The objective of this research is to evaluate the potential of thermal energy storage in supermarkets with CO2 refrigeration systems. Suitable energy storage techniques are investigated and the seasonal storage technology of boreholes is chosen to be the focus of the study. The calculations are done for five supermarket refrigeration systems with different combinations of heating systems and borehole thermal energy storage control strategies. The two heating systems analyzed are the ground source heat pump and the heat recovery from the supermarket’s refrigeration system. The simulation results show that the introduction of thermal energy storage in the scenarios with heat pump can reduce the annual total energy by 6.3%. It is also shown that increasing the number of boreholes can decrease the life cycle cost of the system. Moreover, it is established that a supermarket system with heat recovery consumes 8.1% less energy than the one using heat pump and adding thermal energy storage on the heat recovery system further improves the energy consumption by 3.7% but may become costly.

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No description available.

The major challenge associated with renewable-energy systems especially solar, is the supply intermittency. One effective solution is to incorporate thermal energy storage components utilizing phase change materials (PCMs). These materials have the potential to store large amounts of energy in relatively small volumes and within nearly an isothermal storage process. The primary drawback of today’s PCMs is that their low thermal conductivity values critically limit their energy storage applications. Also, this grossly reduces the melting/ solidification rates, thus making the system response time to be too long. So, the application of heat transfer enhancement is very important. To improve the PCM storage performance, an efficient performing containment vessel (triplex-tube) along with applications of various heat transfer enhancement techniques was investigated. The techniques were; (i) dispersion of solid nanoparticles, (ii) incorporation of metal foam with nanoparticle dispersion, and (iii) insertion of longitudinal fins with nanoparticle dispersion. Validated simulation models were developed to examine the effects of implementing these techniques on the PCM phase-change rate during the energy storage and recovery modes. The results are presented with detailed model description, analysis, and conclusions. Results show that the use of nanoparticles with metal foam or fins is more efficient than using nanoparticles alone within the same volume usage. Also, employing metal foam or fins alone results in much better improvement for the same system volume.

This study investigates the feasibility and performance of a hybrid system integrating photovoltaic (PV) and solar thermal technologies for industrial process heat. By analyzing various parameters including cost, income, energy production, and system specifications, valuable insights are obtained. The study explores the potential of solar heating (SH) systems as a renewable thermal energy source for industrial processes, overcoming challenges of high costs and limited fossil fuel usage in industrial facilities through hybrid configurations. Data analysis includes cost analysis, income generation, energy balance, and system specifications such as temperature ranges, collector sizes, and efficiencies. While acknowledging limitations in simulation simplifications and the use of a single load profile, the study presents conclusions on the system's economic viability, technical capabilities, and potential applications. The findings highlight the importance of hybrid PV and solar thermal systems in enhancing energy efficiency and promoting renewable energy adoption in industrial process heating.

Groundwater is potentially a useful source for storing and providing thermal energy to the built environment. In a nordic context, aquifer thermal energy storage, (ATES) has not been subject to a wider extent of research concerning environmental impact. This thesis intends to study the impact on groundwater chemistry from an ATES that has been operational since 2016 and is located in the northern part of Stockholm, on a glaciofluvial deposit called the Stockholm esker. Analysis of groundwater sampling included a period of 9 months prior to ATES operation as well as a 7 month period after operation and sampling was conducted in a group of wells in vicinity of the installation and within the system as ATES operation began. Means of evaluation constituted a statistical approach which included Kruskal-Wallis test by ranks, to compare the ATES wells with the wells in the surroundings and principal component analysis, (PCA), to study the chemical parameters that could be related to ATES. In addition, a geophysical survey comprising 2D-resistivity and induced polarization, (IP) was done to elucidate whether the origin of high salinity could be traced to nearby possible sources. The analysis was based on foremost the cycle of cold energy storage. The results showed large variations in redox potential, particularly at the cold wells which likely was due to the mixing of groundwater considering the different depths of groundwater being abstracted/injected from different redox zones. Arsenic, which has shown to be sensitive to high temperatures in other research showed a decrease in concentration compared to surrounding wells. There were found to be a lower specific conductivity and total hardness at the ATES well compared to their vicinity. That indicates that they are less subject to salinization and that no accumulation has occurred to date.  It is evident that the environmental impact from ATES is governed by the pre-conditions in  soil- and groundwater. / Grundvatten har förutsättningen att utgöra en värdefull resurs för att lagra och förse byggnader med termisk energi. I en nordisk kontext har termisk energilagring i akviferer, (ATES)  inte varit föremål för någon bredare forskning angående miljöpåverkan. Denna uppsats syftar till att studera kemisk grundvattenpåverkan från ett ATES som togs i drift 2016 i norra Stockholm, i en isälvsavlagring vid namn Stockholmsåsen. Analysen omfattar grundvattenprovtagning 9 månader före ATES driften samt 7 månader efter driftstart och provtagningen genomfördes i ett antal brunnar i närheten av installationen samt i ATES systemet då driften startade. Utvärderingsmetoden bestod av ett statistiskt tillvägagångssätt och omfattade Kruskal-Wallis test by ranks, för att jämföra ATES brunnarna med omgivande brunnar och principal component analysis, (PCA), för att studera kemiska parametrar som kan kopplas till ATES. I tillägg genomfördes en geofysisk undersökning som omfattar 2D-resistivitet samt inducerad polarisation, (IP) för att klarlägga huruvida källan till den höga saliniteten kunde spåras. Analysen baseras på främst på cykeln då kyld energi lagras. Resultaten visar stor variation i redoxpotential, i synnerhet vid de kalla brunnarna vilket sannolikt beror på omblandning av grundvatten med tanke på en differens i djup som grundvattnet infiltrerar/pumpas från med tillhörande skillnad i redox zon. Arsenik vilket har visat sig känsligt för höga temperaturer i annan forskning visade minskade koncentrationer jämfört med omgivande brunnar. ATES brunnarna uppvisade även lägre specifik konduktivitet och totalhårdhet i jämförelse. Det pekar mot att brunnarna är mindre utsatta för salinitet och att ingen ackumulering har skett till dags dato. Det framgår tydligt att miljömässig påverkan från ATES styrs av grundförutsättningarna i mark och grundvatten.

Groundwater is potentially a useful source for storing and providing thermal energy to the built environment. In a nordic context, aquifer thermal energy storage, (ATES) has not been subject to a wider extent of research concerning environmental impact. This thesis intends to study the impact on groundwater chemistry from an ATES that has been operational since 2016 and is located in the northern part of Stockholm, on a glaciofluvial deposit called the Stockholm esker. Analysis of groundwater sampling included a period of 9 months prior to ATES operation as well as a 7 month period after operation and sampling was conducted in a group of wells in vicinity of the installation and within the system as ATES operation began. Means of evaluation constituted a statistical approach which included Kruskal-Wallis test by ranks, to compare the ATES wells with the wells in the surroundings and principal component analysis, (PCA), to study the chemical parameters that could be related to ATES. In addition, a geophysical survey comprising 2D-resistivity and induced polarization, (IP) was done to elucidate whether the origin of high salinity could be traced to nearby possible sources. The analysis was based on foremost the cycle of cold energy storage. The results showed large variations in redox potential, particularly at the cold wells which likely was due to the mixing of groundwater considering the different depths of groundwater being abstracted/injected from different redox zones. Arsenic, which has shown to be sensitive to high temperatures in other research showed a decrease in concentration compared to surrounding wells. There were found to be a lower specific conductivity and total hardness at the ATES well compared to their vicinity. That indicates that they are less subject to salinization and that no accumulation has occurred to date. It is evident that the environmental impact from ATES is governed by the pre-conditions in soil- and groundwater.

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%.

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.

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.