What is the theoretical limit on the energy cost to remove water from air? A dew years back 3m had some super inexpensive way that invovled a reusable water andorber that released its water under only slightly decreased pressure and slightly increased temperature. The incoming air and the waste heat from the downstream ac unit provided all the warming with the pressure change being all that was necessary. It had two banks so one could dump water while the other absorbed. It made the whole system rund double digiymore efficient than just the ac alone. And that was neglecting that the felt temperature would be lower with the dessicated air.