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Notes on data center water usage

Trying something new: I’m not an expert on this topic at all, but here’s my (not high-confidence) basic understanding of the usage of water in cooling data centers after doing internet research.

  • Server racks in data centers produce a ton of heat, running 24/7, so need cooling in order to continue operating efficiently/not melt
    • Some companies put data centers in cold places like Scandinavia (which also have cheap renewable energy) to help with this, since they can vent in fresh air for full cooling, though heat waves can require backup cooling systems. Many data centers are in hot places like Arizona where land & (solar) electricity are cheap, so need even more cooling.
    • Due to the speed of light/internet, we need data centers all over the world to minimize latency (it takes noticeably longer to load websites hosted on other continents), so geographical placement isn’t the solution alone.
    • There’s wacky ideas for floating data centers in bays & oceans. Unclear how the scale of water heating affects these long-term.
  • In earlier eras, servers were cooled with fans & traditional AC systems, but because of the massive amount of electricity required, it’s expensive, carbon-intensive, and inefficient. As chips have gotten more efficient, they operate at higher temperatures and need increasing cooling, so many companies switched to liquid cooling, which is more efficient since water is a better conductor. Traditionally, evaporative cooling is used to vent heat, with potable water.
    • Fans/AC produce a ton of sound pollution, which is bad for local communities
    • Evaporative cooling is highly sensitive to variable outdoor air temperatures, and air pollution: volcanoes, forest fires, vehicle air pollution, etc change how effective cooling is & damage equipment. Poorly maintained cooling towers spread Legionnaires’ Disease (!)
  • For a sense of scale: Google says their annual data center water usage is 4.3B gallons, or 29 southwest US golf courses; one data center uses 450k gallons/day
  • Solutions to this high water usage:
    • Use non-potable water we don’t care about conserving: Google in Georgia heats local municipal wastewater instead of potable water, evaporating the water then treating the solid waste; their facility in Belgium uses industrial canal water. Apple & Microsoft have built water treatment facilities for cities in the PNW.
    • Desalinating saltwater with reverse osmosis filtration can also be useful; the energy needs are so intense it’s usually not cost-effective
  • Relevant energy/carbon-reducing schemes that interact with the cooling:
    • Since we’re burning fuel to produce heat & this is direct heat, it can be used for heat pumps. NREL’s data center (press / source) uses the waste heat to heat offices/lab space in the same building; it can be exported too, but the big challenge is having relevant infrastructure (greenhouses, for instance) nearby enough to be worth connecting.
    • To reduce energy use, thermal store: in cool places, chill water or make ice overnight, then use that as a buffer to reduce energy usage during the peak daytime hours.
  • Feedback loops:
    • Water & electricity usages of data centers are costly, so companies have direct incentives to reduce them. Water is cheaper than electricity so is used with more abandon; though water causes more tensions than electricity with local communities, since new electricity sources are often built for data centers. Recycled or wastewater is cheaper than potable water, though higher facility installation costs mean longer periods for ROI.
    • Since Amazon, Google, & Microsoft (the big players in selling the cloud computing capacity, which power the majority of the web) all have 100% renewable energy goals and >100% water replenishment goals (as does Meta), there’s market pressure. Unfortunately, outside the name brand compute services, less than a third of data center operators even track water usage.
  • I’ve never come across mention of relevant regulations in the US in reading about this. In Europe, the European Green Deal has 2025 & 2030 targets for water conservation.