Using a single-span double-polyethylene greenhouse without plants, the effect of natural ventilation rate on humidity and water use for fog cooling was investigated. A simple and unique control algorithm for fog cooling was proposed and tested. 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 24.5°C. Under several configurations of vent openings, the greenhouse environmental conditions and the outside weather conditions were monitored. The natural ventilation rate was measured continuously by the tracer gas method. The fog generated was collected and measured at 15-min intervals. Results showed that the inside relative humidity decreased with an increase in ventilation rate as expected from simulations based on the steady-state energy balance equations using a software Visual VETH, while the water used for fog cooling increased. For example, the humidity decreased from approximately 80 to 65% on a clear day when the ventilation rate was increased from 1 to 3.5 m3 m-2 min-1, while the water use increased from 18 to 21 g m-2 min-1. There was good agreement between the measured 45-min averages of ventilation rate and the predicted ventilation rates by Visual VETH. The control algorithm which incorporated the adjustment of vent openings demonstrated the possibility of maintaining relative humidity and air temperature simultaneously within a desirable range (65-75% and 24-25°C, respectively) while reducing the water used for fog cooling.
This is an overview of research activities in the areas of flexible automation and robotics (FAR) within controlled environment plant production systems (CEPPS) in the Department of Bioresource Engineering, Rutgers University. In the past thirty years, our CEPPS research has dealt with the topics including structures and energy, environmental monitoring and control, plant growing systems, operations research and decision support systems, flexible automation and robotics, and impact to natural (i.e. surrounding) environment. Computer and modeling/simulation techniques have been utilized extensively. Mechanized systems have been developed to substitute human's physical labor and maintain uniformity in production. Automation research has been directed towards adding, to the mechanized systems, the capabilities of perception, reasoning, communication, and task planning. Computers, because of their programmability, provide flexibility to automated systems, when incorporated with generic hardware devices. Robots are ideal hardware tools to be employed in flexible automation systems. Some technologies developed in our CEPPS research may be readily adaptable to Closed Bioregenerative Life Support Systems (CBLSS).
The South Pole Food Growth Chamber (SPFGC) is an automated hydroponic climate controlled chamber located inside the Amundsen-Scott South Pole station, which produces fresh vegetables and herbs, as well as a psychologically pleasurable environment for station personnel. The objective of this study was to document the SPFGC automated control practices, telepresence support, and resource utilization and crop production. Resource inputs included energy, water, plant nutrients, carbon dioxide, labor and the outputs included food, condensate water and oxygen. Data collected from January through October 2006 were used to evaluate the performance. Various plants (e.g. leafy greens, fruit crops, herbs and edible flowers) were grown within a hydroponic polyculture cropping system within the same controlled environment. Consumed resources included 1.1 kg d-1 of carbon dioxide, 0.21 kg d-1 of dry plant fertilizer salts, 1012 MJ d-1 (281 kWh d-1) of electrical energy, and production included 0.52 kg d-1 of oxygen and 2.8 kg d-1 of edible vegetables (fresh mass). The SPFGC system components and the control elements were described, and an energy balance analysis of the SPFGC was completed, and comparisons were made to various ALS food and oxygen production results.
The primary objective of the investigation was to evaluate the effects of selected perturbations in air temperature on the development of the tomato plant, Lycopersicon esculentum (c.v. Laura, DeRuitter Seeds Laura FI, Tm-C2-V-F2). The approach to this investigation was to quantify the plants responses to air temperature and organize this information to develop an environmental control model for tomato plant growth while integrating the information with machine vision technologies. The focus was on the effect of selected air temperature perturbations on crop growth and scheduling. The objectives were accomplished through growth chamber experimentation and model development in coordination with non-destructive machine vision technologies. Three replications were performed at three different air temperatures (high, normal, low). These experiments were used to develop baseline data for calibration of an empirical model and correlation with machine vision images. The model would allow for the quantity of biomass to be predicted at a given air temperature under constant air temperature conditions. Results from the growth chamber studies indicated that the small air temperature differences had the effect of altering the time to first flower for the tomato plant. However, under the three different temperature regimes the dry weight of the aerial portion of the plant at time of flowering was similar for each crop, and seemingly independent of air temperature. Preliminary, results of the plant model indicated that it was capable of predicting developmental rates and changes in the tomato plant based on the dry weight of the aerial portion of the plant. The correlation of the machine vision images with dry weight can be used with the model for plant developmental predictions and development of a control system for maintaining plant scheduling.
The transplanting of seedlings from high density plug trays into low density growing flats, as currently practiced in the bedding plant production systems, was the operation studied within a prototype workcell utilizing a Selective Compliance Assembly Robot Arm (SCARA) type robot. The concept of a multi-stop local work trajectory surrounding each seedling was incorporated into the workcell design consideration. The trays and flats were envisioned to flow across each other's path at different heights within the workcell. A straight-line robot wrist motion was used between the locations on a tray and a flat. A computer program for checking the interactions of the workcell layout, the robot motions and the flows of materials was developed. The average robot wrist horizontal travel distance per transplanting (AHT) for a given workcell could be readily calculated using this computer program. The AHT was evaluated for its use as an indication of the performance of any given workcell design. For the 12 cases studied, the AHT ranged from 0.381 m to 0.993 m which was found to correlate well with the average cycle time per transplanting.