Economic Greenhouse Decision Support: Embedding a Long Short-Term Memory Network in a Constraint Programming Decision Support System

The increasing global food demand, accompanied by the decreasing number of expert growers, brings the need for more sustainable and efficient solutions in horticulture. Consultancy company Delphy aims to face this challenge by taking a more data-driven approach, by means of autonomous growing inside the greenhouse. The controlled environment of greenhouses enable data collection and precise control. Delphy's current solutions focus on the needs of the crop, but a grower also needs to consider the economic aspect of taking certain decisions on the greenhouse climate. A potential method for solving this complex problem is Constraint Programming (CP). In this work, the applicability of CP for the greenhouse economic optimal control problem will be studied. The contributions of this work are threefold; First, the greenhouse climate is modelled with Long Short-Term Memory (LSTM) and Temporal Convolutional Network (TCN) machine learning models. Secondly, an LSTM model is embedded into a CP model. Lastly, the profit of the grower is optimised through this CP decision support system (DSS). The performed experiments show that both types of time-based machine learning models can model greenhouse temperature and humidity deficit with reasonable accuracy, while light and CO2 are harder to predict. The correctness of the LSTM-in-CP embedding is validated. The implemented DSS is not yet practically applicable, as the search space is too large to come to reasonable results for realistic instances. For small instances however, the DSS is able to improve the decisions of the grower, demonstrating the potential of using CP for economic greenhouse decision making