Evaluation of some agricultural wastes as a cooling pad in greenhouses

The aim of this study was to determine the suitability of some agricultural wastes (hazelnut shells, banana branches and peanut shells) as cooling pads that can be used as alternatives to commercial cellulose pads commonly used in cooling greenhouses. For this purpose, ten different treatments were tested in a high tunnel greenhouse under field conditions: (i) natural ventilation (NV), (ii) natural ventilation + external shading net (NV+ESN), (iii) cellulose pad (CP), (iv) cellulose pad + external shading net (CP+ESN), (v) hazelnut shell pad (HSP), (vi) hazelnut shell pad + external shading net (HSP+ESN), (vii) banana branch pad (BBP), (viii) banana branch pad + external shading net (BBP+ESN), (ix) peanut shell pad (PSP), and (x) peanut shell pad + external shading net (PSP+ESN). According to the obtained results, the cooling effect in front of the pad in CP, CP+ESN, HSP, HSP+ESN, BBP, BBP+ESN, PSP and PSP+ESN applications were measured as 5.6 °C, 6.6 °C, 4.2 °C, 5.1 °C, 4.0 °C, 4.9 °C, 3.9 °C and 4.6 °C lower than the outdoor environment, respectively. The relative humidity values measured in front of the pad were determined to be 30.2%, 32.6%, 22.2%, 21.5%, 20.5%, 19.6%, 15.2% and 18.1% higher than the outdoor environment, respectively. The cooling efficiencies of the applications were calculated as 51.3%, 56.2%, 39.2%, 40.7%, 38.3%, 38.2%, 30.7% and 35.1%, respectively. Cooling capacities are 2.6 kW, 3.1 kW, 2.0 kW, 2.4 kW, 1.9 kW, 2.3 kW, 1.8 kW and 2.1 kW, respectively. The system coefficient of performance values were calculated as 10.5, 12.4, 7.9, 9.5, 7.6, 9.2, 7.3 and 8.5, respectively. Water consumption values were determined as 2.9 L/h, 3.4 L/h, 2.2 L/h, 2.8 L/h, 2.2 L/h, 2.9 L/h, 2.0 L/h and 2.8 L/h, respectively. As a result of the study, it was determined that commercially used cellulose pads have advantages over other applications. However, considering the local availability, initial investment cost, cooling efficiency and capacity of hazelnut shell, banana branches and peanut shell pads, they can be a good alternative to cellulose pads. However, further studies are needed to design these materials in a way that they do not obstruct the air flow rate and to improve their performance by testing them at different water flow rates and pad thicknesses.