H.R. Gislerød, L.M. Mortensen, S. Torre , H. Pettersen, T. Dueck , A. Sand
The greenhouse industry tries to make as much use as possible of the natural light available to crops. The amount of available light is reduced by covering material and greenhouse construction, presently a light reduction of around 30%. In order to save energy, double covering material is often used in addition to one or two energy curtains. These result in a reduction of 70-80% of the natural light compared to outside the greenhouse and an increase in the air humidity, but also a reduction in energy consumption in the same range. Artificial lighting, where up to 40% of the electricity is converted to photosynthetic active radiation (PAR) can be used in connection with different energy saving methods and still ensure good crop growth. Maximum energy saving, and using CO2 combined with artificial light, brings us to the concept of semi-closed greenhouses. Better methods for re-using surplus energy must be developed for this concept.
Gislerød, H.R., Mortensen, L.M., Torre , S., Pettersen, H., Dueck , T. and Sand , A. 2012. LIGHT AND ENERGY SAVING IN MODERN GREENHOUSE PRODUCTION. Acta Hort. (ISHS) 956:85-97
light, energy, carbon dioxide exchange rate (CER), light use efficiency (LUE)

Acta Horticulturae