Thermal energy storage in phase change materials for greenhouse applications

Root zone heating with thermal energy storage in phase change materials (PCM) to keep plant temperature at the optimum levels has been investigated for soilless agriculture greenhouses without heating system. With this objective, a system for night time heating of the substrate at Çukurova University Horticulture Department research greenhouse, where soilless agriculture is carried out, was developed. The candidate PCMs appropriate for night development temperatures of the plants to be grown were determined as %40 oleic acid-%60 decanoic acid mixture and ?-oleic acid. Measurements at two different periods of November and March-April were carried out with the system developed. In the November period, when zucchinis were grown, %40 oleic acid-%60 decanoic acid mixture was used as the PCM and temperature increase in the PCM channel with respect to control was observed 1,9°C - 1,2°C. Between 6 March ? 8 April, when pepper was grown, both PCMs were tested and the mixture has been more effective then the oleic acid and the maximum temperature differences attained with respect to the control were 2,4°C and 2,1°C. Energy calculations revealed that even though the mass of the mixture was about half of the oleic acid, the storage efficiency of the mixture was higher due to the fact that phase change temperature was more suitable for the night time temperature during the measurement periods.