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Climate change has been characterized as the greatest global health threat of the 21st century, therefore, measures in order to address this challenge need to be taken. The integration of renewables to power systems is key to decrease greenhouse gas emissions that negatively contribute to climate change. Furthermore, the coupling of renewable resources with energy storage, and especially long-duration energy storage, is an effective way to further increase renewable penetration to power systems overcoming the intermittency of such resources. Many countries have introduced support schemes for renewable based projects in order to attract investment and facilitate the deployment of renewables. Greece is among these counties having introduced attractive support schemes in order to decarbonize its energy mix which is still dependent extensively on fossil fuels. The aim of this work is to conduct a techno-economic analysis for three different small-scale solar-based energy projects in Greece, namely CSP, CSP with PV, and PV, all coupled with an innovative long-duration energy storage solution. Initially, the identification of existing support schemes is made through an analysis of the Greek electricity market, followed by the quantification of the potential market of solar-based projects in Greece. The study is focused on the Non-Interconnected Islands of Greece, since they present thegreatest potential for the decarbonization of the country’s energy mix. Through the techno-economic analysis the most suitable configuration for each project is identified, and thereafter, the three cases are compared against identified technical and financial Key Performance Indicators. The results of this work show that, with the current support schemes, a CSP project is the most profitable case, while a PV project coupled with long-duration energy storage provides the cheapest solution, presenting great potentials for the decarbonization of the Non-Interconnected Island in Greece. Klimatförändringar har karakteriserats som det största globala hälsohotet under 2000-talet, därför måste åtgärder vidtas för att möta denna utmaning. Integreringen av förnybara energikällor i kraftsystem är nyckeln till att minska utsläppen av växthusgaser som negativt bidrar till klimatförändringen. Dessutom är kopplingen av förnybara resurser med energilagring, och särskilt långvarig energilagring, ett effektivt sätt att ytterligare öka förnybar penetration till kraftsystem som övervinner intermittensen av sådana resurser. Många länder har infört stödsystem för förnybara baserade projekt för att locka till sig investeringar och underlätta spridningen av förnybar energi. Grekland är bland dessa länder som har infört attraktiva stödsystem för att minska koldioxidutsläppen i sin energimix som fortfarande är mycket beroende av fossila bränslen. Syftet med detta arbete är att genomföra en tekno-ekonomisk analys för tre olika småskaliga solbaserade energiprojekt i Grekland, nämligen CSP, CSP med PV och PV, allt tillsammans med en innovativ lösning för långvarig energilagring. Inledningsvis görs identifieringen av befintliga stödsystem genom en analys av den grekiska elmarknaden, följt av en kvantifiering av den potentiella marknaden för solenergibaserade projekt i Grekland. Studien är fokuserad på Greklands icke sammankopplade öar, eftersom de har den största potentialen för avkarbonisering av landets energimix. Genom den tekno-ekonomiska analysen identifieras den mest lämpliga konfigurationen för varje projekt, och därefter jämförs de tre fallen mot identifierade tekniska och finansiella nyckeltal. Resultaten av detta arbete visar att med de nuvarande stödsystemen så är ett CSP projekt det mest lönsamma fallet, medan ett solcellsprojekt i kombination med långvarig energilagring ger den billigaste lösningen, vilket ger stora möjligheter för avkarboniseringen av den icke sammankopplade ön i Grekland.

It is well documented that chemical additives (grinding aid “GA”) during grinding can increase mill throughput, reduce water and energy consumption, narrow the particle size distribution of product...

The present study investigates the thermochemical conversion of spruce wood and its extracted components by thermogravimetric analysis. The extracted components are two pulps, three xylan-lignin samples and one lignin sample; they were produced by the kraft cooking method with different cooking times. The study involves characterization of the biomass through proximate analysis and pyrolysis. A qualitative comparison between the thermal behaviours of the extracted components and wood is also performed. The study showed that the thermal behaviour of the biomass was highly influenced by the content of cellulose and lignin in the samples. Compounds rich in cellulose produced large quantities of volatiles and had a higher rate of pyrolysis compared to compounds rich in lignin, which produced more char and had a slower rate of pyrolysis. It was also shown that, the amount of char is not solely depending on the amount of the lignin; the structure of the compound also plays a role. On the other hand, the original wood sample showed some deviations regarding the trends in volatile and char production and these deviations were attributed to component interactions. Both cellulose and lignin rich compounds had an increase in thermal stability with increasing cooking time. For the pulps the increase in thermal stability is believed to be caused by increase in crystallinity, while for the lignin rich samples is believed to be caused by the increase in lignin content and structural changes in the compounds. The results also show that although changes are introduced in the cooking process, the extracted component still retain properties exhibited by the source biomass.

The production industry is getting more and more automated and that implies higher energy consumption. With the increasing awareness of the earth limited resources and the increasing energy prices, energy conservation grows in relevance, both due to cost reduction and environmental benefits. One way to conserve energy is to optimize the energy usage within the business and reduce the losses. Regenerative braking is already in use today for this purpose in vehicles. The aim of this thesis is to investigate how regenerative braking can be fitted into the production industry and what adaptations need to be made. This thesis is based on an earlier study that has set up a mathematical model for energy regeneration in mechatronic systems and the goal of this thesis is to build a test rig and verify the correctness of these models. One suggested improvement to the automotive systems are the introduction of super capacitors as a secondary energy source because they can charge more rapidly compared to batteries which is required during the expected fast accelerations. In the performed tests an efficiency improvement of 10 % was shown. The earlier study however suggests an efficiency rate of 60% but those models do not include frictional nor electrical losses. The results are complemented by a discussion were a number of changes to the design is proposed. A different motor control system would significantly enhance the rig and a result more like the expected can be achieved. Det ökade antalet elektromekaniska maskiner i industriella tillämpningar medför en ökad energianvändning. Då våra begränsade resurser mer och mer belyses i media och med stigande energipriser ökar intresset hos företagen för att minska sin energianvändning, dels för att reducera sina kostnader och dels för att minska den miljöbelastning slutprodukten medför. Ett sätt att göra detta är att minska energiförlusterna inom sin produktion. Regenerativ bromsning är en teknik som används i fordon idag och kan användas för detta syfte. Detta arbete ska undersöka hur sådan teknik kan användas i tillverkningsindustrin och vilka förändringar som måste göras. Ett tidigare arbete har satt upp teoretiska modeller för detta och det här arbetet syftar till att bygga en tesrigg för att praktiskt undersöka modellernas korrekthet. En förbättring mot det system som används i dagens bilar är att införa superkondensatorer som parallell energikälla då dessa är snabbare på att lagra energi än ett batteri och därför passar bättre för de snabba accelerationer och retardationer som förekommer i industriprocesser. De genomförda testerna påverkades negativt av vissa begränsningar i hårdvaran men resultatet visar ändå att regenereringen kan återföra 10 % av energin till kondensatorerna, det motsvarar däremot inte den mängden som de tidigare uppsatta modellerna förutspådde. Orsakerna är olika förluster i systemet som inte modellerna tar hänsyn till. De viktigaste förlustfaktorerna beror på friktion och styrningen av elektroniken. Med en annan typ av motorstyrning kan förlusterna minskas och ett resultat mer likt det förväntade uppnås.

In the search for environmentally friendly methods to implement renewable energy in the power system residential microgrids have been proposed and proven. The direct current (DC) microgrid topology is a promising implementation of a microgrid system due to the increasing amount of DC-operated loads and production units expected in the near future. In this project, the proposed DC microgrid consists of a solar photovoltaic (PV) power source, a battery, a DC load, and an interlinking bidirectional converter to connect the microgrid to the external three-phase power grid. The PV system is controlled with a Maximum Power Point Tracking (MPPT) algorithm to maximise the power production in all weathers. The DC bus voltage is stabilised by the battery controller and a coordinated control scheme considering the electricity price and battery State of Charge (SOC) is implemented to govern the power exchange with the utility grid. Simulations of the system are shown to validate the functionality of the microgrid and the performance of the controllers in multiple scenarios. The proposed DC microgrid is proven to function in both utility grid-connected mode and in isolation from the utility grid. I sökandet efter miljövänliga metoder att implementera förnybar energi i kraftsystemet har lokalt självförsörjande elsystem för bostäder föreslagits och visats fungera. Den likströmsbaserade topologin är en lovande implementering av ett sådant lokalt elsystem till följd av den ökande mängden likströmsdrivna laster och produktionsenheter som förväntas komma inom en snar framtid. I detta projekt består det föreslagna likströmsbaserade elsystemet av en solenergikälla, ett batteri, en likströmslast och en sammanlänkande dubbelriktad omvandlare för att ansluta det lokala elsystemet till det externa trefasiga elnätet. Solenergisystemet styrs med en maximal kraftpunktföljande algoritm för att maximera kraftproduktionen i alla väder. Likströmsbussens spänning stabiliseras av batteristyrenheten och ett samordnat styrschema som tar hänsyn till elpriset och batteriets laddningstillstånd implementeras för att styra energiutbytet med elnätet. Simuleringar av systemet presenteras för att validera mikronätets funktionalitet och styrteknikens prestanda i flera olika scenarier. Det föreslagna likströmsbaserade elsystemet visas fungera i både nätanslutet läge och isolerat från elnätet. Kandidatexjobb i elektroteknik 2022, KTH, Stockholm

Carbon dioxide (CO2) is becoming increasingly popular in supermarket refrigeration, especially in Scandinavian countries, which have had extensive experience with nearly 100 installations (mostly indirect systems). Since the revival of CO2 as a refrigerant, it has been used in supermarkets in indirect systems as a secondary refrigerant. In recent years, other arrangements, such as cascade and multistage systems, have been used commercially. QC 20100525

The paper presents a daily planning algorithm for a multi-reservoir hydropower system coordinated with wind power. The planning algorithm applies to the real situation where wind power and hydropower are owned by different utilities, sharing same transmission lines, though, hydropower has a priority for transmission capacity. Coordination is, thus, necessary to minimize wind energy curtailments during the congestion situations. The planning algorithm considers an uncertainty of wind power forecast. Forecast error scenarios are modeled with ARMA series. A scenario reduction algorithm is applied to reduce computational time. Only the planning for the spot market is considered. Thus, once the hydropower production bid is placed on the market it cannot be changed. The solution of the stochastic optimization problem should, therefore, fulfill the transmission constraints for all wind power production scenarios. The developed planning algorithm is applied in a case study. The results are compared to the planning results without coordination.

In a seemingly endlessly urbanizing world, the planning field must not forget our cities’ hinterlands and rural regions. Demographic shifts, dying centers, lack of amenities and insufficient mobility options are just a few of the struggles the periphery is facing. With the help of the case study site Pförring, Germany, this report analyzes regional and local plans in relation to social aspects of sustainability and resilience. The results are the identification of crucial elements for successful transformation: vision, competence, support, action, monitoring and adjustment, depicted as an interlinked system of two interactive loops.

Abstract Worldwide, cities are implementing circular economy (CE) strategies to reduce the resources they consume and their environmental impact. However, the evidence of the intended and unintended social consequences of the transition to “circular cities” is scattered. The lack of a coherent overview of the evidence on the subject can hinder effective decision-making in policy and practice. This study examines the extent to which the current literature addresses the social impacts that a transition to a CE produces in cities. We used a methodological approach related to systematic mapping to collate the evidence published over the past decade globally. The study finds that social impacts have rarely been considered in studies of circular cities, and where they have been discussed, the scope has been quite limited, only covering employment (mostly of informal sector workers) and governance practices. This scoping review highlights the need to further analyse and integrate social impact considerations into decision-making connected to transitions towards circular cities.