How the Kyoto Cooling Fan Revolutionizes Data Center HVAC

How the Kyoto Cooling Fan Revolutionizes Data Center HVAC

[Editor's Note: This is a lightly edited version of an interview that originally appeared on Deborah Grove's website, Groves Green IT. It is reprinted with permission.]

I got to know Dr. Robert F. Sullivan through several Uptime Institute events over the years, and he was tremendously helpful to me two years ago when I was doing research on attitudes toward water conservation among data center operators. I caught up with him recently and had the opportunity to talk about one of his favorite topics: the Kyoto fan. Dr. Bob is best known for his Cold Aisle/Hot Aisle innovations.

Deborah Grove: Dr. Bob, tell my readers what the Kyoto fan is and why it is both a traditional and innovative product.

Dr. Bob SullivanBob Sullivan: Kyoto Cooling (named after the Kyoto Accord) is an idea created by four young engineers in The Netherlands. The basic concept has been used in building and industrial air conditioning installations for over 60 years. In building AC systems a heatwheel is used to precool hot air in summer and warm cold air in winter. The key component of the system is an aluminum honeycomb wheel that absorbs heat in one airflow stream and dissipates it in another.

In the traditional configuration the system is set up to draw fresh air into the building, precondition the air to lighten the load on the HVAC system and then exhaust the air after it has passed through the building.

In a data center, this design is tweaked so that there are two isolated circulation paths, rather than an intake and exhaust path. The computer room is configured with an isolated hot aisle and the hot air is circulated, the heat is absorbed by the honeycomb wheel, and the cooler air is recirculated back into the computer room.

The wheel is constantly rotating at low speed and the "hot" wheel rotates into a chamber where outside air is circulated through the honeycomb. Outside air is returned to the ambient environment, carrying the computer room heat load with it.

This cooling technique is not only extremely efficient on its own but also isolates the computer room from the ambient environment and all the problems associated with bringing huge volumes of outside air into the data center. This includes dirt, fine combustion particles, gasses, air with low or high dew point. In this way the energy used or lost to contain these elements is minimized.

Because of the inherent efficiency of the system and the isolation of the computer room and ambient air, this system works in cold climates, arid/desert climates, and the tropics. For example, in north and south latitudes the mechanical efficiency (Mechanical load / IT load) may be as low as 0.04, to an efficiency of 0.08 in marine climates, and 0.25 in the dessert of the Middle East and tropics of Singapore. KyotoCooling provides airside economizer cooling -- without the air transfer.

DG: How big is it? How little is it? What are the small and large parameters?

BS: There are many installations in Europe using both the large wheels and the modules.

The cooling technique is versatile, with units as small as 90 kW of cooling capacity, deploying an 8' diameter wheel, a 300 kW using a 12' wheel, a 450 kW requiring a 14' wheel, and the largest: a 600 to 850 kW system using a 20' diameter wheel.

DG: Where are some of them currently installed?

BS: There are four installations in North America, one using 90 kW modules, two using 300 kW modules, and one using 450 kW modules.

I recently visited two installations in the U.S. One in the northern latitudes of the U.S. has three 300 kW-rated modular units installed. During commissioning, at 28 degree Fahrenheit ambient conditions, they were able to achieve 1 MW of cooling with just two units operating, both at 50 percent capacity. The second installation has two 450 kW units operating and were able to achieve 1.1 mW of cooling at 40 F ambient temperature without stressing the capacity of the units. In both implementations, supplemental cooling was not required to achieve these cooling levels.

DG: Tell me how acceptance in Europe has fared verson in the U.S.

BS: There is more pressure to implement economizer cooling techniques in Europe than in North America. Compliance with the E.U. rules, plus the higher cost of energy, make highly efficient cooling techniques essential there. In contrast, the drivers in North America are different with less regulation and a lower cost for energy.

I've found the data center community in North America to be very conservative and risk averse. There is a bias toward waiting for a "new" technology to be mature before it is considered. My belief is that some of this is related to job protection -- fear of losing one's job if new technologies do not work.

Dr. Sullivan will be presenting at the Uptime Institute Symposium on Green IT, taking place May 9-12 in Santa Clara, Calif.