Earlier studies led to the design of an optimal greenhouse cover (Kempkes et al. 2015) with high light transmission in the winter months. The outcomes of these studies were used for the design of the Winterlichtkas which was built in 2016 at test location IDC-Energie at Wageningen University & Research BU Greenhouse Horticulture in Bleiswijk. During the winter months, 10% more light enters this greenhouse than a standard Venlo greenhouse. During the years 2017-2019, 4 cucumber crop cycles took place in the Winterlichtkas with the aim to find an optimal crop and climate strategy in which this extra amount of light can be converted into assimilates and thus fresh produce. Principles from ‘Het Nieuwe Telen’ were key as well as the aim to realize a low energy use. Yields of 112 kg/m2, 118 kg/m2 and 77 kg/m2 for respectively year 2017, 2018 and 2019 can be considered as good results. De crop cycle of 2019 started in December and ended in July. The yields of 2017 and 2018 achieved in the Winterlichtkas were 10-16% higher than the production achieved by commercial reference growers in that period. Energy use in the Winterlichtkas was 40-50% lower for all crop cycles compared to commercial growers. During winter, energy was saved through intensive use of screens. On average the screens were used 50% more than by the commercial growers. Because no minimum pipe temperature was used, the energy use during summer was also significantly lower than at the commercial growers who used a minimum pipe temperature because of CO2 production.
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