Stuart
Guest
Hi Nicholas
The PV panels themselves are very lightweight and as little as 33 pounds. The aluminium frame is the heaviest component.
There are a number of options for flat-roofs, depending on if the installation is part of roof restoration/build or retrofit.
The easiest and non-penetrating option is Renosol:
Traditional mounting-brackets that screw into the roof woodwork are available and can be used together with flashing points to weather-proof.
Hope this helps.