The Experimental Determination of The Impact of Overall Heat Consumption Coefficient and Thermal Screens on Heat Saving in Plastic Greenhouses

This study was conducted to experimentally determine the effect of thermal screens used for heat saving and overall heat consumption coefficient on heat loss in greenhouses. The trial was established in three different lettuce greenhouses with 150 m(2) in floor size using different plastic covering materials between January and April. Hot air vent heaters were used for heating. The heaters were positioned 30 cm above ground level. The heating was done between 08.00 p.m. and 05.00 a.m. Plant level and roof level as well as external temperature and relative humidity were measured with data loggers. These measurements were used to statistically calculate overall heat consumption coefficient based on wind speed. The results demonstrate that thermal screens created a resistance against heat loss, thus reducing heat losses. The effect of thermal screens on heat loss depending on the wind speed was also determined. It was found out that heat saving ratios in greenhouses varied between 8% to 22% under very low wind speeds and between 17% - 36% under a wind speed of 4 m s(-1).