The Water Footprint of ICT
Green ICT is concerned with all resources consumed in creating e-gear and operating ICT infrastructures. Significant amounts of water are used in everything from chip fabrication to PC manufacture to data center operation. This makes ICT vulnerable to droughts and other water constraints.
A Looming ICT Water Crisis?
A July 2012 New York Times article notes, "[The United States'] energy system depends on water. About half of the nation’s water withdrawals every day are just for cooling power plants. In addition, the oil and gas industries use tens of millions of gallons a day, injecting water into aging oil fields to improve production, and to free natural gas in shale formations through hydraulic fracturing…All told, we withdraw more water for the energy sector than for agriculture." How is this connected to ICT?
Data centers are thirsty creatures just by virtue of the energy they consume. "The national weighted average for thermoelectric and hydroelectric water use is 2.0 gal (7.6 L) of evaporated water per kWh of electricity consumed at the point of end use," said the National Renewable Energy Lab in 2003. This means that a 5000 square foot, 1000 kW data center could be responsible for an annual consumption of over 17 million gallons of water just for its electricity.
Cooling adds another level of water consumption. Our hypothetical data center could consume almost 9 million gallons of water a year in cooling, for a total footprint of ~26 million gallons.
Any reduction in power consumption is also a reduction in external water consumption. Reducing the need for evaporative cooling through hotter operating temperatures and use of outside air ('free air' cooling) are two techniques to reduce internal water consumption.
The New York Times goes on to suggest looming water/energy problems in the United States. "The multiyear drought in the West has lowered the snowpack and water levels behind dams, reducing their power output. The United States Energy Information Administration recently issued an alert that the drought was likely to exacerbate challenges to California’s electric power market this summer, with higher risks of reliability problems and scarcity-driven price increases. And in the Midwest, power plants are competing for water that farmers want for their devastated corn crops." One has only to look to post-tsunami Japan to see how reduced power generation might affect ICT operations.
Despite all this, a 2012 survey indicates that only a third of data centers monitor water usage. This is unfortunate, as there is much data centers could be doing to reduce direct (site) and indirect (source) water consumption.
What Data Centers are Doing About Water
Any reduction in energy consumption is a reduction in indirect water consumption. Beyond that, there are site innovations.
Google noted other techniques as far back as 2009: "two of our facilities [already] run on 100% recycled water…and we are planning for recycled water to provide 80% of our total data center water consumption by 2010…The idea behind this is simple: instead of wasting clean, potable water, use a dirty source of water and clean it just enough so it can be used for cooling. Cooling water still needs to be processed, but it's much easier to treat it enough for data center use compared to cleaning it for drinking use. For example, the data center we're building in Belgium will use water from an industrial canal and treat it in an on-site water purification facility before it is evaporated in the cooling towers. Other sites will use alternative sources of recycled water, such as city wastewater or rain water collected on site."
An Google report says, "The water filtration system at our facility in Belgium uses 100% recycled water. The ability to use recycled water was one of the reasons for choosing this site. Here's how it works: dirty water from an industrial canal enters the system and runs through a number of treatment steps, including large tanks that are filled with a fine sand to filter out small particles. At the end of the process, the water is completely clear and looks like regular water. Although it is not suitable for drinking, it is clean enough for environmentally friendly and highly efficient cooling."]
Google and a a local Georgia water/sewer authority announced in March 2012 that they have partnered to let Google's Douglas County data center recycle grey water for cooling. "The system, financed by Google and owned by [the authority],…pumps water from [the wastewater] facility to the sidestream plant, which is located about five miles west of the data center. The reuse (also known as grey- or recycled) water flows into the cooling towers, which are devices that cool water via direct evaporation. The cooling towers draw heat away from the computers. The sidestream system provides additional cleaning of the water through sterilization, filtration and chlorination…[After use by Google, the] water is cleaned and returned to the Chattahoochee River clean, clear and safe.”
Of its Hamina, Finlnad data center, Google says, "We had the unique opportunity to salvage an old paper mill in Hamina, Finland and use the pre-existing infrastructure to build a data center there. The large site sits on the beautiful Baltic Sea and is able to use raw sea water, piped through a pre-existing tunnel, to cool our servers naturally. After the cooling process, we dissipate the remaining heat and mix it in with more seawater before using it for cooling again." See images of the Hamina data center.
Yahoo's 2010 "Chicken Coop" data center consumes "at least 95 percent less water than conventional data centers."
Microsoft reports, "…our latest air-cooled data centers in Iowa, Ireland, Virginia, and Washington are designed to use 1-3 percent of the water required for a traditional data center, and the only water loss in these new systems is through evaporation, resulting in no waste water."
The Green Grid offers a new data center metric called Water Usage Effectiveness. "WUE represents the third metric (along with PUE and CUE) in the xUE family of metrics…Like PUE and CUE, the WUE metric uses the familiar value of IT Equipment Energy as its denominator. Once determined for PUE or CUE, the same value should be used as the denominator for this new metric as well…Unlike PUE, WUE and CUE have dimensions (covered in Section III below), 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. There is no theoretical upper boundary for PUE. CUE and WUE both have an ideal value of 0.0, indicating that no carbon or water use is associated with the data center’s operations. CUE and WUE also have no theoretical upper boundary, like PUE."
How will WUE handle the question of direct water use versus that embodied in a facility's energy consumption? The Green Grid told me, "This is a topic the Green grid is putting the finishing touches on, but the current preferred direction is as follows: WUE will come in two forms, a facility only form which will be used for day-to-day operations and site optimization around water usage and a source-based WUE to aid in design questions and site selection that will capture the embodied water in the energy as well."
ICT Water Beyond the Data Center
The gear installed in a data center has an additional water footprint. See The Water Footprint of a Chip Fabrication Plant.
Water consumption is an issue with edge gear, too. Computer Aid cites a 2003 analysis reporting that the production of a PC consumes 1,500 kg. of water. After production, much edge gear ends up generating heat in offices conditioned by evaporative cooling.
The NREL and Computer Aid statistics are from 2003. Please comment below if you know where to source more up-to-date information.
Photo courtesy Microsoft