Sean T. Convery, P.E., Cator, Ruma & Associates, Co.
The Engineering 2 Building at Colorado State University (CSU) is a 120,000-square-foot facility housing high-tech engineering laboratories consisting of wet laboratories and electronic laboratories, offices, and classrooms. In addition, a 2,000-square-foot data center is included. The data center will be a hybrid of low-density racks consolidated from other parts of campus mixed with high-density racks to be installed in the future.
With the laboratory air system requiring 100 percent outside air, the data center provides a perfect opportunity to truly recover energy. With the data center in the penthouse adjacent to the outside air intake louvers, hot air can be relieved out of the data center back into the main outside air intake and then taken down to the air handling units in the basement to be used for primary heating of the rest of the building. This hot air recovery comes from the low-density racks that can be cooled with conventional overhead air conditioning. With the expected 85° to 95° air coming from the hot aisles, heat can be recovered for the building any time the outside air temperature is below 50°F, which is more than 58 percent of the year in this area of the country. When temperatures are above 50°F, the warm air is simply relieved out of the building while all of the air handling units remain in outside air economizer mode. (Note that CSU does not require its data centers to be humidified, which allows it to save more energy by not wasting humidified air.) A spreadsheet energy analysis determined that the monetary value of the energy recovered was greater than $15,000 per year. In comparison, the only added component was a secondary relief duct and damper, which only cost $6,000, making the investment less than a half-year payback. Coordinating the placement of the outside air intake plenum for the building immediately adjacent to the data center was key to the quick energy payback. Additional energy recovery was gained by using this concept for the uninterruptible power supply (UPS) room once flywheel UPS units were chosen over battery UPS units.
For the high-density racks (greater than 12 kilowatts), a water-cooled in-row system must be used for this building due to the floor-to-floor height and available duct size. In-row cooling must be accomplished with higher chilled water temperatures to avoid condensation from forming on the cooling coils. Because the building is served from the campus chilled water loop, which operates more efficiently with a higher "delta-T," the best method of energy performance is to use the chilled water twice by using the return chilled water from the air handling units in the building at 55°F to cool the process loop to 58°F. Using the chilled water twice keeps the delta-T on the building's chilled water system in the 15°F to 20°F range versus the typical 12°F to 15°F range. This application can also be used for other process cooling systems, such as chilled water for chilled beam systems.
These two simple methods, along with economizer control and evaporative cooling, have proven to be great energy reduction solutions for integrating a data center in a laboratory building.
Sean T. Convery joined Cator, Ruma & Associates, Co., a mechanical/electrical engineering consulting firm of 93 persons, in 1995, and is a principal in its Mechanical Department. Mr. Convery has a Bachelor of Science in mechanical engineering and is a professional engineer in Colorado. Mr. Convery has a broad array of experience in the design of mechanical systems focusing on higher education campuses and research laboratories. Recent laboratories include the Colorado State University (CSU) Research Innovation Center (LEED® Gold), CSU Engineering 2 Building (LEED Gold Pending), University of Colorado (CU) Boulder System's Biotechnology Building (LEED Platinum Pending), and CU Denver Anschutz Medical Campus Research Complex energy efficiency upgrades. Mr. Convery was a presenter at the past two Labs21 Annual Conferences and has received Engineering Excellence Awards from the American Council of Engineering Companies in Colorado for his designs at complex biosafety level 3 campuses.