Renewable energy has come a long way in the past few years. Gone are the days of 'token' deployments: power-hungry facilities worldwide are turning to sustainable means to reduce their reliance on the traditional grid.
Here, Information Age runs down the top six sources of sustainable power used in Australia and overseas.
NEXTDC's 401kW solar array on the roof of its M1 data centre in Melbourne is one of the best-known examples of solar use on a data centre in the region. Since it commenced operations in October 2013, the array has produced 619.69 megawatt hours of power, the company revealed to Information Age.
"When you're spending more than $1.2m on a project like solar, people always ask questions like what are the paybacks? How does that compare to other investments we make in the business? And why is solar important?" NEXTDC's CEO Craig Scroggie said.
Scroggie said he expected the investment to pay for itself in between seven and ten years, "subject to the prevailing price of electricity". However, he noted that the decision to go with solar wasn't based on finance alone. "If you only looked at the economic investment you'd struggle to say that a 7+ year return horizon was a good decision," he said. "There's got to be other motivating factors". Some of those benefits include CO2 avoidance, and the ability to on-sell renewable power to customers.
Outside Australia, Apple is one of the biggest backers of solar power for data centres. It built a solar farm to power a facility in Nevada in 2013, and has just announced plans for a US$2 billion facility in Arizona that will also take advantage of a huge solar array.
Wind power is cheap and not as unreliable as mythology suggests. Amazon is putting its money where its mouth is, partnering with a firm called Pattern Development for a 150 megawatt wind farm in the US state of Indiana. It is expected to be operational as early as January 2016, with the output used to "power both current and future AWS cloud data centres".
Likewise, Google has committed to buy the entire output of a wind farm in The Netherlands to power its under-construction Eemshaven data centre, and Facebook is using wind power for its Altoona data centre in Iowa, which came online in late 2014.
Closer to home, Telstra has looked at wind power for smaller exchange buildings or mobile towers. "Wind is a little bit difficult," Telstra Property's executive director John Romano told Information Age. "We've tested it, but we don't have a lot of sites where the wind is going to generate a lot of energy."
Telstra has been testing fuel cells as an alternative to battery back-up arrays at small telephone exchanges and mobile base station sites since late 2013. Executive director of Telstra Property, John Romano, told Information Age the telco has deployed almost 20 fuel cells across its network - powered by either hydrogen or methanol.
One of the hydrogen fuel cells used on a Victorian exchange was recently profiled because it uses solar power to create hydrogen from rainwater. That hydrogen is then stored for use in case mains power to the site goes out.
Like others, Telstra is looking to a future where fuel cells can be the primary source of power to a facility, rather than the back-up. Apple and eBay are known to run data centres off-grid using fuel cell technology.
When Hewlett-Packard Laboratories published a "hypothetical" paper in 2010 on the use of cow manure to power data centres, the world took notice. The researchers estimated they would need the output of 10,000 dairy cows to produce enough power for a 1-megawatt data centre. "As a result of the publicity, we had a lot of farmers, including the American Dairy Association, contact us," HP Labs senior fellow and chief engineer Chandrakant D. Patel told Information Age. "We got invited to and visited several dairy farms."
One farm Patel visited produced cheese for a supermarket chain. The farmer had 1200 dairy cows, and used their manure to create biogas using an anaerobic digester. That biofuel is fed into a turbine for conversion into electricity. "He was getting 500kW output," Patel said. "It was flat as can be. You could put a ruler through it." Patel also discovered that the farmer was putting waste cheese into the digester, "allowing him to go to 700kW with 1200 dairy cows. So subsequent to our paper we found out that we had over-estimated the number of dairy cows needed."
HP went on to conduct a feasibility study on poo power. Despite showing the concept was feasible, they could not convince an operator to take the leap.
Patel believes low-cost electricity contracts played a part in making biogas unattractive. "When you have a good contract for energy one is not too concerned [about sustainability]," he said.
Traditional decision-making criteria used by data centre operators is also likely to have played its part in poo power's lack of success to date. Operators are traditionally more concerned with close proximity to connectivity and the users they serve, than to an energy source.
"At the end of the day the data centre needs to serve its purpose," NEXTDC's chief operating officer Simon Cooper told Information Age. "You don't build a data centre just to consume energy, you build a data centre to create a location that's highly connected and - depending on the overall role of the data centre - close to the population that uses it."
Patel believes that thinking should be challenged. "We should go to the source of power," he said. "In today's day and age we should not be held to a given location."
Microsoft built a data centre near a wastewater treatment plant to create electricity using similar methods. However, the facility stayed small and was ultimately donated to research purposes.
Embracing HP's philosophy of bringing data centres closer to energy sources, Hydro66 is building an 8000m2 data centre within 500m of a hydro power station in Sweden. The facility is expected to be ready-for-service in May 2015.
Last year, Apple took over a hydroelectric project near its Prineville data centre in Oregon. Other hydro fans include French ISP OVH.com, which uses hydro power to run a data centre outside Montreal; TELUS, which also has a Canadian facility; and Green Mountain, which has co-located its facility close to two Norwegian hydro power stations.
Google made waves in 2008 when it filed for a US patent for a "water-based data centre". The idea was to stack containers of gear on barges, and harness energy from the surrounding ocean to power it up, the NY Times Bits blog reported at the time.
Another proposal arose a year later for a tidal powered facility in Scotland; however it was killed by costs and slower-than-expected development of tidal power systems. Others have looked into the potential for autonomous, self-powered data centres that could roam the world's oceans.