Abstract

Nowadays, Moving Packed Bed Heat Exchanger (MPBHE) are being gradually applied in the field of industrial waste heat recovery and solar energy due to its clean energy and low cost. In this paper, heat transfer performance of plate with three different mixing parts are researched by discrete element method. The results show that, there is strong mixing between particles after flowing through the mixing part. Compared with elliptical mixing plate (ELL-MP) and trigonal mixing plate (TRI-MP), the mixing ratio and feature velocity of trapezoidal mixing plate (TRA-MP) are the largest. The mixing parts can significantly improve the heat transfer performance, and TRA-MP is the best. The heat transfer coefficient of TRA-MP increases by an average of 40% than that of plate in the downstream region of the mixing part.

Abstract

The efficiency of biomass heating networks has become an increasingly important issue in recent years. Studies have shown that the most effective measure for increasing efficiency is to install a heat pump along with a flue gas condenser in the boiler of a biomass heating system. With a view to further enhancing efficiency, this study focuses on the thermodynamic analysis and optimization of a heat pump design used for heat recovery in a biomass heating network and its impact on the overall system. The study demonstrates that the choice of target exhaust gas temperature has a significant impact on both heat pump sizing and overall system efficiency. There is an optimum exhaust gas temperature at which the maximum overall system efficiency can be achieved. The supply temperature of the heat pump and the choice of refrigerant have little effect on the system overall, but they do affect the size of the heat pump. The supply temperature should be as low as possible. R600a is recommended as a refrigerant for the heating networks studied, due to its physical properties and beneficial behavioral characteristics at different temperatures.

Abstract

Rather high energy penalty of CO2 capture is the critical gap deterring the deployment of CCS technologies in last twenty years. Deeper understand of mechanism of energy consumption for CO2 capture will lay the basis for reducing the energy consumption. Accordingly, this paper introduced a thermodynamic analysis method with new criterion to reveal the mechanism of energy consumption in power system integrating CO2 capture from new angle. Coal-fired power plant with post-combustion had been taken as the typical case and some enlightening results had been achieved. Although energy consumption for separation process is generally recognized as the dominant part of capture penalty, deterioration of energy utilization in power system due to providing energy for CO2 separation is nonnegligible, which also exhibits attractive potential for energy saving in some cases. For separation efficiency improvement, the ceiling of 50% separation efficiency indicates as low as 5.9 percentage points penalty (with CO2 compression), and the CO2 capture cost of around 24 $/t CO2 can be anticipated for 50% separation efficiency.

Abstract

Hydrate phase equilibrium in the most important foundation for other hydrate, especially for marine environment condition. In this study, a three-phase liquid water-hydrate-vapor equilibrium conditions for methane hydrate in aqueous solutions of NaCl + CaCl2/MgCl2/SrCl2 mixture with a salinity of 34.5 in the temperature and pressure range of 283.65 – 288.85 K and 8.84 – 13.2 MPa have reported using a temperature search method. The ion categories, ion concentrations, temperature and pressure range were determined based on the situ conditions of haima cold seep. And the in situ concentrations of Mg2+, Ca2+, Sr2+ in haima cold seep were 1000 mg/L, 300 mg/L, 8 mg/L, respectively. Comparison of ions in the same ionic conditions with different ionic concentrations at the same salinity revealed that methane hydrate phase equilibrium in high salinity containing Ca2+, Mg2+ ion is mainly affected by salinity while the influence of cation concentration can be ignored, however, it is clearly observed that the inhibitory effect of Sr2+ on hydrate phase equilibrium increases with increasing cation concentration at a salinity of 34.5. This may be because Sr2+ has the smallest electron density and the smallest electrostatic force to interact with water molecules when intruding into the hydrogen bonding network within the water molecule, and has the weakest inhibitory effect on the hydrate. The inhibition effect of Sr2+ concentration on hydrate was more significant than Ca2+, Mg2+ at the same salinity.

Abstract

A sunlight driven multi-energy complementary utilization system based on concentrating spectral beam splitting strategy is proposed for CO2 recycling. The high-energy shortwave part of solar spectrum is converted into electricity by photovoltaic cells to activate water electrolysis reaction for H2 production, while the residual energy is transformed into heat by an evacuated heat-collecting tube to trigger the decomposition of saturated CO2 adsorbents. Subsequently, the released CO2 reacts with the previously generated H2 to form fuel, realizing autothermic CO2 conversion. Thermodynamic analysis of this model system reveals that the optimized solar-to-methane efficiency and heat-collecting efficiency could reach up to 8.08% and 68.79% respectively, when the splitting waveband for photovoltaics-water electrolysis is 600-900 nm. The current work provides a viable solution for the short-term implementation of solar-driven CO2 conversion technology into large-scale energy markets.

Abstract

Electrochemical hydrogen gas evolution on the electrode surface will occupy the limited active sites thus significantly increases the reaction overpotential. It is crucial to study and optimize the bubble behavior on the electrode surface to improve the reaction efficiency and lower the energy loss. Herein, a microfluidic electrochemical reactor (MER) was constructed to optimize the surface kinetic behavior during the gas evolution process. The obtained results demonstrate the feasibility of microfluidic design in manipulating the bubble behavior at the electrode interface through the self-generated gas-liquid two-phase flow, which can simultaneously reduce the overpotential and facilitate the mass transfer. Compared with the traditional H-cell, the hydrogen evolution efficiency can present a remarkable intensification. Our work reveals a new strategy for guiding the design of the electrochemical reactor for water splitting.

Abstract

Bivalve shellfish farming is expected to be performed as the effective mitigator of the growing pressure for global animal protein demand. Carbon emission reduction in the whole farming process of the bivalve shellfish has great potential in reducing carbon emissions in food production in the future. However, the hatchery stage of oyster, with high energy input, may be a high carbon emission process and necessitates effective carbon emission reduction. This study uses life cycle assessment (LCA) to analyze the carbon footprint of the farming of Pacific oyster (Crassostrea gigas), a shellfish with the largest farming yield in the world, in Fujian province in China. The results show that the total carbon footprint, from cradle to gate is 70.81 kgCO2-eq/tonne fresh oyster, which suggested that oyster farming perform favorably against livestock farming for protein products and can justifiably be promoted as a low-carbon food product. Hatchery culture contributed 62.2% of the total carbon emission. The feed production in the hatchery culture stage, account for about 2.27 % of carbon emission, were not the major emission factor. Carbon emission form energy consumption and material inputs are about half and half. The carbon footprint of Pacific oyster can be reduced by employing energy-conserving transport technology and utilizing renewable energy. The improvements could be helpful for sustainable production of Pacific oyster farming.

Abstract

In this study, a rigid diazide cross-linker, 2, 6-bis (4-azobenzylidene)-4-methylcyclohexanone, wasintroduced into a quaternary ammonium modified polymer of intrinsic microporous (PIM) anion exchange membrane (AEM), QPIM-1, by impregnation, which wasthen cross-linked by thermal initiation to prepare a rigid cross-linked microporous anion exchange membrane cQPIM-1. The effects of crosslinking on the structures and performances of membrane are investigated. The
presence of cross-linker and incomplete reaction are observed by the results of Fourier-transformed infrared (FT-IR). The cross-linked AEM shows significantly enhanced the tensile strength of the membrane is obviously increased through dynamic tensile test. Notably, the swelling ratio (SR) and water uptake (WU) are only 6.08% and 11.93% at 80 ℃, which are only 42.8% and 26.8% lower than that of QPIM-1 before cross-linking. In addition, a desirable OH_x0002_conductivity of
39.10 mS/cm at 80 ℃ can be obtained, owing to the inter-chain microporous structure of PIM alleviating the blocking effect of cross-linking reaction on ion conductivity.

Abstract

About 35% of the total energy consumption comes from house appliances. Home energy management system (HEMS) is a household optimal system that can improve the efficiency of electricity consumption, increase the consumption of new energy and reduce carbon emissions. At present, the research of HEMS is simulated under the fixed load setting, and the adaptability of the model to the users’ uncertain behaviors is not considered. In this paper, an optimization model of HEMS based on deep neural network (DNN) and reinforcement learning (RL) algorithm is presented. The model aims to minimize the electricity cost and the comfort cost. For the residential case in this paper, the model can reduce 34.2% total cost. The simulation results show that the proposed model can better adapt to the uncertain behaviors of users than the optimization model based on genetic algorithm (GA).

Abstract

The innovation of hydrogen energy and fuel cell technology promotes the development and application of fuel cell vehicle, which also requires the real time follow up of relevant standards. This paper summarizes the domestic and foreign existing conditions of FCV related standard system at beginning, which contributes to a comprehensive comparative analysis. Subsequently, the potential gaps of existing standard system are summarized, and the possible reasons are analyzed. Finally, the development of fuel cell standards in China is presented. In the future, it is important to strengthen the construction of related standard system, so as to promote the high quality and high level development of fuel cell vehicle industry.