An integrated transient model in TRNSYS for thermal management of the tomato growth process in a greenhouse with a PV-aided heat pump-assisted HVAC system

Greenhouses are the most common agricultural structures for controlled environment agriculture, and it is not easy to control the indoor climate due to the complexity of the heat and mass transfer mechanisms. Therefore, numerical models help to simulate the greenhouse indoor environment under various design alternatives, obtain the heating and cooling rates, and determine the appropriate control strategy. In this study, a novel transient thermal model of a greenhouse is developed in MATLAB and implemented in TRNSYS software to simulate the thermal management procedure for the tomato growth process. A PV-aided HVAC system with a heat pump is integrated into the greenhouse to meet the heating/cooling load and maintain the temperature and relative humidity of the indoor ambient within the desired ranges. It is assumed that the greenhouse has three tomato growth seasons annually. The temperature and relative humidity of the indoor air and the heating and cooling rates of the HVAC system are determined, and the temperature and relative humidity variations are compared against a greenhouse without an HVAC unit. The simulations are conducted with TRNSYS for four climatically different cities: Izmir, Valencia, Casablanca, and Tunis. The results reveal that the electricity consumption of the heat pump-assisted HVAC system is highest in Izmir, with 742,230 kWh/year. Besides, the highest photovoltaic electricity production is determined in Tunis, with 417,960 kWh/year. The highest reduction in carbon emissions is determined in Casablanca, with 112,541.4 kg CO₂ eq./year.