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Generating power from solar thermal systems is an effective method for realizing grid-scale dispatchable power generation and replacing conventional energy. The central receiver plays a vital function in the entire power generation system. A special type of tubular receiver was proposed in this study. The proposed receiver was intensively investigated to decrease the tube wall temperature and improve the receiver efficiency and working life. In the proposed design, the panels consist of bayonet tubes instead of circular ones. The new bayonet tube consists of two concentric tubes with different diameters, which are connected by a bayonet end cap. The heat transfer performances of the traditional, inner bayonet, and outer bayonet tubes were compared by establishing a 3D model of the tube. When no boundary heat loss is incurred, the wall temperature of the traditional tube and the molten salt temperature of the outer bayonet tube are the highest among the three. The molten salt and tube wall temperatures of the inner bayonet are the lowest, which is the desired outcome. When the boundary heat loss is considered, the outer wall temperature of the inner bayonet tube is lower than that of the traditional straight one. When the flow rate is 4.4 kg/s, the thermal efficiencies of the straight and inner bayonet tubes are 91.5 % and 96.7%, respectively. When the heat flux is non-uniform, the tube wall temperature is uneven because of the cosine effect of the heating surface. The maximum temperature of the outer wall of the inner bayonet tube is lower than that of the straight one, which indicates that the proposed design is promising in the perspective of thermal efficiency. Further simulations were performed to investigate the influence of flow rate and heat flux variations.

In this work, an incubator is developed for vaccine cold chain transport based on paraffin/SiO2 aerogel composite with polystyrene board for coupling packaging. The morphology and thermal property of PCM was characterized. A combined numerical and experimental study has been conducted to study the multi-level gradient heat transfer behavior. The coupling between the outer insulation board and the inner layer PCM can achieve great synergistic gain, it is reflected in the fact that maintain time increased by 99 times compared to the condition with only insulation board. The optimal double layer board configuration is optimized as XPS/PCM and the thickness ratio is determined as 1:3. The lifting rate of the holding time presented an increasing trend with the overall size of the incubator increasing, providing alternative basis for the cold chain transport configuration under different requirements.

Expanded graphite based composite phase change materials is a good candidate for latent thermal energy storage system, while suffering large volume expansion in the phase changing process. In this work, a self-assembly method is presented to build novel 3D-graphite block, and phase change composite based on the block is prepared via casting way. The new phase change material exhibits large thermal conductivity and low volume expansion. The continuous 3D-graphite network of the carbon skeleton leads to high thermal conductivity of 15.6 W m−1·K−1 and volume expansion lower than 1%. The SEM characterization, XRD patterns, impact strength and electrical conductivity results reveal that the 3D block has network interaction and percolating threshold. Then, a new model is proposed to predict the thermal conductivity of new composite. The new phase change material has great thermal energy charging/discharging performance, which has promising application foreground as heat capacitance in thermal energy systems.

The overcharge safety and behaviors of lithium-ion batteries (LIBs) with LiCoO2 cathode are investigated under a successive constant current (CC) and constant voltage (CV) charge mode. It is indicated that in the case of smaller charge currents, a higher probability for the LIBs passing the overcharging test can be obtained. The batteries can safely pass CC overcharge test at 0.25C to 10 V, and then about 80% batteries can also pass CV overcharge test. Whereas, with increasing the CC currents to 0.33C, 0.5C, and 1C, about 50%, 30%, and 10% batteries can directly pass the overcharge test at the CC step, and then about 20%, 10%, and 0% batteries approach 10 V and subsequent pass CV overcharge test, respectively. Besides the charge current, it is also demonstrated that whether the LiCoO2/graphite batteries are likely to achieve energy balance and pass the overcharge test basically depends on the formation of the internal short-circuit pathways derived from the cobalt and lithium deposition in the separator during the overcharge process. The cobalt deposition will be more uniform when the battery core has shape stability of assembly-structure, which can be used as an effective measure to raise LIBs through the overcharge test. In addition, relative more uniform cobalt dendrites can also be formed if a double layer separator is adopted, which reduces the local short-circuit risk caused by the melting or shrinkage of the separator and correspondingly improves the ratio of LIBs passing through the overcharge test. These risk reduction measures can be used in the battery manufacture to improve the overcharge safety of LIBs.

NaxMn0.54Ni0.13Fe0.13O2 (x = 0.46, 0.67) with P2-type hexagonal phase are synthesized via a sol-gel method as novel cathode materials for sodium-ion batteries. The followed characterization indicates the existence of coaxial hexagonal phase structure in two samples, among which Na0.46Mn0.54Ni0.13Fe0.13O2 (NMNF-0.46) presents neat hexagonal nanosheets with a sharp edge, whereas Na0.67Mn0.54Ni0.13Fe0.13O2 (NMNF-0.67) shows granular structure. Tested in sodium-ion batteries at the potential window of 2.0–4.2 V, the specific capacity of NMNF-0.46 is 132.5 mAh g−1 at a current density of 0.1C, and the capacity retention rate was 78% after 50 cycles. In contrast, the specific capacity of NMNF-0.67 is 99.5 mAh g−1, but a high capacity retention rate of 86.8% is delivered. The promising electrochemical performance of NaxMn0.54Ni0.13Fe0.13O2 provides a meaningful reference for developing advanced cost-effective electrode materials for sodium-ion batteries.

Phase change materials are most potential candidates for storing solar thermal energy with large enthalpy and high exergy. However, the intrinsic drawback such as poor optical absorptive capacity, low thermal conductivity and poor tensile strength restrict the thermal efficiency of phase change materials. To overcome drawback, expanded graphite is used to encapsulate the paraffin then thermoplastic elastomer is used to mix with the powders with twin-screw extrusion technology. The highly flexible phase change composite shows a melting enthalpy of 124.6 J g−1 and a thermal conductivity of 2.2 W m−1 K−1 with 70% of expanded graphite/paraffin. The tensile strength of 2.1 MPa and a breaking elongation of 220%. This flexible phase change composite demonstrates good photo-thermal energy charging/discharging property and shows much larger exergy than traditional fluids in the solar thermal energy systems.