The Green Grid continues to expand the data center efficiency metrics. Last week it announced a deal with global data center groups on a unified approach to metrics. This task force of “mega powers” continues to attempt to standardize Power Usage Effectiveness (PUE), and has also expanded and harmonized three new metrics: Green Energy Coefficient (GEC), Energy Reuse Factor (ERF) and Carbon Usage Effectiveness (CUE). The global taskforce has reached agreement on measurement protocols for GEC, ERF and CUE, and continues the discussion on additional energy efficiency metrics in a white paper.
The reason for this ongoing work is simple; escalating demand and rising energy prices have operators of mission critical facilities looking to improve their energy efficiency and Greenhouse Gas (GHG) metrics. However, metrics are not yet applied consistently on a global level. So this group of global leaders has been looking to standardize approaches and reporting for key metrics.
In February 2011, an agreement was reached on measurement protocols for PUE, which has become the leading metric for data center energy efficiency. Since then, the work has expanded to providing guidelines and next steps for GEC, ERF and CUE. The organizations that have participated include the U.S. Department of Energy’s Advanced Manufacturing Office and Federal Energy Management Programs, U.S. Environmental Protection Agency’s ENERGY STAR Program, European Commission Joint Research Center Data Centers Code of Conduct, Japan’s Ministry of Economy, Trade and Industry, Japan’s Green IT Promotion Council, and The Green Grid.
The white paper outlines methods, desired outcomes and guiding principles. While it includes the general consensus reached in regards to PUE, the big addition is its findings in regards to measuring GEC, ERF and CUE. The following is a summation of these new metrics and their purpose:
GEC: Green Energy Coefficient
This is the percent of a data center's energy that is green. This metric quantifies the portion of a facility’s energy that comes from green sources. Green energy is defined as any form of renewable energy which the data center owns the rights to the green energy certificate or renewable energy certificate.
Complexity arises because of regional and local differences as to the definition of renewable/green energy. This report looks to standardize that definition, as well as the calculation of GEC. This task force recognizes green energy as any energy for which the data center owns the legal right to the environmental attributes of green/renewable generation. The recommendation is that all public reporting of GEC includes the source issuer of certificates.
GEC has a max value of 1.0, which would indicate that 100% of the total energy used is green as defined.
ERF: Energy Reuse Factor
This metric addresses the increasing reuse of waste heat energy from the data center in other parts of the facility or campus with beneficial results. The purpose of this metric is to incentivize the reuse of energy outside of the data center rather than rejection of energy. This metric identifies the portion of energy exported for reuse outside of the data center. Reuse energy is measured as it exits the data center control volume. The control volume is an imaginary boundary around the data center and its infrastructure support areas.
ERF ranges from 0.0 to 1.0, with 0.0 meaning no energy is exported and 1.0 means all energy brought into the data center is reused outside of the data center. The report details how to compute ERF, as well as other considerations.
CUE: Carbon Usage Effectiveness
CUE: This metric assesses total Greenhouse Gas (GHG) emissions of a data center relative to its IT energy consumption. An office building would measure CUE relative to square footage, an automobile manufacturing plant might calculate it per automobile produced – the data center should calculate it relative to IT energy consumption. The task force includes emissions from energy consumption and excludes emissions generated in the manufacturing of the IT equipment, its shipping to the data center, as well as construction of the data center, as they are impractical factors in the calculation.
The ideal value of CUE is 0.0, indicating that no carbon use is associated with the data center’s operations.
These expanded metrics aide in measuring renewable energy and re-use of energy to reduce carbon. The ultimate purpose of these metrics is to better measure the actual IT work output of the data center compared to actual energy consumption. The taskforce is primarily focused on measuring the potential IT work output compared to expected energy consumption; and measuring operational utilization of IT equipment. It continues to evaluate their applicability through industry trials.
The report makes some clarifications in regard to PUE calculation as well, such as stating that total energy should be measured at the point of the utility hand-off to the data center. All measurements should be made from the point where energy is purchased. It also gives global average source energy weighing factors to express each fuel in the single common unit of kWh. It provides guidelines for how to measure PUE in a mixed use building, for example, when a sales or marketing team are also housed within a building or a shared elevator. Basically, it says that certain ancillary energy loads should be excluded and declared while calculating PUE. There are also more granular details, for example, natural gas should be measured at the purchase point, and not by the secondary energy it produces.
While PUE is a simple concept, measurement of it, and other metrics, needs to be consistent across data centers for it to mean anything. The expanded metrics are a more granular, agreed upon set of standards to measure the efficiency of a data center. Standards are important in light of PUE increasingly being used as a marketing tool rather than an efficiency tool (this is a bit of editorializing here, not a statement from any of the organizations in the white paper). However, it can be generally agreed upon that achieving the best efficiency possible, as well as going green, are extremely important to the industry.
As usual, this is just a high level summation of the report, which can be found at The Green Grid web site. The report has more defined protocols in the measurement of GEC, ERF, and CUE, as well as how they are calculated and the desired outcomes for these metrics. It outlines progress to date and next steps.