Abstract
In this study, we propose a building energy simulation model of a multi-span greenhouse using a transient system simulation program to simulate greenhouse microenvironments. The proposed model allows daily and seasonal control of screens, roof vents, and heating setpoints according to crop needs. The proposed model was used to investigate the effect of different thermal screens, natural ventilation, and heating setpoint controls on annual and maximum heating loads of a greenhouse. The experiments and winter season weather conditions of greenhouses in Taean Gun (latitude 36.88° N, longitude 126.24° E, elevation 45 m) Chungcheongnam-do, South Korea was used for validation of our model. Nash–Sutcliffe efficiency coefficients of 0.87 and 0.71 showed good correlation between the computed and experimental results; thus, the proposed model is appropriate for performing greenhouse thermal simulations. The results showed that the heating loads of the triple-layered screen were 70% and 40% lower than that of the single-screen and double-screen greenhouses, respectively. Moreover, the maximum heating loads without a screen and for single-, double-, and the triple-layered screens were 0.65, 0.46, 0.41, and 0.34 MJ m−2, respectively. The analysis of different screens showed that Ph-77 (shading screen) combined with Ph-super (thermal screen) had the least heating requirements. The heating setpoint analysis predicted that using the designed day- and nighttime heating control setpoints can result in 3%, 15%, 14%, 15%, and 40% less heating load than when using the fixed value temperature control for November, December, January, February, and March, respectively.
Highlights
In the greenhouse sector, energy saving is one of the most significant challenges since heating costs have increased to more than 40% of total production costs [1]
In one of our previous studies, [30] we provided a comprehensive review of the application of the transient system simulation (TRNSYS) program in agricultural greenhouses
4 detailswas the greenhouse operating conditions occurring during timeboth when the greenhouse temperature controlled by natural ventilation
Summary
Energy saving is one of the most significant challenges since heating costs have increased to more than 40% of total production costs [1]. Night thermal screens are widely used inside greenhouses to save energy by reducing heat loss to the ambient environment during winter. During nighttime in winter seasons, thermal screens are controlled transiently. Screens are deployed to reduce heat loss and retracted during the day to allow more solar radiation to enter the greenhouse. This passive heating method provides an effective and low-cost approach to decrease heating energy demand. Ventilation is controlled in a greenhouse by an inside greenhouse temperature setpoint. To the best of our knowledge and from the literature review, no study has been conducted using any tool to simulate greenhouse microenvironments that considers all control parameters together and depends on the real-time greenhouse condition as operated in the field
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