What are you wanting to clean?
The visible roof tiles don't look as though they need a clean, but the moss-like stuff/weeds on the solar panels need to be removed. That could be done just by tearing them off, but not sure how you access solar panels without risk of breaking them.
If there are moss and weeds under the solar panels that you want removed then I think the only way to do it is to remove the panels first.
The issue of debris, birds' nests etc accumulating on and under solar panels has been little discussed, and solar panel installers would of course rather not do so.
I think it's going to become an increasing issue as solar panel installations age.
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