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  • Dynamic energy balance mode...
    Zhang, Guanshan; Ding, Xiaoming; Li, Tianhua; Pu, Wenyang; Lou, Wei; Hou, Jialin

    Energy (Oxford), 05/2020, Letnik: 198
    Journal Article

    Taking only the mean value of cover transmittance and cover absorbance would lead to a large error in estimating the thermal performance of a greenhouse. This paper discusses an innovative dynamic energy balance model of a glass greenhouse, incorporating dynamic cover absorbance and transmittance. Different cover absorbances and transmittances for diffuse, beam, and ground-reflected radiation are used. The model primarily comprises nine differential energy conservation equations for indoor air, seven layers of soil, and the greenhouse’s cover. Greenhouse temperature trends are acquired by solving the unsteady-state equations with MATLAB. The model was verified using experimental data recorded during three non-continuous periods of 15 days each in northern China (36.08°N, 116.95°E), during which the daily maximum outdoor solar radiation flux intensity fell between 191 and 894 Wm-2, the outdoor air temperature fell between −12.3 °C and 24.5 °C, the ground surface temperature fell between 0.6°C and 44.3 °C, and the indoor air temperature fell between −9.0 °C and 51.8 °C. The estimates agree well with the measurements, suggesting that the dynamic model is valid. Meanwhile, the dynamic cover absorbance and transmittance, the solar radiation absorbed by the cover, the solar radiation transmitted into the glass greenhouse and the proportion of solar radiation from each surface are discussed. •The model considers dynamic cover absorbance and transmittance with an improved performance.•Use of a sub-model of seven-layer soil resulted in an improved performance.•The solar radiation transmitted into the greenhouse from side walls was studied.•Study of the dynamic absorbance and transmittance of various greenhouse surfaces.•Analysis of solar radiation absorbed by cover and solar radiation transmitted into the greenhouse.