Recipient Organization
NORTH CAROLINA STATE UNIV
(N/A)
RALEIGH,NC 27695
Performing Department
BIOLOGICAL & AGRICULTURAL ENGINEERING
Non Technical Summary
Greenhouse cooling designers have no recognized procedures for developing their designs. This results in greenhouse cooling systems that are inadequately design for certain climates. The purpose of this project will be to provide greenhouse cooling designers with appropriate procedures for designing cooling systems for different parts of the world.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
To increase the number of options available to greenhouse cooling designers. This will include: 1. developing specific guidelines for estimating the evapotranspiration coefficient, E, 2. developing an appropriate user-interface for CoolMod, the computer model presented in Willits (2003b), and incorporating modifications to increase flexibility, and 3. following up on the examination of the Ludvig Svensson shade cloths.
Project Methods
Evapotranspiration Coefficient: Extensive analysis of the data from the previous studies will be conducted to determine the number of parameters available for use in predicting E. This is critical since E is a function of outside weather; crop type, age, and configuration; whether or not evaporative cooling is used; and the inside design conditions specified. An insufficient range of these parameters will limit the usefulness of the guidelines developed. It may be necessary to conduct additional studies to increase the range of these parameters available in the data. These studies would be conducted at the Horticultural Field Laboratory on the NCSU campus. The facilities consists of two fan-ventilated greenhouses, 6.7 x 12.2 m, double polyethylene covered quonset style. Two naturally ventilated greenhouses are also available. The naturally ventilated houses are oriented so that a continuous sidewall opening (3/4 m high) faces south, the direction from which the
prevailing wind comes in the summer, and a continuous roof vent (3/4 m wide) faces north. When fully open, the combined vent area is approximately 28% of the floor area, based on the guidelines for natural ventilation. CoolMod: A user-friendly interface will be added to CoolMod. Optionally, features will also be added to increase its applicability to different crops and different greenhouse configurations. The degree to which these modifications can be made will depend upon the amount of outside funding that can be secured, but a user friendly interface will be added regardless. This will be done as a Visual Basic front end for the Matlab calculation engine. Shade Cloths: The current study examining the Ludvig Svensson shade cloths will be continued through at least May of 2008. This study is designed to compare two 60% shade rated LS cloths, one with aluminum strips on top and white plastic on the bottom and a second with white plastic strips on top and black plastic on the bottom,
to a 60 % shade rated, black plastic knit cloth. The pairs of cloths to be compared are placed over two nearly identical greenhouses, each growing a crop of tomatoes. These cloths are alternated between the houses to eliminate house differences. The houses are instrumented to determine air temperatures and humidities throughout the house, plus leaf temperatures in the canopy. Comparisons of cooling will depend upon differences in these parameters between houses. Similar studies may be done in subsequent years with other LS shade cloths as long as the company continues to provide funding. The TKSolver model will be modified and refined to accommodate discrepancies between the predicted and observed results of these studies. Once refined, it should be possible to propose improvements to the existing cloths.