In late 2009, Dutch tomato grower Vereijken invested in new greenhouses with an installation to blow outside air into the nursery. This way, the humidity in the greenhouse can be more controlled, so that the two energy screens can be closed more often, to keep the heat inside. Because of these advantages, two years later a similar system was installed in an existing greenhouse in Aarle Rixtel. The treatment of outside air also appears to have a positive effect on the climate, and the number of stems with Botrytis is much lower than in the years before the air handling units.
However, the energy reduction in the Aarle Rixtel nursery now seems to be a disappointment. This can be partly blamed on the screen installation, that has not been adjusted. But there’s more. Growers Eric Vereijken, Geert-Jan van Rixtel and Thijs Goorts checked the numbers and deduced that much more air exchange took place than in a comparable greenhouse without foil and without air-conditioning units.
It turns out that energy can indeed be saved using the outside air, but only if the system is deployed when absolutely necessary. The consensus appears to be that not every drop of condensation needs to be removed from the foil. Many waterdrops on the foil sometimes indicates low humidity, which means it’s not necessary to dehumidify even more.
To sum up, air insufflation alone does not lead to energy savings. If too much air is blown in, the energy consumption increases even more. The savings must come from increased use of energy screens. Proper use of the air conditioning units can make this more feasible.
Source: Energiek2020
