Agro Fossil Free - Autonomous greenhouse microclimate through hydroponic design and refurbished thermal energy by phase change material

General Description

The rapidly increasing demand for agricultural food needs coupled with rising energy costs marked challenges for ensuring food bigger than any previous period. Therefore, greenhouses agriculture is a main focus for farmers, engineers and greenhouses designers in view of ways of improvement that provides. Compared to the conventional greenhouses, hydroponics warrant better quality, greater nutrient content, higher yield, efficient water and fertilizer use, but also more energy requirements. A new Hydroponic Greenhouse was designed and installed in the Research and Technology Center of Energy in Tunisia. A Solar Air Heater with Latent thermal storage using Phase Change Material was also realized for the hydroponic greenhouse heating taking into account the thermal heat loads of the specific application. In this work, the microclimate of the Hydroponic Greenhouse without heating was pursued to evaluate the performance of the hydroponic design. Hydroponic greenhouse allowed better environment than conventional greenhouses. During daytime, the new greenhouse temperature exceeded 18 °C and the difference between the inside and the outside reached mostly 6 °C. The relative humidity ranged between 20 and 35% the day and 70–85% at night.
Several measurements were also carried out after the heating to pursue the Solar Air Heater contribution. The temperature of the hydroponic greenhouse during nighttime after the heating raised by 6 °C and the nocturnal temperature was mainly over 15 °C. The diurnal temperature of the Heated Hydroponic Greenhouse was generally higher than 32 °C. Compared to conventional solar heating, the two packed beds of latent storage energy improved the indoor greenhouse environment especially during harsh and nocturnal periods.