Daily Temperature Integration: a Simulation Study to quantify Energy Consumption

A combined greenhouse climate and control model was used to study energy consumption in year-round cut chrysanthemum. Temperature was either controlled for energy saving with temperature integration within 24 h using the margin between heating and ventilation temperature b as control (TI) or the temperature integration regime was restricted within 24 h by a set point for negative temperature difference between average day and average night temperature TDIF to attain a temperature regime for stem length control (TIDIF). Energy consumption was reduced by both regimes compared to a standard regime according to commercial practice when heating in winter was shifted to nighttime using a screen. With increasing weather fluctuations in spring and autumn, weekly energy consumption could decrease by more than 60% for TI with ±6°C temperature bandwidth. With TIDIF in the same period, only 37 or 17% (TDIF of −6 and −12°C, respectively) less energy was used than with a standard recommended climate regime (TP). In general, TIDIF reduced energy demand compared to TP, but energy saving was higher with TI. In deciding whether to apply either TI or TIDIF, the actual cultivation period is the most important criterion. Controlling stem length with a negative temperature difference in spring and autumn has the highest additional costs, control with almost no negative day to night temperature difference is possible in summer; during winter, both temperature control regimes result in an almost similar greenhouse climate.