Efficient greenhouse design:Evapotranspiration approximated by a linear function of global radiation

Abstract

Comprehensive greenhouse design procedures may require numerous lengthy simulation-optimizations over a range of model parameters and over several years. One reason for the long computing time is the use of an implicit (here Stanghellini's) evapotranspiration (ET) model, involving an iterative procedure to solve for the indoor climate. It is suggested here that formulating ET as an explicit function of just global (solar) radiation could be sufficient, if the goal is to identify the most promising design alternative (best parameter set), while reducing computing time by two orders of magnitude. This is demonstrated by ordering various design alternatives (here bounds on the indoor environment) according to the expected resulting economic performance of the greenhouse system. It turns out that the same order is obtained with the simple explicit ET model as with the established implicit model. • Greenhouse models with implicit ET formulation require very long computing time. • Optimal greenhouse evapotranspiration (ET) is linearly related to solar radiation. • A solar-based ET model requires two orders of magnitude less computing time. • A solar ET model may be used to order design options according to their performance.