I think what you are trying to do is simply cleanse the panel of dirt and debris. I dont think you need high pressure for this. It is not like you are trying to strip of mildew from the side of your house.
If I am not mistaken most people use their showers for this sort of job. Thus if you have hand held shower head, I'd set it to the 'soft' setting and simply rince the panels with lukewarm water.