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If anyone knows how to protect against power outages caused by extreme weather, it is Jeff Biggs. The vice-president of operations and engineering for Peak 10, a fast-growing US datacentre operator, Biggs has taken many steps to harden the company’s collocation facilities in Florida against the annual threat of hurricanes.

These include making sure Peak 10’s Jacksonville datacentre taps into the city’s underground power lines in two places, in case one substation or line goes down, and buying a massive 1,500 kilowatt back-up diesel generator for Peak 10’s Tampa Bay datacentre, 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 other parts of the US, which left areas of Denver, Seattle and St. Louis 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 says.

The continued growth of the internet, combined with cheaper PC-based technologies, has led to a doubling of the number of servers worldwide since 2000, according to market research company IDC.

Much attention has been paid to how to cut the spiralling costs of powering and cooling these servers. But less thought has been devoted to how to better protect datacentres from power outages, now that incidents of turbulent weather caused by global climate change appear to be on the rise.

One major US airline’s Seattle reservations datacentre went dark on 15 December, when its back-up generator failed to turn on after windstorm-induced blackouts, says Mark Svenkeson, president of datacentre building firm Hypertect.

"They had all of the right pieces in place; it just wasn’t well-implemented, so it shut the business down," he says.

Experts say datacentre managers must increase both the diligence and the scope of their outage-proofing efforts, especially when few electrical utility firms will invest in upgrading their fragile infrastructures.

Perhaps the most obvious infrastructure upgrade -- burying above-ground electrical lines, especially in areas where wind, hail, heavy snow or falling trees are perennial threats to electricity poles and towers -- is still not viable nor even desirable in most cases, experts say.

"In terms of safety, reliability and especially cost, underground lines are the least preferred choice of engineers," says 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, 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, says Pieper, with 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 above ground: 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, says utility safety consultant Carl Potter.

High-voltage power lines are only found underground in the US in dense commercial areas, such as major city centres, where above-ground lines interfere with traffic and buildings.

While underground wires appear less vulnerable than above-ground power lines, they have several disadvantages. Above-ground lines are typically uninsulated and are 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 in the same steel piping. That oil must be constantly cleaned to maintain its cooling properties and to keep it from breaking down into hydrogen gas, which can be explosive, says Stan Johnson, a manager at the North American Electric Reliability Council (NERC) a US watchdog agency.

An alternative is to cool underground lines by letting a certain amount of electricity "bleed through" to the ground, Potter says. This 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 what Peak 10’s Biggs calls the JCB “mating season”.

Repairing underground wires also takes longer. And they are not necessarily less prone to storm damage, says NERC’s Johnson, who points out that salt water brought in by hurricanes can cause as much damage to underground lines as winds do to the overhead variety.

Experts say extensive studies by electrical utility firms and third parties show that installing underground power lines, especially high-voltage ones, can cost up to £10m ($20m) per mile -- about 10 to 20 times more than stringing them overhead.

Even reliability watchdogs such as NERC do not 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," says Johnson.

On the other hand, a dense underground power grid can be benefit datacentre operators by allowing them to tap into lines twice or more for redundancy’s sake. "That’s the holy grail for datacentres if you can do that," says Biggs, who says it helped his facility in Jacksonville, Florida, achieve Tier 1 certification.

But other experts point out that the high cost of premises is causing many firms to move datacentres 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 says.

Hypertect’s Svenkeson recommends that datacentres have two back-up generators, or a "backup for their backup". But he says that due to new requirements from the US Environmental Protection Agency which came into effect at the start of this year, back-up generators have become both pricier and harder to find. Peak 10’s Biggs claims that the backlog of orders at many manufacturers is so heavy that it would take a year for a generator ordered today to be delivered.

In future, underground power may slowly become more practical as the technology to cool and insulate the cables improves. One plastic insulator, cross-linked polyethylene (XLPE), now allows underground transmission lines to carry up to 345,000 volts, says Pieper. That amount of voltage was first carried underground in project in the US state of Connecticut, which was completed in October last year.

And laboratory technologists are now working on superconductors that can use liquid nitrogen to cool conductive wires, allowing electricity to travel over long distances with no power loss.

Eric Lai writes for Computerworld (US online)