• Energy Research
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Abstract In the present paper we demonstrate the efficient use of shape controlled flower-like ZnO (Zinc oxide) nanostructured particles as multifunctional electrode for both energy conversion and storage applications, i.e. Dye-sensitized Solar Cells (DSCs) and lithium-ion batteries. As regards DSC (Dye-sensitized Solar Cell) device, ZnO flower-like particles, prepared by a simple, low-cost and reliable hydrothermal method under mild reaction temperature, are efficiently used as photoanode in a microfluidic architectured cell in combination with NMBI (N-methylbenzimidazole), employed as additive of the electrolytic solution for the first time in a ZnO-based DSC. We obtain a remarkable sunlight conversion efficiency of 3.6%. As regards storage applications, a stable long-term ambient temperature cycling behavior in lithium cell is demonstrated, even at increasingly higher currents. Remarkable charge-discharge efficiency and specific capacity are obtained up to 200 cycles, which is the highest number of cycles reported so far for similar systems. Noteworthy, such results are achieved without the addition of foreign additives, nor during the synthesis process neither during the electrode preparation, and also no carbon coating on ZnO surface is used. The originality of the present paper consists not only in showing for the first time the efficient operation of such ZnO particles as anode in Li-ion batteries for prolonged cycling, but also in demonstrating the versatile and multifunctional use of the same material for two different energy related applications. The reported results enlighten indeed the promising prospects of the flower-like ZnO nanostructured material for the successful implementation as stable and long-term performing anodic material in the next generation of both energy conversion and storage devices.

Abstract In view of the forecast indicating lower growth rates for the consumption of electricity, the HTR 500 nuclear power station offers the advantage of electricity generating costs comparable with modern 1300 MWe light-water reactors, requiring at the same time lower initial investment costs. In the middle of 1988 a contract was signed between a group of German and Swiss utilities and Asea Brown Boveri for preparation of a Safety Analysis Report; it was completed in March 1989. The design of the HTR 500 makes considerable use of the technology applied in the THTR 300. The simplifications and optimizations reflected in the HTR 500 design are based on practical experience with the THTR 300 and will be verified by a R&D-program.

Greenhouse gas (GHG) emissions contribute to climate change. The public water utility of Amsterdam wants to operate climate neutrally in 2020 to reduce its GHG emissions. Energy recovery from the water cycle has a large potential to contribute to this goal: the recovered energy is an alternative for fossil fuel and thus contributes to the reduction of GHG emissions. One of the options concerns thermal energy recovery from drinking water. In Amsterdam, drinking water is produced from surface water, resulting in high drinking water temperatures in summer and low drinking water temperatures in winter. This makes it possible to apply both cold recovery and heat recovery from drinking water. For a specific case, the effects of cold recovery from drinking water were analyzed on three decisive criteria: the effect on the GHG emissions, the financial implications, and the effect on the microbiological drinking water quality. It is shown that cold recovery from drinking water results in a 90% reduction of GHG emissions, and that it has a positive financial business case: Total Cost of Ownership reduced with 17%. The microbial drinking water quality is not affected, but biofilm formation in the drinking water pipes increased after cold recovery.

Abstract Climate change is a key problem of the 21st century. Climate change is mainly caused by anthropogenic CO2 emissions, and one solution to this problem is to capture and store CO2 in deep coal seams, where it is immobilized by adsorption to the coal surface. Here we propose to modify the coal with methyl orange (MO), a typical dye that is also a major pollutant of the hydrosphere and removed thereby. Thus, raw and MO-modified coals were characterized to investigate their thermal stabilities, textural properties, carbon contents, surface characteristics, and CO2 adsorption on the coal samples was measured at typical storage conditions (323 K and pressures up to 37.5 bar). CO2 adsorption dramatically increased in the MO-coal, from 1.95 mol. kg−1 (raw coal) to 18.7 mol. kg −1. This work thus aids in the development of improved methods for CO2 storage, to significantly mitigate climate change.

Abstract The approach selected is the fabrication of holographic optical elements which will focus to either a line or a point. A concentrating mirror is replicated in the hologram, which consists of dichromate gelatin exposed to a laser beam. The dichromate gelatin can be processed to produce a non-uniform microstructure, which gives the hologram a significant waveband width. Even so, it becomes necessary to stack at least three holograms, with each reflecting a different region of the solar spectrum, if we are to reflect most of the solar energy. To achieve high efficiency, it is necessary to obtain adjacent quasi-square waves for the efficiency—wavelength profile of each of the holograms in the stack. Profile information was obtained by the use of a monochromator coupled to a computer. An optical efficiency in excess of 50% was measured for a three-hologram stack. This represents approximately 70% of the efficiency achievable within the limited measuring range of the monochromator. A line-focus holographic concentrator model has been built for demonstration purposes. A cost analysis for mass producing holographic concentrators indicates that holographic concentrators become cost effective in relation to mass-produced conventional concentrators when the holographic optical efficiency exceeds 70%. To surpass this number, it becomes necessary to produce a five-hologram stack and to broaden the monochromator optical sensitivity range.

Biomass-derived chemical looping gasification (BCLG) is a novel technology for lignocellulose energy applications. Ca-Fe oxygen carriers have been proven to be a potential material for efficient lignocellulose conversion and hydrogen-enriched syngas production in process studies. In this study, Thermogravimetry-mass spectrometry (TG-MS), pyrolysis chromatography-mass spectrometry (Py-GC-MS) and fixed-bed experiments were conducted, and the cellulose BCLG product was analyzed to explore the mechanism of reaction between Ca-Fe OCs and biomass char or volatiles. The mechanism of the synergistic effect of Ca-Fe was analyzed to explain the characteristics of the OCs. The results showed the Ca-based materials act as catalysts to promote the decomposition of cellulose monomers at primary reaction and char at secondary reaction. And also promote the reforming and oxidation of volatiles by chemisorption. Ca participates in the construction of inert substances, such as Ca 2 Fe 2 O 5 , to avoid the deep oxidation of CO and H 2 . Fe-based material supplies oxygen and promotes the reforming of volatile. Compared with Fe 2 O 3 and CaO/Fe 2 O 3 , CaFe 2 O 4 showed a better performance on carbon conversion and H 2 production below 850 °C.

Abstract A comprehensive study on the design and nonlinear characterization of a two-degree of freedom piezoaeroelastic energy harvesting system with freeplay and multi-segmented nonlinearities in the pitch degree of freedom is explored and discussed. The nonlinear governing equations of the considered piezoaeroelastic energy harvesting system are derived and the unsteady representation based on the Duhamel formulation is employed to represent the aerodynamic loads. Nonlinear piezoaeroelastic response analysis is carried out in the presence of freeplay and multi-segmented nonlinearities before and after the linear onset of flutter. Such nonlinearities can be introduced to piezoaeroelastic energy harvesters for performance enhancement through the possible existence of subcritical Hopf bifurcation and aperiodic responses due to the grazing and grazing/sliding bifurcations. It is shown that the existence of discontinuous effects result in the possibility of harvesting energy at lower speeds than the linear onset speed of instability due to the activation of the subcritical Hopf bifurcation. Additionally, the increase of the strength of the multi-segmented nonlinearities leads to the existence of aperiodic responses with the presence of several bifurcations limiting the system's dynamics at low pitch angles with limiting stall issues. It is proved that an effective design with harvesting energy at low wind speeds can be carried out for wing-based energy harvesters by carefully selecting the linear stiffness of the pitch degree of freedom, gap and type of the multi-segmented discontinuity, and electrical load resistance.

Ethanol steam reforming (ESR) was performed over Pd-Rh/CeO2 catalyst in a catalytic membrane reactor (CMR) as a reformer unit for production of fuel cell grade pure hydrogen. Experiments were performed at 923 K, 6–10 bar, and fuel flow rates of 50–200 µl/min using a mixture of ethanol and distilled water with steam to carbon ratio of 3. A static model for the catalytic zone was derived from the Arrhenius law to calculate the total molar production rates of ESR products, i.e. CO, CO2, CH4, H2, and H2O in the catalytic zone of the CMR (coefficient of determination R2 = 0.993). The pure hydrogen production rate at steady state conditions was modeled by means of a static model based on the Sieverts' law. Finally, a dynamic model was developed under ideal gas law assumptions to simulate the dynamics of pure hydrogen production rate in the case of the fuel flow rate or the operating pressure set point adjustment (transient state) at isothermal conditions. The simulation of fuel flow rate change dynamics was more essential compared to the pressure change one, as the system responded much faster to such an adjustment. The results of the dynamic simulation fitted very well to the experimental values at P = 7–10 bar, which proved the robustness of the simulation based on the Sieverts' law. The simulation presented in this work is similar to the hydrogen flow rate adjustments needed to set the electrical load of a fuel cell, when fed online by the pure hydrogen generating reformer studied. Peer Reviewed