Abstract

The energy consumption of data centers is reported to be a number between 1-3% in the United States or the world. With the new era of Internet-of-Things and the increased use of artificial intelligence, one can assume these numbers will grow substantially. This article investigates this problem and presents the current situation and potential future developments.

1. Introduction

It is not possible to think about computing and networking today without con- sidering data centers. They are where computing and networking equipment is concentrated for the purposes of collecting, storing, processing, distributing or allowing access to large amounts of data. Their construction costs about $20B a year worldwide [1], and they cause approximately as much CO2 emissions as the airline industry [2]. According to a report by Lawrence Berkeley National Labora- tory, data centers in the United States consumed about 70 billion kilowatt hours of energy in 2016 [3]. This corresponded to 1.8% of all the energy consumed in the United States that year. The United States Department of Energy currently states up to 3% of all electricity may be consumed by data centers today [4]. Globally, electricity demand by data centers in 2018 was an estimated 198 terawatt hours, or almost 1% of demand for electricity in the world [5]. It is estimated that the electrical energy consumption by the information technology industry across the globe is less than only the United States and China and is more than the third country on the list [1]. On the other hand, global Internet traffic has tripled between 2015 and 2019 and is expected to double by 2022 [6]. Increased use of artificial intelligence and the large number of sensors expected to be deployed in the Internet-of-Things era bring up the question how much more energy use in data centers will increase. The crucial question is whether it will increase exponentially as Internet data traffic is growing and what this growth will mean for the release of CO2 worldwide. The latter question becomes important when one considers that 63.5% of electricity generation in the United States during 2018 was from fossil fuels [7].

2. Significance of the Problem

The Internet search engine Google disclosed in 2011 that its data centers consume 260 megawatts and made the estimation that this is sufficient to power 200,000 homes [8]. Google estimated that one Google search is responsible for emitting 0.2 grams of CO2 per year [9]. It also estimated its carbon footprint as being 1.5 million metric tons in 2011 [10]. Considering the increase in Internet traffic during this period, that number may be even higher today. On the other hand, in 2019, the company announced that it has made purchases of renewable energy equivalent to 1,600 megawatt, increasing its share of renewable energy sources to 5,500 megawatt, making it 40% of its total energy consumption.

Today, streaming video is the most significant part of global data traffic. The Internet company Cisco predicts that streaming video will make up 82% of all Internet traffic by 2021, up from 73% in 2012. Currently, one third of Internet traffic in North America is already dedicated to streaming Netflix services [1]. The global non-governmental environment organization Greenpeace shows a strong interest in energy consumption by Internet companies. To that end, Greenpeace began benchmarking the energy performance of the Information Technology sector in 2009, challenging the largest Internet companies to substantially increase their use of renewable energy. The advocacy group uses an annual report to rate big Internet and cloud companies on their use of renewable power.  In the report in 2017, Greenpeace denounced Netflix for substantial energy inefficiency [11]. Netflix does not own data centers; instead it uses contractors such as Amazon Web Services (AWS). Greenpeace also denounced AWS for being completely non-transparent about the energy footprint of its massive operations. AWS has some of its largest operations in Northern Virginia, which receives less than 3% of its energy from renewable sources [1]. Decisions by Internet and cloud companies can be surprising. Northern Virginia, with such a bad record for renewable energy, has the largest concentration of data centers in the world [1]. The location where energy is generated is actually very important in terms of its efficiency. For example, to generate 1 kilowatt hour of energy, it takes 3 grams of CO2 in Norway, 100 grams in France, 600 grams in Virginia, and 800 grams in New Mexico. Most of the energy is used to keep the processors cool. Very surprisingly, most of the world’s largest data centers are located where the temperature is hot [1]. However, through various efforts, Internet and cloud companies seem to be listening. Netflix declared in 2017 that they now purchase renewable energy certificates to match their non-renewable energy use and fund renewable energy production from sources such as wind and solar [12]. AWS has declared that it is committed to achieving 100% renewable energy use for their global infrastructure [13].

A measure used to gauge the energy efficiency of data centers is called the

Power Use Effectiveness (PUE). PUE is the ratio of the amount of energy used in the center by the amount to run the processors. It is a number larger than or equal to 1 and it is desirable to make it close to 1. In other words, a smaller PUE is better because it shows smaller energy is used for operations other than running the processors. An industry analysis a decade ago found an average PUE of 2.5. An organization, known as the Uptime Institute, publishes average PUE figures for the industry. In 2009, this number was declared to be 2.5 [14]. It is encouraging that this number is actually dropping very fast. In 2011, the Uptime Institute declared the PUE for the industry to be 1.8 [15]. An Uptime Institute study in 2014 studied the PUE of cloud data centers from Google and Facebook public disclosures plus AWS internal data, all of which show PUEs under 1.2 [13]. These numbers appear to be very good, since in 2008, the Uptime Institute declared that the typical data center has an average PUE of about 2.5, but that number could be reduced to about 1.6 employing best practices [16].