Evaluation of condensation and energy consumption during the night in heated rose greenhouses
Condensation is a process that occurs in greenhouses whenever humid air is in contact with a surface which temperature is equal or lower than the air dew point temperature. It favors the development of plant diseases, and reduces greenhouse cover light transmission during the day. In this study we measured and recorded several climatic parameters and different surface temperatures inside heated plastic greenhouses with rose at Batalha, Portugal, along six consecutive nights, in order to evaluate the incidence of internal condensation and relate it with climatic variables and energy consumption. The methodology consisted of automatic continuously monitoring internal and external climatic variables and hourly measurements of surface temperatures in the period 08:00 pm to 07:00 am. The surfaces inside the greenhouses included the coverage, walls, thermal curtain and plant leaves. The dew point temperature was computed from the air temperature and relative humidity. The boilerRSQUOs natural gas consumption for heating was also recorded for each period. Results showed that condensation usually started on the greenhouse cover, than at the end walls and lastly on the plant leaves. Plant leaves condensation occurred more often from 09:00 pm to 11:00 pm and from 06:00 am to 07:00 am. Water dripping occurred mainly from the coverage but also some times from the thermal curtain. The calorific energy provided by the boilers was a total of 184.8 GJ and it corresponded to a gas cost of 0.17 m-2 during the test period, being the consumption more influenced by the outside air temperature than the wind speed.
Ferreira Filho, A.C., Leal, P.A.M. and Meneses, J.F. 2017. Evaluation of condensation and energy consumption during the night in heated rose greenhouses. Acta Hort. (ISHS) 1170:263-268
climate control, dew point temperature, incidence of condensation, heating system