A VALIDATED PHYSICAL MODEL OF GREENHOUSE CLIMATE

In the greenhouse model the momentaneous environmental crop growth factors are calculated as output, together with the physical behaviour of the crop. The boundary conditions for this model are the outside weather conditions; other inputs are the physical characteristics of the crop, of the greenhouse and of the control system. The greenhouse model is based on the energy, water vapour and CO₂ balances of the crop-greenhouse system. While the emphasis is on the dynamic behaviour of the greenhouse for implementation in continuous optimization, the state variables temperature, water vapour pressure and carbondioxide concentration in the relevant greenhouse parts crop, air, soil and cover are calculated from the balances over these parts. To do this in a proper way, the physical exchange processes between the system parts have to be quantified first. Therefore the greenhouse model is constructed from submodels describing these processes:

1. Radiation transmission model for the modification of the outside to the inside global radiation.
2. Ventilation model to describe the ventilation exchange between greenhouse and outside air.
3. The description of the exchange of energy and mass between the crop and the greenhouse air.
4. Calculation of the thermal radiation exchange between the various greenhouse parts.
5. Quantification of the convective exchange processes between the greenhouse air and respectively the cover, the heating pipes and the soil surface and between the cover and the outside air.
6. Determination of the heat conduction in the soil. The various submodels are validated first and then the complete greenhouse model is verified.