Energy storage using the reaction cycle: Methyl alcohol/acetaldehyde

The kinetics of the exothermic reaction of acetaldehyde with methyl alcohol has been studied using calorimetry in the temperature range of 263–283 K. Based on this study the reaction rate constant for the reaction was found to be and the heat of reaction was found to be These kinetics were based on the assumption of a pseudoisothermal first-order reaction.     

Effect of Y-doping on the catalytic properties of CuO/CeO2 catalysts for water-gas shift reaction

CuO/ceria and CuO/Y-doped ceria catalysts were synthesized. The Y-modified supports (1.0, 2.5 and 5.0 wt% Y₂O₃) were prepared by coprecipitation. CuO (3 wt% Cu) was loaded by deposition-precipitation. Having in mind the known effect of Y³⁺ modification for the generation of oxygen vacancies in ceria, its positive role on the water-gas shift (WGS) performance was expected. However, the catalytic test showed a trend of decreased WGS activity by increasing the Y-dopant amount, nevertheless that the differences were not very substantial. On the basis of XRD, XPS, EPR, Raman spectroscopy and H₂-TPR results the explanation related to the key role of the oxygen mobility influenced by Y-doping could be proposed. The reason of the inferior WGS performance with increasing Y-content would be the higher amount of surface oxygen vacancies around Y³⁺ ions which disturbed the Cu–O_vac–Ce active sites for WGS reaction. Though, during the long run catalytic tests in WGS reaction a positive effect of Y-doping for improved stability of CuO/ceria catalysts was evidenced.     

Optical,structural and phase transition properties of Cu2O,CuO and Cu2O/CuO: Their photoelectrochemical sensor applications

Cu₂O and CuO provide a unique possibility to tune the band gap into the middle of the efficiency maximum for photoelectrochemical (PEC) and solar cell applications. Photoactive materials containing Cu₂O, CuO and Cu₂O/CuO have been prepared with high quality and stability in various compositions by an economic, simple and reliable electrodeposition (ED) method. These materials based on copper oxide have been characterized and compared using XRD, SEM, EDX, UV–Vis, PL, FTIR, Raman spectroscopy and electrochemical techniques. Based on the electrochemical production conditions; phase changes of photoactive materials and, at which conditions which phase or phases are present, were evaluated in detail. It was carried out that a full phase change from single-phase Cu₂O to single-phase CuO. The crystal dimensions expand as the cube-shaped Cu₂O transforms into CuO, crystal surface areas increase, crystal shapes change and turn gradually into flower-shaped crystals. Here, the band gap of copper oxide material can be altered within a broad scale by adjusting the element ratios. The semiconductors have been found to have direct band gap that is more preferred for solar energy applications. PEC performances of the copper oxide electrodes containing a different phase structure were determined, and the changes of PEC activities were examined comparatively. Copper oxide semiconductors have p-type conductivity and they act as photocathodes.     

Theoretical and experimental aspects of a two-step short cycle,based on ZnO and CdO intended for storage of solar energy

In the present paper, chemical and energetical considerations about hybrid thermal electrochemical cycles based on zinc and cadmium oxides are developed. Intermediate reactions have been taken into account. Numerical data obtained from decomposition experiments of the oxides in a solar furnace and from electrolysis experiments with Zn and Cd metals (or metal-oxide mixtures) used as an anode, are discussed. The energy balance for the hydrogen production using the mentioned cycles is compared with a direct electrolytic water-splitting process working with thermopiles or photopiles solar plants as electricity source.     

Comparative study of CeO2/CuO and CuO/CeO2 catalysts on catalytic performance for preferential CO oxidation

The CeO₂/CuO and CuO/CeO₂ catalysts were synthesized by the hydrothermal method and characterized via XRD, SEM, H₂-TPR, HRTEM, XPS and N₂ adsorption–desorption techniques. The study shows that the rod-like structure is self-assembled CeO₂, and both hydrothermal time and Ce/Cu molar ratio are important factors when the particle-like CeO₂ is being self-assembled into the rod-like CeO₂. The CuO is key active component in the CO-PROX reaction, and its reduction has a negative influence on the selective oxidation of CO. The advantage of the inverse CeO₂/CuO catalyst is that it still can provide sufficient CuO for CO oxidation before 200 °C in the hydrogen-rich reductive gasses. The traditional CuO/CeO₂ catalyst shows better activity at lower temperature and the inverse CeO₂/CuO catalysts present higher CO₂ selectivity when the CO conversion reaches 100%. The performance of mixed sample verifies that they might be complementary in the CO-PROX system.     

Analysis of the current energy storage market and energy storage economy

储能在未来电网以及可再生能源的应用中将起到至关重要的作用.它的应用范围涉及发电,传输,分配乃至终端用户.本文简要分析并总结了储能市场的经济性,重点阐述了储能应用的主要瓶颈问题----成本.通过分析与计算,确定了储能产品的目标成本,并且以历史上光伏产业规模效应的经验曲线为基础分析了能够降低储能成本的可行途径.储能应用市场将为传统能源结构带来根本性的变化,给社会经济带来巨大的福利,它的应用势在必行.但是,要实现储能的大规模应用还有诸多艰巨的任务与挑战,其中最重要的是要降低储能系统的成本,而实现这个目标需要多方面的共同努力.     

Cu(OH)2 and CuO nanotube networks from hexaoxacyclooctadecane-like posnjakite microplates: Synthesis and electrochemical hydrogen storage

Our recent progress shows that Cu(OH)₂ and CuO nanoribbon arrays exhibit notable electrochemical hydrogen storage capacities of 180 and 160 mAh/g, respectively, which also suggests that porous or tubular nanostructures can have a higher ability of hydrogen uptake. Two dimensional (2D) networks consisting of crossed Cu(OH)₂ nanotubes were prepared by a simple topotactic transformation process, including the fabrication of hexaoxacyclooctadecane-like intermediate posnjakite microplates and their subsequent chemical transformation into Cu(OH)₂ nanotube networks, which further dehydrated to produce CuO nanotube networks with partial morphological preservation. The formation of half-tube and half-ribbon structures, nanoribbons, and nanotubes during the transformation processes revealed that the deformations of corrugated posnjakite sheets to give lamellar Cu(OH)₂ with rolling into tubular structures could be responsible for the growth of Cu(OH)₂ nanotube networks from posnjakite microplates. The Cu(OH)₂ and CuO nanotube networks could electrochemically charge and discharge with higher hydrogen storage capacities of 220 and 188 mAh/g than the Cu(OH)₂ and CuO nanoribbon arrays at room temperature, respectively, which made them promising candidates for hydrogen storage, high-energy batteries and catalytic fields. Based on the rolling mechanism of layered structural materials, this simple topotactic transformation route might be extendable to the preparation of novel nanotube networks with higher capacities of hydrogen storage if appropriate precursors of numerous materials with layered structures were treated in solution.     

Industrial scale modelling of the thermochemical energy storage system based on CO2 + 2NH3 ↔ NH2COONH4 equilibrium

The thermochemical storage of energy by the system carbon dioxide, ammonia and ammonium carbamate is studied in detail. In particular, the kinetics and the thermodynamics of the reversible reaction is studied. We give two industrial models for the operation of this system. In the first, the separation of the gases NH₃ and CO₂ is achieved by compression and liquefaction of NH₃. In the second, a method of separation of the gases is proposed which is based on the solubility of NH₃ in ethanol while CO₂ is practically insoluble. The operation of this system is examined both in closed form and in the case in which CO₂ is rejected in the atmosphere, and it is taken from alcoholic fermentation or from the combustion gases of power plants burning lignite. The mass and energy balance is given, for each case, and the amount of energy losses by the use of this storage system is calculated. Finally, we give some estimates for the area of solar collectors and the amount of chemicals which are required in order to cover the energy needs of a community.     

Energy storage efficiency for the ammonia/hydrogen-nitrogen thermochemical energy transfer system

Energy storage efficiency is calculated for the solar thermochemical energy transfer system based on ammonia/hydrogen-nitrogen. the calculation for this system involves generation of thermodynamic data not available in the literature by a method in which use is made of the available phase equilibrium measurements together with application of the criterion that the correct value of separation work for a two-phase mixture must be generated internally by degradation of mixing heat. Energy storage efficiencies for ammonia/hydrogen-nitrogen are derived from the generated thermodynamic data and are shown to increase towards unity as the endothermic reaction approaches completion, with efficiencies greater than 0.90 being obtained for reaction extents exceeding 0.60. the validity of the analysis has been tested successfully by comparison between the thermodynamic predictions and experimental data in the form of measurements of the waste heat rejected from a counterflow heat exchanger operated with liquid ammonia feed and ammonia/hydrogen-nitrogen output.     

CO oxidation over the Cu2O/CuO hollow sphere heterojunction catalysts with enhanced low-temperature activities

In this work, a series of the Cu₂O/CuO hollow sphere heterojunction catalysts with various Cu⁺/Cu²⁺ ratios were designed and synthesized to improve the low-temperature catalytic activity of CO oxidation. The physicochemical properties of all the catalysts were characterized by the SEM, TGA, N₂-physisorption, XRD, FT-IR, XPS, and H₂-TPR. The results revealed that the Cu₂O hollow sphere catalyst had the large specific surface area due to the formation of the hollow structure, which could provid more accessible active sites for the gaseous reactants. Meanwhile, the Cu₂O/CuO hollow sphere heterojunction catalysts possessed high concentration of the surface oxygen vacancies and further promoted the adsorption and activation of O₂. As a result, the apparent activation energy of the CO oxidation was decreased and thus low-temperature activity of the CO oxidation was finally promoted. Therefore, the Cu₂O/CuO hollow sphere heterojunction catalysts were considered as a series of high-efficient catalyst candidates for CO oxidation with promising low-temperature performance.     

Improving the hydrogen storage performance of lithium borohydride by Ti3C2 MXene

Two-dimensional layered material of Ti₃C₂ has been used to improve the hydrogen desorption properties of LiBH₄. The results of temperature-programmed dehydrogenation (TPD) and isotherm dehydrogenation (TD) demonstrate that adding the Ti₃C₂ contributes to the hydrogen storage performance of LiBH₄. The dehydrogenation temperature decreases and the dehydrogenation rate increases with increasing the adding amounts of Ti₃C₂. The onset dehydrogenation temperature of LiBH₄ + 40 wt% Ti₃C₂ composite is 120 °C and approximately 5.37 wt% hydrogen is liberated within 1 h at 350 °C. Furthermore, the activation energy of LiBH₄ + wt.% Ti₃C₂ is also greatly reduced to 70.3 kJ/mol, much lower than that of pure LiBH₄. The remarkable dehydrogenation property of the LiBH₄+ 40 wt% Ti₃C₂ may be due to the layered active Ti-containing Ti₃C₂ and the high surface area of MXene.     

Mesoporous CuO/MgO synthesized by a homogeneous-hydrothermal method and its catalytic performance for the ethynylation reaction of formaldehyde

Mesoporous CuO/MgO catalyst was synthesized by hydrothermal homogeneous precipitation using urea as precipitating reagent. The CuO/MgO catalyst was characterized by BET-N₂, X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), transition electron microscopy (TEM), Raman spectra and thermogravimetric analysis (TG). The results indicate that CuO/MgO catalyst possesses extremely fine dispersion of Cu nanoparticles (NPs) with a high specific surface area of 232 m²/g and pore sizes of 6.5 nm. The mesoporous CuO/MgO exhibits excellent catalytic activity for the formaldehyde reaction of acetylene.     

储能电池在风光互补发电系统中的容量配置分析

储能电池是分布式发电系统的关键组件。增加储能电池的容量可以提高发电系统的可靠性,但会增加系统的投资和运行费用。基于上海地区全年8 760 h的气象数据,计算了风光互补发电系统在不同储能容量下的负荷缺电率和能量溢出率的变化。对于独立的风光互补发电系统,在满足能量溢出率小于0.3的情况下,如果系统缺电率维持在1%左右时,需要配置3天的储能容量;如果系统缺电率为0,则需要配置5天的储能容量。     

Screening of novel water/ionic liquid working fluids for absorption thermal energy storage in cooling systems

Absorption thermal energy storage (ATES) is significant for renewable/waste energy utilization in buildings. The ATES systems using ionic liquids (ILs) are explored to avoid crystallization and enhance the performance. Property model and cycle model have been established with verified accuracies. Based on the preliminary screening, seven ILs are found feasible to be ATES working fluids, while four ILs ([DMIM][DMP], [EMIM][Ac], [EMIM][DEP], and [EMIM][EtSO₄]) have been selected for detailed comparisons. The coefficient of performance (COP) and energy storage density (ESD) of the ATES using different H₂O/ILs are compared with H₂O/LiBr. Results show that the operating temperatures of LiBr are constrained by crystallization, limiting the COPs and ESDs under higher generation temperatures and lower condensation temperatures. With varying T_g, [DMIM][DMP] yields higher COPs with T_g above 100°C and [EMIM][Ac] yields comparable ESDs (67.7 vs 67.1 kWh/m³) with T_g around 120°C, as compared with LiBr. The maximum COP is 0.745 for [DMIM][DMP]. With varying T_c, [DMIM][DMP] yields higher COPs with T_c below 38°C and [EMIM][Ac] yields higher ESDs with T_c below 33°C, as compared with LiBr. The maximum ESD is 87.5 kWh/m³ for [EMIM][Ac]. With varying T_e, [DMIM][DMP] yields higher COPs with T_e above 8°C, as compared with LiBr. The maximum ESD of ILs is 104.0 kWh/m³ for [EMIM][EtSO₄]. Comparing with the volume-based ESDs, the differences between ILs and LiBr are smaller for the mass-based ESDs. This work can provide suggestions for the selection of novel working fluids for ATES for performance and reliability enhancement.     

Assessment of integration of methane-reduced ceria chemical looping CO2/H2O splitting cycle to an oxy-fired power plant

In this paper, we investigated the effect of reaction kinetics and moving bed reactors for chemical looping (CO₂/H₂O) splitting unit (CL) that produces syngas and fed back to the power plant to gain the efficiency loss due to carbon capture. The reduction reactor (RED) produces methane is partially oxidized to make syngas and reducing the non-stoichiometric ceria which is transported to oxidation reactor (OXI) where the flue gases (CO₂ and H₂O) split to produce syngas. We developed the kinetics for methane reduced ceria and CO₂/H₂O splitting in a tubular reactor for an operating temperature range of (900–1100 °C) for different methane concentration which yielded to Avrami-Erofeev (AE3) model fits well for both redox reaction with different reaction constants. A moving bed reactors system is developed representing RED and OXI reactors of CL unit with kinetics hooked to the model in Aspen Plus with FORTRAN code. The effect of thermodynamics and the kinetics of redox reaction was investigated in the proposed integrated plant. The CL unit efficiency obtained is 42.8% for kinetic-based CL unit compares to 64% for thermodynamic based CL unit. However, the maximum available efficiency of the proposed layout lowered as 50.9% for kinetic-based CL unit plant compare to than 61.5% for thermodynamic based CL unit. However, the proposed plant shows an improvement in the energy efficiency penalty from 11.3% to 3.8% after CCS.     

Analysis and design of the capacity and efficiency of a flywheel energy storage system

分析了飞轮储能系统能量、功率参数特性。飞轮储能系统单机可实现储能0.5 ～ 100 kW·h、功率2～ 3000 kW。提出了储能100 kW·h级飞轮的方案,采用中低转速合金钢飞轮转子,储能密度13～ 18 W·h/kg,计算许用应力为800 MPa。尺寸为米级的飞轮转子整体锻造难度较高,可采用多圆盘轴向联接的结构设计。采用3层或4层纤维缠绕复合材料高速飞轮转子结构,分别进行了径向等应力结构设计,计算表明9000 r/min三层纤维缠绕复合材料飞轮和15000 r/min四层纤维缠绕复合材料飞轮均能够满足工作转速下的结构强度要求,储能密度50 ～ 70 W·h/kg。     

Thermal energy storage with chemical reaction of NaINH3 system—I. Region of liquid phase

A liquid phase in the reaction of solid sodium iodide with gaseous ammonia offers a method of thermal energy storage at temperatures for air-conditioning. Although the maximum temperature where the solid ammoniate exists, is around 31°C under 2.7 kg/cm² ammonia pressure, a considerably wide range of liquid phase can be used for storage of thermal energy. In addition to that, the liquid region extends to temperatures below zero under higher pressure than atmosphere. The density of the liquid ammoniate varies depending on temperature and ammonia pressure, but the maximum value observed in the present experiments was 1.7 g/cm³.     

Thermal energy storage of phase change materials in the solidification process inside the quasi-square heat exchanger: CFD simulation

The high latent heat of phase change materials (PCMs) makes them one of the most important sources of heat energy storage systems. However, due to the slow rate of heat transfer in these materials, using conductive materials such as fins and nanoparticles could improve the thermal efficiency of these energy storage systems. So in this article, cross-shaped fins and Copper(II) oxide nanoparticles with different synthesized forms and various volume fractions have been employed to increase the thermal efficiency of paraffin PCMs. In this simulation, three fin models based on the installed size, the shape of the synthesized nanoparticles in brick, cylindrical, and platelet forms, and the nanoparticle volume fraction of the Copper(II) oxide is 1%–4% are studied. Increasing the volumetric ratio of nanoparticle and shape coefficient decrease the time of solidification, while increasing the length of the cross-shaped fins raises the solidification rate and improves heat transfer. Finally, it was found that when the inner and outer walls play a role in the solidification process at the same time, the solidification rate will increase by more than 66% as more zone of the surface is exposed to cold.     

A new approach of sizing battery energy storage system for smoothing the power fluctuations of a PV/wind hybrid system

In this paper, a new approach for optimally sizing the storage system employing the battery banks for the suppression of the output power fluctuations generated in the hybrid photovoltaic/wind hybrid energy system. At first, a novel multiple averaging technique has been used to find the smoothing power that has to be supplied by the batteries for the different levels of smoothing of output power. Then the battery energy storage system is optimally sized using particle swarm optimization according to the level of smoothing power requirement, with the constraints of maintaining the battery state of charge and keeping the energy loss within the acceptable limits. Two different case studies have been presented for different locations and different sizes of the hybrid systems in this work. The results of the simulation studies and detailed discussions are presented at the end to portrait the effectiveness of the proposed method for sizing of the battery energy storage system. Copyright © 2016 John Wiley & Sons, Ltd.     

Economic analysis of PV/diesel hybrid system with flywheel energy storage

This paper analyzes a hybrid energy system performance with photovoltaic (PV) and diesel systems as the energy sources. The hybrid energy system is equipped with flywheel to store excess energy from the PV. HOMER software was employed to study the economic and environmental benefits of the system with flywheels energy storage for Makkah, Saudi Arabia. The analysis focused on the impact of utilizing flywheel on power generation, energy cost, and net present cost for certain configurations of hybrid system. Analyses on fuel consumption and carbon emission reductions for the system configurations were also presented in this paper.