Parametric study on a simplified model for the estimation of the heating and the cooling loads of a closed-span greenhouse: a case study in Korea

Abstract

The modeling of greenhouse heating and cooling loads at the required operating conditions is important for greenhouse managers or planners. However, the conventional model for the greenhouse thermal load prediction is complex for staff without sufficient academic background. Therefore, a steady-state simplified model based on the estimation of related heat transfer parameters was developed to predict the hourly heating and cooling requirements of the closed greenhouses in Korea and the Northeastern Asian region. In the suggested approach, the thermal load was simplified as a function of greenhouse size, the temperature difference between the setting indoor temperature and the ambient temperature, total horizontal solar radiation, overall heat transfer coefficient, and the fraction factor of solar conversion. Except the designed parameters and the climatic variables, the overall heat transfer coefficient and the fraction factor of the solar conversion were restored using an inverse procedure based on a linear regression approach, which was assessed with synthetic data calculated using the TRNSYS software. The climatic data from meteonorm assisted the simulations for six Northeastern Asian locations. The short-term load profiles and the monthly thermal energy consumptions from eight case studies with different greenhouse sizes and locations were validated with the TRNSYS solutions. The mean bias error and the coefficient of variation of the root-mean-square-error of annual loads were controlled within 5% and 11%, respectively. Satisfactory results suggested that the simplified model could be used for the greenhouse thermal load estimation especially in Korea and the Northeastern Asian region. However, the model should be tested with more regions in future work for extensive applications.