Establishment And Validation Of Solar Radiation Model For The Living Wall System

The living wall is a new type of vertical greening,which can alleviate various ecological and environmental problems caused by the drastic reduction in the rate of greening in the process of urbanization.At the same time,as a part of the building envelope structure it performs well in the building energy conservation.The growth state of the plants in the living wall varies with the external environment,and its thermal indicators are dynamic and difficult to calculate.In order to promote the development of the living wall of the building,it is necessary to study the mechanism of solar radiation on the living wall.In this paper,the energy transmission process of the living wall is analyzed,and takes the mechanism of the solar radiation acting on the living wall as the core content.From the perspective of the interdisciplinarity of architecture and botany,it analyzes from two aspects.One is the solar radiation on the vertical wall surface,and the two is the spatial distribution of the plant canopy when the plant growth in a vertical wall,then establishes a living wall solar radiation model to obtain the ability of intercepting the solar radiation of living wall plants.The model calculates the transmissivity of the plant canopy based on the vertical plane,describes the heat of the solar radiation reaching the outer surface of the living wall matrix,defines the most uncertain external boundary conditions in the heat transfer calculation of the living wall,and then The the accuracy of the model was experimentally verified on a living wall laboratory in Wuhan.At the same time,the thermal performance of the south facing living wall of the experimental laboratory in the winter was measured.The experimental results show that the measured data are in good agreement with the simulated data,and the solar radiation model of the living wall has high accuracy,and the following conclusions are obtained:(1)for the building living wall,when the angle of the sunlight incident light and the wall is less than 90 degrees,the living wall is exposed to the sun directly.With the increase of the incident angle,the extinction coefficient of the canopy increases,the direct light transmittance decreases and the scattered light transmittance increases.(2)the transmittance of the solar radiation in the living wall is related to the physical parameters of the living wall plant.The greater the x of the leaf angle of the living wall plants,the higher the transmittance,the smaller the x of the leaf angle,the lower the transmittance.The leaf area index of living wall plants increased,and the transmittance decreased.On the contrary,leaf area index decreased and transmittance increased.(3)for the different direction living walls with the leaf area index of 0.35 and the leaf inclination x of 2,the transmittance of the South living wall in the summer is 0.44,which can block more solar radiation and improve the heat insulation and cooling of the building,and the increase of the transmittance in winter is 0.55,which can transmit more solar radiation,which is beneficial to the heat absorption of the building.The transmittance of the East and West live walls in summer and winter is about 0.3,and the north wall is around 0.09.The south facing living wall satisfies the needs of building for solar radiation.