System for greenhouse climate monitoring in three dimensions

Abstract

The greenhouse in Throckmorton Hall at Kansas State University (KSU) has a temperature and humidity monitoring system. The system updates its measurements every thirty minutes online, and air temperature is controlled by an automated system. Each room has one temperature and humidity sensor box, which provides a suitable reference but is insufficient for more detailed plant research. To provide a distribution of temperature and humidity, a sensing system should be composed of a collection of sensors that gather data simultaneously. The new multi-point greenhouse monitoring system presented here can be helpful for plant research on a low budget. The demonstration system uses 27 sensor boxes in a 3x3x3 sensor grid (nine sensors at the same height and three different heights). Each sensor box contains temperature, humidity and light sensors that record data once per minute. MATLAB plots of these data indicate that temperature varied between 20 and 25 °C at night. Daytime temperatures are increased by sunlight, and rise to a maximum around noon. Sun-lit areas have higher temperatures than shaded areas, and during cloudy days all areas were almost the same temperature. Relative humidity is inversely related to temperature changes; when the temperature is stable, humidity is also stable. Humidity drops at noon because of increasing temperature and rises again at night. When researchers water the plants, humidity increases immediately. Greenhouse light intensity depends on the room design and the angle of the sunlight. Direct sunlight makes an obvious difference in shaded areas, and cloudy days promote even light distribution. Lighting at night time diffuses well at lower heights.