Smart Agricultural Technology (Oct 2023)
Comparison of heating modules for suspension-type multipoint temperature variability management in smart greenhouses
Abstract
Managing the temperature inside greenhouses is essential for optimum crop growth and the control of diseases and physiological disorders in plants. In large-sized greenhouses, the automatic operation of small-sized multipoint suspension-type heating modules can facilitate better site-specific temperature management by providing favorable uniformity. The objective of this study was to evaluate efficiency of candidate heating modules before the prototype fabrication of a small-sized heating module for smart greenhouses temperature management. Three different heating modules (i.e., finned tubular (FT), fin element positive temperature coefficient (PTCf), and honeycomb positive temperature coefficient (PTCh)) were tested inside a closed chamber (41 m3) and a small greenhouse (98 m3). A wireless sensor network (WSN) was established to monitor the inside environment, operate heating modules, and detect their operational status. In the closed chamber, the PTCf module exhibited a temperature rise rate 8.59% and 7.36% higher than those of the FT and PTCh modules, respectively, while maintaining a superior average temperature variability range of 1.43 – 5.16 (±0.55 – ±0.85) °C. The elapsed times for the three modules were 12.70%, 8.30%, and 10.85% longer than their calculated times, indicating the effectiveness of the heating modules in regulating the environment. During the tests in the small greenhouse, the PTCf module demonstrated a greater average temperature difference between the inside and outside, followed by the FT and PTCh modules. The respective average temperature variability levels inside the greenhouse were recorded as 5.80 – 10.15 (±1.30 – ±2.68) °C, 4.90 – 8.93 (±1.35 – ±2.36) °C, and 4.86 – 9.38 (±1.25 – ±2.35) °C for the three modules. The performance of the PTCf module was better compared to the other two during the experiments in terms of efficiency and maintaining uniformity. However, large-scale field tests with multiple heating modules are required to verify these experimental findings.
