A microcomputer-based system for all-year-round temperature control in greenhouses in dry arid lands

Abstract

A microcomputer-based control system has been developed for maintaining environmental conditions for greenhouse crops, such as tomato and cucumber, grown in hot and dry arid lands. These regions are characterized by severe weather conditions in summer, with high thermal intensity during most of the day-time. The system consists of a data acquisition unit which controls real-time activities, and a host microcomputer which is used for program development, program downloading, and for accessing and processing collected data. It monitors absolute values of the average inside and outside air temperatures, and, depending on the outcome of these measurements, the cooling, heating and/or ventilating devices are switched on or off. The system was tested during the winter and the summer peak (1991), these being the two extreme seasons of the year. Results showed that it is possible to maintain an optimum temperature range of 16–30°C throughout the year, with a smooth transition from the day-time optimum to the night-time optimum, while the outside air temperature varied between a minimum of 8.5°C and a maximum of 45.5°C.