The International Energy Agency’s Global Status Report 2017 estimates that existing buildings must undergo deep energy renovations, which reduce the energy intensity of buildings by 50% - 70% in order to achieve the “Beyond 2°C” scenario [1]. Many buildings in Bitola, The Republic of North Macedonia, will need considerable upgrades to meet these goals. Among them, health care facilities and education centers have the greatest potential, with energy savings that could reach 35 to 40% [2]. PHI Clinical Hospital Bitola is the largest health care facility in the southwestern region of North Macedonia with a capacity of 500 beds, providing care to almost 300.000 patients annually. It has a heating system based on heavy fuel oil, and an inefficient distribution system which has not been upgraded since the 1970s. There is no centralized ventilation or cooling systems, making it necessary to open and close windows in order to regulate the indoor temperature and generate natural ventilation. This study aims to replace the use of heavy fuel oil (HFO), reduce building related GHG emissions, and increase the primary renewable energy fraction of PHI Clinical Hospital Bitola, by investigating a replacement energy system using heat pumps and solar energy. Special consideration is given to increasing the level of comfort of patients and improving the safety of the indoor environment. Space conditioning, domestic hot water, and electricity demands for three critical buildings are considered in Polysun over a 1-year period. The costs and benefits of technologies including air and ground source heat pumps, solar photovoltaics, and ice thermal energy storage are analyzed. It is determined which of these technologies can be implemented in an energy and cost-efficient manner in the Republic of North Macedonia, thus contributing to the reduction of building related greenhouse gas emissions and other pollutants that contribute to poor air quality. Ground source heat pumps perform superior to air source heat pumps, however, the total life cycle costs of ground source heat pump systems are much higher than air source heat pump systems, making the marginal gains in the technical performance not worth the investment in a borehole field. When using ice thermal energy storage within the cooling and domestic hot water systems the benefits of improved heat pump performance and reduced electricity consumption are not observed. The configuration of thermal storage tested here uses the domestic hot water system to withdraw heat from the thermal storage tank, creating ice, which is then used to decrease the need for cooling using the chiller. However, the cooling load is much larger than the hot water demand, and so any ice generated in the tank is depleted within the first few days of cooling. Many other configurations and control strategies for thermal storage exist which could be the subject of further research. When selecting a renewable energy system that could replace the current HFO boiler in the hospital, the results of this study suggest that an air source heat pump system with solar PV is the recommended solution. For buildings 1 and 2, the final results achieved a primary renewable energy fraction of 62%, a GHG emissions savings of 840 tons of CO2eq equating to a 26% reduction, coming at a capital cost of nearly 2,7 million €, and reducing annual energy expenses by 47%. For building 4 the final system delivers a primary renewable energy fraction of 64%, GHG emissions savings of 109 tons CO2eq or 17%, while costing 0,67 million € in capital expenses and lowering annual energy expenses by 50%. / Den internationella energi byråns globala status rapport 2017 uppskattar att existerande byggnader måste undergå djupgående energi renovationer, som ska reducera byggnadernas energiintensitet med 50% - 70% för att uppnå i scenariot “Beyond 2°C” [1]. Många byggnader i Bitola (Republiken av nora Makedonien), kommer att behöva betydande uppgraderingar för att uppfylla dessa mål. Bland dem har hälsovårdsanläggningar och utbildningscenter den största potentialen, med energi besparingar där dessa kan uppnå 35% till 40% [2]. PHI Kliniskt Sjukhus Bitola är den största sjukvårdsanläggningen i den sydvästra regionen av Nora Makedonien med en kapacitet på 500 sängplatser, som ger vård till nästan 300.000 patienter årligen. Det nuvarande värmesystemet är baserat på tung eldningsolja och ett ineffektivt distributionssystem som inte har uppdaterats sedan 1970-talet. Det finns inga centraliserade ventilations- och kylsystem, vilket gör det nödvändigt att öppna och stänga fönster för att reglera inomhustemperaturen och generera naturlig ventilation. Denna studie syftar till att ersätta användningen av tung eldningsolja, minska byggnadsrelaterade växthusutsläpp och öka den primära förnyelsebara energifraktionen av Kliniskt Sjukhus Bitola. Genom att undersöksöka ett ersättande energisystem med värmepumpar och solenergi. Särskild hänsyn tas till öka patienternas komfort och förbättra säkerheten i inomhusmiljön. Värme och kyla, varmvatten och el-krav för tre kritiska byggnader betraktas i Polysun under en 1- års period. Kostnaderna och fördelarna med tekniken inklusive luft och markvärmepumpar, solceller och termisk energilagring analyseras. Det fastställs vilken av dessa tekniker som kan implementeras på ett energi- och kostnadseffektivt sätt i Republiken av nora Makedonien, vilket bidrar till att minska byggnadsrelaterade växthusgasutsläpp och andra föroreningar som kan bidra till dålig luftkvalitet. Markvärmepumpar har högre prestanda än luftvärmepumpar, men de totala livscykelkostnaderna för ett markvärmepumpsystem är mycket högre än för ett luftvärmepumpsystem. Vilket gör den marginella vinsterna för den tekniska prestandan inte värda investeringen av ett borrhåls fält. Vid användning av is som termisk energilagring och kylning och varmvattensanläggningar, tog ingen hänsyn till fördelarna med en förbättrad värmepumps prestanda och minskad elförbrukning. Konfigurationen av termisk lagring som testas här använder det inhemska varmvattensystemet för att ta bort värme från den termiska lagringstanken, vilket skapar is som sedan används för att minska behovet av nedkylning av byggnaden. Kylbelastningen är emellertid mycket större än varmvattenbehovet. Vilket betyder att all is som genereras i tanken används upp efter några dagar av kylning. Många andra konfigurationer och styrstrategier för termisk lagring finns och kan vara till ändamål för framtida forskning. När val av ett förnybart energisystem görs som ska kunna ersätta den nuvarande tung eldningsolja pannan på sjukhuset antyder resultatet av denna studie att ett värmepumpsystem med luftkälla och sol-PV är den rekommenderade lösningen. För byggnad 1 och 2 uppnådde det slutliga resultatet en primär förnyelsebar energifraktion på 62%, vilket skulle innebära en besparing av växthusgasutsläpp med 840 ton CO2 ekvivalenter. Vilket motsvarar en minskning med 26%, med en kapitalkostnad på nästan 2,7 miljoner €. Samt minskade årliga energikostnader med 47%. För byggnad 4 levererar det slutliga systemet en primär förnybar energifraktion på 64%, med en -5- besparing av växthusutsläpp på 109 ton CO2 ekvivalenter eller 17%. Medan det kostar 0,67 miljoner € i kapitalutgifter och sänker den årliga energikostnaden med 50%.

A proprietary Ocean Thermal Energy Conversion (OTEC) modeling tool, the Makai OTEC Thermodynamic and Economic Model (MOTEM), is leveraged to evaluate the accuracy of finite-time thermodynamic OTEC optimization methods. MOTEM is a full OTEC system simulator capable of evaluating the effects of variation in heat exchanger operating temperatures and seawater flow rates. The evaluation is based on a comparison of the net power output of an OTEC plant with a fixed configuration. Select optimization methods from the literature are shown to produce between 93% and 99% of the maximum possible amount of power, depending on the selection of heat exchanger performance curves. OTEC optimization is found to be dependent on the performance characteristics of the evaporator and condenser used in the plant. Optimization algorithms in the literature do not take heat exchanger performance variation into account, which causes a discrepancy between their predictions and those calculated with MOTEM. A new characteristic metric of OTEC optimization, the ratio of evaporator and condenser overall heat transfer coefficients, is found. The heat transfer ratio is constant for all plant configurations in which the seawater flow rate is optimized for any particular evaporator and condenser operating temperatures. The existence of this ratio implies that a solution for the ideal heat exchanger operating temperatures could be computed based on the ratio of heat exchanger performance curves, and additional research is recommended.

This study encompasses various aspects of corrosion in chloride molten salt environments, employing electrochemical techniques and a forced convection loop. It explores corrosion thermodynamic properties, electrochemical corrosion kinetics, and flow-induced dynamic corrosion. The study developed a novel electrochemical method for measuring thermodynamic properties of corrosion products and develops a new analysis theory for potentiodynamic polarization data obtained from cathodic diffusion-controlled reactions. Additionally, the design and operation experience of a forced convection chloride molten salt loop is shared. Particularly, the study presents novel findings on the turbulent flow-induced corrosion phenomenon and mechanism of Fe-based alloys in Mg-based chloride molten salt. These outcomes provide valuable insights into the corrosion mechanisms and flow-induced corrosion of Fe-based alloys in chloride molten salt. The results and experiences shared in this paper have implications for the successful implementation of molten salt as an advanced heat transfer fluid and thermal energy storage material in high-temperature applications, benefiting the nuclear and concentrating solar communities. / Doctor of Philosophy / This study explores the corrosion behavior of materials chloride molten salt, which is used in advanced energy systems. By using advanced techniques, the researchers investigated how these materials react and corrode in different conditions. They developed new methods to measure the properties of the corrosion products and analyzed how different factors affect the corrosion process. Additionally, they shared their experiences in building and operating a flow loop to simulate these conditions. The study discovered interesting phenomena, such as how the flow of molten salt can cause corrosion in certain types of metals. These findings provide important insights for improving the use of molten salt as a heat transfer fluid and energy storage material in advanced energy technologies.

Global energy consumption has been increasing continuously every year. Many energy sources are utilized. Conventional fossil fuels are not sustainable, and their environmental impacts are more apparent than ever before. For heating purposes, most of the heat still comes from combustion of both non-renewable and renewable energy sources. According to IEA (2019), only 10% of heat supply in industrial sectors and buildings comes from renewable sources. Hence, 40% of the carbon emission in the energy sector comes from heat. Therefore, shifting from non-renewable to renewable energy sources is essential in reducing the environmental impact from heat production. Sweden has a long tradition of solar thermal in district heating for cities. Therefore, this study tried to look at the application of solar thermal energy for heat production to supply the District Heating (DH) system and compare its environmental performance to other types of energy sources. The system that was examined in this study is the solar thermal collector field from Absolicon in Härnösand. A Life Cycle Assessment (LCA) was conducted to evaluate the life cycle environmental impacts of this solar collector field. The assessment was done by collecting primary data provided by Absolicon and its suppliers and secondary data from the literatures. The results showed that Absolicon solar thermal collector field generated less overall environmental impacts than conventional energy sources in heat production. Moreover, the result for carbon footprint of the solar collector is 4.4 kg CO2/MWh, which is at least 3-4 times less lifetime emissions when compared to other solar energy technologies. / Den globala energiförbrukningen har ökat kontinuerligt varje år. Många energikällor används. Konventionella fossila bränslen är inte hållbara och deras miljöpåverkan är mer påtaglig än någonsin tidigare. För uppvärmningsändamål kommer det mesta av värmen fortfarande från förbränning av både icke-förnybara och förnybara energikällor. Enligt IEA (2019) kommer endast 10 % av värmeförsörjningen i industrisektorer och byggnader från förnybara källor. Därför kommer 40 % av koldioxidutsläppen i energisektorn från värme. Därför är en övergång från icke-förnybara till förnybara energikällor väsentligt för att minska miljöpåverkan från värmeproduktion. Sverige har en lång tradition av solvärme inom fjärrvärme för städer. Därför försökte denna studie titta på tillämpningen av solvärmeenergi för värmeproduktion för att försörja fjärrvärmesystemet (DH) och jämföra dess miljöprestanda med andra typer av energikällor. Systemet som undersöktes i denna studie är solfångarfältet från Absolicon i Härnösand. En livscykelanalys (LCA) genomfördes för att utvärdera livscykelns miljöpåverkan av detta solfångarfält. Bedömningen gjordes genom att samla in primärdata från Absolicon och dess leverantörer och sekundärdata från litteraturen. Resultaten visade att Absolicon solfångarfält genererade mindre total miljöpåverkan än konventionella energikällor vid värmeproduktion. Dessutom är resultatet för solfångarens koldioxidavtryck 4,4E kg CO2/MWhvilket är minst 3-4 gånger mindre livstidsutsläpp jämfört med andra solenergitekniker.

yes / A computational network heat transfer model was utilised to model the potential of heat energy recovery at multiple locations from a city scale combined sewer network. The uniqueness of this network model lies in its whole system validation and implementation for seasonal scenarios in a large sewer network. The network model was developed, on the basis of a previous single pipe heat transfer model, to make it suitable for application in large sewer networks and its performance was validated in this study by predicting the wastewater temperature variation in a sewer network. Since heat energy recovery in sewers may impact negatively on wastewater treatment processes, the viability of large scale heat recovery across a network was assessed by examining the distribution of the wastewater temperatures throughout the network and the wastewater temperature at the wastewater treatment plant inlet. The network heat transfer model was applied to a sewer network with around 3000 pipes and a population equivalent of 79500. Three scenarios; winter, spring and summer were modelled to reflect seasonal variations. The model was run on an hourly basis during dry weather. The modelling results indicated that potential heat energy recovery of around 116, 160 & 207 MWh/day may be obtained in January, March and May respectively, without causing wastewater temperature either in the network or at the inlet of the wastewater treatment plant to reach a level that was unacceptable to the water utility.

The Internet of Things (IoT) is an infrastructure of physical objects connected via the Internet that can exchange data to achieve efficient resource management. Billions of devices must be self-powered and low-cost considering the massive scale of the IoT. Thus, there is a need for low-cost ambient energy harvesters to power IoT devices. It is a challenging task since ambient energy might be unpredictable, intermittent and insufficient. For example, solar energy has limitations such as intermittence and unpredictability despite utilizing the highest power availability and relatively mature technology. Designing a multi-source energy harvester (MSEH) based on continuous and ubiquitous ambient energy sources might alleviate these issues by providing versatility and robustness of power supply. However, combining several energy harvesters into one module must be done synergistically to ensure miniaturization, compactness and more collected energy. Also, additive manufacturing techniques must be used to achieve low-cost harvesters and mass manufacturability. This dissertation presents two different kind of ambient energy harvesters, namely radio frequency energy harvester (RFEH) and thermal energy harvester (TEH). Each harvester is individually optimized and then synergistically combined into a MSEH. First, RFEH is designed for triple-band harvesting (GSM900, GSM1800, 3G2100) using the antenna-on-package concept and fabricated through 3D and screen printing. TEH collects energy from temperature fluctuations of ambient environment through a combination of thermoelectric generators and phase change materials. It is adapted specifically for the desert conditions of Saudi Arabia. Later, TEH and RFEH are combined to realize MSEH. Smart integration is achieved by designing a dual-function component, heatsink antenna, that serves as a receiving antenna of RFEH and a heatsink of TEH. The heatsink antenna has been optimized for both antenna radiation performance and heat transfer performance. Field tests showed that the MSEH can collect 3680μWh energy per day and the outputs of TEH and RFEH have increased 4 and 3 times compared to the independent TEH and RFEH respectively. To validate the utility of the MSEH, a temperature/humidity sensor has been successfully powered by the MSEH. Overall, sensor’s data can be wirelessly transmitted with time intervals of 3.5s, highlighting the effectiveness of the synergistic MSEH.

With the growing capacity of renewable energy production sources, nuclear energy, once a mainstay of power generation, faces challenges due to its limited adaptability to fluctuating energy demands. This inherent rigidity makes it less desirable than the more flexible renewable sources. However, integrating thermal energy storage (TES) systems offers a promising avenue, enabling nuclear power plants (NPPs) to enhance their operational flexibility and remain competitive in an evolving renewable market. A comprehensive ranking methodology has been introduced, delineating the criteria and processes to determine the most synergistic TES/NPP design couplings. This methodology considers the unique characteristics of both current and prospective reactor fleets, ensuring broad applicability across various nuclear technologies. Economic analysis further supports the case for TES integration. Findings indicate that when equipped with TES systems, NPPs can remain price competitive, even with carbon-neutral alternatives like solar power generation. A lab-scale TES system was meticulously designed and constructed to validate these theoretical propositions. For its control, the Python GEKKO model predictive control (MPC) was employed, a decision influenced by the proven efficacy of GEKKO in managing complex systems. Tests conclusively demonstrated the feasibility and efficiency of using GEKKO for MPC of TES systems. A novel methodology for the MPC of a RELAP5-3D input deck has been proposed and elaborated upon. This methodology was rigorously tested at two distinct scales. The initial focus was on a thermal-hydraulic model of the lab-scale TES system. Subsequent efforts scaled up to control a more intricate thermal-hydraulic model, representing a small modular reactor (SMR) paired with an oil-based TES system. In both scenarios, GEKKO exhibited exemplary performance, controlling the RELAP5-3D models with precision and ensuring they met the stipulated demand parameters. The research underscores the potential of RELAP5-3D MPC in streamlining the licensing process for TES systems intended for NPP coupling. This approach could eliminate the need for expensive and time-consuming experiments, paving the way for more efficient and cost-effective nuclear energy solutions.

Thermal energy storage (TES) consists in storing heat for a later use, thereby reducing the gap between energy availability and demand. The most diffused materials for TES are the organic solid-liquid phase change materials (PCMs), such as paraffin waxes, which accumulate and release a high amount of latent heat through a solid-liquid phase change, at a nearly constant temperature. To avoid leakage and loss of material, PCMs are either encapsulated in inert shells or shape-stabilized with porous materials or a nanofiller network. Generally, TES systems are only a supplementary component added to the main structure of a device, but this could unacceptably rise weight and volume of the device itself. In the applications where weight saving and thermal management are both important (e.g. automotive, portable electronics), it would be beneficial to embed the heat storage/management in the structural components. The aim of this thesis is to develop polymer composites that combine a polymer matrix, a PCM and a reinforcing agent, to reach a good balance of mechanical and TES properties. Since this research topic lacks a systematic investigation in the scientific literature, a wide range of polymer/PCM/reinforcement combinations were studied in this thesis, to highlight the effect of PCM introduction in a broad range of matrix/reinforcement combinations and to identify the best candidates and the key properties and parameters, in order to set guidelines for the design of these materials. The thesis in divided in eight Chapters. Chapter I and II provide the introduction and the theoretical background, while Chapter III details the experimental techniques applied on the prepared composites. The results and discussion are then described in Chapters IV-VII. Chapter IV presents the results of PCM-containing composites having a thermoplastic matrix. First, polyamide 12 (PA12) was melt-compounded with either a microencapsulated paraffin (MC) or a paraffin powder shape-stabilized with carbon nanotubes (ParCNT), and these mixtures were used as matrices to produce thermoplastic laminates with a glass fiber fabric via hot-pressing. MC was proven more suitable to be combined with PA12 than ParCNT, due to the higher thermal resistance. However, also the MC were considerably damaged by melt compounding and the two hot-pressing steps, which caused paraffin leakage and degradation, as demonstrated by the relative enthalpy lower than 100 %. Additionally, the PCM introduction decreased the mechanical properties of PA12 and the tensile strength of the laminates, but for the laminates containing MC the elastic modulus and the strain at break were not negatively affected by the PCM. Higher TES properties were achieved with the production of a semi-structural composite that combined PA12, MC and discontinuous carbon fibers. For example, the composite with 50 wt% of MC and 20 wt% of milled carbon fibers exhibited a total melting enthalpy of 60.4 J/g and an increase in elastic modulus of 42 % compared to the neat PA. However, the high melt viscosity and shear stresses developed during processing were still responsible for a not negligible PCM degradation, as also evidenced by dynamic rheological tests. Further increases in the mechanical and TES properties were achieved by using a reactive thermoplastic matrix, which could be processed as a thermosetting polymer and required considerably milder processing conditions that did not cause PCM degradation. MC was combined with an acrylic thermoplastic resin and the mixtures were used as matrices to produce laminates with a bidirectional carbon fabric, and for these laminates the melting enthalpy increased with the PCM weight fraction and reached 66.8 J/g. On the other hand, the increased PCM fraction caused a rise in the matrix viscosity and so a decrease in the fiber volume fraction in the final composite, thereby reducing the elastic modulus and flexural strength. Dynamic-mechanical investigation evidenced the PCM melting as a decreasing step in ’; its amplitude showed a linear trend with the melting enthalpy, and it was almost completely recovered during cooling, as evidenced by cyclic DMA tests. Chapter V presents the results of PCM-containing thermosetting composites. A further comparison between MC and ParCNT was performed in a thermosetting epoxy matrix. First, ParCNT was mixed with epoxy and the mixtures were used as matrices to produce laminates with a bidirectional carbon fiber fabric. ParCNT kept its thermal properties also in the laminates, and the melting enthalpy was 80-90 % of the expected enthalpy. Therefore, ParCNT performed better in thermosetting than in thermoplastic matrices due to the milder processing conditions, but the surrounding matrix still partially hindered the melting-crystallization process. Therefore, epoxy was combined with MC, but the not optimal adhesion between the matrix and the MC shell caused a considerable decrease in mechanical strength, as also demonstrated by the fitting with the Nicolais-Narkis and Pukanszky models, both of which evidenced scarce adhesion and considerable interphase weakness. However, the Halpin-Tsai and Lewis-Nielsen models of the elastic modulus evidenced that at low deformations the interfacial interaction is good, and this also agrees with the data of thermal conductivity, which resulted in excellent agreement with the Pal model calculated considering no gaps at the interface. These epoxy/MC mixtures were then reinforced with either continuous or discontinuous carbon fibers, and their characterization confirmed that the processing conditions of an epoxy composite are mild enough to preserve the integrity of the microcapsules and their TES capability. For continuous fiber composites, the increase in the MC fraction impaired the mechanical properties mostly because of the decrease in the final fiber volume fraction and because the MC phase tends to concentrate in the interlaminar region, thereby lowering the interlaminar shear strength. On the other hand, a small amount of MC enhanced the mode I interlaminar fracture toughness (Gic increases of up to 48 % compared to the neat epoxy/carbon laminate), as the MC introduced other energy dissipation mechanisms such as the debonding, crack deflection, crack pinning and micro-cracking, which added up to the fiber bridging. Chapter VI introduces a fully biodegradable TES composite with a thermoplastic starch matrix, reinforced with thin wood laminae and containing poly(ethylene glycol) as the PCM. The wood laminae successfully acted as a multifunctional reinforcement as they also stabilized PEG in their inner pores (up to 11 wt% of the whole laminate) and prevent its leakage. Moreover PEG was proven to increase the stiffness and strength of the laminate, thereby making the mechanical and TES properties synergistic and not parasitic. Finally, Chapter VII focused on PCM microcapsules. The synthesis of micro- and nano-capsules with an organosilica shell via a sol-gel approach clarified that the confinement in small domains and the interaction with the shell wall modified the crystallization behavior of the encapsulated PCM, as also evidenced by NMR and XRD studies and confirmed by DSC results. In the second part of Chapter VII, a coating of polydpamine (PDA) deposited onto the commercial microcapsules MC. The resulting PDA coating was proven effective to enhance the interfacial adhesion with an epoxy matrix, as evidenced by SEM micrographs. XPS demonstrated that the PDA layer was able to react with oxirane groups, thereby evidencing the possibility of forming covalent bond with the epoxy matrix during the curing step.

Cooling, Heating, and Power (CHP) is an emerging category of energy systems consisting of power generation equipment coupled with thermally activated components. The application of CHP systems to residential and small commercial buildings is known as micro-CHP (m-CHP). This instructional module has been developed to introduce engineering students to m-CHP. In the typical engineering curriculum, a number of courses could contain topics related to m-CHP. Thermodynamics, heat transfer, HVAC, heat and power, thermal systems design, and alternate energy systems courses are appropriate m-CHP topics. The types of material and level of analysis for this range of courses vary. In thermodynamics or heat transfer, basic problems involving a m-CHP flavor are needed, but in an alternate energy systems course much more detail and content would be required. This instructional module contains both lecture material and a compilation of problems/exercises for both m-CHP systems and components.

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