Groundwater Cooling and the Sustainable Data Centre

By: Bob Landstrom

Global power consumption by data centres last year was in excess of 40 GW. In the U.S. alone, data centre electricity consumption is projected to increase to roughly 140 billion kilowatt-hours annually by 2020 – the equivalent annual output of 50 power plants. As data centre demand continues to grow, operators are increasingly focused on cost and stewardship of energy. Interxion is facing this challenge head-on by pioneering new approaches to energy efficiency and sustainability, setting an example in the industry, and managing our Power Usage Effectiveness (PUE) by tapping Mother Nature for help.

Much of a data centre’s energy use is driven by the mechanical (cooling) system. Of that, the chiller is a prominent component, accounting for as much as 65 percent of the mechanical system’s energy consumption. If one can find ways to reduce the demand on the mechanical chiller, significant energy savings will likely result.

Interxion’s engineering team is always exploring new ways to reduce energy consumption across our data centre footprint. At the Copenhagen location our team saw an opportunity to tap nature, rather than the electrical grid, to offset energy expenditures.

In that location, Interxion takes advantage of the local subterranean geology, which lends itself to containing water with thermal stability, without exposure to the local aquafer. Two reservoirs were created, 70 metres below ground level, in subterranean limestone deposits. Water in the reservoirs is naturally cooled by the Earth to around 10-11°C. By pumping the cool water from one reservoir to the other through a heat exchanger in the data centre, the cooling capability of the water is exploited while simultaneously reducing load on the chiller. The reduced chiller burden results in an annual energy savings of more than 1,200 MWh. (See Figure 1)

(Figure 1) Artist rendering of Interxion’s Copenhagen groundwater cooling apparatus

There are other unlikely benefits to the groundwater cooling system. The greater Copenhagen community profits from an additional water source, since the water stored in the reservoirs is considered potable. In case of emergency, the residents will have full access to the reserve supply.

Interxion’s groundwater cooling solution is just one more example of continued innovation in engineering and energy efficient operations.