Power trip: The case for cogeneration

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Conservation before cogeneration

Bramfitt says he'd prefer data center managers to look first at installing economizers on air conditioning systems. Those systems conserve energy by taking advantage of outside air temperatures on cold days to cool the data center. "An economizer in some ways takes the steam out of the economics of a cogeneration system" because you already have a source of free cooling, he says.

But the data center managers Bramfitt has approached have been reticent about using economizers, even though PG&E offers incentives that cover up to half the cost of the systems. He says PG&E isn't against cogeneration, and in fact continues to offer rebates for CHP systems. But considering cogeneration first, he says, is tantamount to saying, "Let's generate our way out of the problem rather than conserve our way out of the problem." Conservation is also less risky, he points out, since it doesn't require the business to manage a power plant or worry about escalating fuel costs.

For its part, NetApp already uses air-side economizers and finds the technology to be complementary. "When we use the economizer, we don't need our cogeneration system because we have free cooling," Hoffman says. But cogeneration makes sense in the middle of the summer, when outside air temperatures are too warm to use the economizer. "We balance between the two," he says.

Data center managers also may be reluctant to support the technology because they're wary of the added complexity of running a power plant. While some designs use turbines, Hoffman says his system uses a gas-powered internal combustion engine that is similar to the backup diesel generators that his staff is already familiar with.

"I have clients who have looked at this stuff and decided that it's too early in the cycle to do this," says Rakesh Kumar, an analyst at Gartner Inc.

That was Ben Stewart's conclusion. Stewart is the vice president of facilities engineering at Miami-based Terremark Worldwide Inc., a Miami-based operator of integrated Internet exchanges and data center operations. He has been considering installing a CHP system for Terremark's newest data center. That system would use natural gas turbine generators from United Technologies Corp. to provide full-time power. While the generators would eliminate the cost of cost of electric chillers, Stewart has decided to pass on installing it in the data center, which a hosting company is building in Culpepper, Va. "It's kind of cutting-edge technology," he says. "We're not sure how to build the rest of the infrastructure around it."

NetApp's Robbins has no regrets. "When we sold the project to the... CIO, we told him we were responsible for providing reliable power and cooling and managing the energy cost, and I think that still holds true today," he says.

Kumar thinks data center managers should at least consider the technology.

While using CHP in data centers isn't common, the technology itself isn't new. "People are just starting to consider on-site generation and particularly CHP," Gross says.

Even Stewart says he hasn't entirely ruled out some role for it. "If we do it, we'll try it on a smaller site" first, he says.

Copyright © 2007 IDG Communications, Inc.

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