Hi Jack. Sorry I was not on computer or iphone,just out of hospital after a week laid up with kidney stones, from last wed evening . Now that im back and getting caught up with the craic again. Just wash the solar panel with luke warm water and a a wee drop of mudbuster will take off any film of alge or other foreign material and the Mudbuster will prevent the alge from reforming for quite a while again. especially if the Motorhome is parked anywhere near trees. Cheers and great to be back pain free.