A new shade cloth for horticulture features a retractable solar foil. This allows horticulturists to use the shade cloth to control the shading on their crops in detail, while generating energy at the same time.
The shade cloth was developed by TNO and Verzuu Screen Development in collaboration with partners. The development is part of a project aimed at developing a system that both generates energy and optimises climate conditions in the greenhouse. The shade cloth enables detailed control of crop shading, with any desired percentage from 0-100% at any time during the day. The aeration capacity of the greenhouse is fully maintained in the process.
Less sensitive and thinner
TNO uses a solution for the fabric where the stacking of layers in a solar cell is less sensitive to continuous movement. Important, since the shade cloth is rolled in and out with great frequency depending on the sun. A thinner stack of solar cells also means that the rolled-up shade cloth is less thick and therefore easier to handle.
The shade screen system is designed for the standard 'Venlo greenhouse', which is the most widely used type of greenhouse in the world. The Venlo greenhouse has a foundation of concrete, a structure of galvanised and/or coated steel, and a deck and gable system of aluminium or steel.
Various challenges
The development of the shade film with integrated solar panels took three years. In the process, the researchers ran into several challenges. Among them around the cabling to get the generated power from the moving parts to 'outside'.
Another challenge was the partial shading of the solar cells, which can lead to rising temperatures. In addition, this also affects the robustness of the solar modules. In some cases, partial shading led to a temporary reduction in power generation. In extreme cases, modules even broke down as a result.
Peter Toonssen explains: "During innovative projects, you sometimes run into unexpected issues during test phases. That's why test periods are very important for us. We now know what the system can do and where we can still improve things."
Also interesting for buildings and carports
Toonssen reports that the shade cloth is not only interesting for use in horticulture, but can also be further developed for other applications. Think of sun protection on buildings and carports.
Daniel Verzuu of Verzuu Screen Development: "We started this project because we see a future in this kind of innovative application. A next step is a demonstration of the concept on a larger scale."
Author: Wouter Hoeffnagel
Image: Arielle Leenheer via Pixabay
