S06 - Session P1 - Validation of an empirical heat pipe energy model for practical use in the decision support system `InfoGrow´

Authors: Katrine Kjaer, Shuping Chen, Jesper Aaslyng *, Niels Holst, Jakob Skov Pedersen

InfoGrow is a model-based decision support system for greenhouse energy and production management, which integrates monitoring of resource use and plant growth. We installed InfoGrow in four greenhouse compartments: in two similar compartments at a pot plant grower and in two dissimilar compartments at a herb grower. This allowed us to compare the resource use efficiency between different climate control strategies, and to validate the energy model in greenhouses of different designs and configurations. Energy and climate sensors were installed in all four greenhouse compartments and the data were logged continuously. The heat pipe energy model consists of a single non-linear equation that predicts the outlet temperature from two time-varying variables: the pipe inlet temperature and the greenhouse temperature. The model requires three parameters: one is the water transit time, which can be estimated from pipe geometry, and further two, which can be calibrated (i.e., estimated) by the best-fit to a time series of logged greenhouse data, as exemplified by this study. We calibrated the heat pipe energy model to the four greenhouse compartments, obtaining parameter estimates specific to each compartment, and discussed the possible reasons for variation in the estimated parameter values. We found that even small differences in climate control strategy, greenhouse orientation, neighbouring buildings, and daily operation can cause marked difference in energy expenditure.