SUBSEA WHAT’S IN AN EFFICIENCY METRIC?
The Case of Power Usage Effectiveness (PUE) at the Cable Landing Station BY IAGO BOJCZUK, ELLA HERBERT, MICHAEL BRAND, HESHAM YOUSSEF, AND NICOLE STAROSIELSKI
T
he Sustainable Subsea Networks research project, an initiative of the SubOptic Foundation, recently released the Report on Best Practices in Subsea Telecommunications Cable Sustainability. In that report, we concluded that there was a need for sustainability metrics in the industry. Many of our interviewees reported, “If you can’t measure it, you can’t manage it.” Metrics can not only help to set internal benchmarks, but also to shape future investments and regulation. We believe that metrics can also help the subsea cable industry explore possible win-win scenarios that are good both for business and the planet. As a first step, we begin with an investigation of existing metrics from adjacent industries. There is no need to reinvent the wheel when it comes to measurement. At the same time, the struggles over metrics — and their limitations — are instructive as we attempt to develop appropriate metrics for the subsea cable network. In this month’s column, we focus on a metric that has been established to gauge energy efficiency of facilities housing information technology (IT) equipment worldwide: Power Usage Effectiveness (PUE). This is one of the most widely disseminated metrics in the data center industry. It has been codified in ISO standards and absorbed into regulation. In our research, we have found that
10 SUBMARINE TELECOMS FORUM MAGAZINE
some Cable Landing Station (CLS) facilities are already using PUE as an internal measurement. Is this use of PUE a good idea for the subsea cable industry? What are the limitations of this metric? In this article, we cover the basic definitions of PUE and describe how it became used across the globe. We also describe the pitfalls of PUE. As academic and industry literature has shown, PUE can at times lead to misleading conclusions, especially when it is used to compare facilities around the world. We conclude that, by itself, using PUE as a gauge of the sustainability of the CLS is far from sufficient. However, as the subsea cable industry faces the challenge of identifying, developing, standardizing, and adopting the right suite of metrics, it is nonetheless a good starting point.
THE RISE OF PUE AS AN ALLENCOMPASSING METRIC
In its original definition, the Power Usage Effectiveness (PUE) (per ISO/ IEC 30134-2) of a facility refers to the ratio between total power used by a data center and the power used by its IT systems. A lower value indicates greater energy efficiency, ideally approaching 1.0 — this signifies that a greater portion of the facility’s power consumption is being used directly for computing, rather than cooling or other overhead, thus indicating higher operational efficiency. PUE as a metric was first developed by the Green Grid in 2007, and was the first standardized metric measuring the energy efficiency of an entire data center (Lin et. al, 2021). Since its inception, the main goal of implementing PUE measurement has been to motivate data center operators to eliminate waste in their facility power