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Biomass is a sustainable energy source which, through thermo-chemical processes of biomass gasification, is able to be converted from a solid biomass fuel into a gas mixture, known as syngas or biosyngas. A solid oxide fuel cell (SOFC) is a power generation device that directly converts the chemical energy of a fuel to electricity. Therefore, biomass-powered SOFCs could be highly efficient. Typically, in addition to carbon dioxide and water vapor, the major components of syngas produced from biomass gasification include hydrogen, carbon monoxide and methane which are potential fuels for SOFCs, which make integration possible between SOFCs and biomass gasifiers. However, the syngas is also comprised of trace species such as tars, H2S, HCl, and alkali compounds, among others, which could be detrimental to SOFCs if they are contained within the feeding syngas stream. Therefore, the syngas must be pretreated in order to reduce these trace species to a level that SOFCs are able to tolerate. With various gas treatments, the overall system performance would fluctuate, and therefore, the influence of the gas treatment methods on the system performance must be understood. The most prominent among the trace species is tar. The effect of tars on the performance of SOFCs has yet to be studied, however, it is known that, even though tar can possibly poison the fuel cell through carbon deposition, it may also become a fuel for SOFCs. Furthermore, SOFC systems are currently designed in general for employing natural gas. Due to the fact that SOFC systems are very sensitive to the fuel types, it is necessary to completely understand the system response when switching from natural gas to biosyngas to enable a better controllability for future experiments. The research scope of this thesis is limited to the aforementioned issues. The objective of this thesis is to provide a fundamental study to ensure a safe and efficient system integration. The study is limited to an existing downdraft fixed-bed gasifier and a 5 kWe SOFC CHP system due to these two units entering the commercial market. The approach utilized, however, could be further adopted for the large scale power plants based on biomass gasifiers and SOFCs. The research begins with the evaluation of technologies involved biomass-powered SOFCs in chapter 2. Technologies regarding biomass gasification, gas cleanup and fuel cells are discussed based on literature surveys. The review begins by briefly summarizing conventional gasifiers including fixed-bed and fluidized bed gasifiers, which are implented for biomass gasification. Following that, details are indicated for SOFC performance affected by the trace species such as particulates, H2S and available cleaning technologies. The combination of biomass gasifiers with fuel cells including proton exchange membrane fuel cells (PEMFC), molten carbonate fuel cells (MCFC), and SOFCs is then reviewed with an emphasis on the development of SOFC technology and the study of integration between biomass gaisifers and SOFCs. Chapter 3 presents a thermodynamic study of the influence of cleaning technology on the energetic and exergetic performance of the integrated gasifier–SOFC system with distinctive system configurations. Two gas cleaning systems, specifically, a combined high and low temperature gas cleaning system and a high temperature gas cleaning system are considered to connect the gasifier with the SOFC system. The influence of the steam addition for the suppression of carbon deposition and various heat sources for steam generation on the system performance is evaluated. The performance of the SOFC system operating with natural gas and biosyngas is also compared. The installed SOFC system, particularly the embedded pre-reformer and anode off-gas recirculation was initially designed for natural gas. This design is desirable as it effectively uses the steam in the anode off-gas and the heat generated in the stack. As SOFC performance is very sensitive to gas composition and operating conditions, both of which are affected by the anode recirculation, an evaluation of the recirculation behavior on safety issues regarding carbon deposition and nickel oxidation and system performance are presented in chapter 4. An important finding is that, by not implementing the recirculation, the biosyngas-fueled SOFC system effectuates a much higher net electrical efficiency, less initial investment and simpler system configuration in comparison to that when recirculation is implemented. Tolerance of SOFCs to the trace species from biomass gasification is not yet fully understood. The influence of biomass gasification tars on SOFC performance and mitigation of carbon deposition are experimentally evaluated in chapter 5&6. Well-controlled operational conditions assist in the suppression of carbon deposition. Chapter 5 presents the influence of operating conditions including steam levels, current density and time on stream on the performance of SOFCs with Ni–YSZ anodes fueled by tar-containing biosyngas at 800 °C. Changes in impedance spectra and polarization curves of SOFCs following tar exposure were analyzed to assess the cell performance. The biosyngas composition and the tar concentration employed in these measurements were identical to those measured from the commercial air-blown biomass gasifier that is to be connected to the studied SOFC system. Operating this type of SOFC with the tar concentrations could result in severe damage to the cell due to carbon formation on the anodes. Scanning Electron Microscopy (SEM) indicated carbon deposition which affected the performance of the SOFC, as is exhibited by the impedance spectra and anode polarization curves of the cells after exposure to tars. However, the risk of carbon deposition could be alleviated by increasing steam levels and current loads. Chapter 6 presents a similar study of the effects of tar on SOFC performance, but possesses a focus on Ni–GDC anodes and various operating temperatures levels (700, 800 and 900 °C) under both dry and wet conditions. Polarization behavior, electrochemical impedance spectroscopy, and cell voltage degradation were analyzed to evaluate the cell performance. It is most likely that the cells with Ni–GDC anodes did not suffer from carbon deposition under the wet conditions studied. Dry tar-containing syngas for SOFCs is unlikely to cause carbon formation under a mild current load; however, it may induce carbon formation at open circuit. The effect of carbon dioxide that is capable of suppressing carbon deposition was experimentally investigated, and an enhanced performance was observed under the conditions studied. Under carbon risk-free operating conditions, the cell voltage increases when raising the feeding tar concentration, indicating that tar performs as fuel for SOFCs. Numerical simulation is an efficient tool for the evaluation of SOFCs’ response when switching fuels. Chapter 7 presents such a numerical study with the focus on the evaluation of kinetic models for methane steam reforming for SOFCs operation with multiple fuels. Three frequently employed kinetic models were selected in order to examine their impacts on the performance of a tubular SOFC. The resulting thermo-electrochemical behaviors derived from these models were compared. It was discovered that all three kinetic models are reasonably accurate in terms of the polarization behavior, but they significantly affected the local thermo-electrochemical performance. A more rapid kinetic model was adopted based on the evaluation of these three kinetic models in order to evaluate the performance of the tubular SOFC in terms of local electrochemical performance, anode oxygen partial pressure and overall SOFC performance when performing with multiple fuels. Chapter 8 draws the conclusions regarding the work presented in this dissertation, and recommendations are suggested for future research activities.

In recent years, prices for photovoltaics have fallen steadily and the demand for sustainable energy has increased. Consequentially, the assessment of roof surfaces in terms of their suitability for PV (Photovoltaic) installations has continuously gained in importance. Several types of assessment approaches have been established, ranging from sampling to complete census or aerial image analysis methodologies. Assessments of rooftop photovoltaic potential are multi-stage processes. The sub-task of examining the photovoltaic potential of individual rooftops is crucial for exact case study results. However, this step is often time-consuming and requires lots of computational effort especially when some form of intelligent classification algorithm needs to be trained. This often leads to the use of sampled rooftop utilization factors when investigating large-scale areas of interest, as data-driven approaches usually are not well-scalable. In this paper, a novel neighbourhood-based filtering approach is introduced that can analyse large amounts of irradiation data in a vectorised manner. It is tested in an application to the city of Giessen, Germany, and its surrounding area. The results show that it outperforms state-of-the-art image filtering techniques. The algorithm is able to process high-resolution data covering 1 km2 within roughly 2.5 s. It successfully classifies rooftop segments which are feasible for PV installations while omitting small, obstructed or insufficiently exposed segments. Apart from minor shortcomings, the approach presented in this work is capable of generating per-rooftop PV potential assessments at low computational cost and is well scalable to large scale areas.

In this paper, a linear mathematical and numerical model for analysing the dynamic response of a flexible electroactive wave energy converter is described. The Wave Energy Converter (WEC) is a floating elastic tube filled with slightly pressurised sea water. It is made of Electroactive Polymers (EAPs).Under simplifying assumptions, a set of governing equations is formulated for the flow inside the tube, the flow outside the tube and the behaviour of the tube wall. By combining them, the evolution of the flow velocity in the tube can be written as a wave equation. The corresponding eigenmodes of vibration are calculated. Then, using spectral decomposition, the equation of motion for the response of the tube in waves is derived. Experiments were carried out on a scale model of the wave energy converter in the wave tank of Ecole Centrale de Nantes in 2011. Numerical results are compared with experimental results in regular waves, showing rather good agreement, which validates the model and the initial modelling assumptions. Finally, estimates are made for the energy performance of a possible prototype.

Abstract Solutions containing hydrofluoric acid (HF), hydrochloric acid (HCl), and hydrogen peroxide (H2O2) were investigated as novel acidic, NOx-free etching mixtures for texturing of monocrystalline silicon wafers. High etch rates of up to 13.3 nm s−1 were observed at room temperature, which are comparable to the etch rates of KOH-IPA solutions. The silicon surface was investigated by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM), indicating pyramidal textures for diamond wire and SiC-slurry sawn as well as saw-damage etched (polished) wafers. Non-stirred baths generate random pyramidal structures while constantly stirred solutions generate novel random inverted pyramidal surface structures. The light trapping efficiency of wafers etched by the HF-HCl-H2O2 solutions was compared by UV/vis-reflectivity measurements to KOH/i-propanol specimens indicating lower reflectivities for the HF-HCl-H2O2-treated samples. Using the ‘wafer ray tracer’ (pvlighthouse.com) the light absorption properties of monomodal and random inverted pyramid structures were simulated and compared to well-known random and monomodal textures for PERC solar cells, clearly indicating the best performance for random inverted pyramids. Besides, simulation of a PERC solar cell on a roof top at our university was performed, indicating improved performance, especially for random inverted pyramid textures.

Smart charging of Electric Vehicles (EVs) reduces operating cost, allows more sustainable battery usage, and promotes the rise of electric mobility. In addition, bidirectional charging and improved connectivity enable efficient power grid support. Today, however, uncoordinated charging, e.g., governed by users’ habits, is still the norm. Thus, the impact of upcoming smart charging applications is mostly unexplored. We aim to estimate the expenses inherent with smart charging, e.g., battery aging costs, and give suggestions for further research. Using typical onboard sensor data we concisely model and validate an EV battery. We then integrate the battery model into a realistic smart charging use case and compare it with measurements of real EV charging. The results show that i) the temperature dependence of battery aging calls for precise thermal models for charging power greater than 7 kW, ii) disregarding battery aging underestimates EVs’ operating cost by approx. 30%, and iii) the profitability of Vehicle-to-Grid (V2G) services based on bidirectional power flow, e.g., energy arbitrage , depends on battery aging costs and the electricity price spread.

Abstract The impact of a twisted turbulator in a parabolic solar collector on the improvement of thermal–hydraulic performance (THP), as well as energy and exergy Efficiency of MgO-Cu/water hybrid nanofluid (HNF) is numerically evaluated. The main goal of this study is to use a twisted turbulator with pitch ratios (γ) of 1, 1.5, 2, and 2.5 for Reynolds numbers (Re) of 8000 to 32,000 and volume fractions (ϕ) of 1, 2, and 3% of MgO and Cu nanoparticles. Numerical simulation findings are reported in the form of graphs of average Nusselt number (Nuave), pressure drop (Δp), THP, energy Efficiency ( η c ) , and exergy Efficiency ( η ex ) . It can be concluded that Nuave and Δp depends on ϕ and Re and augments linearly with their values. Moreover, Nuave and Δp increases significantly by increasing the pitch ratio of the turbulator. The results revealed that the maximum values of augmentation of η c and η ex are respectively 23.79% and 21.15% by raising Re from 8000 to 32000. In a SC with a turbulator with γ = 2 and ϕ = 3%, η c is raised by 24.16% by increasing Re from 8000 to 32000; while, in the case of γ = 2.5 and ϕ = 3%, η c is enhanced by 18.2%.

Virtually developing of automotive power systems is currently experiencing increasing significance due to elevated vehicular electrification and automation of driving functions. The analysis of system-inherent disturbances requires accurate simulation models for both short-term transients or long-term driving cycles. The electrical behavior of electromechanical actuators such as brake or steering highly depends on the mechanical environmental interaction being dependent many variables. This contribution presents a methodology to extract abstracted models of machine driven actuators on the basis of an electric steering. The dynamics of a complex electromechanical model are investigated using pulse response analysis for differentiated operation points. The obtained model reduction is implemented in a frequency-dependent equivalent circuit.

Owing to the complexity of the sector, industrial activities are often represented with limited technological resolution in integrated energy system models. In this study, we enriched the technological description of industrial activities in the integrated energy system analysis optimisation (IESA-Opt) model, a peer-reviewed energy system optimisation model that can simultaneously provide optimal capacity planning for the hourly operation of all integrated sectors. We used this enriched model to analyse the industrial decarbonisation of the Netherlands for four key activities: high-value chemicals, hydrocarbons, ammonia, and steel production. The analyses performed comprised 1) exploring optimality in a reference scenario; 2) exploring the feasibility and implications of four extreme industrial cases with different technological archetypes, namely a bio-based industry, a hydrogen-based industry, a fully electrified industry, and retrofitting of current assets into carbon capture utilisation and storage; and 3) performing sensitivity analyses on key topics such as imported biomass, hydrogen, and natural gas prices, carbon storage potentials, technological learning, and the demand for olefins. The results of this study show that it is feasible for the energy system to have a fully bio-based, hydrogen-based, fully electrified, and retrofitted industry to achieve full decarbonisation while allowing for an optimal technological mix to yield at least a 10% cheaper transition. We also show that owing to the high predominance of the fuel component in the levelled cost of industrial products, substantial reductions in overnight investment costs of green technologies have a limited effect on their adoption. Finally, we reveal that based on the current (2022) energy prices, the energy transition is cost-effective, and fossil fuels can be fully displaced from industry and the national mix by 2050.