Figure 1: A non-penetrating, ballasted PV array on the roof of a municipal water reservoir. A containment vessel is not a roof deckOn a water tank, the design avoids penetrating the roof, so the array is ballasted, held down by weight rather than fasteners. Keeping the reservoir serviceableA PV array lasts decades; the reservoir beneath it is expected to serve far longer and cannot be allowed to fail because solar got in the way. About the AuthorArchit Patnaik, PE, PMP, is a senior project manager at Pure Power Engineering specializing in solar PV and battery energy-storage systems. He leads electrical engineering for solar and storage projects serving developers, EPCs, and asset owners, and is a NABCEP-certified PV Installation Professional.