The transition towards sustainable and recyclable roofs is ongoing but is not without challenges. For example, tens of square kilometres of asbestos roofing still exist in The Netherlands, despite efforts to have them removed. This mainly affects farmers’ barns and industrial buildings. For the owners, the removal of these roofs is an ideal opportunity to replace them with solar roofs. Thanks to an invention by TNO, this can be done in any shape or size. Installing separate panels on a roof is a thing of the past.

The core of the solution developed by TNO and various market players is the ability to produce flexible photovoltaic (PV) semi-finished products which can be integrated into roofing materials. This involves a production process with solar cells embedded in a foil, a so-called roll-to-roll laminate. This has several advantages: the foils can be produced at a high speed and the resulting solar modules are flexible, lightweight and can be manufactured in any size.

From vacuum to roll-to-roll laminate

The use of foil with solar cells on roofing is still subject to all kinds of limitations. The dimensions are fixed, so the roof surface can never be optimally covered. This is due to the current production method of vacuum lamination. TNO has now developed a method to replace that process with roll-to-roll lamination, making it possible to produce solar modules much faster at lower temperatures in unlimited lengths, as well as to incorporate these into existing construction products. This makes it possible to cover the large roof surfaces of industrial buildings or agricultural barns in one go, for example.

Collaboration with industry

In developing this method, named Rollaflex, TNO has worked closely with industry. The ultimate aim is for Dutch companies to integrate the semi-finished laminates into their products. The company Maan Group, for instance, is working on the development of the machines that will soon manufacture the roll-to-roll laminates. Yparex plays an important role in making the connecting layer (encapsulant) between the solar foils suitable for roll-to-roll lamination. As a roofing company, WeKa Daksystemen wants to serve customers with lightweight roofs in which solar cells can be integrated regardless of material, size or shape. TNO has already tested, validated and demonstrated various flexible semi-finished products for roofing made from different materials, including the necessary electronics.

Lightweight flexible roof elements with solar cells on a stable of a farm at Hoevelaken.

Easy-to-install prefabricated roof elements

This invention makes the large-scale replacement of asbestos roofs for roofs with PV functionality an attractive prospect, particularly in the agricultural sector. The potential bottleneck here is the labour-intensive – and therefore expensive – installation of standard panels even though the total surface area can never be fully utilised. TNO’s solution makes it possible to produce large, lightweight prefabricated roof sections with integrated solar cells that are relatively easy to install. This is also a solution for large industrial buildings such as distribution centres. It also offers a solution to the constraints caused by the maximum roof load, which makes it impossible to install regular glass-based modules.

A range of companies are also involved in the development of flexible, lightweight roof elements for barns, including Energiedak, Solarge, Taylor, Expice, Kameleon Solar and VDL Werkt. The product is currently being demonstrated on a realistic scale on a farm in Hoevelaken. Solar thermal PV panels manufactured through the same process are also being tested there, which means that the same surface area can supply even more energy.

Photos: Den Besten Service

Looking for more information on customised solar cells into the roof tops?

Please contact Peter Toonssen

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