Using Computational Fluid Dynamics to Evaluate High Tunnel Roof Vent Designs

Freestanding high tunnels are cost-effective, plastic film-covered growing structures that use very little to no modern environmental control technology. Natural ventilation is used to control temperature and humidity. Typically, ventilation openings are created along the sides by manually rolling up a section of the plastic film cover. While common on greenhouses, roof vents are not typically part of high tunnel designs used in the United States. This paper focuses on high tunnel ventilation during the summer, when maximizing the air exchange rate results in a low differential between inside and outside air temperatures. Computational fluid dynamics (CFD) simulations were used to evaluate the effects of several roof vent designs on the air flow rate through the high tunnel and the inside air temperature. The CFD models were developed and validated using environmental data collected at the Pennsylvania State University High Tunnel Research and Education Facility (Rock Springs, PA, USA). Five ventilation designs were simulated using a commercial CFD software package that was augmented with a radiation and crop architecture model. A root mean square error of 0.87 °C was found between the measured and simulated high tunnel temperatures (n = 144). The designs with roof vents were found to increase mass-based ventilation rates through the high tunnel by 20% to 78%. However, they did not lower inside air temperature more than 0.1 °C compared to the traditional design with roll-up side vents only. Additional research is needed to evaluate whether the control of other environmental parameters and weather conditions warrants the use of high tunnel roof vents, especially for humidity control and the combination of high temperature with low wind speed conditions

What You May Not Realize about Vertical Farming

Vertical farming (VF) is a newer crop production practice that is attracting attention from all around the world. VF is defined as growing indoor crops on multiple layers, either on the same floor or on multiple stories. Most VF operations are located in urban environments, substantially reducing the distance between producer and consumer. Some people claim that VF is the beginning of a new era in controlled environment agriculture, with the potential to substantially increase resource-use efficiencies. However, since most vertical farms exclusively use electric lighting to grow crops, the energy input for VF is typically very high. Additional challenges include finding and converting growing space, constructing growing systems, maintaining equipment, selecting suitable plant species, maintaining a disease- and pest-free environment, attracting and training workers, optimizing the control of environmental parameters, managing data-driven decision making, and marketing. The objective of the paper is to highlight several of the challenges and issues associated with planning and operating a successful vertical farm. Industry-specific information and knowledge will help investors and growers make informed decisions about financing and operating a vertical farm

What You May Not Realize about Vertical Farming

Vertical farming (VF) is a newer crop production practice that is attracting attention from all around the world. VF is defined as growing indoor crops on multiple layers, either on the same floor or on multiple stories. Most VF operations are located in urban environments, substantially reducing the distance between producer and consumer. Some people claim that VF is the beginning of a new era in controlled environment agriculture, with the potential to substantially increase resource-use efficiencies. However, since most vertical farms exclusively use electric lighting to grow crops, the energy input for VF is typically very high. Additional challenges include finding and converting growing space, constructing growing systems, maintaining equipment, selecting suitable plant species, maintaining a disease- and pest-free environment, attracting and training workers, optimizing the control of environmental parameters, managing data-driven decision making, and marketing. The objective of the paper is to highlight several of the challenges and issues associated with planning and operating a successful vertical farm. Industry-specific information and knowledge will help investors and growers make informed decisions about financing and operating a vertical farm