Chinese Taipei

Methanol is regarded as an important feedstock for hydrogen production due to its high energy density and superior transportability. A tubular packed-bed reactor performing the methanol steam reforming (MSR) process was modeled by adopting computational fluid dynamics (CFD) software to analyze its performance. Kinetic parameters of the reactions were adjusted according to the literatures and our previous experimental results. The methanol conversion the hydrogen production rate and the CO concentration in the produced mixture were evaluated by considering different levels of the length and temperature of the catalyst bed the steam-to-carbon ratio and the space velocity of the feedstocks. Moreover the correlation between the dimensionless parameter Damköhler number and the methanol conversion was also investigated.

Power-to-fuel systems via solid-oxide electrolysis are promising for storing excess renewable electricity by efficient electrolysis of steam (or co-electrolysis of steam and CO₂) into hydrogen (or syngas) which can be further converted into synthetic fuels with plant-wise thermal integration. Electrolysis stack performance and durability determine the system design performance and long-term operating strategy; thus solid-oxide electrolyzer based power-to-fuels were investigated from the stack to system levels. At the stack level the data from a 6000-h stack testing under laboratory isothermal conditions were used to calibrate a quasi-2D model which enables to predict practical isothermal stack performance with reasonable accuracy. Feasible stack operating windows meeting various design specifications (e.g. specific syngas composition) were further generated to support the selection of operating points. At the system level with the chosen similar stack operating points various power-to-fuel systems including power-to-hydrogen power-to-methane power-to-methanol (dimethyl ether) and power-to-gasoline were compared techno-economically considering system-level heat integration. Several operating strategies of the stack were compared to address the increase in stack temperature due to degradation. The modeling results show that the system efficiency for producing H₂ methane methanol/dimethyl ether and gasoline decreases sequentially from 94% (power-to-H₂) to 64% (power-to-gasoline) based on a higher heating value. Co-electrolysis which allows better heat integration can improve the efficiency of the systems with less exothermic fuel-synthesis processes (e.g. methanol/dimethyl ether) but offers limited advantages for power-to-methane and power-to-gasoline systems. In a likely future scenario where the growing amount of electricity from renewable sources results in increasing periods of a negative electricity price solid oxide electrolyser based power-to-fuel systems are highly suitable for levelling the price fluctuations in an economic way.

Hydrogen sourced from energy recovery processes and conversion of waste materials is a method of providing both a clean fuel and a sustainable waste management alternative to landfill and incineration. The question is whether waste-to–hydrogen can become part of the zero-carbon future energy mix and serve as one of the cleaner hydrogen sources which is economically viable and environmentally friendly. This work critically assessed the potential of waste as a source of hydrogen production via various thermochemical (gasification and pyrolysis) and biochemical (fermentation and photolysis) processes. Research has shown hydrogen production yields of 33.6 mol/kg and hydrogen concentrations of 82% from mixed waste feedstock gasification. Biochemical methods such as fermentation can produce hydrogen up to 418.6 mL/g. Factors including feedstock quality process requirements and technology availability were reviewed to guide technology selection and system design. Current technology status and bottlenecks were discussed to shape future development priorities. These bottlenecks include expensive production and operation processes heterogeneous feedstock low process efficiencies inadequate management and logistics and lack of policy support. Improvements to hydrogen yields and production rates are related to feedstock processing and advanced energy efficiency processes such as torrefaction of feedstock which has shown thermal efficiency of gasification up to 4 MJ/kg. This will affect the economic feasibility and concerns around required improvements to bring the costs down to allow waste to viewed as a serious competitor for hydrogen production. Recommendations were also made for financially competitive waste-to-hydrogen development to be part of a combined solution for future energy needs.

Photoanodes comprising a transparent glass substrate coated with a thin conductive film of fluorine-doped tin oxide (FTO) and a thin layer of a photoactive phase have been fabricated and tested with regard to the photo-electro-oxidation of water into molecular oxygen. The photoactive layer was made of a mat of TiO₂ nanorods (TDNRs) of micrometric thickness. Individual nanorods were successfully photosensitized with nanoparticles of a metal–organic framework (MOF) of nickel and 12-benzene dicarboxylic acid (BDCA). Detailed microstructural information was obtained from SEM and TEM analysis. The chemical composition of the active layer was determined by XRD XPS and FTIR analysis. Optical properties were determined by UV–Vis spectroscopy. The water photooxidation activity was evaluated by linear sweep voltammetry and the robustness was assessed by chrono-amperometry. The OER (oxygen evolution reaction) photo-activity of these photoelectrodes was found to be directly related to the amount of MOF deposited on the TiO₂ nanorods and was therefore maximized by adjusting the MOF content. The microscopic reaction mechanism which controls the photoactivity of these photoelectrodes was analyzed by photo-electrochemical impedance spectroscopy. Microscopic rate parameters are reported. These results contribute to the development and characterization of MOF-sensitized OER photoanodes.

The effects of baking on the mechanical properties and fracture characteristics of low-carbon boron (10B21) steel screws were investigated. Fracture torque tests and hydrogen content analysis were performed on baked screws to evaluate hydrogen embrittlement (HE) susceptibility. The diffusible hydrogen content within 10B21 steel dominated the fracture behavior of the screws. The fracture torque of 10B21 screws baked for a long duration was affected by released hydrogen. Secondary ion mass spectroscopy (SIMS) result showed that hydrogen content decreased with increasing baking duration and thus the HE susceptibility of 10B21 screws improved. Diffusible hydrogen promoted crack propagation in high-stress region. The HE of 10B21 screws can be prevented by long-duration baking.

This paper presents the design of a solid oxide fuel cell (SOFC) tri-generation system that consists of an SOFC-combined heat and power subsystem an adsorption refrigeration subsystem and coupling devices between the two subsystems. Whereas typical extant designs use absorption techniques the proposed design employs adsorption refrigeration. In this paper the dynamics of adsorption refrigeration are reported in detail to evaluate the feasibility of the tri-generation system design. The design of the coupling devices and instrumentation strategies of the overall system are discussed in detail. Simulation results indicate that the proposed SOFC trigeneration system can output 4.35 kW of electrical power 2.448 kW of exhaust heat power and 1.348 kW of cooling power. The energy efficiency is 64.9% and the coefficient of performance of the refrigeration is 0.32. Varying the electrical output power results in the variation of exhaust heat power but not the cooling power; varying the cooling power affects the exhaust heat power but not the electrical power. These favorable features can be attributed to the proposed heat exchange sequence and active temperature controls of the system.

In our previous studies of a plasma reformer system the effects of temperature of the reactants and input voltage have not been considered. In the present investigation the plasma reformer system has been modified to study the influence of the reactants’ temperature and input voltage on hydrogen production experimentally. The plasma reformer system includes a supersonic atomizer a plasma generator and a controlling device. In the experiment the operating parameters include the temperature of the reactants and the input voltage. The temperature of the reactants varies from 25 °C to 50 °C and the input voltage ranges from 12.5 V to 14.5 V. Results show that the increase in temperature of the reactants and input voltage will improve the production of hydrogen. In addition the improvement of heating on the reactants shows significant influence on hydrogen production.

In this study an energy exergy and environmental (3E) analyses of a plasma-assisted hydrogen production process from microalgae is investigated. Four different microalgal biomass fuels namely raw microalgae (RM) and three torrefied microalgal fuels (TM200 TM250 and TM300) are used as the feedstock for steam plasma gasification to generate syngas and hydrogen. The effects of steam-tobiomass (S/B) ratio on the syngas and hydrogen yields and energy and exergy efficiencies of plasma gasification _{(hEn;PG hEx;PG)} and hydrogen production_{(hEn;H2 hEx;H2 )} are taken into account. Results show that the optimal S/B ratios of RM TM200 TM250 and TM300 are 0.354 0.443 0.593 and 0.760 respectively occurring at the carbon boundary points (CBPs) where the maximum values of _{hEn;PG hEx;PG hEn;H2} and _hEx;H2 are also achieved. At CBPs torrefied microalgae as feedstock lower the_{hEn;PG hEx;PG hEn;H2} and _hEx;H2 because of their improved calorific value after undergoing torrefaction and the increased plasma energy demand compared to the RM. However beyond CBPs the torrefied feedstock displays better performance. A comparative life cycle analysis indicates that TM300 exhibits the highest greenhouse gases (GHG) emissions and the lowest net energy ratio (NER) due to the indirect emissions associated with electricity consumption.

The effect of metastable austenite on the hydrogen embrittlement (HE) of cold-rolled (30% reduction in thickness) 301 stainless steel (SS) was investigated. Cold-rolled (CR) specimens were hydrogen-charged in an autoclave at 300 or 450 °C under a pressure of 10 MPa for 160 h before tensile tests. Both ordinary and notched tensile tests were performed in air to measure the tensile properties of the non-charged and charged specimens. The results indicated that cold rolling caused the transformation of austenite into α′ and ε-martensite in the 301 SS. Aging at 450 °C enhanced the precipitation of M23C6 carbides G and σ phases in the cold-rolled specimen. In addition the formation of α′ martensite and M23C6 carbides along the grain boundaries increased the HE susceptibility and low-temperature sensitization of the 450 °C-aged 301 SS. In contrast the grain boundary α′-martensite and M23C6 carbides were not observed in the as-rolled and 300 °C-aged specimens

This paper discusses the performance improvement of a green building by optimization procedures and the influences of load characteristics on optimization. The green building is equipped with a self-sustained hybrid power system consisting of solar cells wind turbines batteries proton exchange membrane fuel cell (PEMFC) electrolyzer and power electronic devices. We develop a simulation model using the Matlab/SimPowerSystemTM and tune the model parameters based on experimental responses so that we can predict and analyze system responses without conducting extensive experiments. Three performance indexes are then defined to optimize the design of the hybrid system for three typical load profiles: the household the laboratory and the office loads. The results indicate that the total system cost was reduced by 38.9% 40% and 28.6% for the household laboratory and office loads respectively while the system reliability was improved by 4.89% 24.42% and 5.08%. That is the component sizes and power management strategies could greatly improve system cost and reliability while the performance improvement can be greatly influenced by the characteristics of the load profiles. A safety index is applied to evaluate the sustainability of the hybrid power system under extreme weather conditions. We further discuss two methods for improving the system safety: the use of sub-optimal settings or the additional chemical hydride. Adding 20 kg of NaBH4 can provide 63 kWh and increase system safety by 3.33 2.10 and 2.90 days for the household laboratory and office loads respectively. In future the proposed method can be applied to explore the potential benefits when constructing customized hybrid power systems.