Pañol is a "nautical term" for storage space, as you say. Generally in a sailing school, yacht club, harbour, boatyard it's the place where the sails are stored. Sails need to be folded and stored properly out of the sun if they are to last. The boats (in a sailing school they're small,) are usually outside stored on racks, under a roofing. I'd therefore go for sail loft rather than storeroom, even though they're bound to store other gear there like tillers, cordage, wet and dry suits, etc