A decision-support system for real-time management of Easter lily (Lilium longiflorum Thunb.) scheduling and height--I. System description
Abstract A decision-support system was developed for recommending night and day temperature settings to control the timing and height of Easter lily ( Lilium longiflorum Thunb.). Existing biological models and qualitative rules were combined into an overall model of the response of plant development rate to temperature. A process control algorithm was used to determine appropriate height control actions based on a graphical control chart of plant height over time. A knowledge-based system checked the feasibility of output from the development and height control models and generated a text report. This model was implemented on a personal computer in a program called “The Greenhouse CARE System” and has been linked directly with an environmental computer to control greenhouse temperatures. A companion article describes validation of this model.
IntelliGrow: a greenhouse component-based climate control system
Abstract A new greenhouse climate control system has been constructed with the objective of decreasing energy consumption while maintaining, or even increasing, plant production. The system is based on the use of mathematical models for estimating the absorption of irradiance, leaf photosynthesis and respiration. The model builds on a general leaf model that with a few modifications can be used for different greenhouse crops. The temperature, which was controlled according to the natural irradiance, was allowed to vary considerably more than in a standard climate. Under low light conditions, energy use was reduced because the temperature was lowered. In contrast, when irradiance is higher, the plants seem able to utilize both a higher temperature and CO2. During nighttimes the temperature was lower than in standard climate. The thermal screens were used according to a screen simulation system. The system balances the energy costs saved via isolation against the production loss caused by the decrease in irradiance. A six-month trial of the system resulted in energy savings ranging from 8% in late spring (April–June) to 40% in early spring (March–May). During the winters 1997–98 and 1998–99 the accumulated energy savings per season varied between 20% and 38% at two different locations in Denmark.
An autocalibrating model for simulating and measuring net canopy photosynthesis using a standard greenhouse climate computer
Abstract A model for measuring net canopy photosynthesis in commercial greenhouses is described. The problem of calculating CO 2 fluxes at high ventilation rates with sufficient accuracy with commercially available equipment is discussed, and a solution is suggested, using two cooperating submodels and an autocalibration algorithm. The first is a CO 2 -balance model which calculates the canopy photosynthesis as the residual accounting for the other CO 2 fluxes. The model stresses the importance of CO 2 infiltration at low ventilation rates and maintains an experience database of measured photosynthesis rates and related climatic variables. Model 2 is a black-box photosynthesis calculation that simulates the crop's photosynthetic response using temperature, irradiance, and CO 2 concentration as variables Model 2 takes over at higher ventilation rates, when model one cannot function with sufficient accuracy. The autocalibration algorithm uses the experience database from model 1 to tune model 2's performance to actual crop characteristics by performing regression routines once every day. The model was implemented using a previously described standard model interface on a standard climate computer system and allowed hourly monitoring of photosynthesis rates in standard greenhouses.