When the logic and value of solar PV are understood by property owners it’s hard for them to hold back. In Australia, more than 2 million systems up to 100kW are installed on the rooftops of homes and businesses. Commercial and industrial energy users are catching on. Last year, there were enough systems between 100kW and 5MW to make 230MW of capacity around the country.
All of that good news overlooks a couple of problems with solar. First, it’s far more appealing to property owners if they live under the roof it’s installed on. Owners of rentals aren’t that eager to pay for a system when someone else gets the bill savings.
The second problem is one we hear less about. Many rooftops around the country that are plenty big enough to take generous arrays of panels are just not structurally capable of carrying the weight.
With a generic 60-cell glass-and-aluminium residential module weighing about 17kg, and a larger 72-cell commercial panel weighing around 22kg, large arrays can add tonnes of extra mass to old rooves.
Where there’s a problem, of course, there’s always opportunity for someone to come up with a solution. And it helps if you already have 60 patents in photovoltaic technology to your credit.
Dr Zhengrong Shi saw the potential for lightweight panels after completing the installation atop the Sydney Theatre Company for his former company Suntech in 2010. Looking around the Emerald City’s famous harbour he saw the potential for more solar was limited by a shortfall of sturdy rooves and the problem of glare bothering neighbours.
Dr Shi, who has since then founded solar companies SunMan and Energus, wondered why glass and aluminium, heavy materials, should be universally chosen to protect solar cells. The rectangular technology is proven and manufactured by the millions, but that doesn’t mean it can’t be improved.
Were solar cells really regarded as being so valuable that they needed to be wrapped in cotton wool? Such thinking would only hold the world back, he figured, as solar becomes the cheapest form of generation and consumers turn to solar as “something that can be integrated on the surface of any object”.
According to Shi, 40% of rooftops can’t take the weight of conventional glass-and-aluminium panels. His solution is Energus’s eArche module, where a polymer coating and plastic frame cut heaviness by 75%, he says.
In mid-August a 235kW array of 812 eArche panels installed on the Australian National Maritime Museum’s Wharf 7 Maritime Heritage Centre building in Darling Harbour was switched on, with expectations of cutting electricity consumption by about 25%, or $50,000 a year.
“When I developed eArche, I knew it could unlock the potential for solar on buildings which were previously unable to support conventional glass solar panels,” Dr Shi said at a press event to mark the project going live. “For conventional panels you’re talking about 15kg per square metre; this panel is 1.6 square metres and weighs 5kg.”
It’s a breakthrough for the museum, which started investigating solar about five years but drew a blank for having a roof with a 30-degree pitch that couldn’t take the weight.
On the surface
The next stage is to integrate the technology into building skins and facades, as the flexible materials allow it to be mounted directly onto flat or curved surfaces, and even bonded to surfaces. “Because the panel is so thin, heat can be dissipated very quickly from the surface,” Dr Shi tells EcoGeneration.
The panel achieves 22% efficiency, like many of its heavier peers, but an irregular polymer surface removes gloss. Seen from a distance, the system on the museum’s rooftop looked more like blue satin under direct sunlight than a vast collection of mirrors. The polymer surface has the same texture as coarse-woven sacking, but smoother to the touch.
Rectangular shiny blue solar panels aren’t everyone’s favourite sight as they ponder the built environment and Dr Shi is working on breaking out with green, yellow, red and even white variations of the eArche. “It can be done,” he says. “It just requires another special coating on this surface. We want to reflect only a narrow band [of light wavelength], so we don’t lose a lot of power.”
Coloured panels would see about a 10% reduction in efficiency, is his estimate so far.
What you pay for
The eArche panel comes at a price premium, according to an installer EcoGeneration spoke to, although any extra cost would have to be considered against savings from using less racking, if any, and not having to spend money bolstering a roof that isn’t deemed fit enough to take the weight of regular glass-fronted modules.
Our installer contact knew of two projects where the Energus panels had made the difference between an operation running on solar or having none at all: a mobile hospital and a roof in a rural setting that simply couldn’t take the weight.
Dr Shi says panel cost is one variable in a solar project. “Because of volume these are slightly more expensive than glass panels,” he says, “but because it’s easy to install you save cost in EPC and balance of system.”
Conventional panels deliver a four-year return on investment, he says, and the Energus panels about five years. “It’s not a great difference.”