Cooperative Institute for Research in Environmental Sciences

NSIDC Green Data Center Retrofit Project: Massive energy use reduction on a budget

David Gallaher(1), Ron Weaver (1), Ben Weerts (1)

(1) NSIDC

The Green Data Center Project was a successful effort to significantly reduce the energy use of the National Snow and Ice Data Center (NSIDC). Through a full retrofit of a traditional air conditioning system, the cooling energy required to meet the data center’s constant load has been reduced by over 70% for summer months and over 90% for cooler winter months. The new cooling system design includes a unique cooling system that uses both airside economization and a new air conditioner that uses the efficient Maisotsenko Cycle. This cycle uses both direct and indirect evaporative cooling to produce a supply air state that is 30° to 40° Fahrenheit below the incoming air temperature. A patented heat and mass exchanger divides the incoming air stream into two streams: working air and product air. The working air is directed into channels with wetted surfaces and cooled by direct evaporation. At the same time, adjacent channels carry product air without any water added or wetted surface. The adjacency of these airstreams allows for indirect evaporative cooling of the product air. Working air, warm and saturated, is ultimately exhausted to the outside, or directed into the space when room humidity is below the humidity setpoint. The room humidity can drop below 25% relative humidity if the outside humidity is very low (which happens often in Colorado), and the AHU is in economizer mode, providing a significant amount of outdoor air to the room. In the winter months, this effect is even more pronounced and working air is directed into the space most of the time.
One of the goals of this project was to create awareness of simple and effective energy reduction strategies for data centers. Although this particular project was able to maximize the positive effects of airside economization and indirect evaporative cooling because of its geographic location, similar strategies may also be relevant for many other sites and data centers in the U.S.
The Green Data Center project was separated into several components: server consolidation and virtualization and installing a more efficient cooling system and finally a 50kW solar array. Overall, the power utilization of the datacenter was reduced 70%. It is important to realize that some energy reduction was achieved by simply reducing the IT load through server virtualization and server room consolidation.