CFD Simulations of Wind Effect on Net Solar Heat Gain of South Walls with Internal Insulation

Computational fluid dynamics( CFD) techniques are used to investigate effects of both wind direction and wind speed on net solar heat gain of south wall with internal insulation in winter.Results show that wind effect has a significant influence on the net solar heat gain,where the impact of wind direction is stronger than that of wind speed. For regions in lower reaches of the Yangtze River,difference of their average net solar heat gains( NSHGS) is about 20% due to various wind speeds and wind directions.Buildings in districts with a dominant wind direction of north achieve the highest solar energy utilization.

Cyclohexane Dehydrogenation in Solar-Driven Hydrogen Permeation Membrane Reactor for Efficient Solar Energy Conversion and Storage

Cyclohexane dehydrogenation in the solar-driven membrane reactor is a promising method of directly producing pure hydrogen and benzene from cyclohexane and storing low-grade solar energy as high-grade chemical energy.In this paper,partial pressure of gases,conversion rate of cyclohexane,and energy efficiency of the reactor are analyzed based on numerical simulation.The process of cyclohexane dehydrogenation under four temperatures(200℃,250℃,300℃,and 350℃)and four permeate pressures(0.050 MPa,0.025 MPa,0.010 MPa,and 0.001 MPa)were studied.A complete conversion rate(99.9%)of cyclohexane was obtained as the reaction equilibrium shifts forward with hydrogen separation.The first-law thermodynamic efficiency,solar-to-fuel efficiency,and exergy efficiency could reach as high as 94.69%,46.93%and 93.08%,respectively.This study indicates that it is feasible to combine solar energy supply technology with cyclohexane dehydrogenation reaction integrated with membrane reactor.

Performance Evaluation and Optimization of a Novel System Combining a Photovoltaic/Thermal Subsystem&an Organic Rankine Cycle Driven by Solar Parabolic Trough Collector

A novel coupling system that combines a photovoltaic/thermal(PV/T)subsystem and an Organic Rankine Cycle(ORC)driven by solar parabolic trough collector(PTC)is presented in this paper.The mathematical model is initially built.On the basis,the influence of area ratio of two collectors(PV/T and PTC)on the performance of system is discussed.The results show that the optimal area ratio of PV/T to PTC is 8:2,which can achieve the maximum energy output.Moreover,the performance of the coupling system and two independent systems(PV/T and ORC system)are compared and analyzed.The results show that the coupling system is more reliable and its total output energy(heat and electricity)is the highest,compared with the other two independent systems.The solar energy utilization efficiency of the coupling system is 40%higher than that of the other two independent systems in the steady-state simulation.Moreover,the annual output energy per unit area collector of the coupling system is 13%higher than that of the other two independent systems in the dynamic simulation.Furthermore,in the dynamic simulation of a typical day,the PV panels’temperature of the coupling system is 5℃–7℃ lower than that of the independent PV/T system.It means that the power generation efficiency of PV panels can be increased by 1.5%–3.5%.This study aims to explore the operation characteristics of the novel solar energy utilization coupling system and promote the development of renewable energy utilization models,which provides a reference for the design and optimization of related energy systems.