A new Slop University paper reports a pre-registered stepped-wedge trial of quarterly rooftop-solar washing at forty community sports clubs, finding an effect of 0.11 percentage points against equivalence bounds fixed before the first wash.
A pre-registered trial across forty community sports clubs finds the wash equivalent to no wash, with rainfall accounting for the recovery it was procured to deliver
The rain was already doing it. Work released today through the Office of Research Outputs puts a figure on how little the quarterly wash of a community sports club’s rooftop solar array adds to what the weather manages unaided.
Forty clubs in one metropolitan council’s portfolio were randomised into four sequences, each crossing from no scheduled wash to a quarterly wash at a different quarter, over eight quarters in all. Generation was read from the clubs’ own inverters against irradiance sensors installed a year before the first wash. The bounds below which the School would treat the wash as making no difference were registered in advance, and the estimate landed well inside them.
A schedule is easy to start and has no natural moment at which anyone asks it to justify itself again. We picked one, and it answered honestly.
— Dr Marit Osayande, Lecturer and Convenor of the Living Dashboard
Days following rain moved the arrays further than a wash did, by roughly an order of magnitude, and no individual club returned an estimate outside the registered bounds. The paper reports the result as a null rather than as an inconclusive finding, a distinction the School of Continuous Improvement regards as load-bearing and one the University is glad to see made in its own name.
“The Observatory spends most of its time on how often a thing is reviewed rather than on whether it ought to be,” said Dr Osei Vandermeer, Research Fellow and Convenor of the Review Cadence Observatory. “This is one of the uncommon cases where both questions could be put at once, and the University is the better for having an answer on the record.”
The wash remains on the council’s maintenance schedule, where it is now recorded as evidence that the roof was accessed and the array inspected.
The full paper is available from the University’s research repository under an open licence, doi:10.5555/slop.wj3ab9.