| A greenhouse crop production system involves high rates of energy usage to impose air temperatures and light levels to achieve high productivity, correct crop timing, and ideal crop specifications. In this research, the greenhouse crop and its microclimate was analyzed as an integrated system driven by solar radiation and external energy input. Models were developed to optimize greenhouse temperature set-points with respect to crop productivity and energy consumption. The work consists of three parts: (1) modeling responses of crop development and growth to the greenhouse microclimate; (2) simulating the greenhouse climate as affected by weather conditions and heating/cooling operations; and (3) integrating the greenhouse climate models with the crop models, to establish optimal temperature control strategies for improved crop productivity and energy use efficiency of greenhouse production.; Using Geranium and cut roses as examples, models were constructed to simulate how crop development and growth response to the greenhouse climate. Special attention was given to the effects of various temperature trajectories on crop timing and productivity. Greenhouse energetic models were constructed to simulate energy and mass exchange processes between various greenhouse components and ambient atmosphere. The temperature and light regimes were simulated by quantifying the greenhouse energy budget under typical weather patterns. The simulation of greenhouse climate models provided basic inputs for crop modeling, including PAR flux density, air temperature, CO2 concentration and humidity. Finally, the crop models and the greenhouse climate models were coupled to evaluate the shading effects on crop productivity and energy savings for cooling, and to establish optimal temperature set-points for improved greenhouse climate management. The overall objective of optimal environment control is to maximize the difference between crop gain and the energy cost. By simulating this system, the cost of implementing a particular greenhouse climate, and the impacts on crop development and productivity can be estimated. |
