Composites benefit roof-mounted solar PV modules

Based in Eindhoven, the Netherlands, TULiPPS is currently developing prototypes for testing. It hopes to have commercial products, initially focused on light, flat roofs common to large industrial buildings, by 2012.

The company’s COSMOS™ PV module is reported to demonstrate numerous benefits over conventional systems, including:

  • reduced weight and cost;
  • faster installation;
  • increased energy output per unit area;
  • lower maintenance; and
  • improved functionality.

Problems with conventional systems

Conventional solar PV modules for flat roofs are said to have several problems.

Current installation technology requires a lot of labour, which accounts for a significant percentage of the total cost of ownership for the system.

Another issue with traditional module installations is that their height and angle of tilt necessitate a separate frame and support structure (generally aluminium) in which the glass PV module sits, plus ballast (usually concrete block or stones) that is loaded onto the support structure’s flat base. The ballast stabilises panels in high winds or near the edge of roofs where wind vortices are common.

Hauling ballast up to a roof and distributing it throughout a large solar array is time consuming and hard work for installers. It also adds so much mass that the systems are often too heavy for safe use on 'light' flat roofs. The alternative to ballast for light flat roofs is drilling through the roof membrane to bolt modules to the understructure, an option deemed unacceptable due to cost, time, and the risk of causing leaks.

COSMOS module

Developed in partnership with companies in the automotive composites, roofing and PV industries, and with financial support from the Province of Noord-Brabant in the Netherlands, the COSMOS module from TULiPPS has been designed to address these deficiencies with conventional PV systems.

The COSMOS system combines tough automotive-grade composites, an integral frame and support system, with plug-'n-play functionality, thin-glass PV modules, and a roof-anchor system that does not penetrate the roof membrane.

Central to the system’s design is a thin 2 mm (0.08 inch) glass PV laminate that is integrally bonded to the composite module base, forming a strong box-beam structure that eliminates the need for an external frame and reduces weight by 50% or more. This helps the system achieve a low roof load of less than 10 kg/m2 (2 lb/ft2).

Owing to a much flatter installation angle (5°), shadowing of units further back in an array is greatly reduced, allowing rows of modules to be placed much closer together – around 0.3 m (1 ft) apart rather than 0.6-1.5 m (2-5 ft) apart. Although the shallower angle is considered less efficient at generating energy on a per-module basis, the fact that more modules can be installed per unit area leads to a reduction in the cost per watt of energy generation and shorter payback time on the investment.

In addition, TULiPPS has focused on integrating features and functions that will make the modules easier and faster to install, effectively reducing labour as well as material costs. For example, plug-'n-play functionality permits modules to be quickly connected to low-profile feet assuring rapid but secure installation or removal. A proven roof anchor system that uses no screws or bolts and does not penetrate the roof membrane helps further reduce installation time and labour costs. The lightweight, smooth-edged modules are also safer for workers to handle and install. And since the modules are essentially frameless, there are no edges or corners to trap dirt and dust or encourage the growth of algae. Debris simply washes off, helping keep the units operating efficiently.

The long fibre polypropylene (PP) thermoplastic composites used in the support system were formulated to provide high bending strength at very low weight. Preliminary flame retardancy testing indicates the materials will qualify with a V-0 flame-retardance listing with Underwriters Laboratories Inc (UL) 94 specifications in a halogen-free/ECO-compliant formulation, enabling modules to meet current and future requirements for roof-mounted polymeric components.

Since TULiPPS plans to warrant its units for 25 years, materials have also been formulated for long-term weatherability and ultraviolet (UV) stability. Special colorant packages have been formulated to broaden the long fibre thermoplastic colour palette from black and natural to also include grey, green and blue, without interfering with mechanical properties.

In-line compounding and moulding on commercial scale equipment have also verified that the composite materials process easily and produce parts with an excellent balance of physical and mechanical properties even under accelerated aging tests. And unlike aluminum frames, there is no need to electrically ground the support structure, because the polymers are inherently non-conductive.

Automotive experience

"For 40 years, the automotive industry has proven that replacing metals with plastics offers the advantages of weight reduction, higher production efficiencies, and feature integration, which lead to better products with more functionality produced at lower costs using less energy," explains TULiPPS managing director Paul Stassen. "As I considered my own experience and that of my colleagues from the automotive plastics market, I wondered whether this knowledge could be applied to make better and less-costly solar panels."

“Together with our partners in the plastics, roofing, and PV industries, we have poured our collective knowledge and experience into designing the next generation of solar PV modules,” continues Stassen. “The true power of this lightweight system lies in the functional integration we were able to achieve with our tough automotive-grade composite module system. We believe this module system has great international sales potential and will be a significant contender in the international drive for less costly and more efficient photovoltaic installations.”