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In this work, two different types of catalysts with MgO support for aqueous phase reforming of glycerol were prepared by the sol-gel method and calcining method, respectively, and the active metals (nickel or/and cobalt) were added by the initial wet impregnation (IWI) method. It is found that the catalyst supported by gelatinous MgO presents better dispersion and the amount of hydrogen produced by the catalyst containing gelatinous MgO support is more than 1.5 times compared with other catalysts. For the Ni–Co bimetallic catalysts, the higher reaction temperature is beneficial to hydrogen yield, but decreases hydrogen selectivity. A high concentration of glycerol increases hydrogen yield and selectivity. Introducing CaO as an absorbent in aqueous phase reforming can improve WGS reaction and reduce methanation reaction through in-situ CO 2 removal and capture. The gelatinous Ni–Co/MgO catalyst presents superior activity and multi-cycle stability. [Display omitted] [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) power generation coupled with proton exchange membrane (PEM) water electrolysis favors improving the solar energy utilization and producing green hydrogen. But few systems proposed focus on achieving all-day stable hydrogen production, which is important for the future large-scale hydrogen utilization. Herein, a PV-Battery-PEM water electrolysis system for hydrogen production was constructed. An energy management strategy (EMS) was proposed to achieve the goal of all-day stable hydrogen production, improve energy utilization efficiency and reduce light discard rate. The PV power generation system, battery system and PEM electrolyzer for hydrogen production system were first established by Matlab/Simulink platform. Then, the overall PV-Battery-PEM electrolyzer system for hydrogen production was constructed, and the effectiveness of EMS was verified. The energy efficiency of the system under different working conditions with and without battery for energy storage was analyzed. The results show that the proposed energy management strategy can meet the purpose of all-day stable hydrogen production. Under the same working conditions, the energy efficiency of the system with battery for energy storage increases by 2–4% compared with the system without battery for energy storage, which indicates that the addition of energy storage can improve the energy utilization and reduce the light discarding. [Display omitted] [ABSTRACT FROM AUTHOR]

Heat storage is an important task in the use of solar energy; in particular, the use of water as the thermal storage medium is one of key technologies in solar thermal energy utilization. With the purpose of improving the thermal stratification of a heat storage tank, a novel equalizer was designed in this paper. To investigate the influence factor of thermal stratification in hot water storage tank, numerical analyses based on the three-dimensional (3D) unsteady Computational Fluid Dynamics (CFD) model were performed using the commercial software ANSYS. The initial and inlet temperatures were considered along with various flow rates. The performance parameters, such as the Richardson number, the MIX number and exergy, were involved in the evaluation. This study was further extended to explore the fill efficiency as the performance parameters of thermal stratification within a storage tank. The numerical model was validated with the experimental data; the results were determined to be in good agreement. The results demonstrate that with the growth of flow rate, the Richardson number decreases, fill efficiency and exergy increased first and later decreased, but the MIX number decreased first and later increased. When the flow rate was 3 L/min, the equalizer performs best, and the storage tank had a better thermal stratification. The RMS error increased first and subsequently decreases before increasing again with the growth of the flow rate. Furthermore, the MIX number reaches a minimum at the dimensionless time of 0.5 in the numerical results, whereas it is 0.4 in the experimental results. It was also observed that the contribution of the equalizer on the flow-suppressing of influent results in a decrease of mixing process between the hot and cold water, which could lead to improvement of the thermal stratification. [ABSTRACT FROM AUTHOR]

Semiconductors often have limited photocatalytic water-splitting performances owing to the narrow light absorption and low effective carrier density. In response to these challenges, we report the discovery of metallic amorphous cobalt boride (Co 2 B) as the first first-row transition metallic photocatalyst. It was prepared via a simple chemical reduction method and performs efficient water splitting spanning the UV, visible light and near-infrared region (NIR) via interband transitions. It achieves bifunctional water splitting activities with H 2 evolution rate of 202.3 μmol h−1 g−1 and O 2 evolution rate of 74.8 μmol h−1 g−1, superior to the existing (semi-)metallic photocatalysts. The material shows over 1 % apparent quantum efficiency (AQE) and 20 % incident photon to current conversion efficiencies (IPCE) at the NIR region >800 nm. Theoretical and photophysical experimental studies synergistically confirm that the metallic nature with high carrier concentrations and amorphous structure with abundant active sites contribute to the good water splitting performance of Co 2 B. This research sets the foundation for the utilization of highly efficient transition metal-based metallic photocatalysts in photocatalysis across the entire solar spectrum. [Display omitted] [ABSTRACT FROM AUTHOR]

Semiconductors often have limited photocatalytic water-splitting performances owing to the narrow light absorption and low effective carrier density. In response to these challenges, we report the discovery of metallic amorphous cobalt boride (Co 2 B) as the first first-row transition metallic photocatalyst. It was prepared via a simple chemical reduction method and performs efficient water splitting spanning the UV, visible light and near-infrared region (NIR) via interband transitions. It achieves bifunctional water splitting activities with H 2 evolution rate of 202.3 μmol h−1 g−1 and O 2 evolution rate of 74.8 μmol h−1 g−1, superior to the existing (semi-)metallic photocatalysts. The material shows over 1 % apparent quantum efficiency (AQE) and 20 % incident photon to current conversion efficiencies (IPCE) at the NIR region >800 nm. Theoretical and photophysical experimental studies synergistically confirm that the metallic nature with high carrier concentrations and amorphous structure with abundant active sites contribute to the good water splitting performance of Co 2 B. This research sets the foundation for the utilization of highly efficient transition metal-based metallic photocatalysts in photocatalysis across the entire solar spectrum. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel nano phase change material emulsion (NPCE) with low supercooling and high thermal conductivity was prepared by sonication method. N -octadecane was employed as phase change material, multi-walled carbon nanotubes (MWCNTs) were utilised as high thermal conductivity material, and octadecanol was utilised as nucleating agent. The characterization and thermal properties of the nanoemulsions prepared with various concentrations of MWCNTs and octadecanol were measured and analysed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle size analyser, differential scanning calorimeter (DSC) and thermal conductivity meter. The results indicated that the nanoemulsions prepared had great stability, low supercooling and enhanced thermal conductivity. The thermal conductivity was enhanced by 4.32% for 10 wt% nanoemulsion with addition of 1 wt% MWCNTs. The supercooling degree of 20 wt% nanoemulsion was decreased by 36.4% from 17.3 °C to 11.0 °C with addition of 1 wt% octadecanol. It can be concluded that the nanoemulsions prepared were able to be utilised as heat transfer and energy storage fluids, with great potential in thermal system applications. • The enhancement ratio of thermal conductivity was 4.32% for 10 wt% nanoemulsion. • The supercooling of 20 wt% nanoemulsion was decreased by 36.4% with addition of 1 wt% octadecanol. • Fabricated nanoemulsions presented good stability and thermo-physical properties. • Fabricated nanoemulsions have great potential application in the thermal systems. [ABSTRACT FROM AUTHOR]

Abstract Thermal storage technology is an important approach to improve the efficiency of solar energy utilisation. To analyse the thermal stratification in a hot water storage tank at an initial temperature of 80 °C and at an inlet temperature of 5 °C, this study thoroughly analysed the impact of the position of PCM balls on the thermal stratification for various flow rates (1, 3, 5, 7, and 9 L/min) under different position. Performance parameters, including the Richardson number, MIX number, and exergy efficiency, were involved in the evaluation. The study was further extended to explore the applicability of Fill Efficiency (FE) as a performance parameter of thermal stratification within a storage tank. The experimental results indicated that, for the same inlet flow rate, an improved thermal stratification of the tank was achieved as the positions of the balls became closer are to the inlet, and the balls with a small diameter also showed remarkable potential for improving the thermal stratification of the water tank. When the flow rate increased, the cold and hot water mixing intensified, and the thermocline thickness in the tank increased. Thus, the thermal stratification weakened. Furthermore, when the water-release process progressed, the mixing of the hot and cold water in the water tank tended to be stable, and formed a stable thermocline. Finally, when the inlet flow rate was less than 7 L/min, the thermal stratification of the water tank exceeded that of the PCM water tank, while for an inlet flow rate in excess of 7 L/min, the thermal stratification of the PCM water tanks was superior to that of the water tank in the case when the balls was on the fourth layer. Highlights • A thermal storage tank containing sodium acetate trihydrate with phase change temperatures of 48 °C and 58 °C are developed. • Impacts of the positions and diameters of PCM balls on the thermal stratification with various flow rates are analysed. • The thermal stratification performances in hot water tank are compared. • Fill efficiency is used as a measurement index to determine the performance of a thermal storage tank. [ABSTRACT FROM AUTHOR]

Abstract: A detailed comparative study on thermodynamic and experimental analyses of glycerol reforming for hydrogen production has been conducted in terms of the effects of temperature, pressure, water to glycerol feed ratio, feeding reactants to inert gas ratio and feeding gas flow rate (residence time). The thermodynamic analysis was conducted by using a non-stoichiometric methodology based on the minimisation of Gibbs free energy. And the experiments were carried out with a pilot scale set-up. The results show that the thermodynamic and experimental data agree fairly well with each other. The measured hydrogen production is slightly lower than that predicted by the thermodynamic analysis, which is mainly because the conversion of steam is incomplete. High temperature, low pressure, low feeding reactants to inert gas ratio and low gas flow rate are favourable for steam reforming of glycerol for hydrogen production. There is an optimal water to glycerol feed ratio for steam reforming of glycerol for hydrogen production which is about 9.0. The glycerol conversion is a strong function of water to glycerol ratio, whereas a weak function of other parameters over the conditions of this work. A novel adsorption enhanced reaction process incorporating water and heat recovery is proposed for further optimisation of hydrogen production from steam reforming of glycerol. [ABSTRACT FROM AUTHOR]