Energy saving measures in optimally controlled greenhouse lettuce cultivation

Efforts to increase the energy use efficiency (EUE) of greenhouses are made in various fields, e.g., crop management and breeding; greenhouse design and technology; and climate control, including optimal control.
Quantifying and comparing the influence of the different components of the greenhouse system on EUE is important for improving greenhouse energy efficiency.
In this study, we examined an optimally controlled greenhouse lettuce system during a winter cycle in the Netherlands.
A model sensitivity analysis of the optimal control problem aimed at minimizing heating was performed to investigate which of the system components had the strongest influence on EUE. The results were compared with a previous study examining energy saving measures in lettuce cultivation.
It was found that a reduction in indoor temperature, an increase in roof transmissivity, and to a lesser extent, an increase in insulation, improved the EUE of an optimally controlled greenhouse in a similar way as a conventionally controlled greenhouse.
A 10% increase in EUE of the optimally controlled greenhouse was achieved by each of the following: a 0.2°C decrease in minimum indoor temperature; a 7% decrease in heat loss through the cover; a 13% increase in yield factor; and a 13% increase in net photosynthesis.
The results suggest that finding ways to decrease the indoor temperature without reducing yield has the highest potential for increasing EUE. In addition, optimal control may be combined with known energy saving measures to achieve a higher EUE than previously found.

XXX International Horticultural Congress IHC2018: III International Symposium on Innovation and New Technologies in Protected Cultivation

D. Katzin, S. van Mourik, F.L.K. Kempkes, E.J. van Henten

energy saving, energy use efficiency, greenhouse modeling, crop modeling, optimal control, sensitivity analysis, lettuce

https://doi.org/10.17660/ActaHortic.2020.1271.36