The clean-energy transition can’t stop at the easy roofs
Australia has installed around 22 GW of rooftop solar on homes but only about 5.6 GW on commercial and industrial (C&I) buildings – even though businesses use more electricity than households, and use much of it during daylight hours when solar is generating.
The Institute for Energy Economics and Financial Analysis (IEEFA) estimates the technical rooftop potential across C&I buildings at close to 40 GW, rising above 80 GW when agricultural buildings are included. Yet forecasts suggest the sector may reach only 17–31 GW by 2050.
Policy, tariffs, connection processes and finance all contribute to that gap. But another barrier gets far less attention: many commercial roofs are curved, shaded, structurally constrained or architecturally sensitive.
These buildings shouldn’t be left out of Australia’s energy transition – they need a different design approach.
The easy-roof economy
The commercial solar market has good reasons to favour simple roofs. A flat or low-pitch metal roof with clear access, minimal shading and spare structural capacity can often be designed from an established template, using standard mounting systems and predictable installation methods. Engineering risk is low and margins are easy to protect.
Complex roofs are rarely rejected outright. More often, they are designed down: the array is confined to the clear, unshaded section, and curved, shaded or load-limited areas are excluded. The project may be technically sound, but it is materially smaller than the site could support.
For businesses, solar is a significant capital investment, and a system sized well below daytime demand leaves the site exposed to grid prices for the next 25–30 years. As business capital and public incentives flow into the C&I segment, design decisions like these will determine how much each project returns – and how much of the sector’s 40 GW potential is ever realised.
A different design pathway
The Melbourne Sports and Aquatic Centre (MSAC) shows how a complex roof can be approached differently.
The venue’s roof is curved and partially shaded by surrounding towers and cables. Structural and aesthetic requirements also limited the suitability of conventional tilted mounting, and a tilted system would have needed wider row spacing to manage inter-row shading, further reducing the usable area. Under a conventional design approach, the project was expected to deliver around 800–850 kW.
Melbourne EPC Next Green Group took a different path, designing around the building’s structural and architectural requirements rather than a standard template.
Power density
The team selected AIKO Comet All Back Contact (ABC) mono-glass modules to maximise generation from the usable roof area. With all electrical contacts moved to the rear of the cell, the front surface has no busbars or grid lines to block light, lifting power density per square metre. On a roof where usable area is the binding constraint, more watts per module means more kilowatts on the same footprint.
Weight
The Comet single-glass modules weigh 28 kg each, giving a high power-to-weight ratio. That mattered: the installation placed 2,016 modules and four kilometres of rail – more than 56 tonnes of equipment – on a steep, curved roof, so every kilogram per module counted against the structure’s limits.
Shade tolerance
In conventional modules, cells are wired in series and grouped behind bypass diodes, typically three per module. A single shaded cell can switch out a whole cell group – about a third of the module – and cause further mismatch losses along the string, while shaded cells that aren’t bypassed can develop hot-spots. That is why designers generally leave shaded roof areas empty.
AIKO’s ABC modules manage shading at the level of individual cells. TÜV NORD testing found they produced up to 30% more electricity than TOPCon modules with a single cell fully shaded, and in separate TÜV NORD hot-spot testing, shaded ABC cells stabilised below 100°C compared with around 170°C for TOPCon. The modules also hold TÜV Rheinland Class A certification for partial-shading resistance. For NGG, that meant the shaded parts of the roof could be designed as generating area.
These characteristics don’t eliminate the roof’s constraints. But they improve the economics of using areas where shading is unavoidable, and give the EPC more design flexibility to use more of the roof and pursue a larger system.
From flexibility to a buildable design
Next Green Group turned that advantage into a buildable design. The team ran a trial installation on the roof’s sharpest curves and completed wind and dead-load testing before full installation. Because tilted racking would have cut across the curved roofline, it installed a flush-mount system that follows the curve – preserving the building’s profile and increasing panel density, since flush-mounted panels don’t need the gaps left between tilted rows.
Flush mounting has a thermal trade-off: with less airflow behind the modules, arrays run hotter, and output falls as cell temperature rises. In independent CEA testing, AIKO’s ABC modules recorded a Pmax temperature coefficient of –0.26%/°C, compared with around –0.29%/°C typical of TOPCon – a difference that applies to every hour of generation over the system’s life.
The completed 1.3 MW array is about 500 kW larger than the roughly 800 kW a conventional, shade-avoiding layout would have allowed – around 60% more capacity from the same roof.
“A complex roof does not necessarily have low solar potential. In many cases, it needs a more site-specific engineering response, paired with modules that can improve the capacity, weight and shading trade-offs.” – Nathaniel Galindo, Executive General Manager – Integrated Energy Solutions, Next Green Group
Generation where the load is
The additional capacity serves MSAC’s energy-intensive daytime load: pools, water treatment, heating and cooling, ventilation, lighting, courts and scoreboards.
The system is expected to generate more than 1 GWh of renewable electricity a year – equivalent to about 254 homes – meeting around one-quarter of the venue’s electricity needs and saving an estimated $70,000 (USD 49,129) a year, according to the Victorian Government.
The SEC owns and operates the system under an agreement with the State Sport Centres Trust. That gives the project a broader public-interest dimension: a higher-capacity rooftop system creates greater value for a major community venue, not just for an individual building owner.
The project also marks a practical shift in how MSAC manages energy. A room beside the main switchboard that once housed a 20-year-old gas cogeneration unit now holds nine 110 kW GoodWe HT Series inverters and the PV distribution board – existing infrastructure repurposed for on-site renewable generation.
Beyond the easy roofs
MSAC is a case study in how detailed engineering and advanced solar technology can overcome roof constraints to deliver materially larger, more valuable solar systems.
For commercial rooftops, the question isn’t simply whether solar can fit. It’s whether the system has been designed to get the full value from the available roof space.
“Many of Australia’s most energy-intensive community and commercial assets have complex roofs. Our aim is to make solar more accessible to these sites, so they can benefit from clean energy rather than being left behind because a conventional design cannot fully respond to their constraints.” – Thomas Bywater, Head of AIKO Australia and New Zealand
Australia’s energy transition won’t be complete if businesses miss out on the benefits of clean energy because their roofs have constraints.
Nor will the full value of the C&I market be realised if systems are designed around what is quickest and most profitable to sell and install, rather than the building’s energy needs and the full potential of its roof.
The views and opinions expressed in this article are the author’s own, and do not necessarily reflect those held by pv magazine.
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