Determination of the Effect of a Thermal Curtain Used in a Greenhouse on the Indoor Climate and Energy Savings

Abstract

In order to reduce the impact of outdoor extreme weather events on crop production in winter, energy saving in greenhouses that are regularly heated is of great importance in reducing production costs and carbon footprints. For this purpose, the variations in indoor temperature, relative humidity and dew point temperature in the vertical direction (2 m, 4 m, 5.7 m) of thermal curtains in greenhouses were determined. In addition, depending on the fuel used, the curtains’ effects on heat energy consumption, heat transfer coefficient, carbon dioxide equivalents released to the atmosphere and fuel cost were investigated. To reach this goal, two greenhouses with the same structural features were designed with and without thermal curtains. As a result of the study, the indoor temperature and relative humidity values in the greenhouse with a thermal curtain increased by 1.3 °C and 10% compared to the greenhouse without a thermal curtain. Thermal curtains in the greenhouse significantly reduced fuel use (59.14–74.11 m3·night−1). Considering the heat energy consumption, the average heat energy consumption was 453.7 kWh·night−1 in the greenhouse with a curtain, while it was 568.6 kWh·night−1 in the greenhouse without a curtain. The average heat transfer coefficient (U) values were calculated at 2.87 W·m−2 °C with a thermal curtain and 3.63 W·m−2 °C without a thermal curtain greenhouse. In the greenhouse, closing the thermal curtain at night resulted in heat energy savings of about 21%, related to the decrease in U values. The use of a thermal curtain in the greenhouse reduced the amount of CO2 released to the atmosphere (116.6–146.1 kg·night−1) and fuel cost (USD 21.3–26.7·night−1). To conclude, extreme weather events in the outdoor environment adversely affect the plants grown in greenhouses where cultivation is performed out of season. A thermal curtain, used to reduce these adverse effects and the amount of energy consumed, is essential in improving indoor climate conditions, providing more economical greenhouse management and reducing the CO2 released into the atmosphere due to fuel use.