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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]

Review: 81 refs. [ABSTRACT FROM AUTHOR]

Biochar-assisted water electrolysis (BAWE) facilitates the high-value utilization of biomass and energy-saving hydrogen production. However, the BAWE efficiency is hindered by slow kinetics of biochar oxidation reaction (BOR) at anode. Herein, to improve the overall efficiency of BAWE, three-dimensional porous nanosheets modified on nickel foam (Ni 1 Fe 2 -LDH@NF) was developed for BOR, and its mechanism was identified. Impressively, the BAWE system exhibited remarkable activity, including a low potential of 1.387 V vs. RHE for BOR over as-synthesized electrocatalyst at current density of 10 mA·cm−2, and excellent long-term stability over 20 h at a high current density of 200 mA·cm−2 and after 1000 CV cycles. The required electricity input was 3.29 kWh·Nm−3H 2 at 10 mA·cm−2 for BAWE with Ni 1 Fe 2 -LDH@NF toward BOR. In addition, the reaction mechanism of BOR including biochar direct oxidation on the electrocatalysts surface and indirect oxidation in the electrolyte was deduced, according to the surface chemistry and composition changes of electrocatalysts and biochar, as well as the products. This work provides an effective strategy towards the enhancement of the BOR process by designing the binder-free electrocatalysts, and facilitates the development of BAWE for energy-efficient hydrogen production and biomass utilization. [Display omitted] • 3D porous Ni–Fe nanosheets modified on nickel foam was developed for enhancing BOR. • Ni 1 Fe 2 -LDH@NF favored the adsorption of OH− and accelerated the charge transfer rate. • Ni 1 Fe 2 -LDH@NF toward BOR demonstrated a potential of 1.387 V vs. RHE@10 mA·cm−2 and stability over 20 h@200 mA·cm−2. • The BOR mechanism including biochar direct oxidation on electrocatalysts and indirect oxidation in electrolyte was deduced. [ABSTRACT FROM AUTHOR]

Highly-efficient and stable non-noble metal electrocatalysts for overcoming the sluggish kinetics of oxygen evolution reaction (OER) is urgent for water electrolysis. Biomass-derived biochar has been considered as promising carbon material because of its advantages such as low-cost, renewable, simple preparation, rich structure, and easy to obtain heteroatom by in-situ doping. Herein, Ni 2 P–Fe 2 P bimetallic phosphide spherical nanocages encapsulated in N/P-doped pine needles biochar is prepared via a simple two-step pyrolysis method. Benefiting from the maximum synergistic effects of bimetallic phosphide and biochar, high conductivity of biochar encapsulation, highly exposed active sites of Ni 2 P–Fe 2 P spherical nanocages, rapid mass transfer in porous channels with large specific surface area, and the promotion in adsorption of reaction intermediates by high-level heteroatom doping, the (Ni 0.75 Fe 0.25) 2 P@NP/C demonstrates excellent OER activity with an overpotential of 250 mV and a Tafel slope of 48 mV/dec at 10 mA/cm2 in 1 M KOH. Also it exhibits a long-term durability in 10 h electrolysis and its activity even improves during the electrocatalytic process. The present work provides a favorable strategy for the inexpensive synthesis of biochar-based transition metal electrocatalysts toward OER, and improves the water electrolysis for hydrogen production. [Display omitted] • Ni 2 P–Fe 2 P spherical nanocages encapsulated in N/P-doped biochar is synthesized. • High-level heteroatom ((N + P + O): C) doping of 30.61 at% is achieved. • OER over (Ni 0.75 Fe 0.25) 2 P@NP/C demonstrates an overpotential of 250 mV@10 mA/cm2. • The synergistic effect of Ni 2 P–Fe 2 P and N/P-doped biochar promotes OER. [ABSTRACT FROM AUTHOR]

[Display omitted] • Au/Co-CC@iron ball shows superior photocatalytic activity, stability and reusability. • High property is due to synergy of active components and foliated iron ball surface. • Au/Co-CC@iron ball is used as packing material to construct packed reactor/module. • Via reactor/module, the removal of 4-NP is unprecedentedly enhanced to 2750 μmol/h. • Reactor/module has great potential in the continuous-flow degradation of 4-NP. Bulk noble metal–semiconductor composites can be chosen as photocatalysts to carry out the flow degradation of 4-nitrophenol (4-NP) whereas their preparation is complex and uncontrollable. Here, bulk Au-Co-CoO x -CeO x @iron ball (Au/Co-CC@iron ball) is designed and prepared by a facile and controllable route without any toxic chemical. The bulk Au/Co-CC@iron ball shows excellent photocatalytic activity and reusability for the 4-NP degradation, which can be ascribed to the synergistic action of active components and foliated iron ball surface. Furthermore, the highly active Au/Co-CC@iron ball is used as packing material to construct a new-type of packed reactor, by which the flow degradation of 4-NP is successfully achieved. As-fabricated packed reactor and its tandem module exhibit superior photocatalytic performance for the flow degradation of 4-NP. Noteworthy, based on the tandem module with six reactors, the removal rate of 4-NP can reach up to 2750 µmol/h. Meanwhile, the reactor and its module display satisfactory operational stability and reusability in the flow degradation of 4-NP. Clearly, the provided route is effective for the preparation of bulk noble metal–semiconductor composites with exceptional performance, which can also be a prospective strategy to obtain bulk packing materials to serve for the flow degradation. [ABSTRACT FROM AUTHOR]

• The mathematical model can accurately predict the melting heat transfer process of PCMs. • The Rayleigh number increased with the heat flux, and the higher the heat flux, the larger the amplitude. • Increasing the heat flux improved the integrated heat transfer coefficient and thermal storage performance of the CPCMs. • Conduction was the primary heat transfer mechanism; however, the proportion of natural convection increased with the heat flux. To investigate the effect of heat flux on the enhanced heat transfer in phase change materials (PCMs) composed of copper metal foam (CMF) and paraffin wax (PX), a semi-cylindrical visualized heat storage device with a varied heat flux of 7.3 kW/m2, 8.5 kW/m2, 9.7 kW/m2, and 10.9 kW/m2 was established in this paper. Moreover, a 3-D mathematical model of composite phase change materials (CPCMs) was established using hybrid grid to study the temperature distribution, imbalance effect, flow, heat transfer mechanisms, and heat storage performance during the melting process. The results showed that the melting time of the CPCMs decreased as the heat flux increased. Compared with a heat flux of 7.3 kW/m2, the melting time was shortened by 10.05 %, 20.71 %, and 27.21 %, respectively. In addition, the Rayleigh number (Ra) increased with the increase in heat flux, and the amplitudes of Ra were 1.45×108,1.54×108,1.61×108, and 1.74×108, respectively, which indicated that the higher the heat flux, the larger the amplitudes. Moreover, the heat transfer mechanism during the melting process was dominated by conduction; however, with the increase in heat flux, the maximum flow velocity of the liquid paraffin increased, which caused the proportion of natural convection to increase from 27.80 % to 31.30 %. Hence, the integrated heat transfer coefficient of CPCMs increased from 5.69 W/(m·K) to 5.81 W/(m·K). However, the temperature imbalance effect of the CPCMs was exacerbated, as evidenced by the increased maximum temperature difference in the vertical direction of the center of the CPCMs from 24.7 K to 35.6 K. Besides, the heat storage performance was enhanced. Compared with a heat flux of 7.3 kW/m2, the heat storage capacities of the CPCMs increased by 4.21%, 9.46%, and 12.66 % with increasing heat flux, and the heat storage rates of the CPCMs increased by 15.3 %, 34.9 %, and 52.3 %, respectively. Furthermore, the relative error of the overall melting time was 3.4 %, indicating that the model provided reasonable predictions. [ABSTRACT FROM AUTHOR]

• The addition of metal oxide particles greatly improves the thermal conductivity of MPCS. • MPCS with metal oxide particles can enhance heat transfer under different flow conditions. • Heating power and flow rates are crucial to the heat transfer of MPCS. • MPCS with metal oxide particles can be used as heat transfer medium and energy storage fluid. ZnO, nano ZnO and nano Al 2 O 3 were mixed with microencapsulated phase change material slurry (MPCS) for improving the heat transfer performance of slurries in this paper. The thermal and rheological properties of MPCS were measured using DSC, thermal conductivity meter and rheometer. The results show that the thermal conductivity of 5 wt% MPCS with 1 wt% ZnO, nano ZnO and nano Al 2 O 3 was 17.9 %, 19.4 % and 23.5 % higher than that of 5 wt% MPCS, respectively. The forced convection heat transfer experiment of slurries was carried out in a loop system with various heat flux and flow conditions. The influences of heat flux, flow rate and metal oxide particles on the flow and heat transfer behaviour of slurries were investigated. The results show that the heat transfer was significantly enhanced for all slurries with metal oxide particles under three flow conditions. Compared with water, the local heat transfer coefficient (h x) of MPCSs with 1 wt% ZnO, nano ZnO and nano Al 2 O 3 increased by 6.5 %, 9.1 % and 12.4 % under laminar flow, 6.6 %, 15.5 % and 14.9 % under transition flow, and 15.7 %, 19.0 % and 21.6 % in turbulent condition, respectively. [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]

[Display omitted] • Uniform submicro-sized cubes are covered on the copper wire surface by etching. • Etched copper wires are used as catalysts for the reduction of 4-nitrophenol. • Etched copper wires exhibit high catalytic activity, recyclability and stability. • Optimized etching provides a novel route to control the surface of metal materials. Up to now, the reported methods to regulate the surface morphology of metals are complicated and thus difficult to achieve. Herein, the etching method is optimized and used to change the surface morphology of copper (Cu) wire. By adjusting the amount of HCl as etching agent and the purity of Cu wire as the raw material, the Cu wire covered by uniform submicro-sized cubes (CWC) is successfully prepared and chosen as catalyst for the reduction of 4-nitrophenol. The CWC shows superior catalytic activity, recyclability and stability. Clearly, the as-provided etching method is effective for the surface morphology control of Cu wire, which can be a prospective strategy to obtain the metal materials with special surface morphology. [ABSTRACT FROM AUTHOR]

A novel sulfur–iodine (SI or IS) cycle integrated with HI–I 2 –H 2 O electrolysis for hydrogen production was developed and thermodynamically analyzed in this work. HI–I 2 –H 2 O electrolysis was used to replace the conventional concentration, distillation, and decomposition processes of HI, so as to simplify the flowsheet of SI cycle. And then the new cycle was divided into Bunsen reaction, H 2 SO 4 decomposition and HI–I 2 –H 2 O electrolysis sections. Through incorporating the user-defined module of HI–I 2 –H 2 O electrolysis with Aspen Plus, the cycle was simulated and 0.448 mol/h (10 L/h) of H 2 was produced. The overall energy and exergy efficiencies of the novel SI system were estimated to be 15.3–31.0% and 32.8%, respectively. Most exergy destruction occurred in the H 2 SO 4 decomposer and condenser for H 2 SO 4 decomposition and Bunsen reaction sections, which accounted for 93.0% and 63.4%, respectively. A high exergy efficiency of 92.4% for HI–I 2 –H 2 O electrolysis section with less exergy destruction was determined, mostly due to the transformation of the overall electricity in electrolytic cell to exergy. Appropriate internal heat exchange and waste heat recovery will favor improving the energy and exergy efficiencies. • A new SI cycle assembled with HI–I 2 –H 2 O electrolysis was thermodynamically analyzed. • Exergy destruction and exergy efficiency for each section were evaluated. • A high exergy efficiency of 92.4% for HI–I 2 –H 2 O electrolysis section was found. • The energy and exergy efficiencies of 15.3–31.0% and 32.8% were estimated for SI cycle. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrochemical activation of biochar was achieved via limited electrooxidation. • Biochar-assisted water electrolysis reduced electricity consumption for hydrogen production. • Oxygen-containing groups enriched on biochar during its electrooxidation. • Upgraded biochar by electrochemical activation enhanced its removal of Cr(VI). • Cr(VI) removal mechanism by upgraded biochar follows attraction-reduction-complexation. Biochar-assisted water electrolysis (BAWE) has the potential to reduce the electricity consumption of hydrogen production. However, prolonged electrolysis leads to over-oxidation of biochar, reduced reactivity, and decreasing hydrogen production at cathode. Herein, we proposed the electrochemical activation of biochar via limited biochar oxidation reaction (BOR) and hydrogen evolution reaction (HER) in BAWE process, and the upgraded biochar was employed to remove Cr(VI). Distinct biochar was first pyrolyzed from three kinds of representative biomass components, cellulose, lignin, and their mixture at different temperatures. All of them exhibited excellent BOR activity, especially the biochar derived by the pyrolyzed cellulose and lignin at 800 °C (MBC-800) required a potential as low as 1.319 V vs. RHE@1 mA cm−2 using Pt electrode in 1 M KOH and achieved a Faraday efficiency almost 100% for hydrogen production. BAWE presented an energy-saving electrical consumption of 4.98 kWh Nm−3 H 2 compared to the conventional water electrolysis of 5.32 kWh Nm−3 H 2. Electrochemical oxidation enriched the oxygen-containing groups on biochar surface, which significantly improved its reductivity towards Cr(VI) and complexation with Cr(III), leading to the removal rate of Cr(VI) more than doubled. Results showed the achievement of electrochemical activation of biochar by limited electrooxidation. These findings provide a new route for the high-value utilization of biochar and energy-saving electrolytic hydrogen production. [ABSTRACT FROM AUTHOR]

SO 2 -depolarized electrolysis (SDE) is the key process in the hybrid sulfur cycle for green hydrogen production, but the detailed SDE characteristics including products generation, current efficiency variation, and side reactions are unclear. Herein, a continuous SDE process was experimentally conducted and theoretically modelled. The H 2 and H 2 SO 4 production was accelerated and the current efficiency for both electrodes was improved with a proper increase in current density (50−100 mA/cm2) or temperature (293−318 K), but further increasing current density to 150 mA/cm2 or temperature to 333 K led to a negative trend because of the anode corrosion or declined SO 2 solubility. The increasing initial H 2 SO 4 concentration (10−40 wt%) facilitated the cathodic H 2 production and current efficiency, while negatively influenced the anodic SO 2 conversion. The parasitic reactions occurred at cathode consumed H 2 and resulted to the cathodic current efficiency well below 100%. A rigorous mathematical regression model correlating the production rates of H 2 and H 2 SO 4 with current density, temperature, and initial H 2 SO 4 concentration was developed, and combined with the analysis of variance, current density was suggested the biggest factor affecting products generation in SDE process. These findings demonstrate a practical avenue for efficient SO 2 conversion and H 2 production in SDE process of hybrid sulfur cycle. [Display omitted] • H 2 and H 2 SO 4 production, current efficiency, and side reactions during SDE process were characterized. • Influence of current density, temperature, and initial H 2 SO 4 concentration on SDE process were emphasized. • Rigorous mathematical regression models concerning H 2 and H 2 SO 4 production rates were developed. • Current density was the biggest influencing factor toward products generation during SDE process. [ABSTRACT FROM AUTHOR]

Three nanoscale metal oxides composed of nano TiO 2 , nano Al 2 O 3 , and nano MgO were added to the phase change microcapsule slurry for optimising the heat transfer behaviour. The thermal and rheological properties of the resulting microencapsulated phase change materials (MPCMs) and microencapsulated phase change material slurries (MPCSs) were characterized to determine the effects of added metal oxides in optimising the performance of MPCSs. The impacts of factors like metal oxides, concentrations, and flow rates on the heat transfer behaviour of MPCSs were investigated by forced convective heat transfer experiment with various working conditions. Compared to 6 wt% MPCSs, the heat transfer coefficients (h x) of 6 wt% slurries containing 1 wt% TiO 2 , 1 wt% Al 2 O 3 , and 1 wt% MgO increased by 4.0 %, 2.5 %, and 7.13 %, respectively. Nano-MgO showed the most significant heat transfer enhancement effect on MPCSs. Moreover, the heat transfer performance gradually enhanced as a function of the concentration for nano MgO. Overall, the addition of metal oxides enhanced heat transfer by increasing the thermal conductivity of the slurry, as well as improved the micro-convection effect. The proposed MPCSs are promising for applications in solar photovoltaic/thermal (PV/T) systems, chip cooling, thermal management, buildings, and automotive cooling. [Display omitted] • Forced convection heat transfer experiment were conducted with bonded triangular tubes. • Heat transfer enhancement achieved by optimising heat transfer medium and tube structure. • Metal oxide type and concentration have significant effect on heat transfer of slurries. • Nano-MgO showed the most significant heat transfer enhancement effect on slurries. [ABSTRACT FROM AUTHOR]

• A flowsheet of SI cycle considering the Bunsen reaction kinetics was developed. • A user-defined Fortran module concerning Bunsen reaction kinetics was established. • Internal heat exchange network was created using pinch point temperature difference analysis. • The theoretical thermal efficiency of SI system was obtained in the range of 14.0–57.4 %. Thermochemical sulfur-iodine (SI) cycle is one of the large-scale, clean, and efficient hydrogen production routes. The Bunsen reaction process is always simulated by a stoichiometric reaction, without considering the realistic Bunsen reaction kinetic process. Herein, a user-defined Fortran module concerning Bunsen reaction kinetics was developed and embedded into a continuous stirred tank reactor (RCSTR), and then a SI flowsheet with 100 L/h hydrogen production was modeled. The key parameter optimization, mass and energy balance were analyzed, the internal heat exchange network was created using the pinch point temperature difference analysis and the principle of energy cascade utilization, along with thermal efficiency evaluation. Bunsen reaction process reaches equilibrium after a period, which is consistent with experiments. The increase of H 2 SO 4 decomposition ratio is beneficial to reduce the energy consumption of system. Increase in temperature has less effect on increasing the equilibrium decomposition ratio of HI. The theoretical thermal efficiency of system reaches 14.0–57.4 % considering the recovery of exothermic heat. This work provides a theoretical basis for the optimization of SI cycle. [ABSTRACT FROM AUTHOR]

• Condensation heat transfer and pressure drop were investigated experimentally with R410A and R32 in four different tubes. • The surface structures inside tubes were smooth, hydrophobic, herringbone and hydrophobic/herringbone, respectively. • The performance enhancement factor and specific sensitivity factor were used to evaluate the influence of overall heat transfer performance. An experimental investigation was performed to evaluate the condensation heat transfer characteristics for R32 and R410A inside four horizontal round tubes with 12.7 mm outer diameter. The saturation temperatures were 35 °C and 45 °C, the vapor qualities ranged from 0.2 to 0.8, and the mass flux ranged from 50 kg m−2 s−1 to 200 kg m−2 s−1. Different inside surface structures of the four tubes were smooth (ST), hydrophobic (HYD), herringbone (HB) and hydrophobic/herringbone (HYD/HB), respectively. Effects of mass flux, vapor quality, refrigerant and saturation temperature on condensation heat transfer in different tubes were discussed with the aid of flow pattern visualizations. Experimental results show that the heat transfer coefficient of R32 was higher than that of R410A due to different physical properties of the refrigerant. HB tube had the highest heat transfer coefficient at low vapor quality and HYD tube was the best at high vapor quality. The performance enhancement factors (PEF) of HB tube and HYD tube were better, ranging from 1.07 to 1.4 and from 1.02 to 1.31, respectively. However, as the composite of HB and HYD, the HYD/HB tube had the lowest overall performance, with the PEF ranged from 0.94 to 1.12. Additionally, the specific sensitivity factor (SSF) was used to evaluate the influence of various parameters on heat transfer and pressure drop. [ABSTRACT FROM AUTHOR]

Carbon-based fuel electrochemical reforming is considered as a promising hydrogen production method. Ethanol is one of the most appropriate carbon-based fuels. In this work, anode performance, especially the flow, ethanol electro-oxidization and energy consumption in the ethanol electrochemical reforming is numerically studied and experimental verified. Take the straight serpentine channel with square cross-section as a base structure in the electrochemical cell (EC), the effects of channel geometry and operating parameters are analyzed. Another five different configurations of flow channels, as well as another three different cross-sections are designed and explored. Results indicate that at the same cross-section area, the wider channel provides the higher effective area for proton transfer, and thereby improves the electrode reactions. The appropriate decrease of inlet velocity or increase of input voltage promotes the anode reaction and reduces the pressure drop in channel, while the operating temperature has the opposite effects on ethanol conversion and pressure drop. The arc channel is found optimal considering its highest ethanol conversion, although its pressure drop is a bit higher. The sector cross-section with uniform flow field distribution is found most favorable for the straight serpentine channel considering the ethanol electro-oxidization. These findings will favor the improvement of EC. • 3-D mathematical model for ethanol electrochemical reforming was developed. • Flow, ethanol electro-oxidization and energy consumption at anode were studied. • Effects of flow channels and operating parameters were characterized. • The favorable channel configuration and cross-section were proposed. [ABSTRACT FROM AUTHOR]

A green, rapid and controllable synthesis of gold nanoparticles (Au NPs) was achieved using the mulberry fruit (MF) extract as reducing and capping agent at room temperature. Obtained Au NPs were characterized by ultraviolet–visible spectrum, transmission electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, selected area electron diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analyses. It could be found that Au NPs had a small size of 4.2–20.1 nm, face-centered cubic crystalline structure and homogeneous dispersion, indicating strong reducing and capping capacities of the MF extract. Meanwhile, the morphology (quasi-sphere/sphere) of Au NPs could be controlled only by adjusting the MF extract concentration. Furthermore, based on the 4-nitrophenol (4-NP) reduction reaction, as-prepared Au NPs exhibited excellent photocatalytic activity and stability in 30 days. Under sunlight irradiation, 4-NP could be completely reduced in 4 min and its rate constant could reach up to 0.91 min−1. And the rate constant could be linearly adjusted by the MF extract concentration or the amount of Au NPs hydrosol. In addition, it could also be found that the light source with short wavelength could obviously elevate the photocatalytic activity of Au NPs, attributed to the hot-electron effect. Clearly, as-obtained Au NPs can have great potential applications in wastewater treatment. [ABSTRACT FROM AUTHOR]

Summary: To improve the sulfur‐iodine (SI or IS) cycle for renewable hydrogen production, direct electrolysis of HIx solution (HI‐I2‐H2O) from Bunsen reaction has been recently proposed. This work concerns the detailed microscopic physical performance and electrolytic processes of HIx electrolysis through theoretical simulation and experimental exploration. A two‐dimensional mathematical model of the electrolytic cell for HIx electrolysis was developed, and was verified by the relevance between the simulated and experimental hydrogen production. The concentration, electric and flow field distributions were characterized. The decrease of anodic HI and increase of cathodic H2 were found along the flow direction. The local potential distribution declined from anode to cathode region. Higher pressure drop from the inlet to outlet of channel as well as the pumping power were required for anolyte than catholyte. More detailed electrolytic processes along the flow channel at different operating conditions were analyzed. Increasing temperature from 303 K to 343 K improved the H2 production rate. A low anode flow rate of 0.2 m/s was favorable for achieving high conversion rate of reactants and low consumed pumping power. The developed models and the clarified characteristics of HIx electrolysis will be further applied to the improved SI cycle. [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]

The sulfur–iodine (SI or IS) thermochemical cycle assembled with solar or nuclear energy has been proposed as a large-scale, clean and renewable hydrogen production method. In present work, an improved SI cycle integrated with HI electrolysis for hydrogen production was developed according to experiments and simulation. The mathematical models of HI electrolysis using proton exchange membrane (PEM) electrolytic cell was developed, and then the user-defined module of HI electrolysis was set up through Aspen Plus and verified by experimental data. After designing and simulating the new flowsheet of the SI cycle based on HI electrolysis, 10 L/h of H 2 and 5 L/h of O 2 were obtained. The theoretic thermal efficiency of flowsheet reached 25–42% in terms of the utilization of waste heat. An ideal thermal efficiency of 33.3% through the proper internal heat exchange in the flowsheet was determined. Sensitivity analyses of parameters in the system were conducted. Increasing proton transfer number of PEM electrolytic cell in HI section improved the thermal efficiency of SI cycle. The ratio of distillate to feed rate and the plate number of distillation column in H 2 SO 4 section were the most sensitive factors to the heat duty of overall SI cycle. The proposed new flowsheet for SI cycle is competitive to the flowsheets previously proposed in the field of flowsheet simplification. • An improved flowsheet of SI cycle based on HI electrolysis was designed. • Mathematical models for HI electrolysis were developed. • User-defined module of HI electrolysis was set up and experimentally verified. • The theoretic thermal efficiency of 25–42% was estimated for the flowsheet. [ABSTRACT FROM AUTHOR]

Transition from bulk surfactant solution to gelatinous surfactant dry solution and the behavior of the methane uptake in GDS droplets during the repeated hydrate formation. • GDS droplets have the merits of the dry water, the surfactant solution and the gelling agent. • The droplets can provide abundant gas channels, considerable gas–liquid contact area and stable gel-like structure. • The droplets facilitate rapid and reversible methane storage in clathrate hydrate. • The droplets maintained relatively high methane storage capacities until the ninth cycle. A gelatinous dry solution (GDS) was prepared by blending sodium dodecyl sulfate solution, gellan gum powder, and hydrophobic silica nanoparticles in air at a high speed. It is essentially a pile of free-flowing micro surfactant droplets supported by a gelling agent. The GDS has the dispersion characteristics of dry water, activity of the surfactant solution and stability of the gel. The flour-like droplets can provide abundant micro channels for gas transfer, a considerable surface area for gas–liquid contact and stable gel-like structure for repeated hydrate formation. Multi-cycle methane consumption experiments were conducted in a stainless steel vessel at 5.0–8.1 MPa and 273.2 K, in order to study the repeated kinetics of methane hydrate formation in GDS. The results demonstrated that the dispersed GDS facilitated rapid and reversible methane storage in clathrate hydrate by enhancing the gas–liquid contact and the stability of the regular droplets. Methane uptake (152.2–163.2 m3·m−3) and maximum uptake rates (4.522–5.690 m3·m−3·min−1) were achieved in the first storage cycle at the experimental pressures. GDS maintained relatively high methane storage capacities (114.3–118.0 m3·m−3) until the ninth cycle, and the capacities only were attenuated by 24.92–27.70% with respect to the first cycle at the above pressures. A hypothesis of "droplets breakage by released gas" was proposed to illustrate the attenuation of gas storage capacity of the droplets. [ABSTRACT FROM AUTHOR]

Hydrogen production from the sulfur–iodine water splitting cycle integrated with solar or nuclear energy has been proposed as a promising technique. Bunsen reaction is one of the three main steps in the cycle and electrochemical method has been applied to this reaction. In present work, a three-dimensional numerical study of the electrochemical Bunsen reaction was conducted. A three-dimensional, steady state, laminar and isothermal mathematical model of electrolytic cell was developed and verified by experiments. The spatial maldistribution of species concentration was found between electrodes and proton exchange membrane (PEM). The electric power drives most H 2 SO 4 and I 2 to the anode and cathode surface, respectively, while the proton attraction contributes to HI enrichment on the surface of PEM. At the high inlet H 2 SO 4 concentration of 50 wt%, the transformation of flow channel from single serpentine to single entry & double serpentine with the same inlet flow rate cannot solve the insufficient problem of SO 2. But the increase of the overall inlet flow rate in the double entry & double serpentine flow channel make SO 2 sufficient for anode reaction. Further decreasing the inlet H 2 SO 4 concentration to 40 wt% and 30 wt% make the initial SO 2 sufficient for overall reactions. The single serpentine channel gives the highest SO 2 conversion rate, followed by the single entry & double serpentine and double entry & double serpentine flow channels. The single serpentine flow channel at the H 2 SO 4 inlet concentration of 40 wt% is found optimal for achieving a high electrochemical Bunsen reaction performance. • Three-dimensional study of electrochemical Bunsen reaction was first conducted. • A 3-D, steady state, laminar and isothermal model of EC was developed. • Transformation of flow channel and key initial conditions were analyzed. • Single serpentine flow channel at inlet H 2 SO 4 of 40 wt% was optimal. [ABSTRACT FROM AUTHOR]

In this study, a critical comparison between two low metal (Ni) loading catalysts is presented, namely Ni/Al2O3 and Ni/AlCeO3 for the glycerol steam reforming (GSR) reaction. The surface and bulk properties of the catalysts were evaluated using a plethora of techniques, such as N2 adsorption/desorption, Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP–AES), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy / Energy Dispersive X-Ray Spectroscopy (SEM/EDX, Transmission Electron Microscopy (TEM), CO2 and NH3– Temperature Programmed Desorption (TPD), and Temperature Programmed Reduction (H2–TPR). Carbon deposited on the catalyst's surfaces was probed using Temperature Programmed Oxidation (TPO), SEM, and TEM. It is demonstrated that Ce-modification of Al2O3 induces an increase of the surface basicity and Ni dispersion. These features lead to a higher conversion of glycerol to gaseous products (60% to 80%), particularly H2 and CO2, enhancement of WGS reaction, and a higher resistance to coke deposition. Allyl alcohol was found to be the main liquid product for the Ni/AlCeO3 catalyst, the production of which ceases over 700 °C. It is also highly significant that the Ni/AlCeO3 catalyst demonstrated stable values for H2 yield (2.9–2.3) and selectivity (89–81%), in addition to CO2 (75–67%) and CO (23–29%) selectivity during a (20 h) long time-on-stream study. Following the reaction, SEM/EDX and TEM analysis showed heavy coke deposition over the Ni/Al2O3 catalyst, whereas for the Ni/AlCeO3 catalyst TPO studies showed the formation of more defective coke, the latter being more easily oxidized. [ABSTRACT FROM AUTHOR]

Algae species like Schizochytrium sp. are resilient photosynthetic factories that produce large quantities of fatty acids that can be converted to biodiesel. These lipids must be extracted from the raw biomass before they can be used as biofuel feedstocks or other bioproducts such as hydrogen. In this paper, hydrogen production by steam reforming of schizochytrium algae oil are studied. The effects of continuous microwave and intermittent microwave, freezing and thawing times of different mass fractions, time of alkali heat and other factors on the ratio of cell disruption and ultrasonic-assisted ethanol extraction are considered. The results show that the highest lipid yield can reach by ultrasonic-assisted ethanol extraction from the schizochytrium algae which are pretreated by alkali heat method. The hydrogen production from steam reforming of the lipids, which are extracted by ethanol with ultrasonic-assisted from algae after alkali thermal pretreated is proposed. • Hydrogen produced by steam reforming of Schizochytrium algae oil. • Algae oil extracted by ethanol with ultrasonic-assisted from pretreated algae. • Algae pretreated by potassium hydroxide at 60 °C. [ABSTRACT FROM AUTHOR]

Molybdenum phosphide (MoP) was firstly used as a catalyst for partial oxidation of methane (POM) and its catalytic performance for POM was compared with that for dry reforming of methane (DRM). It was found that the MoP phase was the dominant active site in POM and DRM reactions, and the activity would gradually decrease when more and more MoP was converted to Mo 2 C phase (non-dominant active site) and then rapid deactivation would occur due to bulk oxidation of catalyst. The redox type mechanism over MoP catalyst was vitally important to keep its structure reasonably well during methane reforming reactions. The MoP catalyst revealed a higher catalytic stability in POM than in DRM, attributing to the higher H 2 yield obtained in POM, which can promote and maintain the redox cycle of catalyst. • The MoP phase was the dominant active site in methane reforming reactions. • The MoP catalyst revealed a higher catalytic stability in CH 4 -O 2 than in CH 4 -CO 2. • The higher H 2 yield obtained in methane reforming reactions can promote and maintain the redox cycle of MoP. [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]

Highlights • Effect of the positions of the PCMs on thermal stratification at various flow rates was analysed. • Higher flow rate resulted in an earlier inflection point time. • Lower position of the PCMs resulted in better thermal stratification in the water tank. • Fill efficiency was used as a measurement index to assess the performance of the thermal storage tank. Abstract Thermal storage technology with phase-change materials (PCMs) is an important approach for improving solar energy utilisation efficiency. In this study, for analysing the stratification of a thermal tank with PCMs at an initial water temperature of 353.15 K and inlet water temperature of 278.15 K, a thermal storage tank containing sodium acetate trihydrate with a phase change temperature of 325.15 K and super-cooling temperature below 278.15 K was developed. This study thoroughly investigated the effect of the positions of the PCMs on thermal stratification characteristics at various flow rates (0.06, 0.18, 0.3, 0.42, and 0.54 m3/h) and with increasing dimensionless time. This study further examined the fill efficiency, which was compared with the exergy efficiency, MIX number, and Richardson number to characterise the stratification of the thermal tank. The experimental results demonstrated that when the temperature of the water storage tank increased from 278.15 K to 353.15 K, the energies of the water tank and PCM tank were 18.81 and 19.34 MJ, respectively. At the same inlet flow rate, increasing the PCMs close to the inlet resulted in improved thermal stratification of the tank. With high flow rates, the cold–hot water mixing intensified and the thermocline thickness in the tank increased, thereby weakening the thermal stratification. Moreover, as the water-release process progressed, the cold–hot water mixing in the water tank tended to be stable, thereby forming a stable thermocline. The thermal stratification of the ordinary tank was superior to that of the PCM tank. However, as the PCMs were located at the bottom of the water tank, the thermal stratification was optimal when the inlet flow rate was higher than 0.42 m3/h. [ABSTRACT FROM AUTHOR]

A visual experimental system was built to explore the effect of low-pore-density copper metal foam (CMF) on the heat transfer during paraffin wax (PX) melting, and the effective thermal conductivities of composite phase change materials (PCMs) were obtained. A three-dimensional mathematical heat transfer model was established, the microstructure of the CMF was characterized using a high-definition camera, and a physical model of the CMF ball was determined. The melting heat transfer mechanism of the composite PCMs was investigated through the experimental and simulation results, including the temperature distribution, velocity vector, solid-liquid interface, volume fraction, heat transfer mechanism, and heat storage performance. The results show that as the CMF filling ratio increased from 0% to 2.13%, the temperature gradients of the composite PCMs were 86.1, 74.6, 29.2, and 12.6 K, indicating that the filling of CMF effectively alleviates the thermal stratification phenomenon during PX melting. Incorporation of the CMF increased the thermal conductivity of the composite PCMs, but suppressed their natural convection. When the CMF filling ratio was less than 1.28%, natural convection dominated the heat transfer type during PX melting; meanwhile, when the CMF filling ratio was greater than 1.28%, heat conduction was the major heat transfer mechanism. The composite PCMs exhibited great heat storage performance when the CMF filling ratio was 1.68%, and the heat storage rate was 13.25% higher than that of pure PX with the same heat storage capacity. In addition, a theoretical calculation model for predicting the heat transfer mechanism of the composite PCMs was established, and the results show that as the CMF filling ratio increased from 0.43% to 2.15%, the natural convection proportion of heat transfer performance decreased from 82.74% to 13.99% during the melting process. • The mathematical model can well predict the melting heat transfer process of PCMs. • The filling of CMF leads the paraffin temperature distribution more uniform. • Natural convection is dominated as the CMF filling ratio is less than 1.28%. • The composite PCM has better heat storage performance as CMF filling rate is 1.68%. [ABSTRACT FROM AUTHOR]

To explore the effect of metal foam(MF)pore density on the melting and heat transfer of phase-change materials(PCMs), a semi-cylindrical visualization experimental setup was established to experimentally study copper MFs with different pore densities coupled with paraffin wax. The results showed that as pore density increases, the melting time of the composite PCMs decreases compared to that of pure paraffin wax by 11.5%, 16.2% and 18.1% for pore densities of 5, 20, and 30 PPI, respectively. Composite PCMs with a pore density of 30 PPI exhibited fastest melting and lowest maximum temperature difference during melting. Considering the relative thermal energy storage(TES) capacity and relative TES rate, composite PCMs with a pore density of 30 PPI exhibited optimal overall thermal storage performance. Furthermore, heat conduction was the primary means of thermal transmission during the melting of the bottom paraffin. However, the melting of the upper paraffin was nevertheless influenced by natural convection, Hence, as pore size decreased, the influence on the weakening of natural convection became more significant. The results of the study provide guidance for the optimal design of latent heat storage devices for semi-cylinders. • The metal foam's pores are smaller the more effectively it transfers heat. • The copper foam with a 30 PPI pore density exhibited the best thermal storage performance. • The natural convection effect was less noticeable as pore size decreased. • The rate of heat storage increased as pore density continued to rise. [ABSTRACT FROM AUTHOR]

[Display omitted] • Correlation between biochar oxidation reaction (BOR) and electrolytes was determined. • Alkaline electrolyte was more favorable for biochar-assisted water electrolysis. • The higher concentration of H 2 SO 4 and S O 4 2 - slowed down the BOR kinetics. • The highest diffusion coefficient of 3.11 × 10−3 cm2∙s−1 for biochar was obtained at pH of 13.98. Biochar-assisted water electrolysis (BAWE) for hydrogen production is employed to reduce energy consumption by replacing the oxygen evolution reaction (OER) with thermodynamically more favorable biochar oxidation reaction (BOR). Electrolyte, as a carrier to dissolve the biochar particles and form conductive solution, is essential for the transfer and transformation of biochar particles and free radical precursors. Herein, the effects of electrolyte type, concentration, and pH on the BOR performance of BAWE system were investigated. Results show that 1 M KOH solution as an electrolyte was more suitable for the BAWE system, and the BOR of the alkaline BAWE system had the higher electrochemical activity (E 10 = 1.649 V vs RHE, 56 mV∙dec−1) compared with the OER in conventional water electrolysis system (E 10 = 1.982 V vs RHE, 189 mV∙dec−1). The anion adsorption phenomenon appeared in acidic media restricted the BOR kinetics. In addition, the diffusion coefficient of anodic reaction components showed a first decrease and then increase trend when the pH increased. And the diffusion coefficient reached the maximum value of 3.11 × 10−3 cm2∙s−1 at pH of 13.98, which was favorable for accelerating the diffusion of reaction components from the bulk solution to the electrode surface. This work can provide guidance for further improving the diffusion of reaction components, the biochar oxidation rate and hydrogen production in BAWE process. [ABSTRACT FROM AUTHOR]

The research describes the synthesis of nanocomposite Ni@ZrO 2 oxygen carriers (OCs) and lanthanide doping effect on maintaining the platelet-structure of the nanocomposite OCs. The prepared OCs were tested in chemical looping reforming of glycerol (CLR) process and sorption enhanced chemical looping reforming of glycerol (SE-CLR) process. A series of characterization techniques including N 2 adsorption-desorption, X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), high resolution transmission electron microscopy (HRTEM), H 2 temperature-programmed reduction (H 2 -TPR), H 2 pulse chemisorption and O 2 temperature-programmed desorption (O 2 -TPD) were used to investigate the physical properties of the fresh and used OCs. The results show that the platelet-stack structure of nanocomposite OCs could significantly improve the metal support interaction (MSI), thus enhancing the sintering resistance. The effect of lanthanide promotion on maintaining this platelet-stack structure increased with the lanthanide radius, namely, La 3+ > Ce 3+ > Pr 3+ > Yb 3+ . Additionally, the oxygen mobility was also enhanced because of the coordination of oxygen transfer channel size by doping small radius lanthanide ions. The CeNi@ZrO 2 showed a moderate ‘dead time’ of 220 s, a high H 2 selectivity of 94% and a nearly complete glycerol conversion throughout a 50-cycle CLR test. In a 50-cycle SE-CLR stability test, the CeNi@ZrO 2 CaO showed high H 2 purity of 96.3%, and an average CaCO 3 decomposition percentage of 53% without external heating was achieved. [ABSTRACT FROM AUTHOR]

This paper describes the synthesis of a series of x CeNi-PSNT (phyllosilicate nanotube) oxygen carriers (OCs) and presents the effect of Ce loading on the performance in chemical looping reforming (CLR) of glycerol. Various characterization techniques including N 2 adsorption-desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), H 2 temperature-programmed reduction (TPR), X-ray photoelectron spectra (XPS) and O 2 volumetric chemisorption were employed to investigate the physicochemical properties of the fresh and used OCs. The characterization results demonstrated that the PSNT structure possessed strong confinement effect and that the Ce promotion improved Ni dispersion and the reducibility of NiO particle and isolated Ni ions. The enhanced reducibility significantly shortened the dead time in the fuel feed step, resulting in the high H 2 generation efficiency. The reactivity and stability tests were conducted in a fixed-bed reactor. A Ce/Ni mass ratio of 0.5 was optimized for CLR with an average H 2 yield of 12.5 wt%, an average NiO conversion of 67%, and an accumulated coke deposition of 3.8 wt% in a 10-cycle stability test. The confinement effect of PSNT and Ce promotion both have positive effects on attaining the excellent performance. [ABSTRACT FROM AUTHOR]

Chemical looping reforming (CLR) of ethanol is a novel method to produce hydrogen. It’s vital to select an appropriate oxygen carrier (OC) with favorable catalytic activity and high stability for successive redox processes. In current research, the intelligent perovskites La 2- x M x NiO 4- λ ( M = Ca, Sr and Ce) were used as OCs and prepared by co-precipitation method. The ‘intelligence’ was embodied in exceptional self-recovery ability of perovskite during oxidation stage of CLR process, which was confirmed by the movement that Ni ions escaped and regained back to original position during oxidation step. The experimental result indicated that the movement effectively restrained the growth of metallic Ni and resulted in high activity of OC during life-time service and aging. Furthermore, the influence of promoters doping on the regeneration characteristics of OCs was investigated by BET, TEM, XRD, ICP-OES, TG and a fixed-bed experiment. From the perspective of catalytic performance, the addition of promoter strongly improved the reducibility of OCs, and the optimal substitution is Ca. The LNO-Ca OC exhibited favorable reducibility of nickel ions, shorter ‘dead time’, higher yield of hydrogen, superior ethanol conversion, stronger anti-carbon ability and excellent reproducibility of perovskite during successive redox reactions. [ABSTRACT FROM AUTHOR]

The compressed air storage connects charging and discharging process and plays a significant role on performance of Adiabatic Compressed Air Energy Storage (A-CAES) system. In this paper, a thermodynamic model of A-CAES system was developed in Matlab Simulink software, and a dynamic compressed air storage model was applied in the simulation, revealing the influence of time-varying temperature and pressure of air on performance indicators, e.g., roundtrip efficiency and energy density. The analysis results can be used as an explanation of the contradicting conclusions on system efficiency from other articles, as well as a reference in the design and operation of an A-CAES plant. There exists an optimal after-throttle-valve pressure when applying energy density as objective function with constant expander inlet pressure. A relatively higher heat transfer coefficient between atmosphere and air in storage tank results in more stored air in charging process and more released air in discharging process, which are of great benefit for A-CAES system in terms of energy density. The dynamic performance characteristic of compressed air storage can affect design capacity of first heat exchanger of expansion train and moreover, reduce roundtrip efficiency and energy density of A-CAES system. [ABSTRACT FROM AUTHOR]

• The condensation heat transfer characteristics of R410A on the outside of three enhanced tubes were experimentally investigated. • Effect of surface structure, mass flux, average vapor quality, and saturation temperature on HTC and frictional pressure drop. • The six correlations are evaluated and the correlation with the highest accuracy is selected and modified to obtain a predictive correlation suitable for the enhanced tubes. Condensation heat transfer characteristics on the outer annular walls of double-sided horizontal tubes having three different enhancement geometries are investigated experimentally. The enhancement geometries are (1) a fine fin array, (2) a rectangular convex platform array, and (3) a T-shaped column array. The inner surface geometries are threads of various pitches. The experiments are with various mass fluxes, average vapor qualities, and saturation temperatures. They were conducted with refrigerant R410A. The results show the effects of enhancement geometry. Six correlations are used to predict the heat transfer coefficients of smooth tube, and the correlation with the highest accuracy is selected and corrected to obtain a new correlation suitable for the enhanced tubes. The new correlation can predict 92% of the data points within a prediction error of +22% to -30%. Frictional pressure drops are correlated with mass flux, average vapor quality, and saturation temperature. The heat transfer performances of the three experimental tubes are compared using a performance evaluation factor and the enhancement geometries with better condensation heat transfer performances are identified. [ABSTRACT FROM AUTHOR]

This work studied an intelligent perovskite of La 2 − x Sr x NiO 4 − λ as oxygen carrier (OC) to produce hydrogen in chemical looping reforming (CLR) process. It was prepared by co-precipitation method and investigated by XRD, TEM, ICP-OES, H 2 -TPR, TGA technologies and fixed-bed experiment. The ‘intelligence’ refers to the self-regeneration ability and structural flexibility of perovskite. The former was verified by the movement that Ni ions repeatedly immerse into and out of perovskite bulk during CLR process. The movement suppressed the growth of Ni particles and maintained its high dispersion. The latter was confirmed by the addition of promoters. The insertion of Sr increased lattice oxygen mobility and greatly strengthened the reversible evolution of metallic Ni, which boosted the carbon-resistance and hold favorable stability of OC. The La 1.4 Sr 0.6 NiO 4 − λ was the optimized composition owing to the superior activity, higher hydrogen selectivity (87%) and admirable stability. Moreover, shortened ‘dead time’ and more ideal self-regeneration property of perovskite were attained due to easier reducibility of Ni ions. [ABSTRACT FROM AUTHOR]

• Electric vehicle driving conditions and component working modes are identified. • An assessment method for thermal management system adaptability is proposed. • Experiments verify the system performance and the evaluation method's feasibility. • An integrated thermal management system with waste heat recovery and utilization is designed. • The waste heat utilization vapor compression heat pump system improves mileage effectively. Concerns about the driving ranges of electric vehicles (EV) have led to higher requirements for vehicle thermal management systems. Efficient thermal management systems should be closely integrated with the vehicle to ensure passenger comfort and maintain adequate component operating ranges. The thermal management functions should thus accurately meet the demands of the EV and its components. Based on the driving conditions for EVs and the component thermal management requirements, this study applies different working modes for the cabin, power battery, electric motor, and electric motor controller systems under various conditions, which combines these modes into 27 feasible system working modes. Subsequently, an integrated thermal management system is designed with multi-modes adjusted by each system component to adapt environmental variations by changing the system's working mode. Also, the energy exchange between components under different modes was investigated to ensure the rationality of the designed system. The best working mode is to ensure the safety and comfort for EVs with fewer components and lower cost. It was proved to meet a wide range of adaptations to environmental changes that can be used as a method to evaluate the integrated thermal management system. The method is then applied to the target thermal management system and proves that the target system offers considerable advantages over two other benchmark thermal management systems that have been used in the mass production of electric vehicles. Finally, the cooling, heating, and defrosting performances are verified experimentally, and the vehicle mileage is calculated. The thermal management system working modes are summarized systematically. The designed thermal management system is a waste heat recovery steam compression heat pump system that can meet the functional and experimental test requirements. This study verifies that the heat management system evaluation method can evaluate the system's applicability effectively and that the waste heat utilization vapor compression heat pump system can effectively improve electric vehicle driving mileage, which manifests the potential for mass production for electric vehicle applications. [ABSTRACT FROM AUTHOR]

Dewatering of sewage sludge (SS) was the prerequisite for saving its drying energy and sustaining its stable combustion. Hydrothermal treatment (HT) has been a promising technology for improving SS dewaterability with high energy efficiency. However, the knowledge of phosphorus (P) transformation and heavy metals (HMs) behaviors in the combined HT and incineration process was still lack. P fractions, P-bioavailability, HMs speciation, and their environmental risk in the ash samples from this combination process were evaluated and compared with those from the co-incineration of SS and CaO. The combination process was superior to the latter one in the light of P and HMs. CaO preferred to enhance the transformation of non-apatite inorganic phosphorus (NAIP) to apatite phosphorus (AP) initially with enriched P and increased P-bioavailability in the resultant ash samples. The combination process further reduced the values of risk assessment code and individual contamination factor with the increment of the stable F4 fraction in HMs. Significant reduction of potential ecological risk was observed with the lowest global risk index of 43.76 in the combination process. Optimum CaO addition of 6% was proposed in terms of P and HMs. The work here can provide theoretical references for the potential utilization of P from SS to mitigate the foreseeable shortage of P rocks. [Display omitted] • Hydrothermal treatment combined with incineration of sewage sludge was studied. • P enrichment and bioavailability in ash were enhanced by combination process. • Reduced mobility and ecological risk of heavy metals were observed in ash. • Combination process was superior to co-incineration of sewage sludge and CaO. • CaO preferred to enhance the transformation of NAIP to AP in combination process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Photocatalyst (ACW) for 4-NP reduction is facilely synthesized via in-situ redox. • In ACW, Au and Cu NPs are loaded on Cu wire surface with submicro-sized Cu cubes. • ACW has a large specific surface area and a high loading density of Au and Cu NPs. • ACW exhibits superior photocatalytic activity, reusability and stability. • In-situ redox provides a novel route to prepare metal NPs-supported bulk catalysts. Based on a normal copper wire, an effective photocatalyst (ACW) for the 4-nitrophenol (4-NP) reduction is successfully synthesized by an in-situ redox method. The constitution of ACW is similar to "ants on a tree", i.e., dense Au and Cu nanoparticles (NPs) are loaded on the copper wire surface covered by submicro-sized Cu cubes. Employing ACW as photocatalyst, the conversion efficiency of 4-NP can achieve to 100% at 2.5 min and the rate constant for the 4-NP reduction can reach up to 1.45 min−1. Moreover, ACW exhibits satisfactory reusability for 25 cycles and stability in 12 months. These excellent performance can be attributed to the synergistic effect of Au NPs, Cu NPs and the Cu wire surface covered with submicro-sized cubes. Clearly, the above in-situ redox method provides a facile route to prepare metal NPs-supported bulk photocatalysts. Meanwhile, as-synthesized ACW can be a promising photocatalyst candidate for the practical treatment of 4-NP. [ABSTRACT FROM AUTHOR]

• A greater proportion of copper metal foam (CMF) can enhance the heat transfer of paraffin wax and reduce the temperature gradient. • A theoretical model was built to calculate the comprehensive heat transfer coefficient of composite PCMs and to determine the intensity change of heat conduction and natural convection of PCMs with different CMF proportions. • Melting time and heat storage capacity of CMF composite PCMs first increased and then decreased with increasing CMF proportion. • Heat storage rate and comprehensive heat transfer coefficient first decreased and then increased with increasing CMF proportion. • Composite PCMs with a CMF proportion of 0.86% exhibit the best heat storage performance. Phase-change materials (PCMs) can overcome the low energy density and utilization efficiency of solar energy. However, the low thermal conductivity of PCMs significantly affects the thermal efficiency of solar devices; thus, improving the thermal conductivity of PCMs has been the focus of many recent studies. In this study, copper metal foam (CMF) composite PCMs were prepared using paraffin wax and high-pore-density CMF. The effect of the CMF proportion on heat transfer enhancement in the PCM melting process was analyzed using experimental equipment for heat storage visualization. Comprehensive heat transfer coefficients of CMF composite PCMs were obtained. The experimental results showed that as the CMF proportion increased from 0 to 2.15%, the melting time of the CMF composite PCMs and their heat storage capacity first increased and then decreased, whereas the heat storage rate and comprehensive heat transfer coefficient first decreased and then increased. The minimum temperature gradient of 8.09 K was reached when the CMF proportion was 2.15%. More importantly, as the proportion of CMF increased from 0.43 to 2.15%, the proportion of natural convection decreased from 87.90 to 17.69%, and natural convection was the major heat transfer mechanism in the melting process of composite PCMs with a low CMF proportion. The composite PCMs with a CMF proportion of 0.86% has the best heat storage performance when the heat storage capacity and heat storage rate were both considered. [ABSTRACT FROM AUTHOR]

The purpose of this study was to obtain the characteristics of CO 2 hydrate formation and dissociation by using different experimental modes and pressures with glass beads. From the experiments, it was found that hydrate forms rapidly in each cycle, especially at high pressure. Hydrate blockage rarely appeared during hydrate formation and dissociation when applying gas flow (Case 2); this approach was significantly better than the other two experimental modes. The maximum hydrate saturations for the three experimental modes were 28%, 24% and 67.5%. The overall hydrate saturation of Case 3 was significantly better than those of the other two cases. When a heating process was applied to induce hydrate dissociation, the rapid backpressure decrease led to migration of the pore solution during depressurization. The minimal residual water after hydrate formation resulted in consistent residual water saturation after hydrate dissociation for Case 2. Considering hydrate saturation and operating pressure, 5.00 MPa is a better choice for hydrate-based desalination and CO 2 capture. If the initial residual solution can be completely converted to hydrate, this technology has potential for industrial applications. [ABSTRACT FROM AUTHOR]

The SO 2 -depolarized electrolysis (SDE) is one of the main processes in the hybrid sulfur cycle for hydrogen production, the microscopic characteristics of which are still not clear. In this work, a numerical analysis of SDE was conducted. The steady-state, laminar and incompressible 2D model of the electrolytic cell (EC) for carrying out SDE was first developed and verified. Physical field characterization indicated that the velocity was almost uniformly distributed in the flow channel, but higher pressure drops and pumping power consumption existed in the anode channel than in the cathode channel. Meanwhile, the continuous conversion of SO 2 to H 2 SO 4 at anode and generation of H 2 at cathode along the channel length were determined. Further exploring the impacts of three main operating parameters implied that an appropriate higher electrolytic potential, lower inlet flow rate (not less than 0.005 m/s) and operating temperature were favorable for improving the SDE. After comprehensive consideration of SDE performance and energy consumption, a feasible operating condition of 0.8 V, 303 K, and 0.005 m/s was proposed for SDE process. The developed model and microscopic characterization of SDE will favor the design and optimization of EC for SDE process. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to understand fluid flow in porous media. Understanding of fluid flow process in porous media is important for the geological storage of CO2. The high-resolution magnetic resonance imaging (MRI) technique was used to measure fluid flow in a porous medium (glass beads BZ-02). First, the permeability was obtained from velocity images. Next, CO2–water immiscible displacement experiments using different flow rates were investigated. Three stages were obtained from the MR intensity plot. With increasing CO2 flow rate, a relatively uniform CO2 distribution and a uniform CO2 front were observed. Subsequently, the final water saturation decreased. Using core analysis methods, the CO2 velocities were obtained during the CO2–water immiscible displacement process, which were applied to evaluate the capillary dispersion rate, viscous dominated fractional flow, and gravity flow function. The capillary dispersion rate dominated the effects of capillary, which was largest at water saturations of 0.5 and 0.6. The viscous-dominant fractional flow function varied with the saturation of water. The gravity fractional flow reached peak values at the saturation of 0.6. The gravity forces played a positive role in the downward displacements because they thus tended to stabilize the displacement process, thereby producing increased breakthrough times and correspondingly high recoveries. Finally, the relative permeability was also reconstructed. The study provides useful data regarding the transport processes in the geological storage of CO2. [Copyright &y& Elsevier]

Biochar-assisted water electrolysis (BAWE) for hydrogen production is an effective way to integrate renewable electricity and biomass utilization. But it is limited by slow biochar oxidation reaction (BOR). Here we adopted the biochar derived from pyrolysis (PB) and hydrothermal carbonization (HB) of rice husk. Replacement of oxygen evolution reaction with BOR leaves a significantly reduced onset potential (E onset) and an increased current density. Strongly related to carbonization temperature, the physicochemical properties of biochar markedly affected BOR. The abundant –OH groups in HB contributed to a low E onset , while the well-developed pore structure and high specific surface area of PB enhanced its reactivity at higher potential. Exposure of functional groups on PB surface after pickling made an increase in current density, but the simultaneous elimination of easily oxidized solutes in HB dominated and caused current density decline. H 2 SO 4 electrolyte of 1 mol/L was most appropriate for the uniform dispersion of biochar particles. The oxidation of PB derived at 800 °C with a slurry concentration of 10 g/L showed the lowest charge-transfer resistance and a favorable kinetics. Continuous BAWE indicated that PB was more superior than HB in increasing current density and H 2 production. This work provides favorable strategies for improving BAWE. [Display omitted] • Biochar derived from rice husk was used for biochar-assisted water electrolysis. • Anodic biochar oxidation reaction (BOR) was more energy-efficient than OER. • Relationships between physicochemical properties and BOR were characterized. • Pyrolytic biochar possess superiority in increasing current density and H 2 production. [ABSTRACT FROM AUTHOR]

To solve the problems of high cost and low efficiency of conventional co-production system of hydrogen and electricity with low hydrogen-to-electricity ratio, a novel co-production system based on coal partial gasification with CO 2 capture is proposed and thermodynamically analyzed. The new system integrates the conceptions of cascade conversion of coal and cascade utilization of syngas to realize the system with high efficiency, low cost, environmental friendliness and flexible hydrogen-to-electricity ratio. The performance of the new system is evaluated by an Aspen Plus model and effects of the operating conditions are also studied. It is found that the system with capturing CO 2 of 59.7% and hydrogen-to-electricity ratio of 4.76 holds a high exergy efficiency of 54.3% when the carbon conversion ratio of the pressurized fluidized bed (PFB) gasifier is equal to 0.7. The carbon conversion ratio of the PFB gasifier is a dominant factor to decide the performance of system. In comparison with the series-type co-production system, the parallel-type co-production system and separate production system, the new system proposed in this study has exergy-saving efficiency of 17.7%, 15.1% and 8.9%, respectively. [ABSTRACT FROM AUTHOR]

Abstract: To solve the problems of high cost and low efficiency of conventional co-production system of hydrogen and electricity with low hydrogen-to-electricity ratio, a novel co-production system based on coal partial gasification with CO2 capture is proposed and thermodynamically analyzed. The new system integrates the conceptions of cascade conversion of coal and cascade utilization of syngas to realize the system with high efficiency, low cost, environmental friendliness and flexible hydrogen-to-electricity ratio. The performance of the new system is evaluated by an Aspen Plus model and effects of the operating conditions are also studied. It is found that the system with capturing CO2 of 59.7% and hydrogen-to-electricity ratio of 4.76 holds a high exergy efficiency of 54.3% when the carbon conversion ratio of the pressurized fluidized bed (PFB) gasifier is equal to 0.7. The carbon conversion ratio of the PFB gasifier is a dominant factor to decide the performance of system. In comparison with the series-type co-production system, the parallel-type co-production system and separate production system, the new system proposed in this study has exergy-saving efficiency of 17.7%, 15.1% and 8.9%, respectively. [Copyright &y& Elsevier]