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California Polytechnic State University, San Luis Obispo

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Full-Text Articles in Life Sciences

Simulated Effects Of Dynamic Row Spacing On Energy And Water Conservation In Semi-Arid Central California Greenhouses, A. Moya, T. Mehlitz, Ilhami Yildiz, S. F. Kelly, C. Hardin Jan 2008

Simulated Effects Of Dynamic Row Spacing On Energy And Water Conservation In Semi-Arid Central California Greenhouses, A. Moya, T. Mehlitz, Ilhami Yildiz, S. F. Kelly, C. Hardin

Bioresource and Agricultural Engineering

Considerable effort is expended to conserve energy and water in current greenhouse systems, and look for alternative energy sources, especially passive heating and cooling strategies. Proper environmental management systems can significantly change the energy and moisture dynamics of greenhouse production systems. In this study, specifically, influences of dynamic row spacing on energy and water conservation were investigated. A dynamic computer simulation model was used to compare different row spacings, plant heights, and leaf dimensions to draw a conclusion about energy and water conservation. The results showed that using smaller spacings between cucumber crop rows (for instance, 0.5 m instead ...


Simulated Effects Of Reflective Mulch On Energy And Water Conservation In Semi-Arid Central California Greenhouses, T. Mehlitz, Ilhami Yildiz, S. Rahman, C. Hardin Jan 2008

Simulated Effects Of Reflective Mulch On Energy And Water Conservation In Semi-Arid Central California Greenhouses, T. Mehlitz, Ilhami Yildiz, S. Rahman, C. Hardin

Bioresource and Agricultural Engineering

In addition to the labor, energy and water consumption are the two main cost drivers in current greenhouse systems. Consequently, considerable effort is expended to conserve energy and water, and look for alternative energy sources. Greenhouses in hot and arid regions also require large quantities of water for irrigation. Proper environmental management systems can significantly change the energy and moisture dynamics of greenhouse production systems. This study aims to focus on reducing energy and water consumption in semi-arid California greenhouses. Influences of mulch (having different reflectivities) on energy and water conservation were investigated. The reflectivity of mulch used as a ...


Simulated Effects Of Various Environmental Management Practices On Water Consumption In Open And Confined Greenhouse Systems, Ilhami Yildiz, D. P. Stombaugh Jan 2008

Simulated Effects Of Various Environmental Management Practices On Water Consumption In Open And Confined Greenhouse Systems, Ilhami Yildiz, D. P. Stombaugh

Bioresource and Agricultural Engineering

The objective of this study was to evaluate the effects of relative humidity, light management, minimum ventilation rates, CO2 enrichment and canopy size on water consumption in three different greenhouse systems (conventional, open heat pump, and confined heat pump) in winter, spring, and summer months. Using different relative humidity set points resulted in almost the same relative humidity regimes within the confined greenhouse system, resulting in similar transpiration rates. No difference was observed in transpiration rates in the open system in winter either, because the inside relative humidity levels never reached the 70% and 80% set points. Some differences ...


Dynamic Modeling Of Microclimate And Environmental Control Strategies In A Greenhouse Coupled With A Heat Pump System, Ilhami Yildiz, D. P. Stombaugh Jan 2006

Dynamic Modeling Of Microclimate And Environmental Control Strategies In A Greenhouse Coupled With A Heat Pump System, Ilhami Yildiz, D. P. Stombaugh

Bioresource and Agricultural Engineering

The purpose of this study was to develop and validate a dynamic simulation model to be employed in accurate prediction of microclimate in a greenhouse as a function of dynamic environmental factors. The model has options to evaluate the effects of location, time of the year, orientation, single and double polyethylene glazings, conventional and heat pump heating and cooling systems, open and confined greenhouse systems, CO2 enrichment, variable shading, and the use of night curtains. Conventional gas furnace and evaporative cooling, respectively, provided heating and cooling in the conventional system. In the heat pump systems, gas-fired heat pump units ...


Simulated Performances Of A Heat Pump System For Energy And Water Conservation In Open And Confined Greenhouse Systems, Ilhami Yildiz, D. P. Stombaugh Jan 2006

Simulated Performances Of A Heat Pump System For Energy And Water Conservation In Open And Confined Greenhouse Systems, Ilhami Yildiz, D. P. Stombaugh

Bioresource and Agricultural Engineering

The purpose of this study was to determine and compare the performances of conventional and heat pump systems for energy and water conservation in open and confined greenhouse systems. Conventional gas furnaces and evaporative cooling, respectively, provided heating and cooling in the conventional system. In the heat pump systems, gas-fired heat pump units provided both heating and cooling. The greenhouse with heat pump units also had an option to be operated as a completely confined system, using one of the heat pump units as a dehumidifier. Average energy consumption in winter was 56.9, 23.5, and 11.3 MJ ...