Marrickville has more commercial rooftop solar than most Inner West suburbs, and both the warehouse arrays and the houses below them collect the same thing: a fine, slightly greasy film off the flight path and the main roads. It builds evenly, so nothing looks dirty and generation just quietly falls away.
Marrickville is an unusual solar environment because the deposit is industrial rather than organic, and because so much of the array area here is commercial.
The suburb's warehouses and light industrial buildings carry large, low-pitch arrays, and the residential streets around them have the smaller systems typical of terraces and semis. Both sit under the airport approach. The particulate that comes with that, combined with soot and brake dust from Illawarra Road and Marrickville Road, settles as a fine greasy film that bonds to glass far more stubbornly than dry dust. Rain does not clear a film like this, it streaks it, and a streaked panel shades unevenly.
Because the deposit is uniform across every panel there is no visual cue at all. Systems here commonly run well below their rated output for years without anyone noticing anything is wrong.
Roof geometry adds to it on the residential side. Terrace and semi roofs are small and often split, so an array is spread across two or three planes at different angles, and low-pitch sections get very little help from rain runoff.
We clean with purified water and a soft brush, no detergent, from ladders and height-safety equipment rather than by walking the array.
Of all the suburbs we service, Marrickville is where solar owners are least likely to realise anything is wrong.
There is no dramatic leaf fall and no coastal salt, so from the ground the array looks fine. What it is carrying is a uniform greasy film, and uniform loss produces no visible symptom whatsoever. The benefit of a clean here is often a discovery rather than a repair: generation steps up noticeably afterwards, and owners realise the system had not simply aged.
For a commercial array the arithmetic is much larger. A warehouse system rated at tens of kilowatts losing several percent to soiling is losing real money every month, either in higher bills or in reduced export income, and the payback period the system was bought on quietly extends.
The greasy nature of the deposit is why it needs proper cleaning rather than rain. It bonds, and it needs to be dissolved and rinsed rather than wiped, which is exactly what tap water and a squeegee cannot do without leaving mineral spotting behind.
Purified water dries clear and leaves nothing on the glass for the film to re-key into.
Yes, commercial properties are part of our work alongside homes and strata. The warehouses and light industrial buildings here carry large, low-pitch arrays that collect the same greasy film as the houses nearby. On a system that size, soiling shows up as higher power bills or reduced export income every month.
It's a mix of particulate from the airport approach plus soot and brake dust off Illawarra Road and Marrickville Road. Together they form a fine, slightly greasy layer that bonds to glass far more stubbornly than dry dust. Rain tends to streak it rather than clear it, and streaked panels shade unevenly.
The roof geometry adds to the soiling problem. Terrace and semi roofs are small and often split, so arrays are spread across two or three planes at different angles, and the low-pitch sections get little runoff. We work from ladders and height-safety equipment instead of walking on the panels.
You usually won't from the ground, because the film covers every panel evenly and gives no visual cue. Comparing your generation figures over time is a better guide. If output steps up after a clean, the film was the cause, and before-and-after photos show what had been sitting on the glass.
How we clean arrays with purified water and no detergent, and why output recovers once the glass is clear.
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