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- PostAlternatives to capitalist development and its sustainability implications(2024) Branbant, Cyprien; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and Environment; Holmberg, John; Holmén, Johan
- PostAnalyzing the climate impact of contrails with the use of sustainable aviation fuels(2024) Marcks, Manuel; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and Environment; Johansson, Daniel; Pettersson, Susanne
- PostThermochemical recycling of complex polymers: General decomposition pathways for pyrolysis of end-of-life-tires(2024) Sköld, Adam; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and Environment; Seemann, Martin; Forero Franco, RenestebanWith an increasing population of the world, our reliance on tires in transportation and production of goods is following suit. As tires are relying on fossil fuels to produce both synthetic rubbers and the filler carbon black, recycling the material in end-of-life tires (ELTs) and closing the carbon loop is of great importance for continuing the production of tires in a sustainable fashion. Thermochemical conversion using pyrolysis is a viable option and has been proven to be commercially viable as the company Scandinavian Enviro System has shown by using the recovered carbon black in new tires, and the oils as feedstock to the petrochemical industry. To be able to predict the results from pyrolysis of ELTs, understanding the process is a must. In this work, the behaviour of the solid and volatile products was investigated using prior experiments, literature review and followed by modelling, done using both an empirical model as well as a simplified reactor model (SRM) using kinetics based radical reactions. The empirical model investigated the feasibility of using key species, i.e. species providing significant information about the process to be used in an implicit fashion to decrease the complexity of both models and analysis in experiments. The solid behaviour indicates the significance of how the particle is heated, as this dictates how if the particle is swelling or shattering as the volatile compounds are leaving the material. The interaction between the solid and volatile vapours leaving the sample was investigate further in a literature review, where the influence of heating rate was shown to affect the amount of carbonisation in the solid yield, where lower heating rates favoured carbonisation. The heating rate was also shown to influence the secondary reactions as yields of aromatic content increase with heating rate at the expense of aliphatic content, along with slightly higher gas production. The empirical model took heating rate into account when predicting the carbon conversion to species in both the oil and gas using a key specie. The models showed the promise of utilizing key species, while the species chosen, ethylene and styrene, should be investigated further in future research. By increasing the complexity in the simplified reactor model, additional insight regarding radical rearrangement could be gleaned, however, significant focus should be put on the kinetic parameters of the different reactions to create a more holistic decomposition model.
- PostAssessing Cost-Effectiveness of Heat Pumps and Biomass CHP in Future Swedish District Heating Systems(2024) Bergander, Samuel; Hellander, Filip; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and Environment; Göransson, Lisa; Goop, JoelDistrict heating systems are predicted to become an essential part of decarbonizing heat generation now and in the future. Power-to-heat technologies, such as heat pumps and electric boilers, could help the transition to sustainable district heating production while working as a flexibility measure in the coupled electricity market. Even though several studies single out heat pumps as a cheap and effective way to produce district heating, the current production mix is mainly based on combustion technologies producing heat with biomass. Additionally, as the share of renewables in the energy mix increases, heat pumps can play an important role in addressing flexibility and utilization of energy. This thesis aims to comparatively analyze elec tric air-source heat pumps and biomass combined heat and power heating systems, in the context of change for the future Swedish energy sector. Costs associated with heat production between two different energy technologies in district heating systems are investigated. A mixed linear optimization model is adapted to minimize the variable operational costs for different systems including heat pumps and biomass combined heat and power, concerning interesting techno economic properties, electricity prices, taxes, and fuel prices. The model is based on a reference system in Nyköping, Sweden, to realistically simulate and create district heating cases over annual periods. The details in energy modeling of district heating and technologies are also investigated, focusing on heat pumps and their coefficient of performance. A present and a future scenario are investigated by using different electricity spot price curves for the years 2019 and 2050. Results show that electricity-based heat pumps perform better in terms of cost-effectiveness in the Swedish district heating sector, both presently and in the future. A temperature-dependent approach is adapted to the coefficient of performance of heat pumps, resulting in a noticeable cost difference, underscoring the importance of accurately incorporating heat pumps in energy models. The possible savings using electricity instead of biomass are even more significant if the price of biomass continues to rise. The thesis also reveals that the power-to-heat tax, a tax on electricity to produce heat, is an important factor in further comprehending the potential of heat pumps in heat production in Sweden.
- PostSpectroscopic study of the astrophysics and astrochemistry of protostars in a clustered region of massive star formation(2024) Andersson, Arvid; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and Environment; Tan, Jonathan; Tan, Jonathan