Executive Summary BackgroundIn June 2010, the National Renewable Energy Laboratory (NREL) completed construction on the new 220,000-square foot (ft 2 ) Research Support Facility (RSF) which included a 1,900-ft 2 data center (the RSF will expand to 360,000 ft 2 with the opening of an additional wing December, 2011). The project's request for proposals (RFP) set a whole-building demand-side energy use requirement of a nominal 35 kBtu/ft 2 per year. On-site renewable energy generation offsets the annual energy consumption. The original "legacy" data center had annual energy consumption as high as 2,394,000 kilowatt-hours (kWh), which would have exceeded the total building energy goal. As part of meeting the building energy goal, the RSF data center annual energy use had to be approximately 50% less than the legacy data center's annual energy use. This report documents the methodology used to procure, construct, and operate an energy-efficient data center suitable for a net-zeroenergy-use building. Development ProcessThe legacy data center on NREL's campus used a number of individual servers, with a utilization of less than 5%. When the total data center power draw was divided among all users, the continuous power consumption rate per person was 151 watts (W). The uninterruptible power supply (UPS) and room power distribution units were 80% efficient. Chilled water was created using one multi-stage air-cooled chiller unit and a backup single-stage air conditioning (AC) chiller unit, delivering chilled water to seven computer room air handlers (CRAHs). This cool air was delivered through an underfloor plenum, which was also a passageway for most cables, conduits, and chilled water pipes. This increased the fan energy required to move air between the CRAHs and the servers. Open hot and cold aisles added to the inefficiency of the existing data center by allowing the chilled supply air to mix with hot return air. Additionally, two walls of the data center were floor-to-ceiling exterior windows with southwestern exposure that introduced solar heat gain to the space and required additional cooling. Evaluation Approach and ResultsThe RSF data center was designed using blade servers running virtualized servers. When the total data center power draw is divided among all users, the continuous power consumption rate per person is 45 W. The UPS and room power distribution is 95% efficient. Evaporative cooling and air-side economizing is designed to cool the air to 74 o F.Cool air is supplied to the servers through dedicated underfloor and overhead plenums. Cooling efficiency is enhanced by having a contained hot aisle. This also allows waste heat from the hot aisles to be recovered and used elsewhere in the building when needed, which reduces heating loads. The new data center is mostly below grade and has no windows, helping to insulate the room from ambient outdoor conditions. ResultsAt 958,000 kWh, the RSF annual data center energy use is approximately 60% less than the legacy data center annual energy use; this results in ...

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