Periodic gratings with different shapes are designed to study spectral reflectivity in normal direction using finite-difference time-domain method.It shows that very low reflectivity in wavelengths can be found with proper grating structures and even zero-reflectance can be found.Influences of depth and slot width of triangle gratings on reflectance are investigated.Parameters for a triangle grating with very low reflectivity in wave bands of 2.75-3.23 μm and 3.84-4.88 μm are found.

Based on comparability of porous material seepage flow and surface evaporation with plant leaf transpiration, a kind of porous material artificial leaf is proposed. Models of artificial leaf and realistic leaf are set. Influence of porosity, thickness and particle diameter of the artificial leaf on surface temperature is discussed. According to simulation under representative ambient conditions, we found that an artificial leaf with thickness of 0.5 cm, porosity of 0.05 and particle diameter of 2.5 mm is able to simulate infrared characteristics of a realistic leaf. Surface temperature difference is within 3℃ in a day.

Physical and numerical model for a thermal radiation-electricity module in a TPV (Thermophotovoltatic) system is constructed. Current/voltage characters of the system consisting of a SiC emitter and GaSb or Si PV cells are obtained. Influences of emitter and cell temperatures are analyzed for a SiC emitter with GaSb cells. As emitter temperature rises from 1 400 K to 1 900 K, system electric power density increases from 0.67 W· cm^-2 to 5.43 W· cm^-2, and cell efficiency increases from 16.3% to 24.8%. However, the rise of cell temperature causes an opposite trend. As cell temperature rises 10K, system electric power density deceases about 0.15 W· cm^-2, and the cell efficiency deceases dramatically. The radiative energy distribution of a selective emitter with GaSb cells is discussed. Unusable radiative energy of the selective emitter can be reduced remarkably compared to a SiC emitter and thus improves system performance and stability effciently.

We analyze the integrand spectrum in the plane wave expansion of spherical functions,and present a standard of(2L,4L) point quadrature for spatial angles satisfying the sampling theorem.Numerical results with the method of moments(MOM) and fast multipole method(FMM) in different quadrature schemes are compared to show the validation of our quadrature scheme.

The feasibility of simulating thermal characteristics of metal constructions with phase change materials(PCM) is investigated theoretically and numerically.Detailed calculations are shown to evaluate the simulation of a serial of metal boards with different thickness,such as 20 mm,30 mm,50 mm and 100 mm.It is found that the low thermal conductivity of the PCM is a significant disadvantage in simulating thicker metal boards.Based on that,the PCM with reinforced thermal conductivity is used to simulate the metal board with a thickness of more than 100 mm.Good simulation results are obtained.Furthermore,PCM simulations for two common metal constructions,a steel wheel and a pipe,are studied.

A method of mutual coupling and circulating iteration is presented to evaluate the thermal resistance and thermal capacity network of unit (differential) sections and separate joint points for the solar energy collecter system based on the model proposed by the second writer of this paper.