Green Grid members are keeping conclusions of a peer review study under wraps until the conference opens. However, one group leader made his opinions clear in an interview late last week.

"High-voltage dc offers some marginal improvements [in energy efficiency], but some users, particularly in Europe, are already outpacing these options with high-voltage ac with a model that's starting to work very well," said John Tuccillo, vice president of industry alliances at American Power Conversion Corp. and a director of the Green Grid

"When you throw in issues about practicality of deployment and other risks" dc seems a nonstarter, Tuccillo suggested.

Researchers at Lawrence Berkeley National Laboratory authored a study on high-voltage dc in the data center about a year ago. It reviewed potential efficiency gains from implementing a dc-based architecture.

Members of the Green Grid finalized late last week a "fairly extensive peer review" of that study. They will present their findings and a white paper on the topic at the forum on Tuesday.

Intel discussed the benefits of shifting from ac to dc power in the data center about a year ago at its Intel Developer Forum. A handful of companies have developed products and services to enable such a shift.

Also at its event this week, the Green Grid will share results of a market study on existing data center practices, provide guidelines on saving power in servers and discuss emerging techniques for measuring the energy efficiency of data centers.

The group will also recommend new practices for consolidating IT and facilities management in data centers. "The organization paying the energy bill is not always the one that is making the biggest decisions about energy use," said John Pflueger, a director of the Green Grid and a technologist at Dell Computer.

The group will emphasize the need for using multiple tools to save power in data centers and that no single metric or tool is sufficient. "We have some of the greatest scientific minds from the leading companies working on [these] problems," said Tuccillo.

The Green Grid now has about 150 members, including a broad range of computer and communications OEMs. The founding members include Advanced Micro Devices, Dell, Hewlett-Packard, IBM, Intel, Microsoft and Sun Microsystems.

The U.S. Environmental Protection Agency filed a report with Congress last year that estimated data centers in the United States consumed about 61 billion kilowatt-hours in 2006 at a cost of about $4.5 billion, figures that could nearly double by 2011, the EPA warned.

One market watcher estimates that the cost of power to run servers could exceed the cost of the server hardware itself by 2015.