From a thermal guy at Dell (Score 1)

The broader message is that there are alternatives that enable better efficiency at both the server level as well as the facility. This is essentially an endorsement of this cooling technology and you may see further endorsements of other systems. If you dig further into the announcement and get down to the supporting white paper, you'll find that it is a joint marketing campaign explaining the efficiency benefits of the XD system and the benefits at the server level of Dell's Energy Smart brand. Energy Smart is part behavioral and part "vendor sorting". By choosing an Energy Smart server you stand to lower your power 10-25% over a standard server depending upon your frame of reference. The "behavioral" part of Energy Smart is driving the user to a low voltage proc. The remainder is sorting of components we do in order to sift out the higher power vendor parts. Because of this sort, we also have the ability to lower fan power since we don't have to satisfy the needs of the higher power components. So, if you compare the Energy Smart Server to the standard server with a low voltage part, you'll only see about a 10% power reduction, but that's also 10% you don't have to cool and 10% that doesn't get lost up the power transmission chain. I'm copying an explanation of the XD efficiency I posted to another blog earlier today.... I have a lab of these cooling units at Dell. As soon as I'm able to measure the chilled water used by the entire XD system, I'll be able to verify the efficiency claims that do originate from Liebert. In theory, here is where the efficiency advantages come from: by being located closer to the racks (either hanging in a cold aisle or directly on top of the rack), the fan energy required to draw air across the cooling coil is much less than it is to push a comparable amount of air through a raised floor air handler and through the raised floor to the vent in front of the rack. The coil units overhead are provided liquid refrigerant via remote heat exchange / pumping units. The system is tuned such that the heat the coil picks up from the IT equipment creates a phase change of the refrigerant to gas as it absorbs the heat. This method of heat transfer is extremely efficient and requires less refrigerant than would a water based heat exchanger that operates as a single phase heat exchanger remaining a liquid. The pumps in the XD pumping unit are smaller and require less energy because they are pumping less fluid. The other efficiency advantage is that the XD system is designed to operate above the room's dew point all the time. There is no condensation in any of the XD coils. Condensation and subsequent re-humidification, which is common in CRACs and CRAHs, is a big energy drain. And yes, if you happen to be fortunate to be located in a climate that enables fresh air cooling, that would generally be even more efficient. ASHRAE TC9.9, the group responsible for environmental recommendations is looking at the possibility of enlarging the recommended humidity ranges for IT equipment. If this happens, more of us can consider free cooling.