| 1. |
- Dreier, Dennis, 1990-
(författare)
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Transition Technologies for Electrification and Optimisation of Bus Transport Systems
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The topical issue of climate change has increasingly become important as scenarios indicate an increase of 2.5–7.8°C in the global mean temperature by the end of this century, if no greenhouse gas emissions are reduced. The transport sector depends strongly on fossil fuels and has been therefore considered as one key sector concerning climate change mitigation. In this regard, a key role is played by cities, since progressing urbanisation will presumably lead to a higher demand for urban transport.This doctoral thesis addresses the transition phase of public bus transport systems by exploring electrification as a vector for decarbonisation. The C40-city of Curitiba in Southern Brazil is used as a case study. The research is of explorative and empirical nature. Quantitative research methods are applied to compare bus technologies as well as new optimisation models and planning tools are developed to support data analytics and research in the areas of simulation, optimisation and (long-term) planning of energy and transport systems at different levels of consideration.The results from the comparison of different buses show large potentials to save energy and reduce emissions during the operation phase, for example, when using hybrid-electric or plug-in hybrid-electric buses instead of conventional buses. Moreover, energy savings in the operation phase also imply avoidance of fuel production and supply. Additionally, electrified buses can also reduce operational uncertainty caused by varying driving cycles and fluctuating fuel prices concerning an absolute variation of both energy use and fuel cost in the operation phase.A real-time optimisation model was developed, and its concept tested to estimate potentials for energy savings and all-electric operation from the operational optimisation of a plug-in hybrid-electric bus fleet. Different management strategies were simulated concerning the charging schedule and all-electric operation of the bus fleet. While energy savings can be significantly increased through a structural change towards more electrified buses, a large potential to increase the total all-electric operation of the bus fleet was estimated through operational optimisation. Consequently, both a structural change and operational optimisation should be jointly applied to maximise the benefits gained from electrification in a bus transport system.The software system OSeMOSYS-PuLP was developed for empirical deterministic-stochastic modelling based on the OSeMOSYS modelling framework, which enables the use of a Monte Carlo simulation. The open source design of the tool shall enhance transparency and trustworthiness in studies. It is transferable to many cases and makes it possible for analysts and researchers to generate new sets of conclusions together with associated probability distributions considering the use of real-world datasets, e.g. from open data initiatives as the one in Curitiba.In summary, the research findings, applied methods and developed tools can be used to support and inform analysts and decision-makers in the area of transport and energy systems planning in data-driven decision-making processes to develop and assess different technological options and strategies at different levels while considering associated uncertainties.
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| 2. |
- Castro Flores, José Fiacro
(författare)
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Low-temperature based thermal micro-grids: operation and performance assessments
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Energy use in the urban environment is vital for the proper functioning of our society, and in particular, comfort heating –or cooling– is a central element of our energy system often taken for granted. Within this context, district energy systems and especially, district heating (DH) systems must evolve to adapt to the upcoming decades-long transition towards a sustainable energy system. This dissertation seeks to introduce, discuss, and assess from a techno-economic perspective the concept of low-temperature (LT) based thermal micro-grids (subnets) as active distribution thermal networks. It explores the role of the subnet at the system distribution level supervised by an active agent (DH substation), performing tasks of heat supply and demand management (storage and dispatch), as well as coordinating bidirectional flows. Here, a mixed methodological approach based on analytical simulation for the assessment of alternatives to evaluate a set of technologies is developed and discussed. This approach covers: the identification of knowledge gaps through the state-of-the-art analysis; a collection of incremental technical and/or economic performance assessments; and the analysis of a measurement data set from an existing LTDH demonstration project. Key findings of this work include: an updated and improved model of aggregated heat loads; identification of differences in load and temperature patterns for certain LT subnets; analysis of benefits and drawbacks of active substations with distributed heat sources and/or storage; and the impact on the reduction of the primary network return temperature as a consequence of the increase in the share of LT subnets, leading to lower generation and operating costs. These outcomes reveal that the integrated design and operation of the active thermal micro-grid have the potential to improve both the performance of the subnet, and that of the primary network. It further enhances the capability of the overall system to integrate unconventional and distributed heat sources together with energy efficient buildings by increasing the system’s flexibility and controllability. Active thermal distribution networks will likely become a subsequent step in the technological development of DH technologies, to address the matter of providing comfort heating in an effective and cost-efficient manner. This work advances the current DH knowledge by identifying synergies and challenges that arise with these new developments, in order for DH technology to play a key role in the future smart and sustainable energy system.
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| 3. |
- PAPPIS, IOANNIS, 1989-
(författare)
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Trade-offs and conflicting objectives of decision-making investments in low-carbon technology portfolios for sustainable development : National and continental insights offered by applying energy system models
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Energy infrastructure and appropriate energy policies are crucial for sustainable development and to meet Sustainable Development Goals (SDGs). Limiting global warming potential below 1.5oC would require “rapid and far-reaching” transitions and unprecedented changes in all aspects of society. Several factors influence investment decisions on energy conversion technologies and their specific locations. The choice, timing, and location of energy investments affect the total system cost, socio-economic development, the environment (e.g., emissions, water use), and a nation's energy security. However, existing national energy modelling initiatives only investigate a subset of these pillars for achieving sustainability.This thesis examines the challenges associated with the energy transition of low-and middle-income countries (Paraguay, Ethiopia, Africa). This work considers national and global policies, focusing on achieving SDG7 and SDG13. The dissertation includes a cover essay and four appended papers. The research conducted in this Thesis examines how energy-systems models can assist in understanding an energy system's complex interactions for sustainable development.Specifically, the results highlight hydropower and solar PV as key technologies to achieve climate change targets, energy security and energy access goals. Hydropower and other renewable electricity can be exported to bolster energy security for the exporting country, although export revenues are eroded by local demand growth and low export prices. The benefits of low-cost electricity provided by cross-border hydropower should be balanced against energy security concerns for the importing country. The research demonstrates the benefits of regional coordination, with trade enabling renewable resources to be harnessed and the electricity transmitted to demand centres. Although RET decreases carbon dioxide emissions and water use compared to fossil-fuel plants and creates more jobs, they require high up-front capital costs offset by the lower operating fuel costs in the long term. Thus, increasing the ambition of climate targets while achieving electricity access results in lower cumulative costs. Also, although hydropower and renewable technologies build climate resilience, hydropower operation depends on climate variability affecting energy security. Thus, mitigation strategies should consider the associated challenges of climate change in hydropower investments.Hydropower and renewables are primarily grid-connected technologies, so off-grid and mini-grid systems are key complements to national-grid expansion when pushing for universal energy access. They also impact energy security, total system costs and socio-economic development. This Thesis's outcomes can support governments in strategic energy planning to identify future renewable energy projects and ensure their financial viability. Energy systems in their transition need to be affordable, reliable and sustainable (e.g., energy secured, combat climate change) by being climate-resilient. The thesis findings demonstrate that nations need integrated energy planning, accounting for the geospatial characteristics of energy technologies, and water resources management to achieve SDG7 and build climate-resilient (SDG13). A broad portfolio of renewable technologies, interconnectors and a decentralized power generation system providing electricity closer to the end-user demand is needed to enhance energy security, decrease environmental pressures and provide affordable electricity for a nation.
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| 4. |
- Peña Balderrama, Jenny Gabriela, 1990-
(författare)
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Exploring low-carbon development pathways for Bolivia - A model-based analysis focused on the energy sector
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Global emissions have continued to rise steadily at levels exceeding the 1.5°C climate stabilization target. Therefore, the increase in the average global temperature and climate change will be determined by how we handle greenhouse gas (GHG) emissions over the next years. Decarbonizing economic growth and development add pressure to all countries in the world, but even more pressure to low and middle-income countries planning to use their fossil fuel resources as a ‘leading sector’ to achieve growth. Low and middle-income countries have limited financial resources and often have to prioritize short-term development goals with immediate local co-benefits over mitigation and adaptation strategies with long-term gains. Reaching the climate stabilization/decarbonization goal will require large investments to decarbonize the energy sector, together with investments and policy measures to ensure resilience and adaptation to climate change.Bolivia has signaled its intent to eradicate poverty and achieve economic growth while preserving environmental sustainability by adopting the seventeen Sustainable Development Goals (SDGs). In line with SDG7, Bolivia aims to achieve universal access to electricity by 2025. Although electricity access has improved significantly with large investments in grid-extension and decentralized systems, currently 61% of the grid generation capacity and 93% of the decentralized generation capacity is fossil-fueled. Other sectors, such as the transport sector, depend mostly on fossil fuels and largely contribute to Bolivia’s GHG emissions. Policies intended to increase energy security in Bolivia focus on the increased use of domestic natural gas, on investments in large-scale hydropower plants, and on first-generation (1G) biofuel production for the transport sector.In line with SDG 7 and SDG 13, this doctoral thesis examines low-carbon development pathways for the main policies addressing energy access and energy security in Bolivia. With methods deriving from systems analysis, the particulars of the Bolivian energy system were scrutinized and the effects of alternative energy planning decisions ‒ such as policies and investments ‒ displayed using scenario analysis. Five research articles answering four research questions form the main part of the thesis.The first research question examines the role of decentralized technologies (primarily micro-grids) and renewable energy for addressing universal electricity access targets. The cost-competitiveness of multi-source micro-grids is assessed using an innovative methodology developed to increase the technical accuracy of load simulation and microgrid system design optimization in an existing geospatial modelling tool. The results highlight the potential of decentralized electrification solutions and identify the location, size and investments required to meet electrification targets in 2025.The second research question focuses on evaluating alternative policies for decarbonizing the power generation sector using an energy system optimization model. The combined effects of inserting carbon taxes and modifying the weighted average cost of capital on the power generation emissions are measured in marginal abatement cost curves. Results from this conceptual and numerical analysis show that a deep decarbonization of the power generation system requires very high carbon prices if the costs of capital are high. Instead, moderate carbon prices combined with low costs of capital can lead to significant emissions reductions and comparably smaller increases in carbon abatement costs.The third research question examines Bolivia’s hydroelectricity export plans in the medium-term using a cost-optimization model of South America. The study also evaluates the fair distribution of benefits using a cooperative game-theory approach and the decarbonization achieved in a scenario of power systems integration in South America. Results of this study indicate that electricity from large-scale hydropower projects could be traded with Brazil and reduce Bolivia’s dependence on natural gas for power generation. The results also show that Bolivia has less bargaining power than its competitors have in the long-term and benefits less from emissions reductions in a scenario of trade with Brazil.Lastly, the fourth research question explores energy security in the transport sector by assessing Bolivia’s sugarcane-based ethanol production targets. Increased sustainability in the ethanol production chain is evaluated quantitatively by identifying opportunities for agricultural intensification and investments in advanced biorefineries in a least-cost optimization model. Results from this analysis demonstrate that Bolivia can cost-effectively reach its medium-term targeted volumes of ethanol production with a moderate expansion of sugarcane cropland and investments in agriculture intensification. The results further suggest that it is cost-optimal to invest in current technological advances (i.e. efficient co-generation plants) to maximize the renewable energy output and the economic benefits of sugarcane-derived ethanol. Finally, the study identifies a range of biofuel-support incentives to promote investments in second-generation biofuel production.
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| 5. |
- Engström, Rebecka Ericsdotter, 1984-
(författare)
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Exploring cross-resource impacts of urban sustainability measures : an urban climate-land-energy-water nexus analysis
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In an increasingly urban world, cities' global resource uses grow. Two fundamental resources for making cities liveable are water and energy. These resources are also closely interlinked – systems that convert and deliver energy to cities require water, and urban water systems use energy. In addition, these two resource systems affect and are affected by land use and climate change. This ‘nexus’ between climate, land use, energy and water (CLEW) systems has been extensively studied in the past decade, mainly with a focus on national and transboundary CLEW systems. This doctoral thesis develops the CLEW nexus research from an urban perspective.Two quantitative analyses examine how different types of sustainability measures in cities affect intended and unintended CLEW systems. First, the CLEW impacts of a set of sustainability measures in New York City are assessed - from water conservation to emission reductions. Results show that every measure affects (to varying degrees) all studied sustainability dimensions - water, energy and climate - and that the impacts can be quantified through a reference-resource-to-service-system (RRSS).The second quantitative study focuses on how CLEW impacts from a city's sustainability efforts spread beyond local and international borders. It investigates how global water and land use are affected in alternative scenarios to achieve climate neutrality in 2030 in the town of Oskarshamn, Sweden, using an energy systems simulation model. The study finds that both the magnitude and the geographical distribution of land and water requirements vary between scenarios. A strategy to achieve climate neutrality that invests in electrification leads to increased national water use, while a strategy that relies on biofuels has a greater impact on water and land use internationally. When results are translated to interactions between the UN's sustainable development goals (SDGs), they reveal that SDG synergies and trade-offs are 'strategy-dependent': different options for achieving SDGs on energy, sustainable cities and climate action have varying consequences for the advancement of SDGs on sustainable water, food production and biodiversity.To shed light on how data challenges affect quantitative urban nexus studies, uncertainty assessments of selected thesis’ results are conducted and complemented with a thematic analysis of a set of recently published urban nexus papers. Together, they indicate that analytical choices, uncertainties in results and - as a consequence - research foci are influenced by data limitations in both this thesis and in other urban nexus studies.Lastly, the finding from the Oskarshamn analysis – that SDG interactions are strategy-dependent – is deliberated with experts within sustainability sciences and SDG interaction research. From this, a research agenda is proposed with measures to make SDG 'spillovers' visible in local level decision-making.Taken together, the thesis contributes to filling several knowledge gaps on how urban sustainability measures within the CLEW systems interact within and beyond city limits, and proposes analytical approaches to quantify these interactions. It further points out how current data challenges constrain quantitative urban nexus analyses and highlights research needs to improve data management as well as other key efforts to enable consideration of nexus interactions, including SDG 'spillovers', in cities' sustainability work.
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| 6. |
- Guédez, Rafael
(författare)
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A Techno-Economic Framework for the Analysis of Concentrating Solar Power Plants with Storage
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Concentrating solar power plants can integrate cost-effective thermal energy storage systems and thereby supply controllable power on demand, an advantage against other renewable technologies. Storage integration allows a solar thermal power plant to increase its load factor and to shift production to periods of peak demand. It also enables output firmness, providing stability to the power block and to the grid. Thus, despite the additional investment, storage can enhance the performance and economic viability of the plants.However, the levelized cost of electricity of these plants yet remains higher than for other technologies, so projects today are only viable through the provision of incentives or technology-specific competitive bid tenders. It is the variability of the solar resource, the myriad roles that storage can assume, and the complexity of enhancing the synergies between the solar field, the storage and the power block, what makes the development of adequate policy instruments, design and operation of these plants a challenging process.In this thesis a comprehensive methodology for the pre-design and analysis of concentrating solar power plants is presented. The methodology is based on a techno-economic modeling approach that allows identifying optimum trade-off curves between technical, environmental, and financial performance indicators. A number of contemporary plant layouts and novel storage and hybridization concepts are assessed to identify optimum plant configurations, in terms of component size and storage dispatch strategies.Conclusions highlight the relevance between the sizing of key plant components, the operation strategy and the boundaries set by the location. The interrelation between critical performance indicators, and their use as decisive parameters, is also discussed. Results are used as a basis to provide recommendations aimed to support the decision making process of key actors along the project development value chain of the plants. This research work and conclusions are primarily meant to set a stepping stone in the research of concentrating solar power plant design and optimization, but also to support the research towards understanding the value of storage in concentrating solar power plants and in the grid.
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| 7. |
- Abdi, Amir, 1987-
(författare)
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Heat Transfer Enhancement of Latent Thermal Energy Storage in Rectangular Components
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Latent Thermal Energy Storage (LTES) is an interesting choice to storethermal energy in a sustainable energy system. The primary benefit of LTESis the relatively high latent heat of fusion of the materials, known as PhaseChange Materials (PCM), used in such a system as the storage medium.However, as the thermal conductivity of PCMs is often very low, there is aneed to enhance the rate of heat transfer within the charging/dischargingprocess and to improve the thermal performance of the LTES systems.This thesis addresses the enhancing effect of extending heat transfer area inrectangular LTES enclosures. A key contribution of this thesis is acomprehensive visualization of the phase change processes for an organicPCM, including solidification and melting, constrained as well asunconstrained, known as Close-Contact Melting (CCM), in a cavity with andwithout fins. Observations have been carried out for fins of different lengthsand numbers with a varying angle of inclination, and a comprehensive analysisin terms of phase change time and thermal power is conducted.The observations show fins are more influential in solidification than inmelting, reducing the solidification time by 80% and increasing the meanpower by 395%, at a cost of 10% loss in the extracted energy. In contrast, inmelting, fins have a modest effect in enhancing the process. The relativeenhancement effect of fin is higher in constrained melting than inunconstrained melting. In a case with maximum enhancement, a reduction by52% in the constrained melting time and a relative enhancement in the meanpower by 90% is achieved at a cost of 9% loss in the stored energy. As thevolume fraction of fin increases, the discrepancies in melting time betweenthe constrained and unconstrained melting diminishes.A numerical model for solidification and constrained melting is validatedbased on the experiments, and a more inclusive sensitivity analysis of finparameters is performed. The enhancing effect of different parameters on thephase change time and the thermal power is analyzed and the relatively moreeffective measures are identified. Analyzing the simulation data withdimensionless parameters for a cavity oriented horizontally and enhancedwith vertical fins, overall dimensionless groups for solidification and constrained melting have been obtained. The dimensionless groupscontribute in general to achieving a better understanding of fins parametersand to facilitating the LTES designs.In addition, this thesis investigates a novel idea of extending the surface areavia incorporating mini-channels into LTES enclosures, used as passages forair as a low thermal conductive Heat Transfer Fluid (HTF). The mini-scaleinternal hydraulic diameter of the mini-channels and their high external areato-volume ratios make a potential for dual enhancement on both the PCMside and the HTF side. An existing design and a conceptual one with thepossibility of adding fins on the PCM side, capable of being manufactured viaproduction methods of extrusion and Additive Manufacturing (AM),respectively, have been simulated and studied.The two mini-channel types provide considerable enhancements in the rateof heat transfer for a PCM heat exchanger working with air. The degree ofenhancement increases as the air flow rate increases, at the cost of anincreasingly higher pressure drop. Regarding this, increasing the number ofchannels is identified as a more effective enhancing measure than adding finsto the PCM side. In addition, the conceptual design with a higher internalhydraulic diameter and considerably a higher aspect ratio has a lower pressuredrop than the existing design, charging/discharging the thermal energy at asimilar rate but with a lower fan power. More optimized designs withminimization of pressure drop, contribute to paving the way in facilitation ofthe utilization of the enhanced air-PCM heat exchanger in variousapplications.
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| 8. |
- Almulla, Youssef, 1984-
(författare)
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Energy-Water and Agriculture Nexus to Support the Sustainable Management of Shared Water Resources
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Throughout history, major rivers and shared water bodies have allowed civilizations to flourish, and the effective management of shared water bodies has always been a priority for societies and nations. Today, about 40% of the world’s population lives in proximity to the 286 transboundary river and lake basins that supply 60% of the world’s freshwater flows and make up about half of the Earth’s land area. Moreover, around 2 billion people in the world depend on groundwater sources, which include over 460 transboundary aquifer systems.The mismanagement of water resources can result in catastrophic disasters that are often exacerbated by a domino effect so that the impacts of poor water management often extend beyond the water system. The interdependency of the water system with other systems such as energy and food, or with land-use, highlights the importance of ”systems thinking and planning” in resource management. Such a concept is not easily encapsulated into policy-making processes in many parts of the world because consideration of the resource systems in isolation as individual entities and ‘silo” thinking still dominate. Climate change adds another layer of complexity and exacerbates the issue of water management. Another important factor is geographical location because precipitation varies among and within continents. This results in some regions suffering from water shortages and some regions facing the risks of water redundancy and floods. The concept of the Water-Energy-Food (WEF) nexus was introduced in 2011 as a response to help address some of the issues mentioned above. Over the last decade, research on the WEF nexus has gained momentum in both the policy and academic areas and several methods have been introduced to operationalize the nexus in different contexts. One of the flagship methodologies is the Transboundary Basins Nexus Approach (TBNA) introduced by the United Nations Economic Commission of Europe (UNECE) in 2015 and designed to assess the nexus in shared (transboundary) water basins.The aim of this thesis is to support shared water management by using the WEF-nexus approach to quantify the benefits of coordinated management, motivate cooperation, and identify trade-offs in the optimal use of resources. To achieve this aim, four research questions are explored over the course of four academic publications. The first question explores the role of the energy sector in motivating shared water cooperation. The second question studies the risks and opportunities emerging from the interplay between climate and renewable energy in shared basins. The third question focuses on groundwater management and explores what benefits the consideration of the energy-water-agriculture nexus could bring to shared groundwater management in water-scarce areas. The fourth question examines how consideration of the energy-water-agriculture nexus could accelerate the low-carbon transition in the agricultural sector. These research questions are examined in two different, yet complementing, geographic locations. One is the Balkans in Southeastern Europe, which faces water redundancy and flood issues and the other is the Middle East and North Africa (MENA) region which suffers from water scarcity. In the first region, the Drina and the Drin River Basins represent the characteristics of Southeastern Europe while the North Western Sahara Aquifer System (NWSAS) and the Souss-Massa basin represent the characteristics of the MENA region. Three of the case applications are transboundary (Drina, Drin and NWSAS) while the last application (Souss-Massa Basin) is a subnational basin.
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| 9. |
- Korkovelos, Alexandros, 1989-
(författare)
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Advancing the state of geospatial electrification modelling: New data, methods, applications, insight and electrification investment outlooks
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- I skrivande stund uppskattas 860 miljoner människor globalt sakna tillgång till el. Målet att uppnå universal tillgång till el under det kommande decenniet – i enlighet med mål 7 av de globala målen för hållbar utveckling (SDG 7) – indikerar att många länder snart kommer att behöva införa riktlinjer, handlingsplaner och policys för att påskynda elektrifieringstakten. Detta utgör en stor utmaning och kräver betydande ekonomiska resurser så att tillgången till el kan nå även den fattiga landsbygdsbefolkningen i de minst utvecklade områdena.En återblick genom historien avslöjar emellertid att en sådan påskyndning inte är unik. Många länder i ”den globala norden” har ställts inför liknande utmaningar för ungefär ett århundrade sedan. Tidigare exempel visar att elektrifieringsplanering – och medföljande politik – kan ta olika former baserat på underliggande sociala, tekniska, ekonomiska och politiska förhållanden. Detta framhäver vikten av att ta hänsyn till input på olika nivåer. Det belyser också behovet av tillförlitlig data och information som på bästa sätt beskriver den lokala kontexten (t.ex. resurstillgänglighet, befolkningsfördelning, ekonomisk verksamhet och infrastruktur). Samtidigt som framsteg inom geospatial informationsteknik har gjorts, har också tillgängligheten till sådan information ökat kraftigt. Fortfarande nyttjas dock inte denna information till sin fulla potential inom elektrifieringsplanering.Denna avhandling syftar till att främja användandet av geospatiala informationssystem inom elektrifieringsplanering genom att presentera nya data, metoder, tillämpningar och insikter. Detta görs med hjälp av fyra artiklar och tre forskningsfrågor.Den första frågan söker efter mönster, politiska dilemman och begränsningar relaterade till elektrifiering genom olika tidsepoker och geografiska områden. Analysen av dessa kan informera aktuella och framtida planeringsaktiviteter för elektrifiering. Därför tar artikel I en tillbakablick på elektrifieringsutmaningar i USA, Storbritannien, Sverige och Kina, samt undersöker strategier, framgångshistorier och misslyckanden i respektive fall. Resultaten avslöjar viktiga lärdomar om utvecklingsfaserna för elektrifiering – med fokus på rollen som lokala isolerade elnät har.Den andra frågan berör huruvida användandet av geospatial information kan introducera nya data och metoder i ett befintligt modelleringsramverk (t.ex. OnSSET) och hjälpa till med hanteringen av olika dilemman som uppstår vid elektrifieringsplanering. Artikel II fokuserar därför på nya öppet tillgängliga dataset för att göra spatialt explicita bedömningar av småskalig vattenkraftpotential i Afrika söder om Sahara. I artikel III beskrivs 26 nya, uppdaterade eller tidigare ej tillgängliga dataset, som efter bearbetning möjliggör nya synvinklar och analys för elektrifieringsplanering.Den tredje forskningsfrågan fokuserar på hur OnSSET kan förbättras, öppnas upp och skalas upp så att en bredare publik på ett snabbt sätt kan utveckla informativa investeringsstrategier för elektrifiering som är både lands- och sammanhangsspecifika. Här utnyttjar artikel III och IV OnSSETs modulära struktur för att kalibrera dess funktioner och utveckla anpassade investeringsscenarion för elektrifiering av Malawi och Afghanistan. Dessa utforskar olika scenarion som är anpassade efter den politiska situationen i vardera av de två länderna (t.ex. gradvis elektrifiering för Malawi eller planering i konflikzoner för Afghanistan). Dessutom har denna avhandling utökat tillämpningen av OnSSET, genom plattformen Global Electrification Platform (GEP). GEP är en öppen plattform som möjliggör öppen åtkomst till 216 investeringsscenarion för elektrifiering (tillsammans med underliggande inputdata och modeller) för 59 länder världen över. All data på plattformen är tillgänglig för granskning, reproduktion och replikering för en bredare publik.
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| 10. |
- Moksnes, Nandi, 1982-
(författare)
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Exploring spatial and temporal resolution in energy systems modelling : a model-based analysis focused on the developing electricity systems
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The energy system is undergoing a transition in many parts of the world with this transition being driven by several factors such as climate change, and economic and social development. Agenda 2030, with its 17 Sustainable Development Goals (SDGs), has set the direction on where development should be focussed. There are still around 675 million people who lack access to electricity (SDG7), mainly in Sub-Saharan Africa. The energy system is also responsible for emitting most greenhouse gas (GHG) emissions and is closely connected to SDG 13, climate action.Energy models can provide insight into the implications of different interventions in the system. However, the transition also poses new challenges for energy modelling. New spatiotemporal questions arise with 1) the penetration of renewable technologies to mitigate GHG emissions, with location-specific intermittent supply options such as wind and solar PV panels, and 2) the low share of the population living near the existing electricity network in many Sub-Saharan countries and the decreasing cost of off-grid and mini-grid supply options.This change increases the number of technologies and details needed in the system which in turn increases complexity in the models. Complexity can be defined in terms of four aspects: spatial, temporal, mathematical and, system scope. However, more detail, both parametrical and structural, can introduce more potential errors and uncertainty into the model. Therefore, energy models should be as simple as possible and as complex as necessary.This thesis aims to give quantifiable and qualitative insights into the mathematical, spatial, and temporal aspects of energy systems modelling for both national and regional system scopes, along with their policy implications. The thesis explores the trade-offs between which mathematical method is applied when modelling electricity access, and the global sensitivity of parametrical and structural parameters in ESOMs.The method for achieving the aim of the thesis uses a four-step approach. First, the geospatial electrification problem is explored by developing two different models, a linear programming model, using the model generator GEOSeMOSYS, and a heuristic method, soft-linking the open-source tools OnSSET and OSeMOSYS. Second, these two models are compared in order to understand the differences between them with respect to computational effort, results, insight, and effectiveness in modelling electricity access in a developing country. Third, the linear programming model developed for this thesis is then explored using the method of Morris global sensitivity analysis to understand the importance of spatial and temporal resolution compared to other parameters such as demand, discount rate, and capital cost. Fourth and finally, the global sensitivity analysis method of factor mapping, using scenario discovery, is explored to understand parameters that determine cost and low carbon futures in the regional multi-country energy systems optimisation model ‘South America Model Base’ (SAMBA).The results show that the two methods for optimising electrification show similar trends when the demand is changed, with low demand predominantly resulting in PV panels and batteries to serve the formerly unelectrified population, while higher demand results in more grid-connected households. The demand level and profile for newly electrified households result in different service levels and possibilities for adding more appliances over time. The competitiveness of PV panels with batteries decreases significantly when the demand profile increases during the night. The two methods in this thesis have different solution times with the linear programming method having a much longer solution time, furthermore, the mathematical approaches to solve the transmission network are different, and both methods have trade-offs in their results. These trade-offs are in the mathematical approach where OnSSET uses a one-at-the-time optimisation leading to a suboptimal overall network, and GEOSeMOSYS rely on the assumption of linearity, which leads to very small incremental installations of transmission lines.The global sensitivity analysis of GEOSeMOSYS for electricity access showed that the structural parameters, spatial and temporal resolution, influence the result parameters and cannot be simplified without changing the results. The temporal resolution had a greater influence on the assessed results parameters than the spatial resolution, indicating that it is more significant. For the South American system, the parameters that determine low carbon emission pathways are low/medium demand and low/medium discount rates.This thesis has therefore shown that, even though models should be as simple as possible, the spatial and temporal resolution cannot be simplified to a one-node analysis or low temporal resolution without this affecting the results. The mathematical choice for selecting the method of electricity access was analysed and trade-offs were highlighted. The main trade-off was in the network expansion where both methods use approximations that can lead to over/underestimating the investment need. The soft-linked method is a good option to understand a higher level to explore electricity access. If the question is more complex (e.g., adding transportation, heating and cooling), then GEOSeMOSYS provides more readily available options for expanding the analysis, but at a coarse spatial resolution. Demand is a critical parameter in energy models, as is shown in this thesis, and determines both the cost and the potential for achieving low carbon futures. Therefore, including more demand functionalities (such as demand side management and price elasticity) in energy models could help to further detail future demands, and this is identified as future work.
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| 11. |
- Vadiee, Amir, 1984-
(författare)
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Energy Analysis of the Closed Greenhouse Concept : Towards a Sustainable Energy Pathway
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The closed greenhouse is an innovative concept in sustainable energy management. The closed greenhouse can be considered as a large commercial solar building. In principle, it is designed to maximize the utilization of solar energy through seasonal storage. In a fully closed greenhouse, there are not any ventilation windows. Therefore, the excess sensible and latent heat must be removed, and can be stored using seasonal and/or daily thermal storage technology. The available stored excess heat can be utilized later in order to satisfy the heating demand in the greenhouse, and also in neighbouring buildings.A model for energy analysis of a greenhouse has been developed using the commercial software TRNSYS. With this model, the performance of various design scenarios has been examined. The closed greenhouse is compared with a conventional greenhouse using a case study to guide the energy analysis. In the semi-closed greenhouse, a large part of the available excess heat will be stored through thermal energy storage system (TES). However, a ventilation system can still be integrated in order to use fresh air as a rapid response indoor climate control system. The partly closed greenhouse consists of a fully closed section and a conventional section. The fully closed section will supply the heating and cooling demand of the conventional section as well as its own demand. The results show that there is a large difference in heating demand between the ideal closed and conventional greenhouse configurations. Also, it can be concluded that the greenhouse glazing type (single or double glass) and, in the case of the semi-closed and partly closed greenhouse, the controlled ventilation ratio are important for the thermal energy performance of the system. A thermo-economic analysis has been done in order to investigate the cost feasibility of various closed greenhouse configurations. From this analysis, it was found that the load chosen for the design of the seasonal storage has the main impact on the payback period. In the case of the base load being chosen as the design load, the payback period for the ideal closed greenhouse might be reduced by 50% as compared to using peak load. Thus, future studies should explore innovative combinations of short term and seasonal storage.Finally, several energy management scenarios have been discussed in order to find alternatives for improving the energy performance of the closed greenhouses. However, no specific optimal solution has so far been defined.
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| 12. |
- Fischer, Markus, et al.
(författare)
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The regional assessment report on biodiversity and ecosystem services for Europe and Central Asia : summary for policymakers
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Regional Assessment Report on Biodiversity and Ecosystem Services for Europe and Central Asia produced by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) provides a critical analysis of the state of knowledge regarding the importance, status, and trends of biodiversity and nature's contributions to people. The assessment analyses the direct and underlying causes for the observed changes in biodiversity and in nature's contributions to people, and the impact that these changes have on the quality of life of people. The assessment, finally, identifies a mix of governance options, policies and management practices that are currently available to reduce the loss of biodiversity and of nature's contributions to people in that region. The assessment addresses terrestrial, freshwater, and coastal biodiversity and covers current status and trends, going back in time several decades, and future projections, with a focus on the 2020-2050 period.
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| 13. |
- Ghaem Sigarchian, Sara
(författare)
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Small-Scale Decentralized Energy Systems : optimization and performance analysis
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Small-scale polygeneration energy systems, providing multiple energy services, such as heating, electricity, cooling, and clean water, using multiple energy sources (renewable and non-renewable) are considered an important component in the energy transition movement. Exploiting locally available energy sources and providing energy services close to the end users have potential environmental, economic, and societal benefits. Furthermore, integration of thermal and electro-chemical storages in the system can decrease fossil fuel consumption, particularly when applying a long-term perspective.Despite their promising potential, the global share of power generation by these systems, including the combined heat and power (CHP) systems, is relatively low in the current energy market. To investigate the applicability of these systems, their competitiveness in comparison with conventional energy solutions should be carefully analyzed in terms of energy, economy, and the environment. However, determining whether the implementation of a polygeneration system fulfills economic, energetic, and environmental criteria is a challenging process. Additionally, the design of such systems is a complex task, due to a system design with various generation and storage modules, and the continuous interaction between the modules, load demand fluctuations, and the intermittent nature of renewable energy sources.In this research study, a method to identify the optimal size for small-scale polygeneration systems and suitable operating strategies is proposed. Based on this method, a mathematical model is developed that can optimize the design in terms of energy, economy, and the environment relative to a reference system for a given application. Moreover, the developed model is used to investigate the effects of various parameters on the performance of the system, including, among others, the selected operating strategy and load characteristics as well the climate zones through a number of case studies. It is concluded that the application of a small-scale polygeneration energy system potentially has considerable energetic and environmental benefits. However, its economic feasibility varies from case to case. The concluding remarks are primarily intended to provide a general perception of the potential application of a polygeneration system as an alternative solution. It also provides a general understanding of the effects of various parameters on the design and performance of a complex polygeneration system.The results from various case studies demonstrate that the developed model can efficiently identify the optimal size of a polygeneration system and its performance relative to a reference system. This can support engineers and researchers as well as investors and other decision makers to realize whether a polygeneration system is a good choice for a specific case.
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| 14. |
- Heier, Johan
(författare)
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Energy Efficiency through Thermal Energy Storage : Possibilities for the Swedish Building Stock
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The need for heating and cooling in buildings constitutes a considerable part of the total energy use in a country and reducing this need is of outmost importance in order to reach national and international goals for reducing energy use and emissions. One important way of reaching these goals is to increase the proportion of renewable energy used for heating and cooling of buildings. Perhaps the largest obstacle with this is the often occurring mismatch between the availability of renewable energy and the need for heating or cooling, hindering this energy to be used directly. This is one of the problems that can be solved by using thermal energy storage (TES) in order to save the heat or cold from when it is available to when it is needed.This thesis is focusing on the combination of TES techniques and buildings to achieve increased energy efficiency for heating and cooling. Various techniques used for TES as well as the combination of TES in buildings have been investigated and summarized through an extensive literature review. A survey of the Swedish building stock was also performed in order to define building types common in Sweden. Within the scope of this thesis, the survey resulted in the selection of three building types, two single family houses and one office building, out of which the two residential buildings were used in a simulation case study of passive TES with increased thermal mass (both sensible and latent). The second case study presented in the thesis is an evaluation of an existing seasonal borehole storage of solar heat for a residential community. In this case, real measurement data was used in the evaluation and in comparisons with earlier evaluations.The literature reviews showed that using TES opens up potential for reduced energy demand and reduced peak heating and cooling loads as well as possibilities for an increased share of renewable energy to cover the energy demand. By using passive storage through increased thermal mass of a building it is also possible to reduce variations in the indoor temperature and especially reduce excess temperatures during warm periods, which could result in avoiding active cooling in a building that would otherwise need it. The analysis of the combination of TES and building types confirmed that TES has a significant potential for increased energy efficiency in buildings but also highlighted the fact that there is still much research required before some of the technologies can become commercially available. In the simulation case study it was concluded that only a small reduction in heating demand is possible with increased thermal mass, but that the time with indoor temperatures above 24 °C can be reduced by up to 20%. The case study of the borehole storage system showed that although the storage system worked as planned, heat losses in the rest of the system as well as some problems with the system operation resulted in a lower solar fraction than projected.The work presented within this thesis has shown that TES is already used successfully for many building applications (e.g. domestic hot water stores and water tanks for storing solar heat) but that there still is much potential in further use of TES. There are, however, barriers such as a need for more research for some storage technologies as well as storage materials, especially phase change material storage and thermochemical storage.
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