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- Bialik, Erik, et al.
(author)
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Ionization of Cellobiose in Aqueous Alkali and the Mechanism of Cellulose Dissolution
- 2016
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In: The Journal of Physical Chemistry Letters. - : American Chemical Society. - 1948-7185. ; 7:24, s. 5044-5048
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Journal article (peer-reviewed)abstract
- Cellulose, one of the most abundant renewable resources, is insoluble in most common solvents but dissolves in aqueous alkali under a narrow range of conditions. To elucidate the solubilization mechanism, we performed electrophoretic NMR on cellobiose, a subunit of cellulose, showing that cellobiose acts as an acid with two dissociation steps at pH 12 and 13.5. Chemical shift differences between cellobiose in NaOH and NaCl were estimated using 2D NMR and compared to DFT shift differences upon deprotonation. The dissociation steps are the deprotonation of the hemiacetal OH group and the deprotonation of one of four OH groups on the nonreducing anhydroglucose unit. MD simulations reveal that aggregation is suppressed upon charging cellulose chains in solution. Our findings strongly suggest that cellulose is to a large extent charged in concentrated aqueous alkali, a seemingly crucial factor for solubilization. This insight, overlooked in the current literature, is important for understanding cellulose dissolution and for synthesis of new sustainable materials.
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| 4. |
- Forsberg, Jonas, 1982-
(author)
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Energy transition in transportation : Applying TIMES-based energy system optimisation models to sub-national levels
- 2021
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Licentiate thesis (other academic/artistic)abstract
- Transportation is embedded in the fabric of society and a key enabler of socio-economic development, but it is also a major source of carbon dioxide (CO2) and local air pollution (AP). Cities collectively account for around three quarters of total energy-related CO2 emissions, and the negative health impacts from local APs are most felt in dense urban environments. Thus, transitioning away from current fossil fuel regime in urban transportation is necessary to address both global and local challenges. Mathematical models as energy system optimisation models (ESOMs) are commonly applied to explore contrasting energy futures and to provide insights on how the energy system (or specific sub-sectors) may evolve under different conditions. However, ‘typical’ national level models are not fully adapted to capture the characteristics of local (city) transportation, and previous city-level ESOM based analyses have focused on decarbonisation of local energy systems, thus omitting other local policy considerations as e.g. air quality, and several studies excluded transportation altogether. In this thesis, a generic city-level ESOM framework (TIMES-City) was further adapted and used to provide policy-relevant insights on the anticipated energy transition of the local transport sector. The underlying work rests on a systems analysis approach, building on careful consideration of the overall system performance and boundaries, understanding of specific system characteristics, and challenges and opportunities facing local ‘system managers’; this has implications for model representation and for quantitative and qualitative modelling assumptions. Further, availability and quality of local transport, energy and emission data needed to calibrate models poses significant challenges, and considerable effort was also put on producing projections for future transport demand (a key model input), using lessons and input data from traditional transport demand models. These considerations were addressed in Paper I. The model was then applied to two different cases (in Sweden) to explore potential conflicts and co-benefits between ambitious climate targets and deep cuts in APs (Paper II), and to assess the roles of local and regional governments in CO2 mitigation when also considering ambitious national-scale policies (Paper III). The results of Paper II indicate that substituting fossil fuels for biofuels in conventional vehicles is the least-cost decarbonisation pathway, however this produces only minor or even negative benefits to air quality. While, zero-emission vehicles cut all local tail-pipe emissions, but their total impact on climate change mitigation is determined by upstream impacts from the conversion and distribution of energy carriers. Thus, ensuring low levels of total CO2 and APs from transportation calls for re-coupling of the local and global responsibilities and motivations into comprehensive mitigation strategies. The results of Paper III indicate that current Swedish national mitigation measures will drive down CO2 emissions in transportation considerably, but biofuel availability and BEV (battery electric vehicles) costs are critical for the rate and extent of the transition, while locally and regionally determined measures to enable shifts (from car) to active travelling, public transportation and home-based work have a much more limited direct impact. Nonetheless, these measures, along with city investments in BEVs and charging infrastructure which pave the way also for residents and local businesses, can help to reduce overall energy intensity of the transport sector, thus slowing down growth in fuel demand and contribute to reaching ambitious climate targets with limited renewable resources (as e.g. biofuels). The two studies (Papers II and III) illustrate the usefulness of applying comprehensive ESOMs also at sub-national levels, providing insights on both global and local sustainability implications as well as deeper understanding of the roles of local and regional decision-makers in enabling and supporting low-carbon transitions in transportation.
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| 5. |
- Forsberg, Jonas, 1982-
(author)
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On the road to climate neutral Swedish transportation: Energy system modelling to support the transition at national, regional, and local levels
- 2023
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Doctoral thesis (other academic/artistic)abstract
- Transportation is a critical pillar of modern society. Over the past decades, growth in mobility of people and goods have been both enabled by and dependent upon fossil fuels. Strong action is needed to break this dependence in order to reduce CO2. The overall aim of this thesis is to support the transition towards climate neutral transportation in Sweden considering local, regional, and national settings, by use of TIMES-based ESOMs. This is addressed by i) developing and adapting transport sector representation in TIMES models considering context specific conditions and preferences, ii) applying the models to define and explore alternative long-term scenarios that meet the overall goals, iii) and identify key measures and policy implications for achieving climate neutral transportation.In Paper I (Local setting) key considerations and requirements in respect of modelling local energy transition of transportation in a TIMES energy system modelling framework was outlined. The model was then applied to address potential trade-offs between global climate concerns and local air quality issues (Paper II – Local setting). The results showed that decarbonisation with biofuels does little to enhance local air quality, while zero-emission vehicles – that eliminate all local tailpipe emissions – can induce significant upstream CO2 emissions (from energy supply sectors). Comprehensive multi-level strategies are needed to drastically reduce both CO2 and local air pollutants. In Paper III (Regional setting), a participatory modelling approach was applied that involved local practitioners from 15 municipalities. The model results showed that strong national policies can drive down CO2 emissions drastically, and that the impacts from sub-national strategies was very limited under these policies. Still, during the discussions with local practitioners it was emphasized that local action is needed for enabling the measures seen as cost-efficient in the model analysis.The TIMES-Sweden model was adapted and used to explore key decarbonisation options in passenger and freight transportation, in a whole-energy-systems perspective. The model was disaggregated to capture underlying contextual heterogeneity in passenger transportation found across the country (Paper IV – National setting). The results showed that different policy strategies have different implications depending on the context, thus, underpinning a shift from one-size-fits-all policies into more regionally tailored strategies. Next (Paper V – National setting), the same model was used to investigate principally different modes of decarbonising domestic freight transportation. The results showed that road freight electrification reduces total demand for electricity over the entire energy system compared to the biofuel and the e-fuel pathways respectively, while also freeing biomass for other purposes than producing biofuels for road vehicles.Finally, the usefulness of ESOMs to identify policies to accelerate the decarbonization of transportation has been demonstrated, while outlining some challenges. For local level, the necessary data to calibrate the model was often not available, or available but with a system boundary representation incompliant with the model approach (e.g., fuel statistics). At the national level, a new approach was introduced that capture the underlying contextual factors of different actors. While capturing differences between urban, suburban and rural conditions, more research is needed to identify policies that ensure a just transition across socioeconomic groups.
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| 7. |
- Forsberg, Jonas, et al.
(author)
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Tailoring climate mitigation strategies for passenger transportation by capturing contextual heterogeneity in TIMES-Sweden
- 2024
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In: Transportation Research Part D. - : Elsevier. - 1361-9209 .- 1879-2340. ; 133
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Journal article (peer-reviewed)abstract
- Meeting ambitious climate targets requires deep cuts in emissions from passenger transportation. Many studies point to electrification and behavioural shifts as key measures. Spatial, demographic, economic, and transport-sector-related factors shape the opportunities and preferences for change, thus setting the direction and pace of the transition. These factors typically differ between urban, suburban and low-population-density settings, a fact that is generally overlooked in comprehensive energy system optimisation models (ESOM). This study introduces a novel contextual representation of passenger transportation within a national ESOM (TIMES-Sweden). When testing the new approach, different cost barriers to electrification are found across various settings, signalling a need for different policy responses. Further, opportunities for – and impact from – shifts in travel behaviours vary significantly across settings. These results highlight the need for climate change mitigation strategies in passenger transportation which are better tailored to specific contexts.
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| 8. |
- Grafström, Jonas, et al.
(author)
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Invention, innovation and diffusion in the European wind power sector
- 2016
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In: Technological forecasting & social change. - : Elsevier BV. - 0040-1625 .- 1873-5509. ; 114, s. 179-191
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Journal article (peer-reviewed)abstract
- The purpose of this paper is to provide an economic analysis of the technology development patterns in the European wind power sector. The three classic Schumpeterian steps of technological development, invention, innovation and diffusion, are brought together to assess the relationship between these. Three econometric approaches are used, a negative binomial regression model for inventions approximated by patent counts, different learning curve model specifications that have been derived from a Cobb-Douglas cost function to address innovation, and a panel data fixed effect regression for the diffusion model. We suggest an integrated perspective of the technological development process where possible interaction effects between the different models are tested. The dataset covers the time period 1991–2008 in the eight core wind power countries in Western Europe. We find evidence of national and international knowledge spillovers in the invention model. The technology learning model results indicate that there exists global learning but also that the world market price of steel has been an important determinant of the development of wind power costs. In line with previous research, the diffusion model results indicate that investment costs have been an important determinant of the development of installed wind power capacity. The results also point towards the importance of natural gas prices and feed-in tariffs as vital factors for wind power diffusion.
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| 10. |
- Lindman, Åsa
(author)
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Essays on energy technology learning and voluntary carbon offsets
- 2010
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Licentiate thesis (other academic/artistic)abstract
- This thesis consists of an introductory part and three self-contained papers, all related to the issue of promoting renewable energy sources. Paper I presents the results from a hypothetical market experiment of Swedish students' stated willingness to purchase emission allowances for carbon dioxide within the European emissions trading system. Methodologically we draw heavily on recent developments in the literature on integrating norm-motivated behaviour into neoclassical consumer theory, and assume that individuals have a preference for keeping a self-image as a responsible and thus norm-compliant person. The results indicate that students' willingness to purchase emission allowances is determined by both price and the presence of norms; people who feel personally responsible for contributing to reduced climate damages are also the ones who appear more inclined to purchase emission allowances. The empirical findings are also consistent with the notion that perceptions about others' stated willingness to purchase emission allowances affect individual norms and ultimately expressed behaviour. Norms are also largely activated by problem awareness and the individual's perception of her ability to contribute to solving the problem. In paper II we conduct a metaanalysis of wind power learning rates, thus permitting an assessment of some of the most important model specification and data issues that influence the estimated learning coefficients. The econometric analysis in this paper relies on over 100 learning rate estimates presented in 35 studies, all conducted during the time period 1995-2010. The empirical results indicate that the choice of the geographical domain of learning, and thus implicitly of the assumed presence of learning spillovers, is an important determinant of wind power learning rates. We also find that the use of extended learning curve concepts, thus integrating most notably public R&D effects into the analysis, tends to result in lower learning rates than those generated by so-called single-factor learning curve studies.Finally, in paper III a critical analysis of the choice of model specification in learning curve analyses of wind power costs is presented. Special attention is paid to the question of the choice of national or global learning (cumulative capacity), and the inclusion of other variables such as R&D, scale effects and the inclusion of a time trend. To illustrate the importance of these methodological choices, a data set of pooled annual time series data over five European countries - Denmark (1986-1999), Germany (1990-1999), Spain (1990-1999), Sweden (1991-2002) and the United Kingdom (1991-2000) - is used to compare the results from different types of model specifications. The empirical results support the notion that the estimates of learning-by-doing rates may differ across different model specifications. In our data set the presence of global learning for wind power appears more important than that of national learning, but the estimates of the (global) learning rate are only marginally influenced by the introduction of R&D and scale effects. The results also show, though, that the impact of cumulative capacity on wind power costs appears to be very sensitive to the inclusion of a time trend in the traditional learning curve model.
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