TNO, Verzuu Screen Development and partners have developed and tested a shade cloth with retractable solar film in a horticultural greenhouse. This system combines energy generation with climate control. Never before has there been an application where solar cells are continuously rolled up and unrolled. This way, shading - at any desired percentage from 0-100% at any time of day - can be distributed exactly evenly over the crop. This while fully maintaining the greenhouse's aeration capacity. The next step is to further develop this technology so that it can be applied on a larger scale. 
© TNO
Roll-up screen
The aim of this project was to develop a system that both generates energy and optimizes greenhouse climate conditions. By integrating flexible solar panels into retractable screens, local shade is created in the greenhouse and electricity is generated at the same time. TNO developed a solution where the stacking of layers in a solar cell is less sensitive to continuous movement. The thinner stacking of solar cells makes the entire rolled-up shade screen manageable (not too thick).
"This project is a milestone in our search for sustainable and affordable energy solutions. This solution is a nice demonstration of the movement and loading of solar foil. A solution that can also be suitable for building shading, carports and using solar energy at sea," said Peter Toonssen of TNO.
More efficient energy generation and lower production costs
The shade screen with solar film is a demonstration that shows that by integrating functionalities, production costs of power generation can be reduced and efficiency can be improved. The shade screen system is based on the standard Venlo greenhouse, which is widely used internationally.
Challenges
During the 3-year project, the researchers ran into several challenges. For instance, getting the generated energy from the moving parts to the outside via robust wiring was complicated. Furthermore, it turned out that partial shading of solar cells can lead to rising temperatures and also affect the robustness of the solar modules. In some cases, this shading led to a temporary reduction in power generation, and in extreme cases, it even led to the modules breaking down, a focus area researchers are working on for implementation in the next phase. Peter Toonssen: "During innovative projects, you sometimes run into unexpected issues during test phases. That is why test periods are very important for us. We now know what the system can do and where we can still improve things."
Looking to the future
Daniel Verzuu: "We started this project because we see a future in this kind of innovative application. The next step is a demonstration of the concept on a larger scale." Further developing these technologies and applying them to larger scale and other surfaces is the next phase. Thus, mass customization is increasingly coming into view. TNO is working in various projects, including SolarNL and with the Dutch province of Noord-Brabant to bring solar panel production back to Europe with innovative concepts like this.
For more information:
TNO
Leeghwaterstraat 44
2628 CA Delft
Tel: +31 88 866 22 00
info@tno.nl
www.tno.nl