Brayton cycles are open gas turbine cycles extensively used in aviation and industrial applications because of their advantageous volume and weight characteristics. With the bulk of waste exhaust heat and engine emissions associated, there is need to be mindful of environmentally-friendliness of these engine cycles, not compromising good technical performance, and economic viability. This research considers assessment of power plants in helicopters, and aeroderivative industrial gas turbines combined-heat-and-power (ADIGT-CHP) in the petrochemical industry. Thus, it consists of two parts: part A focuses on performance analysis of helicopter gas turbines, while part B entails technoeconomic and environmental risk assessment of ADIGT-CHP in the petrochemical industry. The investigation encompasses comparative assessment of simple cycle (SC) and advanced gas turbine cycle options including the component behaviours and the environmental and economic analysis of the systems. The advanced cycles considered include: recuperated (RC), intercooled (IC), intercooled-recuperated (ICR), and low pressure compressor zero-staged (LPC-ZS), cycles. The helicopter engines are analysed and subsequently converted to small-scale ADIGT engines. Also, modelling combined-heat-and-power (CHP) performances of small-scale (SS), and large-scale (LS) ADIGT engines is implemented. More importantly, a large part of the research is devoted to developing a techno-economic model for assessing, predicting, and comparing viability of simple and advanced cycle ADIGT-CHP in the petrochemical industry in terms of net present value (NPV), internal rate of return (IRR), and simple payback period (SPBP). The techno-economic performances of the ADIGT-CHP cycles are measured against the conventional case of grid power plus on-site boiler. Besides, risk and sensitivity of NPV with respect to uncertain changes in grid electricity cost, gas fuel cost, emission cost, and electricity export tariff, are investigated. Two case studies underlie the development of the techno-economic model. One case study demonstrates the application of the model for large-scale (LS) ADIGT-CHP, and the other for small-scale (SS) ADIGT-CHP, all in the petrochemical industry. By so doing, techno-economic and environmental risk analysis framework (a multi-disciplinary preliminary design assessment tool comprising performance, emissions, economic, and risk modules) is adapted to ADIGT-CHP in the petrochemical industry, which is the aim of this research. The investigation and results led to the conclusions that advanced cycle helicopter and ADIGT engines exhibit higher thermal efficiencies than simple cycle, and that savings exist in operational costs of ADIGT-CHP above the conventional case. Thus, for both SS ADIGT-CHP, and LS ADIGT-CHP cases, all ADIGT-CHP cycles are profitable than the conventional case. For LS ADIGT- CHP category, the IC ADIGT-CHP is the most profitable, whereas for SS ADIGT-CHP category, the RC ADIGT-CHP is the most profitable. The contribution to knowledge of this research is the development of a technoeconomic model for assessing, predicting, and comparing viability of simple and advanced cycle ADIGT-CHP in the petrochemical industry in terms of NPV, SPBP, and IRR over the conventional case of grid power plus on-site boiler. A second contribution is the derivation of simple and advanced cycle small-scale ADIGT and ADIGT-CHP from helicopter engines. Cont/D.

The enzymatic conversion of lignocellulosic biomass into fermentable sugars is a promising approach for producing renewable fuels and chemicals. However, the cost of the fungal enzymes usually employed in this process remains a significant bottleneck for manufacturing low value-added products from biomass. A potential route to increase hydrolysis yield, and thereby to reduce hydrolysis cost, would be to supplement the fungal enzymes with their lacking enzymatic activities, such as Beta-glucosidase. To produce such enzymes at a low cost, the bacterium Escherichia coli is a strong contender, owing to its ability to grow rapidly on simple and inexpensive media, and to achieve high levels of productivity. Nevertheless, there is hardly any techno-economic analysis of low-value protein production using E. coli in the literature, and, more generally, there are very few techno-economic analyses of low-value protein production ever reported, with the exception of cellulase production by Trichoderma reesei. In particular, the biotechnological application of recombinant E. coli platforms equipped with toxin-antitoxin systems to ensure plasmid stability remains largely unexplored, and its economic impact, unknown. As such, this work presents a comprehensive techno-economic analysis of the industrial production of a low-cost enzyme (Beta-glucosidase) using both E. coli BL21(DE3) and E. coli SE1, a modified BL21(DE3) strain equipped with a toxin-antitoxin system for plasmid maintenance. Moreover, this study describes the actual cloning and expression of a Beta-glucosidase enzyme into E. coli BL21(DE3) and E. coli SE1, and the development of a novel inoculum production scheme that exploits the features of the SE1 strain, based on repeatedly recycling a fraction of the inoculum cells. The results of the techno-economic analysis project an enzyme production cost of 316 US$/kg in the baseline scenario, which is considerably higher than the values reported in the literature for the fungal cocktails. The facility-dependent cost, which is strongly associated with the cost of equipment, accounts for roughly half of the estimated cost, while the cost of raw materials, especially IPTG and glucose, and the cost of consumables are all quite significant. However, the simulation of multiple scenarios and optimization measures suggest that the enzyme cost can be substantially reduced on many fronts, such as: substituting the carbon source for cheaper alternatives; reducing the amount of IPTG used for induction; using an E. coli strain capable of extracellular production; or eliminating the steps of concentration and stabilization of the enzyme, in the case of on-site enzyme utilization. Developing E. coli strains capable of high rEnzyme volumetric productivities can also significantly reduce the cost of the enzyme, up to approximately 135 US$/kg in the scenario of highest productivity. In addition, based on the experimental results with the E. coli SE1 system, an inoculum recycle strategy that avoids the need of an extensive seed train was simulated, resulting in a significant reduction of the enzyme cost. Finally, the combination of multiple process improvements could lead to an enzyme cost near 20 US$/kg of protein, which comes close to the cost of fungal cellulases and demonstrates the great biotechnological potential of recombinant E. coli platforms. / A conversão enzimática de biomassa lignocelulósica em açúcares fermentescíveis é uma via promissora para a produção de combustíveis e produtos químicos renováveis. No entanto, o custo das enzimas fúngicas usualmente empregadas nesse processo permanece um gargalo significativo para a fabricação de produtos de baixo valor agregado a partir de biomassa. Uma possível estratégia para aumentar o rendimento da hidrólise e, assim, reduzir seu custo, seria suplementar as enzimas fúngicas com suas atividades enzimáticas deficientes, tais como a enzima Beta-glicosidase. Para produzir tais enzimas a um baixo custo, a bactéria Escherichia coli é uma forte candidata, dada a sua capacidade de crescer rapidamente em meios simples e baratos e de alcançar altos níveis de produtividade. No entanto, na literatura quase não há análises técnico-econômicas de produção de proteínas de baixo valor agregado utilizando E. coli e, de forma mais geral, há muito poucas análises técnico-econômicas de produção de proteínas de baixo valor agregado publicadas, com exceção da produção de celulases por Trichoderma reesei. Em particular, a aplicação biotecnológica de plataformas recombinantes baseadas em E. coli dotadas de sistemas toxina-antitoxina para garantir a estabilidade plasmidial segue em larga medida inexplorada, e seu impacto econômico, desconhecido. Assim, este trabalho apresenta uma análise técnico-econômica abrangente da produção industrial de uma enzima de baixo custo (Beta-glicosidase) usando E. coli BL21 (DE3) e E. coli SE1, uma cepa de BL21 (DE3) modificada que possui um sistema toxina-antitoxina para manutenção plasmidial. Além disso, este estudo descreve a clonagem e expressão de uma Beta-glicosidase em E. coli BL21 (DE3) e E. coli SE1, assim como o desenvolvimento de um novo método de produção de inóculo que tira proveito das peculiaridades da linhagem SE1, baseado em reciclar repetidamente uma fração das células do inóculo. Os resultados da análise técnico-econômica apontam para um custo de produção da enzima de 316 US$/kg no cenário-base, valor consideravelmente superior àqueles relatados na literatura para os coquetéis fúngicos. Os custos de overhead da planta, que estão fortemente associados ao custo de aquisição dos equipamentos, são responsáveis por aproximadamente metade do custo total, enquanto o custo de matérias-primas, especialmente IPTG e glicose, e o custo de consumíveis são bastante significativos. Porém, a simulação de múltiplos cenários e medidas de otimização sugerem que o custo da enzima pode ser substancialmente reduzido em muitas frentes, tais como: a substituição da fonte de carbono por alternativas mais baratas; a redução da quantidade de IPTG usado para indução; a utilização de cepas capazes de produzir a enzima extracelularmente; ou a eliminação das etapas de concentração e estabilização da enzima, em caso de utilização da enzima in situ. O desenvolvimento de cepas de E. coli capazes de atingir altas produtividades volumétricas de rEnzima também pode reduzir significativamente o seu custo, chegando a US$ 135/kg no cenário de maior produtividade. Com base nos resultados experimentais com a linhagem E. coli SE1, uma estratégia de reciclagem de inóculo que evita a necessidade de um extenso trem de inoculação também foi simulada, gerando significativa diminuição do custo da enzima. Por fim, a combinação de múltiplas melhorias no processo poderia levar a um custo de enzima em torno de 20 US$/kg de proteína, valor que se aproxima do custo das celulases fúngicas e que demonstra o grande potencial biotecnológico de plataformas de expressão baseadas em E. coli recombinante.

Brayton cycles are open gas turbine cycles extensively used in aviation and industrial applications because of their advantageous volume and weight characteristics. With the bulk of waste exhaust heat and engine emissions associated, there is need to be mindful of environmentally-friendliness of these engine cycles, not compromising good technical performance, and economic viability. This research considers assessment of power plants in helicopters, and aeroderivative industrial gas turbines combined-heat-and-power (ADIGT-CHP) in the petrochemical industry. Thus, it consists of two parts: part A focuses on performance analysis of helicopter gas turbines, while part B entails technoeconomic and environmental risk assessment of ADIGT-CHP in the petrochemical industry. The investigation encompasses comparative assessment of simple cycle (SC) and advanced gas turbine cycle options including the component behaviours and the environmental and economic analysis of the systems. The advanced cycles considered include: recuperated (RC), intercooled (IC), intercooled-recuperated (ICR), and low pressure compressor zero-staged (LPC-ZS), cycles. The helicopter engines are analysed and subsequently converted to small-scale ADIGT engines. Also, modelling combined-heat-and-power (CHP) performances of small-scale (SS), and large-scale (LS) ADIGT engines is implemented. More importantly, a large part of the research is devoted to developing a techno-economic model for assessing, predicting, and comparing viability of simple and advanced cycle ADIGT-CHP in the petrochemical industry in terms of net present value (NPV), internal rate of return (IRR), and simple payback period (SPBP). The techno-economic performances of the ADIGT-CHP cycles are measured against the conventional case of grid power plus on-site boiler. Besides, risk and sensitivity of NPV with respect to uncertain changes in grid electricity cost, gas fuel cost, emission cost, and electricity export tariff, are investigated. Two case studies underlie the development of the techno-economic model. One case study demonstrates the application of the model for large-scale (LS) ADIGT-CHP, and the other for small-scale (SS) ADIGT-CHP, all in the petrochemical industry. By so doing, techno-economic and environmental risk analysis framework (a multi-disciplinary preliminary design assessment tool comprising performance, emissions, economic, and risk modules) is adapted to ADIGT-CHP in the petrochemical industry, which is the aim of this research. The investigation and results led to the conclusions that advanced cycle helicopter and ADIGT engines exhibit higher thermal efficiencies than simple cycle, and that savings exist in operational costs of ADIGT-CHP above the conventional case. Thus, for both SS ADIGT-CHP, and LS ADIGT-CHP cases, all ADIGT-CHP cycles are profitable than the conventional case. For LS ADIGT- CHP category, the IC ADIGT-CHP is the most profitable, whereas for SS ADIGT-CHP category, the RC ADIGT-CHP is the most profitable. The contribution to knowledge of this research is the development of a technoeconomic model for assessing, predicting, and comparing viability of simple and advanced cycle ADIGT-CHP in the petrochemical industry in terms of NPV, SPBP, and IRR over the conventional case of grid power plus on-site boiler. A second contribution is the derivation of simple and advanced cycle small-scale ADIGT and ADIGT-CHP from helicopter engines. Cont/D.

The member states of European Union aim to promote the reduction of harmful emissions. Emissions from combustion processes cause effects on human health and pose environmental issues, for example by increasing greenhouse effect. There are two ways to reduce emissions; one is to promote renewable energy sources and the other to utilize more effectively the available fossil fuels until a long-term solution is available. Hence, it is necessary to strive for CO2 mitigation technologies applied to fossil fuels. Low natural gas prices together with high energy efficiency have made gas turbines popular in the energy market. But, gas turbine fired with natural gas come along with emissions of CO2, NOx and CO. However, these disadvantages can be eliminated by using gas turbine with precombustion CO2 capture, separating carbon from the fuel by using fuel reforming process and feeding pure hydrogen as a fuel. Hydrogen fired gas turbines are used in two applications such as a gas turbine with pre-combustion CO2 capture and for renewable power plants where hydrogen is stored in case as a backup plan. Although the CO2 emissions are reduced in a hydrogen fired gas turbine with a pre-combustion CO2 capture, there are still several challenges such as high flame temperatures resulting in production of thermal NOx. This project suggests a method for application of hydrogen fired gas turbine, using exhaust gas recirculation to reduce flame temperature and thus reducing thermal NOx. A NOx emission model for a hydrogen-fired gas turbine was built from literature data and used to select the best operating conditions for the plant. In addition, the economic benefits of switching from natural gas to pure hydrogen are reported. For the techno-economic analysis, investment costs and operating costs were taken from the literature, and an economic model was developed. To provide sensitivity analysis for the techno-economic calculation, three cases were studied. Literature review was carried out on several journal articles and websites to gain understanding on hydrogen and natural gas fired gas turbines. Results showed that, in the current state, pure hydrogen has high delivery cost both in the US and Europe. While it’s easy to access natural gas at low cost, therefore in the current state gas turbine fired with natural gas are more profitable than hydrogen fired gas turbine. But, if targeted hydrogen prices are reached while fuel reforming process technology are developed in the coming future the hydrogen fired gas turbine will compete seriously with natural gas.

Biomass-based reducing agents have a potential to substitute fossil reducing agents in the steel industry. However, the industrial use of biomass-based reducing agents is currently in an early stage of development and has not yet been considered as a means to reduce fossil CO2 emissions, even though the use of fossil-based reducing agents for the iron and steel making cause the highest share of CO2 emissions. This master thesis presents a techno-economic analysis of a 10 MW biochar production plant integrated with sponge iron production in Höganäs. In this study, a steady-state process model was developed, where state-of-the-art research and development in biochar production for increased biochar yield was applied and adapted, using the principle of bio-oil recycle. The developed process model was used to evaluate the biochar production plant, in terms of conversion efficiency, production costs and CO2 emissions, for different process configurations. The results show that bio-oil recycle with 20 wt.% bio-oil increases the energy yield of biochar with 14%. However, it was found that bio-oil recycle increases the required heat input of pyrolysis which led to reduced plant efficiency with 4%-units and increased biochar production costs of 500-1000 SEK/ton biochar. It was found that system integration with Höganäs can reduce the production cost of biochar from over 5000 SEK/ton to under 2000 SEK/ton, where the most significant integration aspect was flue gas integration. The sensitivity analysis showed that the cost of biomass feedstock and total capital investment were the most sensitive input parameters. It was found that system integration with Höganäs was essential to achieve production costs of biochar below the price of fossil reducing agents. It was also found that co-produced bio-oil becomes a main product, essential for the economic performance of the biochar plant, even though the intended main product was the biochar.

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

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>

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.