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The EU has set out to reduce negative impacts from electricity generation on the environment, human health and towards our dependence on fossil fuels. As the fastest growing renewable source of electricity, photovoltaics plays an important role in the energy transition. The manufacturing of photovoltaic modules requires materials classified as critical, making them prone to supply disruptions. Although these materials are essential to the EU economy, they are not sufficiently recovered at the end of a photovoltaic module’s life. An alternative intermediate solution could be to extend the lifespan of existing modules, to slow down demand for these materials in the future. The aim of this study was to analyse the theoretical options and practical examples of product life extension strategies for photovoltaics. The R-Ladder was used as a guiding framework, which provided examples of life extension strategies. These include Reuse, Repair, Refurbishment, Remanufacture and Repurpose. Aspects for each of these strategies were analysed to find potential benefits and challenges related to four aspects: economics, environment, energy, and materials. The approach of this study includes a literature review to identify the life extension strategies discussed specifically for photovoltaics in the context of the circular economy. This was followed by a multi-case study on practical applications of Reuse, Repair and Repurposing of photovoltaic modules. Findings from literature and the case study were further supplemented with the insights from six experts. These experts had diverse backgrounds in research, manufacturing, and procurement to offer a variety of insights and perspectives on life extension strategies for photovoltaics. Finally, two scenarios were created for possible life extension pathways for used photovoltaic modules to illustrate the potential impacts compared to a commonplace premature replacement scenario. Economics and module performance are key factors in decision-making and acquisition of a photovoltaic ...

The EU has set out to reduce negative impacts from electricity generation on the environment, human health and towards our dependence on fossil fuels. As the fastest growing renewable source of electricity, photovoltaics plays an important role in the energy transition. The manufacturing of photovoltaic modules requires materials classified as critical, making them prone to supply disruptions. Although these materials are essential to the EU economy, they are not sufficiently recovered at the end of a photovoltaic module’s life. An alternative intermediate solution could be to extend the lifespan of existing modules, to slow down demand for these materials in the future. The aim of this study was to analyse the theoretical options and practical examples of product life extension strategies for photovoltaics. The R-Ladder was used as a guiding framework, which provided examples of life extension strategies. These include Reuse, Repair, Refurbishment, Remanufacture and Repurpose. Aspects for each of these strategies were analysed to find potential benefits and challenges related to four aspects: economics, environment, energy, and materials. The approach of this study includes a literature review to identify the life extension strategies discussed specifically for photovoltaics in the context of the circular economy. This was followed by a multi-case study on practical applications of Reuse, Repair and Repurposing of photovoltaic modules. Findings from literature and the case study were further supplemented with the insights from six experts. These experts had diverse backgrounds in research, manufacturing, and procurement to offer a variety of insights and perspectives on life extension strategies for photovoltaics. Finally, two scenarios were created for possible life extension pathways for used photovoltaic modules to illustrate the potential impacts compared to a commonplace premature replacement scenario. Economics and module performance are key factors in decision-making and acquisition of a photovoltaic ...

Steel is an indispensable material for the sustainable maintenance and progress of modern civilization. Its versatility in terms of mechanical and thermal characteristics, corrosion resistance, raw material availability, energy consumption and recyclability provides a clear advantage in a fast-changing technological landscape. In order to adapt to the changing needs, steel production methods have been evolving and improving over time. One such improvement opportunity in terms of energy efficient production is the ”heat pipe assisted annealing” concept. The cold rolling of steel is a process where the steel strip is cold-worked by means of rolls to achieve thickness reduction and better uniformity. This results in the strain hardening of steel. To reduce the hardness of steel and to render it more workable, it is thermally treated by heating it to a target soaking temperature and then cooling it down. This process is called annealing and it is an energy intensive process. Conventionally, heating is achieved with natural gas fired furnaces, whereas cooling is done using convective gas cooling. With this setting, the thermal energy extracted from the steel strip during the cooling stage is not used in any way. Moreover, none of the energy that is introduced during the heating stage is retained in the final product.An alternative technology for the annealing of steel was developed at Tata Steel IJmuiden R&D with the objective of recovering and using some of the heat removed during the cooling stage and thus, achieving more energy efficient annealing. With this technology called heat pipe assisted annealing, the cooling strip is thermally linked to the heating strip with multiple rotating heat pipes. In this way, each heat pipe transfers a certain amount of heat from the cooling strip to the heating strip. Only final heating and cooling of the steel strip is carried out in a conventional way. This concept is applicable to relatively low temperature (sub-critical) annealing where the cooling rate is not crucial. Therefore, packaging steel is a good candidate for the application of this technology.A rotating heat pipe is a highly efficient heat transfer device which is a wickless hollow cylindrical vessel rotating around its symmetric axis and containing a fixed amount of working fluid. The working fluid acts as a thermal energy carrier, transporting heat from one end of the heat pipe to the other. This basically occurs in four steps: (i) heat added to the evaporator part of the heat pipe causes the evaporation of the liquid, (ii) vapor travels to the condenser end of the heat pipe due to pressure difference, (iii) vapor condenses in the condenser section where heat is removed from the heat pipe, (iv) liquid returns to the evaporator with the help of the static pressure head and the centrifugal force induced by rotation. The heat pipe assisted annealing concept has been patented and subsequently further studied by Tata Steel Europe R&D. A water-filled rotating heat pipe test rig integrated with steel strips provided the bulk of the prior work. This test rig served as the proof-of-principle installation and it showed that heat can be transported from a hot strip to a cold one with a rotating heat pipe. In this context, several gaps have been identified to further acquire the knowledge on the system components, the concept performance and feasibility.This thesis focuses on four main aspects of the fundamentals and the feasibility of the heat pipe assisted annealing concept: (i) contact heat transfer between the steel strip and the rotating heat pipe, (ii) computationally efficient modelling of the interior dynamics of a rotating heat pipe, (iii) applicable working fluids for the high temperature range, (iv) behavior of the heat pipe assisted annealing system as a whole. These aspects are studied through a thermal engineering perspective. The heat pipe assisted annealing concept relies on the effective transfer of heat from the strip to the rotating heat pipe and vice versa. Therefore, it is important to understand the underlying physics governing this heat transfer and to be able to predict the heat transfer rate for possible configurations. In this context, in Chapter 2 of this thesis, the contact heat transfer between a steel strip and a rotating heat pipe is investigated both experimentally and numerically. The numerical model is based on first principles. It finds the thickness and the pressure of the gas layer between the strip and the heat pipe and subsequently considers different heat transfer mechanisms. The experimental work was carried out on the proof of- principle test rig. The model is validated with the experimental results. The contact heat transfer coefficient in the uniform region varied between 4,000 to 20,000 W/(m2.K). It showed an increase in the contact heat transfer with decreasing strip velocity and increasing radial stress. For the considered cases, conduction through the gas layer was the dominant heat transfer mechanism. Additionally, a simplified expression has been developed for the calculation of contact heat transfer through multiple regression analysis. The modelling of a rotating heat pipe is a crucial step for the detailed study of the heat pipe assisted annealing technology. Although modelling of rotating heat pipes has been the subject of many studies in the literature, these models are not computationally efficient enough to allow for the simultaneous modelling of multiple heat pipes linked to each other with strips. On this ground, in Chapter 3, a novel computationally efficient engineering model describing the transient behavior of the heat pipe is developed. In this model, the liquid and the vapor cells are allowed to change size radially in order to allow for the tracking of the liquid / vapor interface without the need for fine meshing or re-meshing. The model is also adapted to capillary-driven heat pipes. The model is validated with experimental and numerical studies from the literature. The deviation is computed to be around 2% with the numerical and analytical studies and around 6% with the experimental study.The heat pipe assisted annealing concept requires the operation of heat pipes within a temperature range of 25 °C to 700 °C. In order to operate within this range, different working fluids need to be used for different temperature ranges due to constraints of vapor pressure, life time, performance and safety. These working fluids are studied in Chapter 4. First, a selection of the working fluids is made based on a literature review. This selection yielded water, Dowtherm A, phenanthrene and cesium. Then, a life time test has been carried out with thermosyphons to test the stability of phenanthrene. At the end of a 3 months long test at 460 °C, thermal decomposition of phenanthrene was observed. However, these tests should be repeated with better initial vacuum and at multiple temperatures. Finally, Dowtherm A has been used in a rotating heat pipe setup to test its applicability and performance. It has been shown that Dowtherm A is suitable to be used in a rotating heat pipe at the designated temperature range in terms of performance, provided that annular flow is avoided. With the knowledge gathered from the previous chapters of this thesis, a model of the heat pipe assisted annealing line has been developed in Chapter 5. The aim of this model is to quantify the energy efficiency advantage brought by the concept for different number of heat pipes and to understand the behavior of the system as a whole. The simulations were run for a fixed plant layout with varying number of heat pipes and an average wrap angle of 104°. The energy recoveries for the simulations run for a strip of 0.25 mm and a line speed of 6.133 m/s were 76.5%, 73.4%, 69.4% and 63.9% for a total number of 90, 75, 60 and 45 heat pipes, respectively. From the simulation results it follows that cesium heat pipes are more efficient than organic heat pipes. Finally, the simulation results showed that the thermal cycle requirements can be satisfied with this new technology. Large Scale Energy Storage

Steel is an indispensable material for the sustainable maintenance and progress of modern civilization. Its versatility in terms of mechanical and thermal characteristics, corrosion resistance, raw material availability, energy consumption and recyclability provides a clear advantage in a fast-changing technological landscape. In order to adapt to the changing needs, steel production methods have been evolving and improving over time. One such improvement opportunity in terms of energy efficient production is the ”heat pipe assisted annealing” concept. The cold rolling of steel is a process where the steel strip is cold-worked by means of rolls to achieve thickness reduction and better uniformity. This results in the strain hardening of steel. To reduce the hardness of steel and to render it more workable, it is thermally treated by heating it to a target soaking temperature and then cooling it down. This process is called annealing and it is an energy intensive process. Conventionally, heating is achieved with natural gas fired furnaces, whereas cooling is done using convective gas cooling. With this setting, the thermal energy extracted from the steel strip during the cooling stage is not used in any way. Moreover, none of the energy that is introduced during the heating stage is retained in the final product.An alternative technology for the annealing of steel was developed at Tata Steel IJmuiden R&D with the objective of recovering and using some of the heat removed during the cooling stage and thus, achieving more energy efficient annealing. With this technology called heat pipe assisted annealing, the cooling strip is thermally linked to the heating strip with multiple rotating heat pipes. In this way, each heat pipe transfers a certain amount of heat from the cooling strip to the heating strip. Only final heating and cooling of the steel strip is carried out in a conventional way. This concept is applicable to relatively low temperature (sub-critical) annealing where the cooling rate is not crucial. Therefore, packaging steel is a good candidate for the application of this technology.A rotating heat pipe is a highly efficient heat transfer device which is a wickless hollow cylindrical vessel rotating around its symmetric axis and containing a fixed amount of working fluid. The working fluid acts as a thermal energy carrier, transporting heat from one end of the heat pipe to the other. This basically occurs in four steps: (i) heat added to the evaporator part of the heat pipe causes the evaporation of the liquid, (ii) vapor travels to the condenser end of the heat pipe due to pressure difference, (iii) vapor condenses in the condenser section where heat is removed from the heat pipe, (iv) liquid returns to the evaporator with the help of the static pressure head and the centrifugal force induced by rotation. The heat pipe assisted annealing concept has been patented and subsequently further studied by Tata Steel Europe R&D. A water-filled rotating heat pipe test rig integrated with steel strips provided the bulk of the prior work. This test rig served as the proof-of-principle installation and it showed that heat can be transported from a hot strip to a cold one with a rotating heat pipe. In this context, several gaps have been identified to further acquire the knowledge on the system components, the concept performance and feasibility.This thesis focuses on four main aspects of the fundamentals and the feasibility of the heat pipe assisted annealing concept: (i) contact heat transfer between the steel strip and the rotating heat pipe, (ii) computationally efficient modelling of the interior dynamics of a rotating heat pipe, (iii) applicable working fluids for the high temperature range, (iv) behavior of the heat pipe assisted annealing system as a whole. These aspects are studied through a thermal engineering perspective. The heat pipe assisted annealing concept relies on the effective transfer of heat from the strip to the rotating heat pipe and vice versa. Therefore, it is important to understand the underlying physics governing this heat transfer and to be able to predict the heat transfer rate for possible configurations. In this context, in Chapter 2 of this thesis, the contact heat transfer between a steel strip and a rotating heat pipe is investigated both experimentally and numerically. The numerical model is based on first principles. It finds the thickness and the pressure of the gas layer between the strip and the heat pipe and subsequently considers different heat transfer mechanisms. The experimental work was carried out on the proof of- principle test rig. The model is validated with the experimental results. The contact heat transfer coefficient in the uniform region varied between 4,000 to 20,000 W/(m2.K). It showed an increase in the contact heat transfer with decreasing strip velocity and increasing radial stress. For the considered cases, conduction through the gas layer was the dominant heat transfer mechanism. Additionally, a simplified expression has been developed for the calculation of contact heat transfer through multiple regression analysis. The modelling of a rotating heat pipe is a crucial step for the detailed study of the heat pipe assisted annealing technology. Although modelling of rotating heat pipes has been the subject of many studies in the literature, these models are not computationally efficient enough to allow for the simultaneous modelling of multiple heat pipes linked to each other with strips. On this ground, in Chapter 3, a novel computationally efficient engineering model describing the transient behavior of the heat pipe is developed. In this model, the liquid and the vapor cells are allowed to change size radially in order to allow for the tracking of the liquid / vapor interface without the need for fine meshing or re-meshing. The model is also adapted to capillary-driven heat pipes. The model is validated with experimental and numerical studies from the literature. The deviation is computed to be around 2% with the numerical and analytical studies and around 6% with the experimental study.The heat pipe assisted annealing concept requires the operation of heat pipes within a temperature range of 25 °C to 700 °C. In order to operate within this range, different working fluids need to be used for different temperature ranges due to constraints of vapor pressure, life time, performance and safety. These working fluids are studied in Chapter 4. First, a selection of the working fluids is made based on a literature review. This selection yielded water, Dowtherm A, phenanthrene and cesium. Then, a life time test has been carried out with thermosyphons to test the stability of phenanthrene. At the end of a 3 months long test at 460 °C, thermal decomposition of phenanthrene was observed. However, these tests should be repeated with better initial vacuum and at multiple temperatures. Finally, Dowtherm A has been used in a rotating heat pipe setup to test its applicability and performance. It has been shown that Dowtherm A is suitable to be used in a rotating heat pipe at the designated temperature range in terms of performance, provided that annular flow is avoided. With the knowledge gathered from the previous chapters of this thesis, a model of the heat pipe assisted annealing line has been developed in Chapter 5. The aim of this model is to quantify the energy efficiency advantage brought by the concept for different number of heat pipes and to understand the behavior of the system as a whole. The simulations were run for a fixed plant layout with varying number of heat pipes and an average wrap angle of 104°. The energy recoveries for the simulations run for a strip of 0.25 mm and a line speed of 6.133 m/s were 76.5%, 73.4%, 69.4% and 63.9% for a total number of 90, 75, 60 and 45 heat pipes, respectively. From the simulation results it follows that cesium heat pipes are more efficient than organic heat pipes. Finally, the simulation results showed that the thermal cycle requirements can be satisfied with this new technology. Large Scale Energy Storage

Abstract This paper investigates the spillovers of extreme risks between crude oil and stock markets using daily data of the S&P 500 stock index and West Texas Intermediate (WTI) crude oil futures returns. Based on the method of Granger causality in risk, Value at Risk (VaR) is employed to measure market risk, and a class of kernel-based tests is used to detect negative and positive risk spillover effects. Empirical results reveal that there are significant risk spillovers between the two markets. Extreme movements, past or current, in one market may have a significant predictive power for those in the other market. Prior to the recent financial crisis, there are positive risk spillovers from stock market to crude oil market, and negative spillovers from crude oil market to stock market. After the financial crisis, bidirectional positive risk spillovers are strengthened markedly. The risk spillovers may occur instantaneously, and/or with a (long) time delay. Both positive and negative risk spillover effects exhibit asymmetric correlations.

Abstract This paper investigates the spillovers of extreme risks between crude oil and stock markets using daily data of the S&P 500 stock index and West Texas Intermediate (WTI) crude oil futures returns. Based on the method of Granger causality in risk, Value at Risk (VaR) is employed to measure market risk, and a class of kernel-based tests is used to detect negative and positive risk spillover effects. Empirical results reveal that there are significant risk spillovers between the two markets. Extreme movements, past or current, in one market may have a significant predictive power for those in the other market. Prior to the recent financial crisis, there are positive risk spillovers from stock market to crude oil market, and negative spillovers from crude oil market to stock market. After the financial crisis, bidirectional positive risk spillovers are strengthened markedly. The risk spillovers may occur instantaneously, and/or with a (long) time delay. Both positive and negative risk spillover effects exhibit asymmetric correlations.

The level of advancement in the understanding of the mechanical properties of volcanic rocks is comparatively lower than that of sedimentary rocks. As part of the SUCCEED Project (Synergetic Utilisation of CO2 Storage Coupled with Geothermal Energy Deployment), which aims to investigate the feasibility of injecting captured and produced CO2 into the reservoirs to enhance geothermal production and achieve permanent CO2 storage at the Hellisheiði Geothermal Field in Iceland, this experimental research provides significant insights into the petrophysical and mechanical properties of the volcanic rocks collected from surface outcrops. The subsurface in Hellisheiði is mainly built up of hyaloclastite formations and interglacial basaltic lavas. During a field campaign samples were collected in different outcrops, ensuring that the samples were of high quality and sufficiently diverse to enable comprehensive analysis. Four samples per block and rock type have been prepared from the collected blocks, and they have been subjected to different laboratory tests to evaluate their petrophysical properties, such as porosity, density, and permeability, and their geomechanical behavior, using Unconfined Compression Test (UCS), Active-Source Acoustic Test, and Splitting Tensile Strength Test. Additionally, laboratory experiments have been conducted to investigate the impact of rapid cooling on rock damage due to thermal fracturing. The results show that there are interdependent relationships between porosity, bulk density, ultimate strength, Young's modulus, and wave velocities that can be observed when considering average values per rock. The rocks studied showed a negative correlation between porosity and other parameters and a direct correlation between ultimate strength and Young's Modulus. When examining individual rock samples, no significant correlations were observed between porosity and other parameters, however, those correlations where evident when comparing between different rock types, emphasizing the importance of ...

The level of advancement in the understanding of the mechanical properties of volcanic rocks is comparatively lower than that of sedimentary rocks. As part of the SUCCEED Project (Synergetic Utilisation of CO2 Storage Coupled with Geothermal Energy Deployment), which aims to investigate the feasibility of injecting captured and produced CO2 into the reservoirs to enhance geothermal production and achieve permanent CO2 storage at the Hellisheiði Geothermal Field in Iceland, this experimental research provides significant insights into the petrophysical and mechanical properties of the volcanic rocks collected from surface outcrops. The subsurface in Hellisheiði is mainly built up of hyaloclastite formations and interglacial basaltic lavas. During a field campaign samples were collected in different outcrops, ensuring that the samples were of high quality and sufficiently diverse to enable comprehensive analysis. Four samples per block and rock type have been prepared from the collected blocks, and they have been subjected to different laboratory tests to evaluate their petrophysical properties, such as porosity, density, and permeability, and their geomechanical behavior, using Unconfined Compression Test (UCS), Active-Source Acoustic Test, and Splitting Tensile Strength Test. Additionally, laboratory experiments have been conducted to investigate the impact of rapid cooling on rock damage due to thermal fracturing. The results show that there are interdependent relationships between porosity, bulk density, ultimate strength, Young's modulus, and wave velocities that can be observed when considering average values per rock. The rocks studied showed a negative correlation between porosity and other parameters and a direct correlation between ultimate strength and Young's Modulus. When examining individual rock samples, no significant correlations were observed between porosity and other parameters, however, those correlations where evident when comparing between different rock types, emphasizing the importance of ...

It is increasingly acknowledged that climate change is influencing terrestrial ecosystems by increased drought and rainfall intensities. Soil microbes are key drivers of many processes in terrestrial systems and rely on water in soil pores to fulfill their life cycles and functions. However, little is known on how drought and rainfall fluctuations, which affect the composition and structure of microbial communities, persist once original moisture conditions have been restored. Here, we study how simulated short-term drying and re-wetting events shape the community composition of soil fungi and prokaryotes. In a mesocosm experiment, soil was exposed to an extreme drought, then re-wetted to optimal moisture (50% WHC, water holding capacity) or to saturation level (100% WHC). Composition, community structure and diversity of microbes were measured by sequencing ITS and 16S rRNA gene amplicons 3 weeks after original moisture content had been restored. Drying and extreme re-wetting decreased richness of microbial communities, but not evenness. Abundance changes were observed in only 8% of prokaryote OTUs, and 25% of fungal OTUs, whereas all other OTUs did not differ between drying and re-wetting treatments. Two specific legacy response groups (LRGs) were observed for both prokaryotes and fungi. OTUs belonging to the first LRG decreased in relative abundance in soil with a history of drought, whereas OTUs that increased in soil with a history of drought formed a second LRG. These microbial responses were spread among different phyla. Drought appeared to be more important for the microbial community composition than the following extreme re-wetting. 16S profiles were correlated with both inorganic N concentration and basal respiration and ITS profiles correlated with fungal biomass. We conclude that a drying and/or an extreme re-wetting history can persist in soil microbial communities via specific response groups composed of members with broad phylogenetic origins, with possible functional consequences on soil processes and plant species. As a large fraction of OTUs responding to drying and re-wetting belonged to the rare biosphere, our results suggest that low abundant microbial species are potentially important for ecosystem responses to extreme weather events.