If anyone knows how to protect against power outages caused by extreme weather, it would be Jeff Biggs. The vice president of operations and engineering for Peak 10 Inc., a fast-growing data centre operator, Biggs has taken many steps to harden Peak 10’s co-location facilities in Florida against the state’s annual threat of hurricanes.
Like making sure Peak 10’s Jacksonville data centre taps into the city’s underground power lines in two places, in case one substation or line goes down. Or buying a massive 1,500 kilowatt backup diesel generator for Peak 10’s Tampa Bay data centre, along with emergency refuelling contracts with two separate suppliers in case of an extended outage.
But Biggs admits that recent storm-related power outages in Denver, Seattle and St. Louis, all of which left parts of those cities dark for a week or longer, would have tested and perhaps overwhelmed Peak 10’s precautions.
"An outage that long, oh my God, it would catch even my fuel suppliers off guard," he said.
The continued growth of the Internet, combined with cheaper PC-based technologies, has led the number of servers worldwide to double since 2000, according to market research company IDC.
Much attention has been paid on how to cut the spiralling costs of powering and cooling these servers. But less thought has been devoted on how to better protect data centres from power outages, now that incidents of turbulent weather caused by global climate change appear to be on the rise.
Take one major US airline, whose Seattle reservations data centre went dark on 15 December when its backup generator failed to turn on after windstorm-induced blackouts, according to Mark Svenkeson, president of Hypertect, a builder of data centres.
"They had all of the right pieces in place; it just wasn’t well-implemented, so it shut the business down," he said.
Experts say that data centre managers must increase both the diligence and the scope of their outage-proofing efforts, especially since few electrical utilities will be investing in upgrading their fragile infrastructure.
Perhaps the most apparently obvious infrastructure upgrade -- burying existing overground electrical lines, especially in areas where wind, hail, heavy snow or falling trees are perennial threats to electrical poles and towers -- still isn't viable or even desirable in most cases, say experts.
"In terms of safety, reliability and especially cost, underground lines are the least preferred choice of engineers," said Rick Pieper, a technical director at Henkels & McCoy, an engineering firm that builds both above- and below-ground power lines.
Above and below
According to Pieper, there are three main components of power lines. The first are the lower-voltage lines serving individual homes or businesses or residential neighbourhoods. They include secondary lines connected to homes that carry between 120 and 480 volts, as well as distribution lines inside newer neighbourhoods that typically carry between 12,000 and 34,000 volts. For aesthetic reasons, burying power lines has become the norm in residential neighbourhoods built in the last three decades or so, said Pieper, with the developers passing on the cost to home buyers.
There are also distribution lines transmitting electricity from substations to neighbourhoods along main roads. High-voltage transmission lines carry 69,000 to 765,000 volts of electricity over long distances, such as from distant power-generation plants to substations in towns.
Underground distribution and transmission lines are mainstream in Europe. But the vast majority in the US remain aboveground: aluminium-wrapped steel cables strung along wood or concrete poles in the case of distribution lines or large towers in the case of transmission lines, according to Carl Potter, a utility safety consultant.
High-voltage power lines are only found underground in the U.S. in dense commercial areas such as major metropolitan downtowns, where aboveground lines interfere with traffic and real estate.
While underground wires appear less vulnerable than aboveground power lines, they have several disadvantages. Overground lines are typically uninsulated and cooled by air. Underground lines, in contrast, quickly build up heat.
One way to prevent underground cables from melting is to bathe them in oil travelling inside the same steel piping. That oil must be constantly cleaned to maintain its cooling properties as well as to keep it from breaking down into hydrogen gas, which can be explosive, said Stan Johnson, a manager at the North American Electric Reliability Council, a US watchdog agency.
An alternative is to cool underground lines by letting a certain amount of electricity "bleed through" to the ground, Potter said. That has the disadvantage of making them less efficient, and the resulting electrified ground can harm animals or humans.
Underground wires are also more vulnerable to being accidentally dug up, especially during "backhoe mating season," said Peak 10’s Biggs.
Repairing underground wires also takes longer. And they are not necessarily less prone to storm damage, said NERC’s Johnson, who pointed out that salt water brought in by hurricanes can cause as much damage to underground lines as winds do to the overhead variety.
All told, experts say that extensive studies by electrical utilities and third parties show that installing underground power lines, especially high-voltage ones, can cost up to $20 million per mile, which is about 10 to 20 times more than stringing them overhead.
Even pro-reliability watchdogs such as NERC don’t advocate underground power.
"We push for a more reliable system, yes, but we do not as a general rule push for utilities to build underground lines rather than aerial transmission poles," said Johnson.
On the other side of the ledger, a dense underground power grid can be benefit data centre operators by allowing them to tap into lines two or more times for redundancy’s sake.
"That’s the holy grail for data centres if you can do that," said Biggs, who said it helped his facility achieve Tier 1 certification.
But other experts point out that the high cost of real estate is causing many data centres to migrate to suburban or rural locations, where underground lines are a rarity.
"As the electricity arrives from the generating plant, I can tell you it’s all going to be up in the air somewhere," Henkels’ Pieper said.
Hypertect’s Svenkeson recommended that data centres have two backup generators, or a "backup for their backup." But he says that due to new EPA emission requirements that went into effect at the start of this year, backup generators have both become pricier and harder to find. Peak 10’s Biggs claimed that the amount of backorders at many manufacturers is so heavy that it would take a year for a generator ordered today to be delivered.
Looking forward, underground power may slowly become more practical as the technology to cool and insulate the cables improves.
One plastic insulator, cross-linked polyethylene (XLPE), allows underground transmission lines nowadays to carry up to 345,000 volts, said Pieper. That amount of voltage was first carried underground in a southern Connecticut project completed in October 2006. And technologists in the lab are working on superconductors that would use liquid nitrogen to cool conductive wires to allow electricity to travel over long distances with no power loss.
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