Increase of light transmission by 10% in the Venlo-type greenhouse: from design to results of a cucumber experiment

Abstract

During the autumn and winter at higher latitudes natural light is the limiting factor for crop growth in greenhouses. A new greenhouse and cultivation concept has been developed to increase the overall light transmission of the greenhouse with at least 10%. Several innovative elements have been considered: diffuse glass with an anti-reflective coating, high transmission under wet conditions, increased glass panel size, improved screen material, V-shaped screen installation, highly reflective coatings on constructional parts. This has led to an integral design and realization of a 500 m2 greenhouse in 2016 at Wageningen University & Research in the Netherlands. In an earlier study Kempkes et al. (2017) presented the final results of the new Winterlight greenhouse design. According to model calculations a 10.5% gain in PAR sum could be reached during winter. The greenhouse concept has been tested by growing cucumbers. In cooperation with growers a growing strategy has been developed. Besides maximizing the use of natural light, energy consumption was reduced using two movable screens, a balance ventilation system with heat recovery during dehumidification and growing according to the principles of the ‘New Cultivation Strategies’. Light transmission has been measured and was compared with raytracing simulations. Especially during diffuse light conditions, the accuracy was within 1%. On the long-term the difference between calculated and measured PAR sum was below 3%. Greenhouse climate and energy consumption have been compared with those of commercial growers. Energy savings up to 40% and production increases up to 30% were reached growing cucumber ‘High Power’ in the new greenhouse compared to commercial greenhouses. Light transmission was increased with more than 10%. Energy use was 176 kWh m-2 for heat and 2.5 kWh m-2 electricity for the fans of the balance ventilation and heating system. Additionally, 10.2 kg m-2 of CO2 was purchased. Cucumber production was 120 kg m-2 with good quality (284 pcs). An average Dutch grower using the high-wire system uses about 282 kWh m-2 gas equivalents producing around 95 kg m-2.