U.S. patent application 20170347499 (applicant Amazon Technologies Inc., Seattle, Wash.):
"A data center includes heat producing components and an air handling system that provides reduced relative humidity air to cool the heat producing components. The air handling system includes a thermal storage unit [section shown at right] that removes thermal energy from incoming air under a given set of ambient air conditions and releases thermal energy into incoming air under another set of ambient air conditions. Under the given set of ambient air conditions, the thermal storage unit cools the incoming air and causes water vapor to condense out of the incoming air. Under the other set of ambient air conditions, the thermal storage unit releases thermal energy into the incoming air, thus heating the incoming air. ... [The] thermal storage unit may include a phase change material such as a paraffin wax, salt solution, an inorganic phase change material, or other suitable material with a high heat of fusion."