The Green Grid has proposed the use of two new metrics designed to help improve the sustainability of data center facilities by measuring the effectiveness of carbon and water use tied specifically to the IT energy infrastructure they contain.
The new metrics, called Carbon Usage Effectiveness (CUE) and the upcoming Water Usage Effectiveness (WUE), are joining The Green Grid’s widely-used Power Usage Effectiveness (PUE) metric.
PUE compares the total amount of energy consumed by the data center facility to the total amount of energy consumed by the IT equipment inside it. CUE will help managers determine the amount of greenhouse gas emissions generated in delivering work from the IT gear in a data center facility. Similarly, WUE will help managers determine the amount of water used by the facility, and the amount used to deliver work from IT operations.
Like PUE, CUE uses the familiar value of total IT energy as the denominator. Once determined for PUE, the same value is used as the denominator for the new metric as well. TGG says that this commonality of structure will simplify CUE use.
Unlike PUE, CUE has dimensions while PUE is unit-less; its value is energy divided by energy. Another important difference is the range of values. PUE has an ideal value of 1.0, implying that all energy used at the site goes to the IT equipment, and there is no theoretical upper boundary for PUE.
CUE has an ideal value of 0.0, indicating that no carbon use is associated with the data center’s operations. Like PUE, CUE has no theoretical upper boundary.
Both CUE and PUE cover the operations of the data center. They do not cover the full environmental burden of the life-cycle of the data center and IT equipment. For example, attempting to determine the carbon generated in the manufacturing of the IT equipment and its subsequent shipping to the data center would make the metric far too difficult to measure, calculate, or use.
The Green Grid considers the full life-cycle to be important to the overall sustainability of the industry but, for practical considerations, they are excluded from this metric. For now, CUE is specifically limited to Scope 1 and Scope 2 emissions.
For data centers that obtain their entire power source from the energy grid and generate no local CO2, CUE is defined as follows:
To see alternate approach to calculating CUE and to understand the components for the loads in the metrics, download the CUE whitepaper.
Materials related to WUE will be made available in the first quarter of 2011.
From 2010 to 2015, the U.S. green data center market is projected to increase from $3.82 billion to $13.81 billion, according to EL Insights. This represents a compound annual growth rate (CAGR) of 29% during this time period.