1.  Field of the Invention
This invention relates generally to heat absorbent devices for passive cooling and heating. 
2.  Prior Art
Many large businesses have critical operations rooms that house information technology systems and equipment essential for conducting business.  Examples of critical operations rooms include data centers, call centers, LAN, WAN, file server, hub, switch, and network rooms.  Such rooms are filled with heat-generating electronic equipment, so that they must be cooled at all times.  In high rise commercial buildings, cooling is primarily provided by base-building cooling systems.  Critical operations rooms are typically cooled by supplemental cooling systems which are operated 24 hours a day.  However, base-building and supplemental cooling systems are both dependent on the same electrical, mechanical, and plumbing systems of the building.  In the event of a building electrical or plumbing system failure, both cooling systems will also fail.  Without cooling, rapid heat buildup in critical operations rooms may cause equipment overheating and failure in about 15 minutes, which may result in serious business consequences. 
The risk of cooling system failure can be reduced by using backup systems, such as redundant cooling systems, uninterruptable power supplies, and power generators.  However, these backup systems are expensive to implement, and are still susceptible to electrical, plumbing, or mechanical failure.  Without a backup system, two options are available in the event of a cooling system failure: the first is to repair the cooling system or to provide temporary cooling, such as opening doors or adding portable air conditioners; the second is to shut down the equipment in the critical operations room before they fail from overheating.  In either case, the key element in preventing equipment overheating is time. 
Phase change materials are known to be usable for absorbing solar heat in the day and releasing it at night for heating a building.  A heat absorbing panel disclosed U.S. Pat.  No.  4,178,727 to Prusinski et al.  is comprised of a hollow panel filled with a heat absorbing material.  The panel is usable as a ceiling tile or floor tile for passive heating or cooling.  However, the panel design does not address retrofit into conventional ceiling grid systems.  Its design does not take into account weight limitations and the leak resistant durability necessary to withstand periodical removal and handling for the continual maintenance and upgrade work inherent in critical operations rooms.  In addition, its design does not account for panel penetration by sprinkler heads, smoke detectors and other critical operations room support devices that drop below the ceiling plane.