Gene A Giacomelli

Abstract:

A publicly accessible multimedia instrument for greenhouse education was developed for global use. The instrument consists of (1) greenhouse videos produced on site in Arizona. Vermont. Ohio and Florida that emphasize state-specific production, environmental control, labor, and marketing issues; (2) an interactive Flash-based greenhouse environment simulator that allows users to model greenhouse environments based on climate data from each of the four video locations; (3) a searchable digital repository containing hundreds of useful greenhouse images, videos, and lectures, and (4) a web-based method for instructors to evaluate perceived student learning of greenhouse concepts. The Interactive Greenhouse Environment Simulator is driven bv a mathematical model developed bv engineers which is linked to a Flash-based graphical user interface (GUI). Following user selection of climate, structure and environmental control choices, dynamic environmental information is shown graphically during the simulation, allowing users to model changes in the greenhouse environment.

Abstract:

In addition to ventilation, daily cooling must be provided for greenhouses located in semiarid climates to maintain the desired climate conditions for year-round crop production. High-pressure fogging systems have been successfully developed for greenhouse cooling. However the lack of control strategies, in combination with ventilation systems, especially passive ventilation, has limited their capabilities. A new cooling control strategy, which considered the contribution of humidification and cooling from the crop, was evaluated by computer simulations. The strategy controlled the amount of fog introduced into the greenhouse, as well as the percentage of vent openings to maintain desired values of greenhouse atmospheric vapour pressure deficit (VPD) and enthalpy, respectively, which would consequently affect air temperature. The performance was compared to constant fogging rate strategy, which was based on VPD. On average, the new strategy saved 36% water and consumed 30% less electric energy. Smaller air temperature and relative humidity fluctuations, and more consistent control, were achieved by varying the fog system operating pressure to provide a more optimum amount of fog for evaporative cooling. It was demonstrated by simulations that dynamically varying the fog rate and properly selecting the number of nozzles, savings of water and electric energy were increased, while still maintaining acceptable VPD and temperature. The improvements in the greenhouse climate achieved by the new strategy were due to its ability to dynamically manipulate fog rates, as well as, the vent configurations. © 2011.

Abstract:

Innovations in greenhouse engineering are technical developments which help evolve the state-of-the-art in CEA (Controlled Environment Agriculture). They occur in response to the operational demands on the system, and to strategic changes in expectations of the production system. Influential operational factors include availability of labor, cost for energy, logistics of transport, etc. Influential strategic factors result from broader, regional issues such as environmental impact, product safety and consistency, and consumer demand. These are industry-wide concerns that have the effect of changing the production system in the long term. Global issues are becoming more influential on greenhouse production sustainability, and include less tangible issues such as social acceptance, political stability, quality of life benefits, and environmental stewardship. These offer much more complex challenges and are generally beyond the realm of engineering. However global issues do affect greenhouse engineering innovation. The most effective innovations in greenhouse engineering design, operations and management, will incorporate input from partnerships with the academic, private and public sectors of society. Furthermore, successful applications include, at least to some degree a multi-disciplinary approach of the sciences, engineering and economics, while for ultimate success and sustainability, societal and political support must also be attained. For this overview of innovation in greenhouse engineering a list of influential factors, or "driving forces" affecting the development, application, evolution and acceptance of greenhouse systems have been described. The factors are similar for all greenhouse systems around the world, as they include the plant biology of the crop, the physical components of the structure and production system hardware, the management and logistics of labor and materials, and the mechanism of marketing the crop. Each greenhouse system, wherever located, must resolve similar problems for its specific application. The magnitude of the factors and their relative local importance are different for the specific sites. The design response will be introduced and related to the factors, as examples of innovation.

Abstract:

The ultimate goal of this collaborative project is to develop an effective environmental control strategy to cool the greenhouses for plant production and minimize the water use in semiarid climate. Using a single-span double-polyethylene greenhouse with tomato plant canopy at The University of Arizona, the canopy transpiration rate and the water balance of greenhouse were investigated. The greenhouse was equipped with high-pressure fog nozzles, roll-up side vents with insect screens, and a roof vent. Fogging was operated cyclically with an air temperature set point of 24°C. Under different vent configurations, the transpiration rate was measured using a stem gage. The amounts of generated fog and non-evaporated water droplets were collected and measured. The natural ventilation rate was measured continuously using SF 6 gas as a tracer. Preliminary results showed that the transpiration rate increased linearly with an increase in vapor pressure deficit (VPD) of the air. When the ventilation rate was decreased by reducing the vent openings, the total water use in the greenhouse decreased by 13% and relative humidity increased as expected from simulation based on the steady-state energy balance. The decrease in canopy transpiration was driven by the decrease in VPD, and was at a greater magnitude than that of fog evaporation rate under the present experimental conditions with relatively high humidity ranging 70-94%. These results suggest that by optimizing natural ventilation rate, we could effectively cool the greenhouse with less water use.

Abstract:

Spectral and dynamic morphological features were investigated for plant health monitoring using machine vision techniques. The plants were stressed by withholding all nutrient salts. The spectral reflectance of healthy and stressed lettuce leaves (Latuca sativa cv. `Ostinata') was measured to determine at which wavelength(s) a stressed condition would be apparent. The measured wavebands were between 400 and 1000 nm. A reference waveband was utilized to account for photometric variables such as lighting and surface geometry differences during image acquisition. The expansion of the top projected leaf area (TPLA) was found to be an effective feature to identify stressed plants. The nutrient stressed plant was identifiable within two days after nutrients were withheld from a healthy plant. This was determined by a clearly measurable reduction in TPLA expansion.