SOLAR GAINS AND THERMAL REJECTS BY VENTILATION

Data recorded between September 1983 and February 1985 were analyzed in detail and the main results are as follows :

• Solar radiation covers a large fraction of the daily heat load : in local climatic conditions, between October and June, solar energy provided for nearly 40 % of the heat load of the greenhouse.
  This amount represents 32 % of the incident radiation.

• Thermal excesses that were ventilated during overheating periods (Tint > 24 °C) represent 37 % of the incident solar energy.
  However, due to the seasonal phase differences between the thermal need and the incident solar power, only half of these rejects could potentially be saved by a short term storage system.

• A method was developed for determining the monthy net auxiliary consumption of the greenhouse.
  Solar gains were evaluated by means of a monthly utilization factor (ratio of the solar energy used divided by the absorbed solar energy in the greenhouse). This factor has been experimentally fitted to a function of the gain load ratio (ratio of absorbed solar energy divided by the daytime heat load). The above representation appears to be valid for any type of climate or greenhouse.

• The model also takes into account the effect of wind and radiative heat losses to the sky and calculates the net auxiliary requirements within less than 10 %.

Symposium Greenhouse Climate and its Control

O. Jolliet, J.-B. Gay, T. Bretton, S. Mantilleri, A. Reist, M. Bourgeois, L. Danloy, C. Moncousin

https://doi.org/10.17660/ActaHortic.1985.174.15