A 2nd generation static model of greenhouse energy requirements (horticern) : a comparison with dynamic models

Optimisation of a greenhouse and its components requires a suitable model permitting precise determination of its energy requirements. Existing static models are simple but lack precision; dynamic models though more precise, are unsuitable for use over long periods and difficult to handle in practice. A theoretical study and measurements from the CERN trial greenhouse have allowed the development of new static model named "HORTICERN", precise and easy to use for predicting energy consumption and which takes into account effects of solar energy, wind and radiative loss to the sky. This paper compares the HORTICERN model with the dynamic models of Bot, Takakura, Van Bavel and Gembloux, and demonstrates that its precision is comparable; differences on average being less than 5%, it is independent of type of greenhouse (e.g. single or double glazing, Hortiplus, etc.) and climate. The HORTICERN method has been developed for PC use and is proving to be a powerful tool for greenhouse optimisation by research workers, designers and horticultural advisers. An example is presented at this conference; "Economic Aspects of Energy saving in Greenhouses : Physical Considerations".