Steve

Fans take an inordinate amount of power, both in the server and cooling units. If there is a cheap, reliable and redundant way to extract heat right out of the chip, the fans can be eliminated. So far this has been elusive but at some point rack densities will increase to where it makes financial sense. It's anybody's guess where this point is, possibly the 60-100KW range?

Sounds interesting – tell us more.

Steve

1. Redundancy is much more problematic and expensive with liquid than air. An extra CRAC or two in the data center can be used as a backup for a fairly wide expanse of racks. How do you get cooling redundancy for a 20KW liquid cooled rack? Not impossible but very expensive.

2. Cost of equipment is significantly higher, at least today. Rather than a Single CRAC servicing 20-30 racks, the liquid solutions are most always one per rack. Even with densification of the racks, the costs of liquid cooling equipment inside the data center are many times that of air. The costs outside the data center are nearly equal. Of course with wider adoption and standardization the costs will come down – but when. With bleeding edge IT technology changing so fast it's a brave soul who can bet on a new technology to be around or even supported in 5-10 years, add to this the fact it's much more expensive and it's no wonder liquid is not yet mainstream.

3. How many data centers really have a “SPACE” problem? With the 6-10KW racks of the typical data center replacing the traditional 1-3KW racks, very few sites run out of space before they are up against serious power and plant cooling constraints. 6-10KW is easily handled with traditional cooling solutions and proper airflow design.

Comments?

Wally Phelps
http://www.adaptivcool.com

IBM's cooled back doors are really just a way to add additional CRAC capacity to an existing data center with poor airflow and a need to install high density equipment. You are entirely correct that they are not particularly green or efficient and I commented in the article about the negative impact of delivering cooled exhaust air back to the main room CRAC units.

IBM's cold plate technology uses chilled water (sub 20 degrees C) that must be maintained within very tight tolerances to keep the CPU cases cold enough to over-clock. There is a reduction in the energy costs of moving air in this instance as pumping water is much more efficient from a heat load perspective than pumping air.

My comment about being able to use free air cooled water (at up to 50 degrees C) refers to a possible future technology where we are not trying to over-clock the CPUs and are more interested in cooling very high power components efficiently. Tcase for most CPUs is in the range of 60 degrees C so using 50 degree C water would be possible if the thermal impedance between the case and water could be reduced sufficiently. Then we are talking about HUGE energy savings.

Steve