Abstract
Greenhouses with multi-layered thermal curtains have been widely disseminated. However, the optimization of the timing of opening/closing operation of such curtains deserves additional study. First, the heat dynamics in the greenhouse with multi-layered thermal curtains was modeled by combining steady and unsteady processes of heat transfer, and the model was verifi ed to have a reliable validity. Next, based on the model, the timing thresholds for the opening/closing operation were examined with reference to the room temperature, time of day, and amount of solar radiation. The relationships between the respective timing thresholds and the fuel consumption were investigated at a set room temperature of 12 °C. In the case of the curtain operation based on the room temperature threshold, fuel consumption was the lowest at the threshold of 13 °C (the standard control operation). In the case of the threshold of time of day, the minimum fuel consumption was calculated at the respective thresholds of 8:40 and 15:10 for opening and closing, and the fuel consumption was 46.1 L lower than that in the standard control operation. In the case of the threshold of amount of solar radiation, the minimum fuel consumption was calculated at the threshold of 180 W m-2, and the fuel consumption was 52.1 L lower than that in the standard control operation. Furthermore, it was found that the threshold for the opening operation is more important for energy saving than that for its counterpart closing operation. Resultantly, a method to optimize the thresholds for the opening/closing operation of the greenhouse curtain was proposed in consideration for the fuel consumption and the solar radiation.
