Fabrication and photoelectrochemical study of selenide and oxide heterostructures for solar hydrogen evolution

We report the synthesis and photoelectrochemical (PEC) studies of a novel CdSe/BiVO4 planar heterojunction photoelectrodes for photoelectrochemical water splitting fabricated by chemical bath deposition of CdSe on the spin-coated BiVO4 layers. Temperature and time of chemical bath deposition were investigated to obtain the optimal deposition condition. The optimized CdSe/BiVO4 with enhanced photo absorption yielded a maximum photocurrent density of 2.48 mA under the irradiation of AM 1.5 G (100 mW/cm2) simulated solar light illumination, which is enhanced by 3.87 times compared to bare BiVO4

Heat Absorption and Release Characteristics on Heat Storage Walls with Different Materials

To analyze the storage performance of the envelope structure, based on the law of conservation of energy, the ANSYS software was employed to perform thermal analysis on three conventional wall materials and phase change materials, and the temperature fields and minimum temperature difference of the walls with different materials were obtained. The heat absorption and release characteristics of different wall materials were studied. Comparing the heat absorption and release characteristics of phase change materials, it was concluded that the phase change materials had better heat storage capacity, which provided a basis for promoting and developing low energy consumption technologies for buildings

Numerical investigation of low-velocity filtration combustion instability based on the initial preheating non-uniformity

The effects of the initial preheating perturbation on the dynamical behaviors of FGC wave propagation instability for low-velocity FGC in packed bed are studied numerically. The behaviors of the flame front inclination, break, and shrinking instabilities are always observed in experiments. Based on the experimental phenomena, an initial thermal perturbation model is numerically proposed as to predict the deformation behaviors of the flame front instabilities. The typical flame shapes are obtained depending on filtration velocity, equivalence ratio, and initial preheating temperature difference. It is demonstrated that the development of flame front inclination instability is proportional to the magnitude of initial preheating perturbation. At a lower equivalence ratio, the initial thermal perturbation of 300 K leads to the evolution of flame front break. Increasing filtration velocity leads to the appearance of flame front break, due to the intensification of the hydrodynamic instability. In addition, a perculiar instability of flame front shifting is also confirmed with the initial thermal perturbation of 400 K, which results in a fuel leakage of incomplete combustion

Experimental analysis of a novel Solar PV/T Collector

The output power of the solar photovoltaic panel decreases as the operating temperature increases. The use of photovoltaic/photothermal (PV/T) collectors not only effectively cools the operating temperature of the battery, increases photovoltaic power, but also produces hot water. Therefore, the PV/T collector improves the annual utilization efficiency of solar energy, and can meet the user's demand for different energies. This paper builds an experimental platform to compare the PV/T collector photovoltaic/photothermal performance and experimental comparison with traditional PV. The results show that the PV/T collector has a thermal efficiency of 31.5% and a photovoltaic efficiency of 17.82% at a flow rate of 0.023 Kg/s to achieve high efficiency in solar energy utilization

Experimental Study of Thermal Behavior of Insulation Material Rigid Polyurethane in Parallel, Symmetric, and Adjacent Building Façade Constructions

Both experimental and theoretical methods were proposed to assess the effects of adjacent, parallel, and symmetric exterior wall structures on the combustion and flame spreading characteristics of rigid polyurethane (PUR) foam insulation. During the combustion of PUR specimens, the flame leading edge was found to transfer from a unique inverted ‘W’ shape to an inverted ‘V’ during flame propagation. This phenomenon is attributed to edge effects related to boundary layer theory. The effects of the adjacent façade angle on flame spreading rate and flame height were shown to be nonlinear, as a result of the combined influences of heat transfer, radiation angle, and the chimney restriction effects. A critical angle around 90 degree with maximum thermal hazards outwards by parallel fire was observed and consistent with the mass loss rate and flame height tendencies. For narrow spacing configurations or angles (e.g., 60 and 90 degrees), phenomenological two-pass processing in conjunction showed that increased preheating lengths were associated with enhanced heat transfer. The results of this study have implications concerning the design of safe façade structures for high-rise buildings, and provide a better understanding of downward flame spreading over PUR

The Thermal Behavior of a Dual-Function Solar Collector Integrated with Building: An Experimental and Numerical Study on the Air Heating Mode

This paper presented a novel solar collector that can work in air or water heating mode depending on the seasonal requirement. The dual-function solar collector (DFSC) integrated with a building as well as a reference building without the DFSC were built to test thermal behavior in passive air heating mode during winter. The buildings were equipped with an apparatus to control the room temperature. During the testing procedure, experimental study on the DFSC system was carried out under two conditions, where the indoor temperature was controlled and non-controlled. The results showed that the average temperature of the test room was about 3.43 °C higher than that of the reference room under the non-controlled condition. When the room temperature was controlled at 18 °C, the power consumptions of the test room and reference room were 4.322 kWh and 7.796 kWh, respectively. Consequently, the corresponding daily power consumption saved could reach up to around 3.5 kWh. Moreover, a dynamic numerical model on the DFSC along with the building was developed taking the fin effect of the Cu-tubes into account. The numerical results are found to be well consistent with the measured data. A parametric study on with/without Cu-tubes and depth of the air channel was carried out. It is found that the existing Cu-tubes functioning as water heating can enhance the air heating efficiency when the depth of air channel is of a suitable size