With the goal of reducing power consumption of the ever-expanding population of high-density data centers, the Electric Power Research Institute (EPRI) recently investigated the energy-reduction potential at three U.S. data centers. This included reducing the number of voltage transformations in power distribution systems and retrofitting power supplies with highly efficient 80 PLUS power supplies—a performance specification that requires power supplies in computers and servers to be 80 percent or greater energy efficient at 10, 20, 50 and 100 percent of rated load with a true power factor of 0.9 or greater.
EPRI research also included intelligently managing airflow in server aisles, which uses software to enable servers and air conditioners to work in concert to reduce the energy consumed by the servers, cooling systems and operating servers in higher temperatures. This demonstration highlights that owners of data centers have multiple options for reducing energy bills, extending life of assets and increasing server reliability.
An electric utility in the southwestern United States commissioned an airflow-management and cooling-control system at its main data center. With the advanced control system, the utility managed the cooling of 6,000 square feet of raised floor and more than 50 racks of servers. It also installed dozens of meters and a wireless mesh network to collect measurements over a wide area.
An electric utility in the Northwest hosted a demonstration at its data center, which upgraded to 80 PLUS server power supplies, leading to a significant reduction in power consumption. The utility also installed dynamic power-management software, which is used to capture CPU performance and reduce power levels.
A third electric utility in the southeastern U.S. installed a 30-kilowatt direct current (DC) rectifier/uninterruptible power supply and three information technology (IT) equipment racks capable of running on alternating current (AC) or DC power feeds. Results showed a significant decrease in power consumption using DC versus AC. The utility also commissioned a comparison between DC power supplies and high-efficiency AC power supplies. Laboratory tests indicated that the tested DC power supplies were 2 to 3 percent more efficient.
By employing power supplies that comply with 80 PLUS protocols, data centers can profit from significant energy savings, as high as 20 percent according to EPRI field tests. And, because these energy-efficient power supplies run cooler, an attendant reduction in air conditioning cost is likely.
Airflow, in even the most modern data centers, can be unruly, cooling objects that do not need cooling and bypassing objects that do. By managing airflow velocity to maintain an adequately low server temperature, data centers can shave up to 77 percent from energy consumption of unregulated fans and reduce the total energy consumption by as much as 17 percent.
Thermal maps may provide enough high-resolution evidence for operators of data centers to raise the temperature of their cold aisles by 5°F (for example, from 72 to 77°F). This temperature increase will enable the chillers to work less, resulting in a significant energy savings (3 to 5 percent in some scenarios).
Finally, replacing the standard AC power system used to electrify modern servers with DC systems, data centers can reap the benefit of eliminating multiple AC-to-DC and DC-to-AC power conversions, resulting in a potential energy savings of 15 percent.