
- Chen, Zhe, 1987-
(author)
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Surface Integrity of Broached Inconel 718 and Influence of Thermal Exposure
- 2014
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Licentiate thesis (other academic/artistic)abstract
- Inconel 718 is a nickel-based superalloy that is extensively used as a disc material in gas turbine engines. The service life of gas turbine discs is normally governed by the modes of material degradation and fatigue failure since they work mostly at high temperatures and are subjected to cyclic mechanical loadings. Fatigue failures often start with the initiation of cracks at the surface and the precise details of the failure process significantly depend on the surface conditions. In turbine disc production, one of the last manufacturing steps is to broach root fixings, commonly of fir-tree design, for blade mounting. It has always been a challenge when machining Inconel 718 due to its high strength retention at elevated temperatures, rapid work hardening, as well as low thermal conductivity. This usually leads to rapid tool wear, and consequently shorter tool life, and at the end to the deterioration of the surface integrity of the machined components.The aim of this licentiate thesis is to increase our knowledge about the surface integrity, especially microstructure and residual stresses, of broached Inconel 718 and its stability under thermal exposure. This knowledge can later be used for analyzing the initiation and propagation of fatigue cracks in broached Inconel 718, particularly in the case of high temperature fatigue, thereby giving a better understanding of the failure mechanism of gas turbine discs from a fatigue point of view.A broaching operation has been performed using similar cutting conditions as that used in turbo machinery industries for producing fir-tree root fixings. In addition, service damages were analyzed in a retired dis of Inconel 718. Surface defects, severe plastic deformation and generation of high tensile residual stresses have been found to be the main damages to the surface integrity caused by the broaching operation. The machining induced plastic deformation was found to accelerate the microstructural degradation beneath the broached surface when subjected to thermal exposure. The surface tensile residual stresses can be completely removed after short thermal exposure, the tensile layer in the sub-surface region, however, exhibited a high resistance to stress relief at high temperatures. The damage analysis on the retired disc indicated that presence of the highly deformed layer on the machined surface is negative for preventing the occurrence of fretting fatigue in turbine discs.
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| 3. |
- Lindkvist, Emma, 1984-
(author)
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System studies of biogas production : comparisons and performance
- 2020
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Doctoral thesis (other academic/artistic)abstract
- Biogas has the potential to be part of the transition towards a more sustainable energy system. Biogas is a renewable energy source and can play an important role in modern waste management systems. Biogas production can also help recirculate nutrients back to farmland. Besides all this, biogas is a locally produced energy source with the potential to increase global resource efficiency, since it can lead to more value and less waste, as well as decreased negative environmental effects. However, biogas production systems are complex, including different substrates, different applications for biogas and digestate, and different technology solutions for digestion, pre-treatment and for upgrading the raw gas. To increase the development of biogas production systems, knowledge sharing is a key factor. To increase this knowledge sharing, comprehensible analysis and comparisons of biogas production systems are necessary. Thus, studies are needed to verify the resource efficiency of biogas production systems from different perspectives.The aim of this thesis is to perform a systems analysis of biogas production systems and to explore how to analyse and compare biogas production systems. An additional aim is to study biogas production systems from a systems perspective, with a focus on environment, energy and economy. Studying biogas production systems from different system levels, as well as from different approaches, is beneficial because it results in deeper knowledge of biogas systems and greater opportunities to identify synergies.Systems studies of biogas are important, since biogas systems are often complex and integrated with other systems. In this thesis, biogas systems analyses are performed at different levels. In the widest system study, classifications of different biogas plants are analysed and classifications in different European countries are compared, with the prospect of paving the way for a new common classification for biogas plants in Europe. Today, classifications vary between countries, and hence comparisons of plants in different countries are difficult. In the narrowest system study, a new methodology for analysing energy demand at different biogas production plants has been developed. The aim was to develop a methodology that is applicable for all kinds of biogas plants with energy inputs. The methodology describes the process of analysing energy demand and allocating energy to sub-processes and unit processes.Further, an approach for assessing the resource efficiency of different treatment options for organic waste was designed. The approach includes environmental, economic and energy perspectives, and was applied to five different regions with several food manufacturing companies. A study of treatment options for organic waste from a single food company was also conducted. The results showed that biogas production is a resource-efficient way to treat waste from the food industry. The approach enables a wider analysis of biogas systems, and the results from the applications show the complexity of assessing resource efficiency. It is also shown that it is important to understand that the resource efficiency of a system is always in relation to the substituted system.In this thesis, three different approaches to analysing biogas production systems are presented: categorization, resource efficiency analysis and energy demand analysis. These approaches all contribute to the understanding of biogas systems and can help, in different ways, to increase knowledge about biogas systems in the world. If knowledge about different biogas systems can be easily disseminated, more of the unused potential of biogas production may be realized, and hence more fossil fuels can be replaced within the energy system.
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| 4. |
- Ellencrona, Karin, 1973-
(author)
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Functional characterization of interactions between the flavivirus NS5 protein and PDZ proteins of the mammalian host
- 2009
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Doctoral thesis (other academic/artistic)abstract
- Flaviviruses are found all over the world and affect and infect millions of people every year. Flavivirus infection can lead to severe clinical outcomes resulting in neuronal damages e.g. Tick-borne encephalitis virus (TBEV), or severe hemorrhagic fevers e.g. Dengue virus (DENV). In order to effectively treat infected patients and to prevent these diseases we must understand how these viruses work and how they interfere with the mammalian host. This thesis is focusing on interactions between the virus protein NS5 and human host cell proteins. The interactions presented here might be key factors for out-come of viral disease. NS5 is the largest of the non-structural proteins and is essential for the replication and the capping as it contains both RNA dependent RNA polymerase and Methyltransferase domains. We found that TBEV NS5 interacts with human PDZ domain protein Scribble, a polarization protein important e.g. in regulating membrane trafficking. We determined that the interaction depend on a novel internal motif in TBEVNS5. This interaction could be correlated to NS5s ability to interfere with the immune system as absence of Scribble prevented NS5 from blocking phosphorylation of STAT upon Interferon induction. The role of NS5 in human PDZ domain targeting was addressed further by using a PDZ array system. Both TBEVNS5 and DENVNS5 bind additional PDZ domains using the internal motif. The tight junction protein ZO-1 binds both DENVNS5 and TBEVNS5. DENVNS5 is mainly present in the nucleus and co-localize with ZO-1 in un-polarized cells. In polarized cells TBEVNS5 and ZO-1 co-localize at the plasmamembrane. Putative C-terminal PDZ binding motifs of TBEVNS5 and WNVNS5 were characterized using the PDZ array system. This detected four novel binding partners of TBEVNS5 but numerous of potential WNVNS5 binding partners. We found that TBEVNS5 co-localizes with ZO-2 in the cellular membrane. Further, we found that TBEVNS5 induce the AP-1 by a 2 fold over the control.
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| 5. |
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| 6. |
- Gyllenhammar, Magnus, 1992-, et al.
(author)
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Towards an Operational Design Domain That Supports the Safety Argumentation of an Automated Driving System
- 2020
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In: Proceeding of the 10th European Congress on Embedded Real Time Software and Systems. - Toulouse.
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Conference paper (peer-reviewed)abstract
- One of the biggest challenges for self-driving road vehicles is how to argue that their safety cases are complete. The operational design domain (ODD) of the automated driving system (ADS) can be used to restrict where the ADS is valid and thus confine the scope of the safety case as well as the verification. To complete the safety case there is a need to ensure that the ADS will not exit its ODD. We present four generic strategies to ensure this. Use cases (UCs) provide a convenient way providing such a strategy for a collection of operating conditions (OCs) and further ensures that the ODD allows for operation within the real world. A framework to categorise the OCs of a UC is presented and it is suggested that the ODD is written with this structure in mind to facilitate mapping towards potential UCs. The ODD defines the functional boundary of the system and modelling it with this structure makes it modular and generalisable across different potential UCs. Further, using the ODD to connect the ADS to the UC enables the continuous delivery of the ADS feature. Two examples of dimensions of the ODD are given and a strategy to avoid an ODD exit is proposed in the respective case.
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| 7. |
- Haraldsson, Joakim, 1990-
(author)
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Improved Energy Efficiency in the Aluminium Industry and its Supply Chains
- 2020
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Doctoral thesis (other academic/artistic)abstract
- Energy is an essential resource in the daily lives of humans. However, the extraction and use of energy has an impact on the environment. The industrial sector accounts for a large share of the global final energy use and greenhouse gas (GHG) emissions. The largest source of industrial GHG emissions is energy use. The production and processing of aluminium is energy- and GHG-intensive, and uses significant amounts of fossil fuels and electricity. At the same time, the global demand for aluminium is predicted to rise significantly by the year 2050. Improved energy efficiency is one of the most important approaches for reducing industrial GHG emissions. Additionally, improved energy efficiency in industry is a competitive advantage for companies due to the cost reductions that energy efficiency improvements yield.The aim of this thesis was to study improved energy efficiency in the individual companies and the entire supply chains of the aluminium industry. This included studying energy efficiency measures, potentials for energy efficiency improvements and energy savings, and which factors inhibit or drive the work to improve energy efficiency. The aim and the research questions were answered by conducting a literature review, focus groups, questionnaires and calculations of effects on primary energy use, GHG emissions, and energy and CO2 costs.This thesis identified several energy efficiency measures that can be implemented by the individual companies in the aluminium industry and the aluminium casting foundries. The individual companies have large potentials for improving their energy efficiency. Energy efficiency measures within the electrolysis process have significant effects on primary energy use, GHG emissions, and energy and CO2 costs. This thesis showed that joint work between the companies in the supply chains of the aluminium industry is needed in order to achieve further energy efficiency improvements compared to the companies only working on their own. The joint work between the companies in the supply chain is needed to avoid sub-optimisation of the total energy use throughout the entire supply chain. Better communication and closer collaboration between all the companies in the supply chain are two of the most important aspects of the joint work to improve energy efficiency. An energy audit for the entire supply chain could be conducted as a first step in the joint work between the companies in the supply chains. Another important aspect is to increase the use of secondary aluminium or remelted material waste rather than primary aluminium.The companies in the Swedish aluminium industry and the aluminium casting foundries have come some way in their work to improve energy efficiency within their own facilities. However, the results in this thesis indicate that cost-effective technology and improved management can, in total, save 126–185 GWh/year in the Swedish aluminium industry and 8–15 GWh/year in the Swedish aluminium casting foundries.This thesis identified several demands regarding economics, product quality and performance, and environment placed on the companies and products in the supply chains that affect energy use and work to improve energy efficiency. These demands can sometimes counteract each other, and some demands are more important to meet than improving energy efficiency. This implies that improving the energy efficiency of the supply chains as well as designing products so they are energy-efficient in their use phase can sometimes be difficult. The results in this thesis indicate that it would be beneficial if the companies reviewed these demands to see whether any of them could be changed.Both the economic aspects and demands from customers and authorities were shown to be important drivers for improved energy efficiency in the supply chains. However, placing demands on energy-efficient production and a company’s improved energy efficiency would require those placing the demands to have deeper knowledge compared to demanding green energy, for example. Requiring a company to implement an energy management system to ensure active work to improve energy efficiency would be easier for the customer than demanding a certain level of energy efficiency in the company’s processes. Additionally, energy audits and demands on conducted energy audits could act as drivers for improved energy efficiency throughout the supply chains.This thesis showed that the most important barriers to improved energy efficiency within the individual companies include different types of risks as well as the cost of production disruption, complex production processes and technology being inappropriate at the site. Similar to the supply chains, important drivers for improved energy efficiency within the individual companies were shown to be economic aspects and demands from customers and authorities. However, the factors that are most important for driving the work to improve energy efficiency within the individual companies include the access to and utilisation of knowledge within the company, corporate culture, a longterm energy strategy, networking within the sector, information from technology suppliers and energy audits.
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| 8. |
- Johansson, Magnus, 1976-
(author)
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Role of Islet Endothelial Cells in β-cell Function and Growth
- 2006
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Doctoral thesis (other academic/artistic)abstract
- The pancreatic islets are collections of endocrine cells, dispersed throughout the pancreas. In adult islets, endocrine cells are closely associated with capillary endothelial cells and receive a high blood perfusion. Transplanted pancreatic islets, on the other hand, have a vascular disturbance, manifested as decreased blood vessel density. Besides impaired islet blood perfusion and oxygenation, this means that the normal close proximity between endothelial cells and β-cell in adult islets is interrupted. The aim of the thesis was to investigate if, and to what extent, β-cells and islet endothelial cells can interact with one another. This hypothesis was investigated during physiological growth of pancreatic islets, following transplantation and in vitro. We observed that islet endothelial and endocrine cell replication coincided immediately after birth, as well as during pregnancy. In pregnant animals, β-cell proliferation colocalized to islets with increased endothelial cell replication, indicating that the two processes were interconnected. The pregnancy hormone prolactin favored endothelial cell replication, and these activated cells could then augment β-cell proliferation. We found that prolactin pretreatment increased blood vessel density and oxygen tension in islets after transplantation. Furthermore, prolactin pretreatment improved endocrine function in a minimal islet transplant model. Partial pancreatectomy performed in association with islet transplantation improved revascularization, oxygen tension and glucose stimulated insulin release from the graft. In conclusion, the findings suggest that endocrine and endothelial cells interact with one another to regulate growth and function in pancreatic islets. This may form the basis for interventions aiming to improve revascularization and function of transplanted islets.
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