Optimization of the light entrance of the Venlo and wide span type greenhouses using the IDT method

TNO has developed a computer program to calculate the light interception of the greenhouse structure using an improved half-perimeter method, taking into account reflections and shadowing. This program is used to optimize the light entrance of the Venlo type greenhouse. Furthermore the influence of artificial lighting on the total light interception is considered. The objective is to minimize the light interception of the Venlo type greenhouse concept (with and without lighting equipment). The Product board for Horticulture sponsored the study. The half perimeter theory was the basis of the IDT method. This theory is based on a diffuse light distribution. The effects of reflection and shadowing are added to the theory. The program is widely used by greenhouse construction companies and suppliers to improve the light interception of their greenhouses. The theory is also implemented in the Dutch Greenlabel programme, to stimulate energy efficient greenhouses. The program is used to compare several common types of the Venlo greenhouse type. The following parameters are varied: bay width, glass panel width, airing window size, gutter type and light intensity level of the lighting system. The total range of light interception is about 7 % (difference between maximum and minimum light interception of the greenhouse including lighting system). The range of the lighting system is 3% Concluded is that a 4 meter bay width together with 1,67 meter glass panels is the most favorable Venlo greenhouse type. Integration of the lighting system with the structure can improve the light interception with 0,7%