Gene A Giacomelli

Abstract:

Greenhouse crop production systems are located throughout the world within a wide range of climatic conditions. To achieve environmental conditions favorable for plant growth, greenhouses are designed with various components, structural shapes, and numerous types of glazing materials. They are operated differently according to each condition. To improve the pedagogy and the understanding of the complexity and dynamic behavior of greenhouse environments with different configurations, an interactive, dynamic greenhouse environment simulator was developed. The greenhouse environment model, based on energy and mass balance principles, was implemented in a web-based interactive application that allowed for the selection of the greenhouse design, weather conditions, and operational strategies. The greenhouse environment simulator was designed to be used as an educational tool for demonstrating the physics of greenhouse systems and environmental control principles. Several scenarios were simulated to demonstrate how a specific greenhouse design would respond environmentally for several climate conditions (four seasons of four geographical locations), and to demonstrate what systems would be required to achieve the desired environmental conditions. The greenhouse environment simulator produced realistic approximations of the dynamic behavior of greenhouse environments with different design configurations for 28-h simulation periods.

Abstract:

Experiments have been conducted to determine the correlations between the available hourly and daily photosynthetically active radiation (PAR) and total solar radiation. PAR was measured in the photon flux density unit of mol s** minus **1 m** minus **2 and total radiation was in the radiant flux density of W m** minus **2. Regression equations are presented in this paper for two purposes: (a) to show the predictability of PAR using available total solar radiation data, and (b) to provide empirical equations for estimating direct and diffuse PAR based on total radiation values.

PMID: 11541685;Abstract:

The tomato plant was used as a model to study growth and movement due to temperature changes in the environment. A morphological feature, plant top projection canopy area (TPCA), was used to characterize the plant growth and movement. Three temperature regimes (normal temperature, low temperature, and a step change from normal to low temperature) were used for the study. It is found that the plants have significant cyclic canopy movement. In addition, both plant growth, which is represented by canopy expansion, and canopy movement are affected by air temperature. The response of the plant to a step change of air temperature was also documented.

Abstract:

Recently in some large scale greenhouses, young tomato seedlings have been planted between mature crop rows to enable year-round production. Young seedlings receive light intercepted and transmitted/reflected by leaves of mature crops. Light quality (spectrum) changes by these procedures and affects the seedling growth. In particular, red/far red ratio is of main concern, because this ratio affects the stem extension rate via the change in the phytochrome photostationary state (Pfr/Ptotal)-However, there have been no reports on the light quality in and between tomato crop rows. Measurements of light quality in and between mature tomato crop rows were conducted in a semi-arid greenhouse in Tucson, Arizona on a clear day and profiles of R/FR ratio and Pfr/Ptotal were calculated. When the direct solar radiation penetrated into the canopy in parallel to the row, photon flux density (PFD) in FR at the height of 2.20 m in the passage between the rows was larger than that at the canopy height (3.10 m). Gradual decrease of R/FR with the depth into the canopy was observed in the passage, but in the rows, R/FR took the minimum value at the middle of the height. In the passage, Pfr/Ptotal was almost constant with regard to the height when the direct solar radiation ran parallel to the row, but at other periods slightly decreased with the depth into the canopy from 0.7 at the canopy height to 0.6 at the ground. In the rows, Pfr/Ptotal took the minimum at the middle of the height.

Abstract:

This study was conducted to determine the effects of vent configuration and external wind speed on three-dimensional distribution of air temperature in a naturally ventilated multi-span greenhouse using wind tunnel experiments. The experiments were conducted with the scale models in a wind tunnel with four different vent configurations and at four external wind speeds ranging from 0 to 3 m/s at full scale, with 1 m/s increments. Three dimensional temperature distributions were analyzed and the airflow patterns were observed based on temperature distributions. The highest air temperatures were found to be in spans close to the leeward side vent when the side vents were closed at zero wind speeds in the case when the roof vents were fully open and side vents were closed. The air temperature, measured by thermocouples, was higher on the windward side of the greenhouse than on the leeward side for all wind speeds when only roof vents were used. The distribution of air temperature was more uniform when both side and roof vents were used. As the wind speed increased, the average internal air temperature decreased for all cases. Contribution of side vents for greenhouse ventilation and reduction of air temperature were significant for the particular greenhouse design used in this study.