CO2 Use and Energy Efficiency in Closed Plant Production System by Means of Mini-air Handling Unit

The concept of resource use efficiency is strictly related to crops production in closed plant production system (CPPS). In fact, it is essential to maximize the crop yield with the minimum employment of resources. Among the main ones there are the CO2, to replace that absorbed for photosynthetic activity, and primary energy for the conditioning of the closed environment. In this work the CO2 level inside Controlled Environment Agriculture (CEA) is controlled by means of a mini-air handling unit (MAHU) with heat recovery, which renews the air to keep constant the indoor CO2 concentration. The MAHU is installed in a local firm, and it is equipped as an IoT system and remote control. Both sensors, actuators and controller are not directly connected to the Unit but by mean of a remote unit located in the University laboratory. The overall performance of the connection was evaluated. Tests were conducted in an experimental CPPS for the lettuce production. The air conditioned by the handling unit was supplied in the environment by a perforated duct. CO2 probes allowed to measure the concentration inside the supply duct, exhaust duct, and indoor environment. In addition, a set of probes to measure both physic and energy parameters was installed on MAHU to calculate the Energy Efficiency Ratio (EER) of the system. The performed tests make it possible to evaluate the efficiency of the MAHU both in terms of overall connection performance and in controlling the CO2 inside CPPS. The continuous replacement of the indoor air allows keeping almost constant its concentration, leading to an important saving in terms of CO2 enrichment. Remarkable energy performances were also highlighted. The proposed IoT system well suites the Industry 4.0 paradigm as it allows installation/maintenance of the different parts of the whole system without any other operation on the remaining parts.