| 1. |
- Dreier, Dennis, 1990-
(author)
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Transition Technologies for Electrification and Optimisation of Bus Transport Systems
- 2020
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Doctoral thesis (other academic/artistic)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. |
- Khan, MD. Ershad Ullah, 1979-
(author)
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Renewables Based Polygeneration for Rural Development in Bangladesh
- 2017
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Doctoral thesis (other academic/artistic)abstract
- Despite the country's rural electrification programme, kerosene is the predominant source for lighting, and unsustainable and polluting woody biomass is virtually the only option available for cooking. The rural population also struggles with unsafe drinking water in terms of widespread arsenic contamination of well water. The present work has taken an integrated approach in an attempt to mitigate problems through small-scale polygeneration, a concept linking renewable energy sources to these energy needs via novel energy conversion systems.Anaerobic digesters (AD) for biogas production are promising in the rural setting, and field surveys have identified problems in the construction, maintenance and operation of existing AD, particularly in overall performance of household digesters. Based on these results, a number of operational and technological improvements are suggested for employing digesters in polygeneration units. This study also examines one approach for small-scale, low cost arsenic removal in groundwater through air gap membrane distillation, a thermally-driven water purification technology.Integration of biogas production with power generation and water purification is an innovative concept that lies at the core of feasibility analyses conducted in this work. One of the case studies presents a new concept for integrated biogas based polygeneration and analyzes the techno-economic performance of the scheme for meeting the demand of electricity, cooking energy and safe drinking water of 30 households in a rural village of Bangladesh. The specific technologies chosen for the key energy conversion steps are as follows: plug-flow digester; internal combustion engine; and membrane distillation. One major concern is local feedstock availability for the digester, since a single feedstock is impractical to serve both cooking, lighting and water purification systems. In this circumstance solar PV could be a potential option for integrated hybrid systems.
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| 4. |
- Golzar, Farzin, et al.
(author)
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Impact of wastewater heat recovery in buildings on the performance of centralized energy recovery – a case study of Stockholm
- 2021
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In: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 297
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Journal article (peer-reviewed)abstract
- New concepts and technologies are needed to upgrade conventional energy systems and cope with environmental challenges. However, while emerging new technologies may serve to improve energy efficiency at the local level, they might also have disruptive effects at the system level. This paper investigates the potentially disruptive impacts of upscaling local wastewater heat recovery at the building level on the performance of the wastewater treatment and district heating systems in Stockholm. A hybrid model based on data-driven and process-driven mathematical models was developed to simulate the performance of the wastewater system and interlinkages among different actors. Two types of technologies (heat exchanger and heat pump) and different technology penetration scenarios (10%, 20%, and 40%) are considered for heat recovery in buildings. If 20% of the buildings install heat exchangers, the amount of heat demand in buildings decreases by 3% and total heat losses in the sewerage network decreases by 2%. In the case of local heat recovery using heat pumps in 20% of the buildings, there is a 4% reduction in the heat demand in buildings and 3% decrease in total heat losses in the network. Meanwhile, the heat demand in the wastewater treatment plant increases by 2% (with heat exchangers) or 4% (with heat pumps). Moreover, the district heating company recovers 5% and 9% less heat from the wastewater treatment plant, respectively, as compared to current conditions. These findings indicate that enhanced heat recovery in buildings could have disruptive impacts on currently centralized energy and water service provision over time. This justifies closer consideration of the balance between local and system-level solutions as policymakers define goals for energy efficiency, and evaluate potential societal and economic implications of different alternatives.
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| 5. |
- Golzar, Farzin, et al.
(author)
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Implications of improved heat recovery in builidngs - a case study of Stockholm
- 2020
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In: Applied energy symposium MIT A+B. - Boston, USA.
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Conference paper (peer-reviewed)abstract
- A transition to new energy systems is required at global level to cope with the challenges of climate change. It is widely accepted that new technologies will play an important role in achieving this transition. Yet, the promises and threats of new technologies are prevalent issues in politics and social debates. For example, the choice of energy conversion technologies will have direct impact on greenhouse emissions or the number of jobs that may be created in a given context, and thus be subject of political discussions and preferences.Policymakers often look for guidance to identify and characterize the risks associated with new and emerging technologies. However, while concerns often focus direct negative impacts of specific technologies, some impacts may rather be at system level, leading to disruptive societal effects. At city level, disruptions could affect critical functions such as energy provision, water supply or transport. Such disruptions are more difficult to analyze and communicate, but improved understanding of the implications of system transformation is required to make sure policies are designed to forward optimal solutions and sustainable development. We explore a case in which technological innovation at local level may have implications at system level, leaving the overall societal and environmental benefits unclear.This paper explores the changing context of technological systems options for heat and water recovery in the city of Stockholm, Sweden. We aim at (i) casting light on the overall implications that system reconfiguration may have for resource efficiency, and (ii) guiding policy makers towards next steps in legislation for promoting energy efficiency in buildings.An assessment is carried out on the potential disruptive effects of new technological solutions for heat recovery. We use the system of wastewater heat recovery in Stockholm as a case study. Wastewater heat recovery can be performed locally or at system level. In the former, the heat is recovered where the wastewater is generated, or before the waste water is dispatched from the building. In the latter, the heat is transported with the wastewater, and recovered at the water treatment plant. Although local heat recovery could be beneficial, a broad use of new technologies to recover wastewater heat at the building site might result in disruptive impacts on prevailing centralized systems for water treatment and heat distribution at city level. Potential disruptions include technical adjustments requiring compensation for the reduced heat recovered, change in cost structure of service providers, and security of service supply, among others.Currently, a wastewater treatment plant (WWTP) in the Stockholm region receives wastewater and treats it with combined mechanical, biological and chemical processes. Biogas is produced from digested sludge. The biogas is upgraded for use as bus fuel. The heat content of treated water is recovered by a heat pump (660 MW) and delivered to the district heating company. The district heating company uses various heat sources, including the recovered heat from WWTP, while the water utility company treats the sewage, and provides clean water for buildings.Stricter building regulations together with emerging technological solutions may result in property owners choosing to recover heat locally before discharging the wastewater to the municipal wastewater treatment facilities. At system level, this may reduce energy losses in the sewage network. However, from the point of view of the water treatment utility, the reduced input temperature will lead to higher heat demand for digesters. It means more costs for WWTP and higher prices for the drinking water. As a result, although property owners would pay less for heat due to local heat recovery, they would probably need to pay more for drinking water. There are also consequences for the district heating company, since less heat will be obtained from wastewater, while the heat demand of WWTP is increased. Therefore, the district heating company may need to look for new sources of heat. At present, incineration provides a significant part of the heat used in Stockholm, but development is going in the direction of more recycling and less incineration.In addition to heat recovery from wastewater, also water could be locally recovered. Again, property owners may be tempted to adopt combined systems for water and heat recovery on site, if they have space for it, and if cost-efficient technology options are commercially available. This would result in lower demand for treated water, with direct impact for the water utility. In this case, there are disruptions for both district heating companies and water utilities, reducing their interest to invest in new facilities. Stockholm is a rapidly growing city and this could have impact on energy and water supply security over time.Thus, if local recovery of energy and water is up-scaled, centralized service provision as organized today is likely to be affected in the long run, changing the configuration of water and energy provision in buildings. Since market driven competition is allowed in Sweden when it comes to technological solutions, there is a clear opportunity for new players when it comes to guaranteeing the delivery of energy and clean water in buildings. In this context, there is need for insights into the potential disruptive consequences that decentralized solutions for heat and water recovery may have on established centralized urban energy and water systems. What consequences could present policies for improved energy efficiency in buildings have on energy and water security at city level? Our analysis aims at contributing science-based information that can guide and support policies for improved resource efficiency and reduced climate impact.
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| 6. |
- Gorosabel, Oier Lopez de Briñas, et al.
(author)
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A framework for the assessment of electric bus charging station construction : A case study for Stockholm's inner city
- 2022
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In: Sustainable cities and society. - : Elsevier BV. - 2210-6707. ; 78
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Journal article (peer-reviewed)abstract
- Electromobility has gained momentum in the last years following the efforts to reduce transportation-related emissions. In this context, efficient charging infrastructure is vital to foster the expansion of electric vehicles. This paper presents a standardized framework for micro-scale analysis of potential charging locations for electric buses aiming at easing the analysis process and promoting the expansion of electric buses. The framework is tailor-made for the Municipality of Stockholm and tested in two city-centre public transport hubs, namely Odenplan and Slussen. However, the framework can be used in other locations by implementing minimum changes. Connecting charging stations to the power grid is identified as the main drawback in city-centre locations due to their high impact on the grid. Lack of available capacity at nearby connection points results in long distance connections, reaching up to 1 km in some cases. Such connections impact the overall cost of electrification directly, as they may account for up to 63% of the total cost. Although other issues regarding space availability and operational efficiency also need to be addressed, such as the lack of enough dwell time to charge the batteries, the framework proves the suitability of these inner-city locations as charging points.
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| 7. |
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| 8. |
- Higa, Cecilia, et al.
(author)
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Coalitions towards the Carbon Tax in the Swedish Heating Sector
- 2020
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In: Sustainability. - Switzerland : MDPI AG. - 2071-1050. ; 12:20
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Journal article (peer-reviewed)abstract
- The carbon tax is a cornerstone of the climate policy in Sweden. Historically, it has played a central role in the replacement of fossil fuels in the heating sector. The purpose of this paper was to analyze the policy-making process that led to the formulation and adoption of the carbon tax in the Swedish heating sector, from 1980 to 1991. We used the Advocacy Coalition Framework (ACF), according to which policy actors form coalitions based on shared beliefs. Drawing from both literature and empirical experiences gathered through in-depth interviews, we identified supporting and opposing coalitions that diverged in their views concerning bioenergy development and the potential impact of the carbon tax. This study illustrates the complex conditions for introduction of environmental taxes and expansion of new industries, particularly when established businesses perceive the new activities as a threat. The Swedish experience shows that countries can progress by exploring internal synergies and innovative policy designs, despite potential resistance of established constituencies. The successful adoption of the carbon tax in the Swedish heating sector serves as inspiration for policymakers in other sectors and countries, as they contemplate policies to promote the decarbonization of the energy system.
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