The IAP-115 has built-in downtilt omnidirectional antennas that allow you to mount them at up to 35 feet and still obtain ground coverage. The IAP-114 is the version that requires external antennas, by the way. You could order a couple IAP-115s and survey to see what the coverage is if you mount them every second or third aisle. Examine how the signal looks on your clients at 50 feet and 100 feet to see if it is doable. Since a typical distribution center is coverage, instead of capacity, the RF from the IAP-115 in open space could easily go 100 feet depending on the clients you need to service. Traditionally you would have an external antenna AP for distribution centers because typical omnidirectional APs cannot give you ground coverage at 30 feet. Downtilt omnidirectional antennas can do this without you have to stock and mount additional external antenna parts, which could add up...
Take a look at Chuck L's warehouse presentation here: http://community.arubanetworks.com/aruba/attachments/aruba/tkb@tkb/92/1/Airheads%20Barcelona%202010%20-%20RF%20Design%20for%20Retail%20Warehousing%20Manufacturing.pdf
If you do have an external antenna, it would not require an external power supply, no...