Gene A Giacomelli

Abstract:

Cooling must be supplied for greenhouses located in semiarid climates most of the year to provide desired climate conditions for year-round crop production. High-pressure fogging systems have shown promising results for cooling, however the lack of effective control strategies, especially under passive ventilation, have limited their use. In this study, a new proposed climate control strategy, which considers the contribution on cooling and humidification from plants, is tested through simulation. The developed strategy using variable pressure fogging (VPF) and variable vent configurations was compared to a constant pressure fogging (CPF), fixed vents cooling strategy. In both cases, the control of fog was based on vapor pressure deficit (VPD) set points. Results showed that on average, VPF based system was able to save 15.2% of water and consumed 10.1% less energy. Pump cycling was reduced by 78.5% and lower temperature and relative humidity fluctuations were achieved by adjusting fog rates through manipulating the system working pressure. Finally, simulations also showed that by reducing the number of nozzles, a smaller fogging rate was achieved and the system performance and savings on water and energy were enhanced during morning hours of operation.

Abstract:

Water availability is a common concern in semi-arid regions, such as Southern Arizona, USA, where greenhouse crop production is popular due to high solar radiation. Hydroponic greenhouse crop production greatly reduces irrigation water use; however, water use by evaporative cooling systems has never been quantified. This project investigated water use by two evaporative cooling systems: pad-and-fan (P&F) and high-pressure-fog (HPF) with fan ventilation and a central overhead line. Water use data were collected from a double-layer polyethylene film-covered greenhouse (28 × 9.8 × 6.3 m) with mature tomato plants (1.7 plants m ^-2) from 08:00-17:00 for each ventilation rate tested under semi-arid climate conditions (T Out,Avg=35°C, RH Out,Avg=10%, Solar Avg=900 W m ^-2). Total daily water use by P&F was 3.2, 6.4, 8.5, and 10.3 L m ^-2 for ventilation rates of 0.016, 0.034, 0.047, 0.061 m ³ m ^-2 s ^-1 respectively. Total daily water use by the HPF system was 7.9, 7.4, and 9.3 L m ^-2 for fan ventilation rates of 0.01, 0.016, 0.034 m ³ m ^-2 s ^-1, respectively. Total greenhouse WUE (water use efficiency) was calculated using hydroponie irrigation (4.5 L m ^-2) and evaporative cooling water use. Total WUE values were comparable to sprinkler-irrigated WUE (15-19 L m ^-2) and flood-irrigated WUE (12L m ^-2). Using a "closed" hydroponic irrigation system would increase the WUE greatly and should be implemented to conserve water. Furthermore, HPF water use should decrease under natural ventilation.

Abstract:

The micro gravity pocket (MGP) was designed to be used for continuous cropping of root crops in microgravity within a controlled environment. NASA plans for a 'Salad Machine' to grow carrot and radish in microgravity for consumption by the astronauts. The pocket system was designed to be light weight, easy to plant, monitor and harvest, with no free water and low energy requirements. The MGP system was developed using porous sheets of plastic to wick water to the plant roots. The design was tested with radish, growing horizontally facing a metal halide lamp. The hydrophilic property of the porous sheet made water available to the roots, but the small size of the pores prevented root growth into the sheet. The MGP was not significantly different in yield compared to the porous tube.

Abstract:

The different possible positions for the roof and sidewalls of retractable roof greenhouses allow them to behave either as greenhouses, shadehouses or wind barriers. Radiation and wind control must be part of the control strategy along air temperature which proves to be a poor method of control as it is the case currently. Globe temperature is proposed as a viable controller for retractable roof greenhouses in arid regions, for its ability to integrate in one simple data point temperature, radiation, and wind speed. With the use of two globe thermometers it is possible to merge the data between outdoors and indoors to create an improved environment for vegetable cultivation while maximizing light exposure for the plants.

Abstract:

The effects of the factorial combination of two light intensities (200 and 800 μmol m^-2 s^-1) and two CO2 concentrations (360 and 800 ppm) were studied on the productivity and nutritional quality of spinach (Spinacia oleracea L.) grown under controlled environment. After 6 weeks within a growth chamber, spinach plants were sampled and analyzed for productivity and quality. There were no statistically significant interactions between the effects of light and CO2 for all of the variables studied, except for the nitrate and oxalic acid content of the leaves. High light and high CO2 independently one from the other, promoted spinach productivity, and the accumulation of ascorbic acid, while their interactive effect limited the accumulation of nitrate and oxalic acid in the spinach leaves. The results highlight the importance of considering the effects of the interaction among environmental variables on maximizing production and the nutritional quality of the food when cultivating and modeling the plant response in controlled environment systems such as for bioregenerative life support. © 2013 COSPAR. The Authors. Published by Elsevier Ltd. All rights reserved.