What is it?
Computer room air conditioners (CRACs) supply necessary cooling capacity to embedded or standalone data centers. Many older types of systems work similarly to traditional air conditioning systems. They use direct expansion to cool the air stream, which is delivered by the CRAC to the data center space.
How does it work?
High efficiency CRACs operate like traditional CRAC units, but have more control features and functionalities than older, less efficient units. These can include built-in economizers, variable speed fans and compressors, and more effective heat exchangers. Advanced units use pumped liquid refrigerant economizers to avoid excessive dry air.
What are the most appropriate applications?
There are a wide range of applications for high efficiency CRAC units. They can be used to replace any existing lower efficiency CRAC unit. Packaged CRAC units, with direct expansion refrigeration built-in, are best suited for small data centers. Larger data centers typically use central cooling plants and are not well-suited for standalone CRAC units.
What are the savings?
The efficiency of CRAC units is measured using the Sensible Coefficient of Performance (SCOP)[1]. The top units on the market are upwards of 30% more efficient than the federal standards (2.8 SCOP versus 2.2 SCOP). This translates to 19,200 kWh for a typical 10 ton unit.
What is the cost?
The incremental cost for a high efficiency CRAC unit, on average, is $7500 or $62.50/MBH.
What is the status/availability of the technology?
This technology is readily available through multiple manufacturers.
What kinds of incentives/programs are available?
Many of the projects for high efficiency CRAC units are evaluated through custom programs. However, several states have developed prescriptive savings that can be applied to data centers, which have constant IT processing loads.
[1] SCOP – Sensible Coefficient of Performance. A measure of the net sensible cooling capacity of a CRAC unit, usually defined in kW, divided by the total input power at the testing conditions defined by AHRI standard 1360.
