Solar Panel Mounting System
The Case for GRP Over Steel and Aluminium
The UK solar market is growing across commercial rooftops, agricultural land and utility-scale ground arrays, and the solar panel mounting system underneath every one of those installations is coming under closer scrutiny. Installers are under pressure to fit more kilowatts per day, asset owners want structures that last as long as the panels and the finance behind them, and designers are being asked to cut embodied carbon without adding cost. Galvanised steel and aluminium have been the default solar mounting systems for years, but both carry compromises that show up on site and over the life of the array.
Glass reinforced plastic (GRP) answers most of those compromises in a single material. Engineered Composites has manufactured and supplied GRP structural products from Chester for 40 years, and our new GRP solar mounting system brings that experience to both commercial and domestic installations. Our Managing Director, Gavin Williams, has also written a dedicated book on the subject, the GRP Solar Industry Technical Guide, which covers the material, design approach and specification detail in full.
What a solar panel mounting system has to do
Whether it is a rooftop rail kit or a solar ground mounting structure, the job is the same. It has to hold the modules at the right angle and orientation, resist wind uplift and snow load, and do it for at least the 25 to 30 year working life of the panels without needing attention. The best solar mounting solutions also make the installer’s day easier, with components that are light to handle, simple to cut and fix, and quick to set out across long rows. Where a structure falls short on any of these points, the cost arrives later as corrosion repairs, retightening, re-coating or early replacement, so it pays to judge the material on whole-life performance rather than purchase price alone.
Where steel and aluminium fall short
Galvanised steel is strong and familiar, but it is heavy and its protection is finite. Cut ends, drilled holes and scratched coatings all become corrosion points, and on farmland, where fertilisers, slurry and ammonia are part of the environment, or on coastal sites exposed to salt spray, that process speeds up considerably. Aluminium is lighter and widely used for solar mounting rails, but on most installations it sits alongside steel fixings and other metals, which introduces a galvanic corrosion risk, and its price follows a volatile commodity market.
Both metals are conductive, so every metallic part of the frame has to be considered within the earthing and bonding design. And with steel prices rising sharply, the long-standing argument that metal is the cheaper choice on day one no longer holds in the way it once did.
Why GRP works as a solar mounting structure
GRP pultruded profiles weigh around a quarter of equivalent steel sections, so a solar mounting structure can be carried, positioned and fixed by hand on most jobs. That reduces the need for lifting plant and speeds up installation on roofs and in the field alike. The material does not rust or corrode, so there is no galvanising to damage and nothing to re-coat, and fertiliser, salt spray and ground moisture have no meaningful effect on it. ECL’s GRP pultruded profiles are manufactured to BS EN 13706, the European standard for pultruded structural profiles, giving designers verified mechanical properties to work from, and they carry a design life of 50 years or more under standard conditions, comfortably outlasting the panels they support.
GRP is also electrically non-conductive. A non-conductive frame takes the mounting structure itself out of the bonding picture, which can simplify the electrical design, although module frames and any metallic components still need to be treated in line with the manufacturer’s instructions and BS 7671 by the system designer. The material is non-magnetic, thermally insulating and can be cut and drilled with standard tools on site. Our page on why GRP is replacing traditional materials sets these properties out against steel and aluminium in more detail.
Rails, frames and ground-mount structures in GRP
The same material serves every part of the system. Solar mounting rails and purlins can be formed from channel and angle profiles, while GRP box sections provide the torsional stiffness needed for the legs, rafters and bracing of solar mounting frames. On larger arrays, a GRP ground-mounted structure is light enough to pair with ground screw foundations, which reduces concrete use and keeps disturbance to agricultural land to a minimum.
Around the array itself, fibreglass grating is well suited to inverter platforms and maintenance walkways, and GRP mesh fencing provides a non-conductive, corrosion-free perimeter that will never need painting. Design considerations for wind and snow loading, connection detailing and specification are all covered in depth in Gavin Williams’ solar technical guide.
Two installations, one material
Consider a 2 MW ground-mounted array on arable land. With a galvanised steel system, the installer is moving heavy sections across hundreds of rows, often with lifting plant on soft ground, and the asset owner is budgeting for inspection and corrosion repair from around year ten as fertiliser drift and ground moisture attack the coating at cut ends and fixings. Specify the same layout in GRP and the frames can be carried by two operatives, fixed to ground screws and left alone for the life of the array.
Now take a commercial warehouse roof with limited spare load capacity. Every kilogram of mounting structure counts against the panels the roof can carry, so a lightweight GRP system frees up capacity for more modules while removing any risk of rust staining or corrosion on the roof sheets beneath.
Cost, carbon and specification
With steel prices where they are, GRP is now comparable to steel on up-front cost and comes out clearly ahead on whole-life cost once galvanising repairs, re-coating and replacement are taken out of the equation. GRP also carries lower embodied carbon than equivalent steel over a comparable design life, and ECL’s Environmental Product Declarations, published to ISO 14025, support projects working towards BREEAM and other sustainability targets. All ECL products are manufactured under an ISO 9001:2015 certified quality management system and are typically delivered within one to two days across the UK, which helps keep installation programmes on track.
Conclusion
A solar panel mounting system should last as long as the array it carries, without adding weight, maintenance or complexity along the way. GRP does that by combining a quarter of the weight of steel with no corrosion, no coatings and a design life of more than 50 years, which makes it a strong fit for rooftop, ground-mounted and agricultural installations alike. For the full technical picture, order a copy of the GRP Solar Industry Technical Guide from our online shop.
Speak to the team at Engineered Composites to find out how GRP can meet your project requirements.