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Abstract The hydrogen over-producing Escherichia coli HD701, a hydrogenase up-regulated strain, has the potential for industrial-scale hydrogen production; however, this strain is unable to metabolize sucrose which is a major constituent of many waste organic materials that can be used as feedstock for industrial hydrogen production. Invertase from Sacharomyces cervacea (yeast) was partially purified and characterized where its apparent optimum temperature when using short reaction period (15 min) was 55 °C; however the enzyme couldn't continue active due to its short half-life time at such high temperature. In contrast, a lower optimum temperature (35 °C) was recorded when using long reaction period (5 h) where the enzyme showed long half-life time and stability at such degree of temperature. Consequently, a concomitant hydrolysis of sucrose by yeast invertase and hydrogen production by E. coli at 35 °C was conducted and showed a high potency for industrial application with a hydrogen yield of 0.48 mole hydrogen/mole reducing sugars using batch fermentation at optimum sucrose concentration of 10 g/L. The described approach might be applicable for biotechnologies of other bio-products by E. coli from sucrose as a carbon source.

Abstract Utilization of the excess capacity from power plants by electrocatalytic methods to reduce the products from ammonia-based carbon capture technology to chemicals such as syngas is valuable and meaningful. Direct electrocatalytic reduction of NH4HCO3 electrolyte to syngas without CO2 bubbling is rarely reported. A porous Br-modified Ag catalyst with trace amounts of Br on the surface was investigated in 1.0, 2.0 M, and saturated NH4HCO3 electrolyte without CO2 bubbling. This catalyst can generate CO and H2 at ratios with ranges from 2:1 to 3:1. The highest CO Faradaic efficiency of 77.8% was observed with the CO current density of 13.8 mA cm−2 at −0.6 V vs RHE in saturated NH4HCO3 electrolyte. By contrast, the Ag catalyst with high selectivity for electrochemical reduction of CO2 to CO cannot catalyze CO production under this condition. On the Br-modified Ag catalyst, the trace amounts of Br formed a chemical bond with Ag in the Helmholtz surface, leading to changes in the electronic state and structure of Ag. The results are beneficial to the adsorption of intermediates. Thus, the remaining Br may serve as active contributors to promote the selectivity and catalytic activity of the electrochemical reduction both on the Br-modified Ag catalyst and in the NH4HCO3 electrolyte.

Abstract Highly efficient utilization of the energy potential of waste is a crucial matter in the process of thermal conversion. A vast majority of research studies published to this date on electrical energy and heat recovery have been concerned with large MSW (municipal solid waste) incineration systems. Only few of the publications presented the research on electrical energy and heat recovery in small and medium incinerating plants. They were focused on the production of syngas (waste gasification) and its combustion in gas engines. The research studies described in the article included electrical energy and heat recovery from the medical waste incineration installation with the efficiency of 220 kg/h. The research was carried out in a large hospital facility. The tested installation consisted of three basic elements: HSRG (heat recovery steam generator), MT (microturbine) producing electrical energy and steam/water heat exchanger. The efficiency values of individual units were high: HRSG–78%, MT-79% and HT-99%. The total disposable enthalpy flux of steam entering the turbine was low and it was not possible to produce a sufficient amount of electricity. The average electrical energy flux produced during the tests amounted to Ė ue-MT = 31.6 kWe, which constituted 4.2% of the total flux of usable energy recovered by the installation. The rest was the enthalpy flux of hot water – Ė ue-HE = 729 kW (95.8%). Such installations can be used, provided that there are systems that are capable of receiving that type of heat throughout the entire calendar year. It was proven that the experimental installation had small impact on the environment. The SPB (simple payback period) of the investment expenditures incurred in order to complete the installation amounted to 3.1 years.

Abstract In this study, two-phase flow in a Polymer Electrolyte Membrane (PEM) fuel cell with the converging-diverging flow field was investigated using numerical simulation. A transient, three-dimensional, two-phase flow, and multi-component model, as well as an agglomerate model for oxygen reduction in the cathode catalyst layer, was employed to simulate the performance of the cathode half-cell. The numerical implementation was conducted by developing a new solver in OpenFOAM by the author. An augmentation about 28.2% was observed in the oxygen mass fraction at GDL/Channel interface for a PEM fuel cell with a converging-diverging angle of 0.3° in comparison with the reference cell (straight channels). Moreover, the average of liquid water saturation was decreased by 3.61% in the middle cross-section of gas channels and 9.4% near to the outlet region for reviewed converging-diverging cases. Finally, to investigate the improvement of the cell performance, polarization curve and net output power were presented. It was found that the using converging-diverging flow field was more effective at high current densities, while it had a minor effect at low current densities. The net output power of the PEM fuel cell with converging-diverging channels was enhanced by more than 10% compared with the base cell.

Abstract Lithium-air batteries have attracted extensive attention in the general energy field. To enhance the practical applicability of lithium-air batteries, the overpotential caused by the diffusion of oxygen in the cathode, a significant component of the total overpotential, should be well comprehended. In this work, a wetted model is derived to evaluate the energy loss associated with liquid electrolytes. The oxygen diffusion in both electrolytes and porous cathodes is investigated systematically by taking oxygen concentration distribution into account. By analyzing the factors associated with cathode overpotential, such as the cathode thickness of and the viscosity of electrolyte, our work facilitates the improvement in the electrochemical performance of lithium-air batteries.

Abstract Fuel cells are still undergoing intense development, and the combination of new and optimized materials, improved product development, novel architectures, more efficient transport processes, and design optimization and integration are expected to lead to major gains in performance, efficiency, reliability, manufacturability and cost-effectiveness. Computational fuel cell engineering (CFCE) tools that allow systematic simulation, design and optimization of fuel cell systems would facilitate the integration of such advances, allow less heavy reliance on hardware prototyping, and reduce development cycles. CFCE requires the robust integration of models representing a variety of complex multi-physics transport processes characterized by a broad spectrum of length and time scales. These processes include a fascinating, but not always well understood, array of phenomena involving fluidic, ionic, electronic and thermal transport in concert with electrochemical reactions. In this paper, we report on some progress in both fundamental modelling of these phenomena, as well as in the development of integrated, computational fluid dynamics (CFD) based models for polymer electrolyte membrane (PEM) fuel cells. A new rational model for coupled protonic and water transport in PEMS, as well direct numerical simulations of two-phase flow in porous gas diffusion electrodes are discussed. Illustrative applications of CFD-based simulations are presented for conventional fuel cells and novel micro-structured fuel cells. The paper concludes with a perspective on some of the remaining theoretical, experimental and numerical challenges to achieve truly functional CFCE tools.

Abstract In this paper, the implications of CO 2 emission mitigation constraints in the power sector planning in Indonesia are examined using a long term integrated resource planning model. An approach is developed to assess the contributions of supply- and demand-side effects to the changes in CO 2 , SO 2 and NO x emissions from the power sector due to constraints on CO 2 emissions. The results show that while both supply- and demand-side effects would act towards the reduction of CO 2 , SO 2 and NO x emissions, the supply-side options would play the dominant role in emission mitigations from the power sector in Indonesia. The CO 2 abatement cost would increase from US$7.8 to US$9.4 per ton of CO 2 , while the electricity price would increase by 3.1 to 19.8% if the annual CO 2 emission reduction target is raised from 10 to 25%.

Abstract A forced-convection rubber smoking room aimed to reduce time and save energy on natural rubber sheet drying. Exhaust hot air is recirculated to reduce heat losses and improve thermal efficiency of drying system. Moisture content (% dry basis); thermal efficiency; specific fuelwood, electricity and energy consumption are evaluated for half and full load conditions. Economic benefits were also investigated. The rubber smoking room can dry up to 1500 sheets in 48 h by fuelwood combustion with 0.88 kg/s inlet mass flow rate reduction from conventional drying time of 72 h. Specific fuelwood and electricity consumption were 0.56 kg and 0.075 kWh per kg of dried rubber sheet, respectively. Air flow in the rubber smoking room was uniform with maximum variation of 6.75 °C and the dried products are of high quality. The saving of fuelwood consumption is 55.5% as compare to conventional rubber smoking room. Thermal efficiency of the rubber smoking room is 14.3% under full load condition. The net present value, internal rate of return, and payback period of the smoking room were estimated to be 28,773 USD, 24.6% and 4.0 years. Therefore, new design represents not only a good financial return but also better rubber sheet quality.

Abstract In this study, Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF) after treatment systems integrated 3L diesel engine fueled with BDF20, BDF50, BDF100 biodiesel fuels and JIS#2 diesel fuel are experimentally analyzed at 100 Nm, 200 Nm and full load (294 Nm); while the engine speed and cooling water temperature are constant at 1800 rpm and 80 °C, respectively. The advanced thermodynamic analyses, such as environmental and enviroeconomic analyses with energy, exergy, sustainability, thermoeconomic and exergoeconomic analyses, are applied. It is found that; (i) Utilization of the DOC is effective to reduce the fuel consumption of the BDF50 fuel; while the DOC and DOC + DPF are effective for the BDF100 fuel. (ii) DOC + DPF is more effective for biodiesel fuels. (iii) DOC + DPF decreases the soot concentration of all fuels. (iv) The maximum efficiency is found for the BDF100 fuel. (v) DOC + DPF is generally good option to reduce the CO2 of the fuels, especially for the BDF20 and BDF50. (vi) DOC + DPF is more effective for the BDF20 and BDF50 biodiesel blends; while both of the DOC and DOC + DPF are effective for the BDF50 fuel for reducing the prices of the released CO2. (vii) All fuels are more sustainable at full load.