THEORY AND VALIDATION OF A LIQUID RADIATION FILTER GREENHOUSE SIMULATION FOR PERFORMANCE PREDICTION

A greenhouse is described which has a selectively absorbing liquid rad iation filter (LRF) circulating in double layered cladding. The filter removes much of the near infrared wave band of solar radiation (>700 nm) while transmitting most of the photosynthetic radiation (400-700 n m). This greatly reduces the heat input to the greenhouse and, by tran sferring heat from day to night, facilitates better temperature contro l. This is particularly important for CO2 fertilization, which require s that the greenhouse should remain closed during daylight hours. A co mputer simulation model was developed to study the relationship betwee n design parameters of such a LRF greenhouse and its thermal performan ce under different climatic conditions. The model was based on a small number of governing equations describing the major physical phenomena responsible for the greenhouse climate. Validation of the simulation was performed with data from a 330 m(2) LRF greenhouse, operating in t he Negev (Israel) desert highlands. The predicted greenhouse temperatu res were found to agree with measured values to within one to two degr ees Celsius. Performances of a LRF and a conventional greenhouse were compared using the simulation and hourly meteorological data for centr al Israel. For the summer season of May to October the number of dayli ght hours during which the LRF greenhouse could remain closed was larg er by about two-thirds than that of the conventional greenhouse.