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The societal goal of reaching net-zero CO2 emissions requires development of integrated biorefineries to produce biomass-derived fuels and chemicals. For sustainable second-generation bioethanol production, consolidated bioprocessing with the thermophile Clostridium thermocellum is regarded as a promising concept in view of the microorganism’s native ability to efficiently degrade plant cell wall material. However, for industrial implementation, improvements in ethanol titer and yield are needed. The aim of this thesis was to increase knowledge on the metabolism of C. thermocellum and thereby guide future metabolic engineering strategies to maximize the ethanol yield and titer. Yield improvements and fundamental studies into the metabolism of C. thermocellum would benefit from higher utilization of hexose monomers as well as minimized byproduct formation. To investigate underlying mechanisms for growth on glucose and fructose, laboratory evolution in chemostats together with genome sequence-based reverse engineering was applied. This successfully revealed two underlying mutations with (regulatory) roles in metabolism or transport of the monosaccharides. Together, these mutations enable reproducible and constitutive growth and are relevant for follow-up studies into transport and upper glycolysis. Separately, the mechanism behind the surprising byproduct formation of secreted amino acids was investigated by knock-out studies in NADPH-supplying and -consuming pathways. Physiological characterization in cellobiose- or ammonium-limited chemostats of mutant strains, with deletions in the NADPH-forming malate shunt or in the putatively ferredoxin-dependent ammonium assimilation, demonstrated a central role of NADPH in driving amino acid secretion. The findings indicated that electron availability will be crucial for further yield improvements in the NADH-dependent ethanol pathway. Fundamental mechanisms that might contribute to improved ethanol titer were addressed by studying thermodynamic and biophysical limitations. The pyrophosphate (PPi)-dependent glycolysis of C. thermocellum has been hypothesized to increase the overall ATP yield at the expense of the overall driving force. Knock-out studies combined with functional annotation of potential PPi-sources questioned this trade-off and increased knowledge of the PPi metabolism. The chaotropic effect (biophysical toxicity) of ethanol is commonly counteracted by lowering the cultivation temperature. Here, physiological characterization at varying ethanol titers demonstrated improved growth and fermentation at lower temperature. Comparisons to a non-ethanol producing mutant indicated both thermodynamic and biophysical limitations specifically in the ethanol pathway. Overall, these findings suggest that improvements in ethanol yield and titer would benefit from a simplified glycolysis that is engineered for a high driving force. While this work is beneficial for second-generation ethanol production, these findings can also be broadly applicable in the research and development of C. thermocellum as a cell factory for sustainable production of other fuels and chemicals. Samhällsmålet att nå nettonoll CO2 utsläpp kräver att integrerade bioraffinaderier utvecklas för att producera bränslen och kemikalier baserade på biomassa. För hållbar andra-generationens bioetanol-produktion betraktas konsoliderad bioprocessering med termofilen Clostridium thermocellum som ett lovande koncept, utifrån dess naturliga förmåga att effektivt bryta ner växtcellväggar. Emellertid krävs ökad titer och utbyte av etanol för att nå industriell implementering. Målet med denna avhandling var att öka kunskapen om C. thermocellums metabolism och därmed vägleda framtida strategier för att maximera utbytet och titern av etanol genom metabolic engineering. Förbättringar i utbytet samt fundamentala studier på metabolism hos C. thermocellum skulle gynnas av ett större utnyttjande av C6-mono-sackarider samt minskad produktion av biprodukter. Underliggande mekanismer för tillväxt på glukos och fruktos undersöktes med laboratory evolution i kemostater samt genomsekvensbaserad reverse engineering. I denna studie avslöjades två underliggande mutationer med (regulatoriska) roller i metabolismen eller transporten av dessa monosackarider. Tillsammans möjliggjorde dessa mutationer reproducerbar och konstitutiv tillväxt. Mutationerna är även relevanta för uppföljningsstudier av sockertransport och den övre glykolysen. Därutöver studerades den oväntade biproduktgruppen, aminosyror, genom knockoutstudier på NADPH-producerande och -konsumerande reaktionsvägar. Stammar med knockouts i den NADPH-producerande malatshunten eller i den potentiellt ferredoxin-kopplade ammoniumassimileringen karaktäriserades fysio-logiskt i cellobios- och ammoniumbegränsande kemostater. Detta visade att NADPH har en central roll i att driva aminosyrautsöndring. Dessa upptäckter indikerade att elektrontillgänglighet är kritiskt för att öka utbytet i den NADH-beroende etanolproduktionen. Fundamentala mekanismer som skulle kunna bidra till förbättrad titer av etanol studerades från termodynamiska och biofysiska perspektiv. En rådande hypotes har varit att den pyrofosfat (PPi)-beroende glykolysen hos C. thermocellum ökar ATP-utbytet på bekostnad av den totala termodynamiska drivkraften. Knockoutstudier kombinerat med funktionell annotering av potentiella PPi-källor ifrågasatte denna hypotes och ökade förståelsen av PPi metabolismen. Den kaotropiska effekten (biofysisk toxicitet) av etanol dämpas ofta i industriella processer genom att sänka odlingstemperaturen. Här demonstrerade fysiologisk karaktärisering vid olika etanoltiter att tillväxt och fermentering förbättras vid lägre temp-eraturer. En jämförelse mellan en modifierad icke-etanolproducerande stam och vildtypen indikerade att etanolproduktionen är begränsad av både termodynamiska och biofysiska faktorer. I helhet antyder dessa forskningsresultat att förbättringar i utbytet och titern av etanol skulle gynnas av en förenklad glykolys, konstruerad för att ge en hög termodynamisk drivkraft. Fastän denna avhandling fokuserar på andra-generationens etanolproduktion, kan dessa forskningsrön även appliceras mer brett i forskning och utveckling av C. thermocellum som en cellfabrik för hållbar produktion av andra bränslen och kemikalier. QC 2022-10-11

Abstract Indoor climate control is a major energy demand everywhere. Design and operation of buildings and HVAC systems crucially depend on climate data and real-time meteorological conditions. Energy-efficient buildings also contribute to reduce air pollution and climate change in urban areas as well as regionally and globally. However, the effects of climate and weather on building energy management are still largely overlooked in practice. A main reason for this is the lack of tools for translating meteorological conditions into energy requirements. The combined impact of temperature, solar irradiation, wind and humidity on the energy balance of a building depends on the building itself, i.e., its design, orientation, HVAC system, mode of operation, maintenance, etc. The paper discusses different approaches to model this complex interplay and associated problems at the design as well as in the operation stages. Recent developments in Sweden are reported, including applications to urban planning, building design and real-time operation of buildings and energy systems. The impact of solar irradiation and wind, in addition to that of temperature, is demonstrated. Further, the paper discusses the significance of local site condition versus building characteristics.

We present a price-based approach for congestion management in distribution power systems with renewable generations with the final goal of maximizing a social welfare function which includes net revenues of network users as well as the cost of real power losses. Particularly, we design a combined nodal and uniform pricing mechanism for maximization of the social welfare function while maintaining voltage magnitudes in a desired bound and respecting the grid's actual capacity. Storage systems are considered in order to increase/add elasticity to generations and loads. Simulation results are provided for a modified IEEE-37 bus. A scenario is numerically simulated where the excess of generation in the absence of storage and price signals leads to deviations of voltages from a desired bound. Thereafter, it is shown that the application of the price signals is effective to maintain the voltages within the desired bound while the designed social welfare function is maximized.

AbstractGovernments and civil society are increasingly aware that the decarbonization of energy systems needs to be aligned with justice principles of recognition, distribution, and process. This paper establishes a conceptual linkage between “sustainable development”, “low‐carbon energy transitions” and “energy justice” and examines social priorities to address peoples' competing priorities associated with low‐carbon energy interventions. By analyzing a renewable energy project in Vietnam as a case study, the paper shows that linking social priorities to energy justice provides a useful contribution for energy policy makers toward a better understanding of the multidimensional and complex aspects of low‐carbon energy transitions, and how different segments of society prioritize and perceive them for the achievement of socially just energy decisions.

We briefly consider the tensions between climate change and energy security policy imperatives, and highlight some concepts that may bring additional clarity to decision-making at the nexus of the two areas. We focus on developing countries and use the case of the Medupi supercritical coal plant in South Africa. The justification for the plant's construction stemmed from an Integrated Resource Planning process informed by South Africa's national utility. Often, as in the case of South Africa, there are tensions not easily captured in quantitative algorithms between, inter alia, a lack of access to electricity by millions of people (and associated welfare losses) and greenhouse gas emissions from electricity generation. It is difficult to identify any formal processes that have prioritised climate change considerations over those of energy access. Thus, it becomes imperative to have a clear understanding of the consequences of this reality when considering power system expansion. We find that the processes often employed do not provide an entirely satisfactory precedent for future planning analyses, and the justifications do not adequately reflect the complexity of the decision space. Finally, we highlight some options by which these tools might be enhanced in areas including explicit and formal consideration of risk.

Abstract This paper studies the role of potential investors in financing renewable energy systems—specifically, relating to crowdfunding as a financing mechanism, with the enhancement of internet and social-media tools. The research question in this study is whether crowdfunding with a novel socio-technical product reward program attracts potential customers to a more sustainable milk product with a specific integrated photovoltaic water pumping (PVWP) system. The particular case study we empirically investigated is product reward crowdfunding in dairy milk production in China. The milk production chain was supplied by PVWP system integration, which generated solar energy both for feed production for dairy cows and for the operation of dairy farms. 48 semi-structured in-depth interviews were conducted between the research team and customers in order to perform qualitative analyses of the determinants of customers’ milk purchase behaviors. In addition, 357 online surveys were collected for quantitative analysis. Binary and ordered probit regressions were employed to use survey date to systematically estimate purchase intention and willingness-to-pay for sustainable milk. Customer behaviors, environmental consciousness, and individual socio-demographic factors were investigated as potential explanatory variables. Over 82% of the survey participants showed intentions to purchase the sustainable milk with the PVWP system. In the survey and interview samples, results showed that milk quality, nutrition improvement, emissions reduction, and environmental benefits attributed to the integrated PVWP system were the major factors considered by interviewees who showed intentions to purchase the crowdfunded dairy milk. Regression model results suggested that potential customers with higher income levels, and those of parenting age, and those with young children or planning to have children, had a higher willingness-to-pay than other customers for the crowdfunded sustainable dairy milk. The familiarity with and popularity of online shopping and pre-sale purchases in China made customers more open to and proactive towards pre-pay and crowdfunding mechanisms. This article evaluated key factors which may influence potential customers for crowdfunding, and used a discrete choice model to estimate customers’ willingness-to-pay for reward-based projects. These results could help producers of sustainable milk products to identify potential target groups in China and estimate market demand. This exploratory study could provide a framework with both quantitative and qualitative assessment of crowdfunding for renewable energy systems in a national or international context.

The last ten to twenty years have seen a steadily growing awareness across industries of the benefits of proper asset management, as well as the obvious disadvantages of poor management of assets. This awareness is specifically apparent in the Power Industry, with an aging infrastructure and workforce coupled with economic pressures enforced by reregulation and the current economic downturn. Obviously, an apparent tool for utilities seeking to improving efficiency and effectiveness of asset management strategies is the implementation of IT-systems in support of the operational processes. To investigate current state of the practice regarding FT systems for asset management a survey has been conducted among a number of midsized utilities, and the paper presents the preliminary results of this study. The empirical data for the study comes not only from electric utilities, but also from the pulp and paper industry thereby providing excellent opportunities for benchmarking and comparison across industries. Interestingly, the preliminary findings show large differences in both chosen strategies for asset management as well as use of IT systems in support of the operational processes. The survey also shows that the utilities have chosen very different strategies for improving their asset management processes. In addition, the utilities have very differing priorities when it comes to implementation of IT systems for asset management. In short, five specific areas providing opportunity for improvement regarding IT system use have been identified. These are: asset documentation, resource management, production management, workflow management and maintenance planning tools. Of further interest are the differences between how these areas of improvement are approached among the utilities and pulp and paper industry, respectively. The paper provides, based on the data from the survey, an analysis and discussion on strategies for asset management as well as IT system implementation based on the identified areas of opportunity.

The aim of this paper is to suggest and discuss policy instruments that could lead towards a more sustainable waste management. The paper is based on evaluations from a large scale multi-disciplinary Swedish research program. The evaluations focus on environmental and economic impacts as well as social acceptance. The focus is on the Swedish waste management system but the results should be relevant also for other countries. Through the assessments and lessons learned during the research program we conclude that several policy instruments can be effective and possible to implement. Particularly, we put forward the following policy instruments: “Information”; “Compulsory recycling of recyclable materials”; “Weight-based waste fee in combination with information and developed recycling systems”; “Mandatory labeling of products containing hazardous chemicals”, “Advertisements on request only and other waste minimization measures”; and “Differentiated VAT and subsidies for some services”. Compulsory recycling of recyclable materials is the policy instrument that has the largest potential for decreasing the environmental impacts with the configurations studied here. The effects of the other policy instruments studied may be more limited and they typically need to be implemented in combination in order to have more significant impacts. Furthermore, policy makers need to take into account market and international aspects when implementing new instruments. In the more long term perspective, the above set of policy instruments may also need to be complemented with more transformational policy instruments that can significantly decrease the generation of waste.