Advanced Computing in the Age of AI | Tuesday, November 29, 2022

Swedish Datacenter Saves Big with Seawater 

Datacenter operator Interxion uses seawater to cool its Stockholm facilities, saving over a million dollars in energy costs each year. 

For datacenter operators, the energy required to cool the IT equipment is one of the biggest cost centers. Add to that, the carbon released by the burning of traditional energy sources is contributing to a dire climate change scenario. These factors have led IT providers to explore environmentally- and economically-sustainable cooling solutions.

One company has set aside the inefficient mechanical chillers that were keeping its Swedish datacenters cool and replaced them with a greener alternative, seawater. Netherlands-based collocation provider Interxion rents datacenter space in 11 countries, and uses water pumped from the Baltic Sea to cool the IT equipment at its Stockholm facilities, according to a PCWorld report. The new approach has significantly reduced the company's operating costs and increased its operating load capacity.

Interxion spent approximately one million on the project connecting the datacenter to a network of pipes that was already in place around Stockholm. The collocation provider recouped its initial investment in just one year. Speaking at the recent Uptime Institute Symposium, Interxion's chief engineering officer Lex Coors said the cost of seawater was roughly equivalent to US$0.03 per kWh.

Previously, Interxion spent $2.6 million a year to cool 1 megawatt of IT load. With the seawater system, it spends $5.4 million to cool 5.5 megawatts of IT load (bringing the cost down to less than one million dollars per megawatt of IT load). The company is in effect saving $1.6 million on every megawatt of IT load.

It's also been able to reduce its Power Usage Effectiveness (PUE) rating, a measure of how efficiently energy is used, from 1.95 to 1.09, an enviably low score. For comparison, a reading of 1.0 designates a system as energy neutral.

The cold intake water is used to cool three facilities, exiting each site 10.8 F warmer than when it went in. The water starts out at 42.8 degrees Fahrenheit (6 degrees Celsius), and leaves the final location at 75.2 F (24 C). The "waste heat" is used to heat area homes and businesses.

A known corrosive, seawater never touches the datacenters' HVAC systems. The salt water gets sent to a heat exchanger where it effectively cools fresh water, which is what gets pumped through the facilities.

This is not the first seawater-based cooling system. There are other Nordic area implementations, including Google's datacenter in Finland. According to Coors, however, the Interxion site is the only one using the same water supply to cool several datacenters.

Interxion still maintains onsite chillers as a backup measure in case there is an interruption in the water supply. So far this has only happened one time, and the order came from the government. Coors suspects it was done for environmental reasons to protect jellyfish.

When it comes to using our oceans and other deep bodies of water as sources of "free" cooling, waste heat can be problematic. When the much-warmer water is put back into ecosystem, it can have a dramatic effect on plant and animal life. But there are ways to lessen this impact, including the reuse of waste heat to warm buildings. Environmentalists and industry partners continue to study the issue and work toward an optimal solution.

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