At the end of March the guarding committee (Begeleidingscommissie Onderzoek) of the Winterlight Greenhouse (Winterlichtkas) met again, a good moment to make up the balance of the winter, the greenhouse, and its performance. The Winterlight Greenhouse has had many more screen hours and has let through much more light as was intended.
The goal of the project The Winterlight Greenhouse is to design a greenhouse which lets through 10% more light minimally than a modern quality greenhouse, a covering of 4 meters on 8 meters of bars with a white coated under-structure. That target has most certainly been achieved if compared to such a reference greenhouse. Making a direct comparison with reality however is much more difficult and shows that the different choices people make often have very different backgrounds.
Lot of screening during the day
One of the BCO members has a similar greenhouse to our reference greenhouse, not only regarding the greenhouse itself, but also the furnishing and two movable transparent canvases. Given the energy component in the project and the possibility to dehumidify in the Winterlight Greenhouse, we can make many more screen hours and so we do. These are mostly daytime hours, till the end of March 200 and 450 hours more for the lower and upper screen compared to our BCO member. This has quite an impact on the total light available for the crop to grow. After lots of calculation we came to the conclusion that thanks to our higher transmission, but in spite of our more intensive screen use, that our crops received a bit more light than our BCO member. The question is what would have happened if the grower in question had exactly kept to our screen strategy. He would have had 21% less light available for his crops in the period from December 27 to March 13. That is quite a difference.
It stirred up discussion what the consequences would be for crop development and production if we would let in the maximum amount of light in the Winterlight Greenhouse and we would hardly screen during the day. In winter the amount of light received is a fraction of what we get in the summer. That 10% in winter does not provide huge leaps, but whether a bud will appear in this period can make just the difference for crop development and production. Because we only have one of this type of greenhouse this comparison cannot be made now, but maybe next year? The production and the fruit weight in the Winterlight Greenhouse is just fine up to now, and higher than in the reference greenhouse.
Source: Kas als Energiebron