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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

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.

A membrane assisted process for green hydrogen production from a bioethanol derived feedstock is here developed and evaluated, starting from the conventional Steam Methane Reforming (SMR) process. Such a process is suitable for centralized hydrogen production, and is here analyzed for a large-scale H2 production unit with the capacity of 40.000 Nm3/h. The basic Steam Ethanol Reforming (SER) process scheme is modified in a membrane assisted process by integrating the Pd-membrane separation steps in the most suitable reaction steps. The membrane assisted process, configured in three alternative architectures (Open architecture, Membrane Reactor and Hybrid architecture) was evaluated in terms of efficiencies and hydrogen yields, obtaining a clear indication of improved process performance. The alternative membrane assisted process architectures are compared to the basic SER process and to the benchmark SMR process fed by natural gas, for an overall comparative assessment of the efficiency and specific CO2 emissions and for an economic analysis based on the operating expenditures.

In the UK electricity market, generators are obliged to produce part of their electricity with renewable energy resources in accordance with the Renewable Obligation Order. Since 2009 technology banding has been added, meaning that different technologies are rewarded with a different number of certificates. We analyze these two different renewable obligation policies in a mathematical representation of an electricity market with random availabilities of renewable generation outputs and random electricity demand. We also present another, alternative, banding policy. We provide revenue adequate pricing schemes for the three obligation policies. We carry out a simulation study via sampling. A key finding is that the UK banding policy cannot guarantee that the original obligation target is met, hence potentially resulting in more pollution. Our alternative provides a way to make sure that the target is met while supporting less established technologies, but it comes with a significantly higher consumer price. Furthermore, as an undesirable side effect, we observe that a cost reduction in a technology with a high banding (namely offshore wind) leads to more CO2 emissions under the UK banding policy and to higher consumer prices under the alternative banding policy.

In the current situation with the unprecedented deployment of clean technologies for electricity generation, it is natural to expect that storage will play an important role in electricity networks. This paper provides a qualitative methodology to select the appropriate technology or mix of technologies for different applications. The multiple comparisons according to different characteristics distinguish this paper from others about energy storage systems. Firstly, the different technologies available for energy storage, as discussed in the literature, are described and compared. The characteristics of the technologies are explained, including their current availability. In order to gain a better perspective, availability is cross-compared with maturity level. Moreover, information such as ratings, energy density, durability and costs is provided in table and graphic format for a straightforward comparison. Additionally, the different electric grid applications of energy storage technologies are described and categorised. For each of the categories, we describe the available technologies, both mature and potential. Finally, methods for connecting storage technologies are discussed.