Modeling and analysis of different control strategies for fogging system in a subtropical greenhouse

Abstract

A dynamic environment model was established on the effects of greenhouse cooling on different control strategies in a fogging system, which simulations were then conducted by Matlab. Simulation results showed that by applying a suitable set of control strategy, the indoor temperature dropped and was less than the outdoor temperature of 34.4°C The temperature reduction degree changed within limits and delayed time. Inversely, when relative humidity and time delay were used as the control factors, the indoor temperature rose under high solar irradiation. The above phenomenon can be avoided when temperature control was applied. When operations of the fogging system used the dead zone as the setting control, variations of the indoor temperature was mainly relevant to the upper and lower limits of the zone. In situations where the spraying can reach the shutoff condition, the temperature variance increased as the range was larger, and the actuation frequency fogging system also decreased. When the time delay factor was employed in the fogging system, the indoor temperature varied in terms of fogging time and stop time. In order to narrow down the variation of indoor temperature, the operation and stop time in a cycle must be shortened. In this study, simulations with the cooling effects in a greenhouse were performed by using different control strategies for a fogging system. The results can serve as reference for planning future cooling control strategies for a fogging system.

Key words: Greenhouse, fogging system, control strategy.