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The silicon vertical multi-junction (VMJ) solar cell has low costs and low series resistance, thus it has a good potential in concentration photovoltaics. However, there were few discussions about the thermal and electrical performance of silicon VMJ cell under non-uniform illumination. In this work, the thermal performance of silicon VMJ cell under 1D non-uniform illumination of 500 suns was calculated using finite element method first, and then the electrical performance of the cell was calculated using SPICE software based on the thermal simulation results. It was found that the mean temperature of the cell increased with the degree of non-uniform illumination when the area ratio of the sink to the cell was 500X, and the mean temperature changed few when the area ratio was 2500X. The efficiency of the cell did not decrease with the increase of the degree of non-uniform illumination when the area ratio was 500X, and the efficiency increased with the degree of non-uniform illumination when the area ratio was 2500X. Thus, the silicon VMJ cell had better performance than silicon planar junction cell under 1D non-uniform illumination of 500 suns.

Abstract To ensure techno-economically suitable installation of ground source heat pump (GSHP) systems, thermal and hydrogeological properties of the subsoil need to be investigated. In this paper, the geothermal potential for three types of GSHP installations in the urban area of Wuhan city is assessed based on preliminary geological investigations. The potential for shallow geothermal energy is evaluated for surface water heat pump systems (SWHP), groundwater heat pump systems (GWHP) and ground coupled heat exchanger heat pump systems (GCHP). The mapped shallow geothermal potentials provide essential information for the installation of GSHPs and for the management of geothermal resources of Wuhan city. Furthermore, the heat transfer rates for some typical configured borehole heat exchanger (BHE) are tested by field Thermal Response Tests (TRT). In order to understand the techno-economic feasibility of the GSHPs, different types of the installed systems are measured and analyzed.

Abstract Reliability analysis of IESs (Integrated Energy System) is complicated because of the complexity of system topology and dynamics and different kinds of uncertainties. Reliability is often calculated based on statistic methods, which always focus on historical performances and neglect the importance of their dynamics and structure. To overcome this problem, in this paper, a systematic framework for dynamically analysing the real-time reliability of IESs is proposed by integrating different machine learning methods and statistics. Firstly, the bootstrap-based Extreme Learning Machine is developed to forecast the conditional probability distributions of the productions of renewable energies and the energy consumptions. Then, the dynamic behaviour of IESs is simulated based on a stacked auto-encoder model, instead of using traditional mechanism-based simulation models, for improving computational efficiency. Besides, the variables representing the transient properties of natural gas pipeline networks, such as delivery pressures and flow rates, are taken as the indicators for quantifying the energy supply security in natural gas pipeline networks. The time-dependent relationships among these indicators and their statistic correlations are modelled for improving the effectiveness of the analysis results. Finally, the reliability assessment is performed by estimating the probability distribution of each functional state of the target IES. A case study of a realistic bi-directional IES is carried out to demonstrate the effectiveness of the proposed method. The results show that the method is able to effectively evaluate the reliability of IESs, which can provide useful information for system operation and management.

Abstract In this paper, a series of catalysts loaded with different amount of LaNiO3 on MCM-41 supported were studied for steam reforming of biomass tar reaction using in-situ tar in double fixed-bed. Different methods including XRD, N2 adsorption-desorption, SEM, XPS and TG-DTG were employed for characterization of fresh and spent catalysts. The results of low-angle XRD and N2-adsorption-desorption analysis shown that MCM-41 supported was successfully synthesized. In the first-stage fixed-bed, in-situ tar was produced by pyrolysis of rice husk at 450 °C. Simultaneously, the LaNiO3 and XLaNiO3/MCM-41 (X = 0.025, 0.05, 0.075 and 0.1) catalysts were investigated for hydrogen rich syngas production at various reforming temperature (500 °C–900 °C) and steam/carbon mass ratio (S/C = 0.6–1) in second-stage fixed-bed. Among all the catalysts, 0.1LaNiO3/MCM-41 catalyst displayed a higher gas yield of hydrogen (61.9Nm3/kg) at 800 °C and S/C (0.8). At the same conditions after five-time cycles, 0.1LaNiO3/MCM-41 showed a stable hydrogen gas composition of around 50%, and 0.1LaNiO3/MCM-41 catalyst was effective in catalysis of phenol compound in in-situ tar by GC-MS results. TGA-DTG and Raman analysis revealed the carbon deposition was mostly amorphous on 0.1LaNiO3/MCM-41, and lattice oxygen released to remove deposited carbon was the possible reason for 0.1LaNiO3/MCM-41 catalyst's stable catalytic performance by XPS results.

Abstract This paper focuses on the formulation, fabrication and characterization of a novel composite for high-temperature heat energy storage. The proposed composite is a shape-stable phase change material consisting of the eutectic chloride (MgCl2–NaCl–KCl) as phase change material, expanded graphite (EG) for heat conduction enhancement and shape stability, and SiO2 nanoparticles for the further improvement of specific heat and thermal conductivity. The composite was prepared following a three-step procedure: mechanical dispersion, tableting and sintering. Concerning the material characterization, a suite of techniques were used, including simultaneous thermal analysis (STA) and laser flash analysis (LFA). The consequences demonstrate that using EG and SiO2 nanoparticles ensure the stability and preventing the leakage of the eutectic chloride. A thorough comparison with the pure ternary chloride shows that the composite specific heat increased up to 1.36 times in solid-state and 1.63 times in liquid-state, and the thermal conductivity increased by 23.2 and 9.2 times in the solid and liquid state, respectively. Upon inspection with scanning electron microscopy, a high-density nanostructure was observed and distributed evenly in the pores of EG, which appear to be the reason for the enhancement of specific heat and thermal conductivity of the material. Finally, the nano-SiO2/MgCl2–NaCl–KCl/EG composite has the advantages of wide working temperature range, shape stability, high specific heat and thermal conductivity, which has a promising application in a high-temperature thermal storage system.

Abstract Thermoelectric module can be used as a generator to convert thermal energy into electricity, or as a cooler to convert electricity into heat. In this work, a comprehensive model is proposed to predict the performance of thermoelectric generator and cooler by setting different boundary conditions. Based on the proposed model, the influences of height, cross-sectional area, number of couples, ceramic plate, and heat loss on the generator and cooler are investigated. To balance the output performance and cooling performance of thermoelectric modules simultaneously, a comprehensive study on the thermoelectric module is conducted. The results indicate that (i) A relatively lower leg height enables the enhancement of output power, cooling power, and COP, despite a slight reduction in conversion efficiency; (ii) When increasing the total cross-sectional area of legs, thermoelectric generator should aim at adopting more thermoelectric couples, whereas the cooler should apply a larger area for every single leg; (iii) For the optimization of ceramic plates, more attention should be paid in improving the thermal conductivity. Also, fillers are not recommended for thermoelectric module in general environment. The findings of this work may guide the design and parametric optimization of thermoelectric module used for both power generation and cooling.

202306 bcww ; Not applicable ; RGC ; Published ; 24 months

While previous studies focused on managing charging demand for private electric vehicles (EVs), we investigate ways of supporting the upgrade of an entire public urban electric taxi (ET) system. Concerning the coexistence of plugin charging stations (CSs) and battery swap stations (BSSs) in practice, it thus requires further efforts to design a holistic charging management especially for ETs. By jointly considering the combination of plug-in charging and battery swapping, a hybrid charging management framework is proposed in this paper. The proposed scheme is capable of guiding ETs to appropriate stations with time-varying requirements depending on how emergent the demand will be. Through the selection of battery charging/swap, the optimization goal is to reduce the trip delay of ET. Results under a Helsinki city scenario with realistic ETs and charging stations show the effectiveness of our enabling technology, in terms of minimized drivers’ trip duration, as well as charging performance gains at the ET and station sides.