A storage bay was a type of facility in which various items were kept.
In 2153, a storage bay which contained conduit housings on Enterprise NX-01 was transformed into a command center, to deal with the Xindi threat. (ENT: "The Xindi")
In 2369, a Cardassian attack on Deep Space 9 damaged several empty storage bays on level fourteen of the station. (DS9: "Emissary")
Melora Pazlar visited a storage bay to obtain an astrometric array in 2370. (DS9: "Melora")
In 2373, Neelix's pantry was located in storage bay 3 on the USS Voyager. Captain Kathryn Janeway told Neelix that she was planning on converting storage bay 3 into a containment chamber for sirillium, an energy source the crew had discovered in a class 17 nebula in the Delta Quadrant. Janeway told Neelix that he would have to make other arrangements to relocate his pantry. (VOY: "Flashback")
In 2374, Damar and Weyoun were to meet Jack, Lauren, and Patrick in a storage bay. (DS9: "Statistical Probabilities")