Over recent years, political, technological, environmental and economic factors have combined to increase interest in distributed energy resources (DER), and flexibility in the power system. As a resource which is both distributed and flexible, flexible demand (FD) can be considered to be particularly of interest. However, due to many facets of its nature, understanding the available flexibility, and potential value of that flexibility, is difficult. Further, understanding the effects of FD exploitation on other multi-energy system actors, given the complex nature of modern liberalised energy systems, complicates the picture further. These factors form material obstructions to the assessment of FD, for example, for the construction of business cases. To address these gaps this thesis first assesses the nature and value of various applicable current and potential markets and charging/incentive regimes, before detailing a novel multi-energy domestic demand simulation model, capable of modelling, in detail, domestic FD resources. Subsequently, a multi-commodity stochastic energy/reserve optimisation model, capable of modelling various DERs and taking into account price signals related to various energy-related commodities and services (including user utility) is specified. The separation of price components for application at different aggregation levels, which is applied in the optimisation model, also informs the described value mapping methodology, which illustrates the impacts of any, particularly demand-side, intervention on the wider multi-energy system. The power of the above detailed contributions are demonstrated through various studies, which show the physical and economic impact of various demand side interventions and of greater market participation by FD resources.

abstract: As the global community raises concerns regarding the ever-increasing urgency of climate change, efforts to explore innovative strategies in the fight against this anthropogenic threat is growing. Along with other greenhouse gas mitigation technologies, Direct Air Capture (DAC) or the technology of removing carbon dioxide directly from the air has received considerable attention. As an emerging technology, the cost of DAC has been the prime focus not only in scientific society but also between entrepreneurs and policymakers. While skeptics are concerned about the high cost and impact of DAC implementation at scales comparable to the magnitude of climate change, industrial practitioners have demonstrated a pragmatic path to cost reduction. Based on the latest advancements in the field, this dissertation investigates the economic feasibility of DAC and its role in future energy systems. With a focus on the economics of carbon capture, this work compares DAC with other carbon capture technologies from a systemic perspective. Moreover, DAC’s major expenses are investigated to highlight critical improvements necessary for commercialization. In this dissertation, DAC is treated as a backstop mitigation technology that can address carbon dioxide emissions regardless of the source of emission. DAC determines the price of carbon dioxide removal when other mitigation technologies fall short in meeting their goals. The results indicate that DAC, even at its current price, is a reliable backup and is competitive with more mature technologies such as post-combustion capture. To reduce the cost, the most crucial component of a DAC design, i.e., the sorbent material, must be the centerpiece of innovation. In conclusion, DAC demonstrates the potential for not only negative emissions (carbon dioxide removal with the purpose of addressing past emissions), but also for addressing today’s emissions. The results emphasize that by choosing an effective scale-up strategy, DAC can become sufficiently cheap to play a crucial role in decarbonizing the energy system in the near future. Compared to other large-scale decarbonization strategies, DAC can achieve this goal with the least impact on our existing energy infrastructure. / Dissertation/Thesis / Doctoral Dissertation Sustainable Engineering 2020

The aim of the thesis, which is divided into a theoretical and a practical part, is to describe and analyze the current tendency in a company’s cost management, and suggest a precaution leading to an improvement. The theoretical part compiles the classification of costs, calculations, and tools and processes of cost management. The practical part then describes cost management in the analyzed company. Both vertical and horizontal financial analysis are rendered – from the analyses, precautions are defined, as well as cost items, which are suggested to be paid attention to.

Solar Tower Power Plants with thermal energy storage are a promising technology for dispatchable renewable energy in the near future. Storage integration makes possible to shift the electricity production to more profitable peak hours. Usually two tanks are used to store cold and hot fluids, but this means both higher related investment costs and difficulties during the operation of the variable volume tanks. Another solution can be a single tank thermocline storage in a multi-layered configuration. In such tank both latent and sensible fillers are employed to decrease the related cost by up to 30% and maintain high efficiencies.  The Master thesis hereby presented describes the modelling and implementation of a thermocline-like multi-layered single tank storage in a STPP. The research work presents a comprehensive methodology to determine under which market structures such devices can outperform the more conventional two tank storage systems. As a first step the single tank is modelled by means of differential energy conservation equations. Secondly the tank geometrical design parameters and materials are taken accordingly with the applications taken into consideration. Both the steady state and dynamic models have been implemented in an existing techno-economic tool developed in KTH, in the CSP division (DYESOPT). The results show that under current cost estimates and technical limitations the multi-layered solid PCM storage concept is a better solution when peaking operating strategies are desired, as it is the case for the two-tier South African tariff scheme. In this case the IRR of an optimal designed power plant can be decreased by 2.1%. However, if a continuous operation is considered, the technology is not always preferred over the two tank solution, yet is a cheaper alternative with optimized power plants. As a result the obtained LCOE can be decreased by 2.4%.

Biomass to Liquids via Fischer-Tropsch synthesis (BTL-FT) is regarded as one of the most promising routes for providing alternative solution to growing demand for energy and environmental protection. In Chapter I, the development and key issues of BTL-FT process (especially Fischer-Tropsch synthesis) were reviewed and identified. In Chapter II, Mo/HZSM-5 catalyst was synthesized using Incipient Wetness Impregnation method and tested in nitrogen rich model bio-syngas. Different operation parameters (temperature, pressure, and GHSV) were tested to investigate their influence on the catalytic performance. Those parameters were found to affect the performance significantly. Liquid samples from conversion were mainly composed of C8 to C10 range hydrocarbons. The catalyst characterization revealed that molybdenum species were well distributed on the catalyst support, while dealumination, agglomeration and coke deposition were observed in spent catalyst. The top layer of the spent catalyst had the most coke deposition. A Three-Dimensionally Ordered Macro-porous (3DOM) Fe based Fischer-Tropsch catalyst was developed using a facile in-situ Nitrate Oxidation-PMMA templating technique in Chapter III. Several techniques (including SEM, BET, TPR, HRTEM, XRD, XPS, and DRIFTS) were combined to characterize the morphology, textural properties and microstructures of 3DOM Fe catalysts at different stages. The effects of bio-syngas composition on carbonaceous species formation, iron phase transformation and catalytic performance were investigated and correlated. A novel hybrid bio-refinery process co-converting biomass and natural gas into liquid fuels via FTS with a CO2 recycle loop was developed, modeled and simulated by using Aspen Plus in Chapter IV. The Aspen Plus model utilized experimental data from the 3DOM Fe catalyst. Economic analysis was performed on different scenarios based on the simulation results to determine profitability of the process. Results indicated that 102.65 t/h gasoline and 22.93 t/h diesel can be produced with the co-processing of 100.00 t/h biomass and 112.3 t/h natural gas using 307.78 t/h of recycled CO2 in the process simulation. The carbon conversion rate was estimated to be 81.23% for the hybrid process. Economic analysis revealed that the process can be profitable when using at least 10.00 t/h biomass and 11.23 t/h natural gas.

With increasing awareness of environmental issues and worldwide requirements for sustainable development, renewable energy technologies with lower environmental impact, especially those having abundant resources like wind and solar energy, attract more attention. Concentrating Solar Power (CSP) is one of the most promising solar energy technologies. Indeed, thermal energy storage (TES) units could be integrated into CSP plants, enhancing their flexibility and capacity factor. However, tower based CSP plants still remain cost intensive. This study evaluates the performance of a 55MWe combined-cycle CSP plant with rock-bed TES located in Sevilla, Spain. Sensitivity analysis has been performed to assess the influence of critical parameters. Furthermore, in order to decrease the costs with increasing efficiency, improved CSP plant schemes have been proposed. In the study, EES, SAM and TRNSYS are used to design and simulate the model from technological perspective, then the capital and operational costs are calculated in MATLAB. For one-year simulation of the designed case, the performance of the plant is determined by the trade-off among several conflicting factors. The study focuses on three key indicators to measure the performance- levelized costs of electricity (LCoE), capital expenditure (CAPEX) and efficiency factor (UF). As long as CAPEX is within the acceptable range, LCoE would be the most concerned one-as low as possible, then followed by UF. Compared to conventional CCGT plant, the proposed combined-cycle tower-based CSP plant, with efficiency of 0.49 and LCoE of 196USD/MWe, enables efficiency improvements, while both CAPEX and LCoE are higher. On the other hand, it has to be noticed that CCGT relies on fuel (natural gas) price, which means higher risks and operational expenditure (OPEX). A sensitivity study is involved varying gas turbine expansion ratio (to vary its outlet temperature and therefore supply power for the bottoming Rankine cycle), size of TES and solar multiple (SM). It can be found that same LCoE and UF could be achieved with lower CAPEX by setting appropriate parameters. The study also introduces two improved CSP plant schemes with sensitivity study. To some extent, the LCoE decreases due to increasing power output and the efficiency of the system simultaneously increases. / Med ökad medvetenhet om miljöfrågor och globala krav på hållbar utveckling lockar förnybar energi teknologi med lägre miljöpåverkan, särskilt de som har stora resurser som vind och solenergi, mer uppmärksamhet. Concentrating Solar Power (CSP) är en av de mest lovande solenergi teknologierna. Faktiskt kan värmeenergi lagringsenheter integreras i CSP-anläggningar, vilket förbättrar deras flexibilitet och kapacitetsfaktor. Träbaserade CSP-anläggningar är dock fortfarande kostnads intensiva. Denna studie utvärderar prestandan för en 55MWe CSP-anläggning med kombinerad cykel med TESsandbädd i Sevilla, Spanien. Känslighetsanalys har utförts för att bedöma påverkan av kritiska parametrar. För att minska kostnaderna med ökad effektivitet har dessutom förbättrade CSP-anläggningsprogram föreslagits. I studien används EES, SAM och TRNSYS för att designa och simulera modellen ur teknologiskt perspektiv, sedan beräknas kapital och driftskostnader i MATLAB. För ett års simulering av det planerade fallet bestäms anläggningens prestanda av bytet mellan flera motstridiga faktorer. Studien fokuserar på tre nyckelindikatorer för att mäta prestandanivå kostnaderna för el (LCoE), investeringar (CAPEX) och effektivitetsfaktor (UF). Så länge CAPEX ligger inom det acceptabla intervallet, skulle LCoE vara den mest bekymrade en så låg som möjligt, följt av UF. Jämfört med konventionell CCGT-anläggning möjliggör den föreslagna träbaserade CSP-anläggningen med kombinerad cykel med effektivitet 0,49 och LCoE på 196USD / MWe effektivitetsförbättringar, medan både CAPEX och LCoE är högre. Å andra sidan måste man notera att CCGT förlitar sig på bränslepriset (naturgas), vilket innebär högre risker och driftsutgifter (OPEX). En känslighetsstudie är involverad med varierande utvidgning förhållande för gasturbin (för att variera dess utloppstemperatur och därmed leverera ström för botten Rankine-cykeln), storlek på TES och sol multipel (SM). Det kan konstateras att samma LCoE och UF skulle kunna uppnås med lägre CAPEX genom att ställa in lämpliga parametrar. Studien introducerar också två förbättrade CSP-anläggningar med känslighetsstudie. I viss utsträckning minskar LCoE på grund av ökad effekt och systemets effektivitet ökar samtidigt.

Rapid growth of digitalization has urged Data Centres (DC) to be more energy efficient by recovering waste heat from server racks that would otherwise be wasted. This techno-economic study is focused on upgrading low temperature waste heat from typical Air-Cooled DC for District Heating Network (DHN) market in Stockholm region. The methodology is carried out by four system configurations that are experimented with different historical electricity data, impacts of climate change with simulated weather data, and variations in DHN temperature as the heat supply scenario development. The results show that DC configuration with combination of both free-cooling and waste heat recovery can foster techno-economic benefits by reducing cooling consumption by 55.6%, compared to DC configuration with free-cooling only; and further lowering Power Usage Effectiveness (PUE) from 1.95 to 1.52. Lifecycle Operational Expenditure (LCO) has also been used as the economic indicator to represent the maximum initial investment that data centre should accept when deciding to recover the waste heat to the DHN. Moreover, the new technical Key Performance Indicators (KPIs) were introduced to support the decision-making in the supply of recovered waste heat to DHN. The electricity price was further identified to have greater impact than the effect of climate change for the overall techno-economic performance. On one specific hand, heat supply with Price-Limit scenario concluded that 40.18% of available waste heat from DC is not profitable should it be injected to DHN in the case of low electricity price. In the case when the electricity price is high, the amount of waste heat not injected to DHN increases to 58.57%. / <p>The thesis defense presentation was held digitally on Zoom on June 19th 2023 at 09.00 CEST</p>

To mitigate the global greenhouse gases (GHGs) emissions, carbon dioxide (CO2) capture and storage (CCS) has the potential to play a significant role for reaching mitigation target. Oxy-fuel combustion is a promising technology for CO2 capture in power plants. Advantages compared to CCS with the conventional combustion technology are: high combustion efficiency, flue gas volume reduction, low fuel consumption, near zero CO2 emission, and less nitrogen oxides (NOx) formation can be reached simultaneously by using the oxy-fuel combustion technology. However, knowledge gaps relating to large scale coal based and natural gas based power plants with CO2 capture still exist, such as combustors and boilers operating at higher temperatures and design of CO2 turbines and compressors. To apply the oxy-fuel combustion technology on power plants, much work is focused on the fundamental and feasibility study regarding combustion characterization, process and system analysis, and economic evaluation etc. Further studies from system perspective point of view are highlighted, such as the impact of operating conditions on system performance and on advanced cycle integrated with oxy-fuel combustion for CO2 capture. In this thesis, the characterization for flue gas recycle (FGR) was theoretically derived based on mass balance of combustion reactions, and system modeling was conducted by using a process simulator, Aspen Plus. Important parameters such as FGR rate and ratio, flue gas composition, and electrical efficiency etc. were analyzed and discussed based on different operational conditions. An advanced evaporative gas turbine (EvGT) cycle with oxy-fuel combustion for CO2 capture was also studied. Based on economic indicators such as specific investment cost (SIC), cost of electricity (COE), and cost of CO2avoidance (COA), economic performance was evaluated and compared among various system configurations. The system configurations include an EvGT cycle power plant without CO2 capture, an EvGT cycle power plant with chemical absorption for CO2 capture, and a combined cycle power plant. The study shows that FGR ratio is of importance, which has impact not only on heat transfer but also on mass transfer in the oxy-coal combustion process. Significant reduction in the amount of flue gas can be achieved due to the flue gas recycling, particularly for the system with more prior upstream recycle options. Although the recycle options have almost no effect on FGR ratio, flue gas flow rate, and system electrical efficiency, FGR options have significant effects on flue gas compositions, especially the concentrations of CO2 and H2O, and heat exchanger duties. In addition, oxygen purity and water/gas ratio, respectively, have an optimum value for an EvGT cycle power plant with oxy-fuel combustion. Oxygen purity of 97 mol% and water/gas ratio of 0.133 can be considered as the optimum values for the studied system. For optional operating conditions of flue gas recycling, the exhaust gas recycled after condensing (dry recycle) results in about 5 percentage points higher electrical efficiency and about 45 % more cooling water consumption comparing with the exhaust gas recycled before condensing (wet recycle). The direct costs of EvGT cycle with oxy-fuel combustion are a little higher than the direct costs of EvGT cycle with chemical absorption. However, as plant size is larger than 60 MW, even though the EvGT cycle with oxy-fuel combustion has a higher COE than the EvGT cycle with chemical absorption, the EvGT cycle with oxy-fuel combustion has a lower COA. Further, compared with others studies of natural gas combined cycle (NGCC), the EvGT system has a lower COE and COA than the NGCC system no matter which CO2 capture technology is integrated. / QC 20111123

Global carbon emissions are higher than ever before and in the last decade of 21st century, focus has shifted on reducing these emissions in various ways possible. Carbon capture, utilization and storage (CCUS) has been identified as one of the important ways to reduce carbon emissions and meet climate targets. For a long time, Sweden has promoted the use of biomass as fuel for heat and power generation which has enabled it to meet its climate targets earlier than projected. Now, major Swedish energy companies are looking into coupling exiting biomass fired heat and power plants with CCUS. This opens up the possibility of attaining negative emissions, also known as Bio Energy Carbon Capture and Storage (BECCS). With the right policy framework in place, BECCS can be a major boon and help Sweden attaining net zero carbon emissions. As a contribution in meeting net zero targets, this thesis is aimed to evaluate the installation of a carbon capture plant to abate flue gas emissions from District heating facility in Jordbro which is a ~70 MW (fuel) CHP plant running on biomass.  Among the available carbon capture technologies, Calcium oxide-based carbon capture has been expected to show great promise due to its lower environmental impacts and possibility to extract high quality energy when installed. Hence a concept system for integration calcium looping at Jordbro has been developed through the use of modeling tools like ASPEN. A techno economic assessment was needed to be performed to give conclusive results on the overall viability of the process. Further, key process indicators like energy penalty, plant footprint and cost of capture per tonne of CO2 were identified for making the final evaluation. Finally, through a strategic collaboration with SaltX, major process improvements were introduced and applied to the modeled process.  It was concluded that with the current average flowrates at Jordbro it was possible to capture 154,000 tonnes of CO2 annually. The required amount of energy input to the calciner is 48MW (7.29 MW/kg-CO2 captured) which is one of the major findings of this study. Even though a significant amount of heat is recovered, the main boiler is not capable of producing heat over 900 οC and additional biomass needs to be combusted, leading to an additional CO2 emission of about 125 000 tonnes annually. Considering an optimal integration, the energy penalties became 6.25 %.  However, the plant footprint increased substantially due to requirement for burning additional biomass in the regeneration reactor and addition of several auxiliary units that come along with calcium-based carbon capture. Further, the total capital investment for this project is 1,219 MSEK with reactor costs being most capital intensive. Assuming a plant life of 25 years, the cost of capture per tonne of CO2 (excluding the costs for carbon transport and storage) was evaluated at 988 SEK, which is 58% higher than the reference Mono-ethanol amine based chemical absorption case. The innovative improvements from SaltX substantially reduced the plant footprint but capture costs did not reduce since material transport costs proved to be the major bottleneck.  Upon comparison of this technology with the amine-based technology it was found that Calcium oxide-based carbon capture would need further research and improvements to be more viable than amine-based carbon capture. Integration of thermal energy storage and process intensification can be the possible paths for further improvement.

High and medium-voltage digital substations play an essential role in the energy transition since they are part of the equipment required to deploy smart grids. With the gradual increase of smart grids, energy systems are becoming more flexible with the growing penetration of renewable energies and distributed energy generation. Simultaneously, the energy system’s efficiency increases, with load supply precisely where required and reduced losses. Medium voltage stations have not been upgraded gradually like high voltage stations; therefore, most of Stockholm’s medium voltage stations are considered old and do not include digital remote monitoring or remote-control features. These conventional stations must be retrofitted with digital technology or replaced with new digitized stations. Previous studies show the technical potential of updating non-digitized stations to reduce interruption times. Still, a systematic assessment of these types of projects’ profitability is missing. This project aims to perform a techno-economic assessment for retrofitting conventional urban medium voltage substations with digital technology, modeling different configurations of digitalization (levels 1 and 2) to suggest the most convenient set-up, balancing the technical and economic facets. Furthermore, it investigates the prospect and profitability of reducing interruption times by 50% with the digitization of substations. The methodology proposed used a reference test system based on the most representative type of network for an urban medium voltage network in Stockholm: A Double cable – open loop structure consisting of 5 single cable secondary substations. A calculation method was performed to obtain the expected results evaluating all the possible combinations of digitalized stations in the feeder line. Results suggest that the best outcome is formed by the last station retrofitted with remote control (level 2) and the other four stations with monitoring (level 1). This setup could reduce SAIDI by 71% and the total customer costs by 26.3%. To make this outcome profitable, a reduction in Omexom Labor Costs of 13.6% is required if a discount rate of 7% is used, but if this value is below 4.65%, a reduction in Labor Costs is unnecessary. Furthermore, results show that a set-up of 5 monitoring digitized stations can reduce SAIDI by 56.8%. Thus, it aligns with Ellevio’s objective to reduce by half their interruption times. A reduction of 12.9% in Labor Costs would be required to achieve this as a profitable setup; on the other hand, if the discount rate is below 4.65%, it is unnecessary. / Digitala hög- och medelspänningsstationer spelar en avgörande roll i energiomställningen eftersom de är en del av den utrustning som krävs för att implementera smarta elnät. Med den gradvisa ökningen av smarta elnät blir energisystemen mer flexibla med den ökande penetrationen av förnybar energi och distribuerad energiproduktion. Samtidigt ökar energisystemets effektivitet, med lastförsörjning precis där det behövs och minskade förluster. Medelspänningsstationerna har inte uppgraderats gradvis som högspänningsstationerna; därför anses de flesta av Stockholms medelspänningsstationer vara gamla och inkluderar inte digital fjärrövervakning eller fjärrstyrningsfunktioner. Dessa konventionella stationer måste antingen uppgraderas med digital teknik eller ersättas med nya digitaliserade stationer. Tidigare studier visar den tekniska potentialen att uppdatera icke-digitaliserade stationer för att minska avbrottstiderna, men en systematisk bedömning av lönsamheten för sådana projekt saknas. Detta projekt syftar till att utföra en teknisk-ekonomisk utvärdering för att uppgradera konventionella urbana medelspänningsstationer med digital teknik, genom att modellera olika konfigurationer av digitalisering (nivå 1 och 2) för att föreslå den mest lämpliga uppställningen, där tekniska och ekonomiska aspekter balanseras. Dessutom ska möjligheterna och lönsamheten för att minska avbrottstiderna med 50% genom digitalisering av stationer undersökas. Den föreslagna metoden använder ett referenstestsystem baserat på den mest representativa typen av nätverk för ett urbant medelspänningsnät i Stockholm: en dubbelkabel - öppen slingstruktur bestående av 5 enskilda kabelunderstationer. En beräkningsmetod användes för att få de förväntade resultaten genom att utvärdera alla möjliga kombinationer av digitaliserade stationer i matarledningen. Resultaten antyder att det bästa resultatet uppnås genom att den sista stationen uppgraderas med fjärrstyrning (nivå 2) och de andra fyra stationerna med övervakning (nivå 1). Denna uppställning kan minska SAIDI med 71% och totala kundkostnader med 26.3%. För att göra detta resultat lönsamt krävs en minskning av Omexom arbetskostnader med 13.6% om en diskonteringsränta på 7% används, men om detta värde är under 4.65% behövs ingen minskning av arbetskraftskostnader. Dessutom visar resultaten att en uppställning med 5 övervakningsdigitaliserade stationer kan minska SAIDI med 56.8%. Detta stämmer överens med Ellevios mål att halvera sina avbrottstider. En minskning av arbetskraftskostnader med 12.9% skulle krävas för att uppnå detta som en lönsam uppställning. Å andra sidan, om diskonteringsräntan är under 4.65%, finns det ingen anledning att minska arbetskraftskostnader.