David Sonner, Vice President Marketing,
Liebert AC Power at Emerson Network Power
Many data center managers expanded their IT equipment and supporting infrastructures during the IT capacity boom years from 2003 to 2008. Given that data center infrastructure investments typically follow a 10 to 15-year planning cycle, many data centers are still being supported by these older “legacy” power systems. Since significant advancements in performance and efficiency were made after 2008, legacy power systems lag behind modern technologies in their ability to solve the challenges data center managers now face.
When looking to better manage data center budgets, increase efficiency and achieve more accurate future planning, data center managers can choose to implement best practices, make incremental upgrades or purchase all new infrastructure equipment. This last option can deliver significant operational savings, improve performance, provide a clearer path for growth and return your investment in less time than you might think. A number of modernization strategies will help you realize these benefits, and here we will discuss a few ways to improve efficiency and asset utilization.
Improving UPS Efficiency
While the period from the mid-1990s through the mid-2000s was characterized by high IT growth, improving power infrastructure efficiency was not dead-center on data center managers’ radars like it is now. UPS systems manufactured for enterprise data centers before about 2010 typically operate at a peak efficiency of 91 to 92 percent at 100 percent load (85 percent efficiency at 40-60 percent load). The other 8 to 9 percentage points are lost due to the energy it takes to dissipate the heat generated by a double-conversion UPS during the AC-DC-AC conversion process. This has traditionally been accepted as a reasonable price to pay for the protection provided by the UPS system.
With modern high-efficiency options, however, the conversion process can be bypassed, thus increasing efficiency when data center criticality is not as great or when utility power is of the highest quality. Today’s transformer-free UPS systems operated in double-conversion mode are 96-97 percent efficient at 100 percent load and 94 to 95 percent efficient at 40 to 60 percent load.
Additional strategies, such as operating the UPS in eco-mode, can bring UPS efficiency up to 98 percent at full load. As you will see at the end of this discussion, points matter.
Boosting Power Distribution Unit (PDU) Efficiency
At the PDU level, the efficiency of the transformer technology has improved and meets certain mandated efficiency standards that are in place today. The National Electrical Manufacturers Association (NEMA) mandates the standard TP 1-2007, which specifies minimum efficiency levels based on transformer size. Generally, the specified efficiencies are greater than 98.5 percent for the most common PDU sizes used today. Before the TP 1-2007 standard, PDU efficiency was typically around 96 to 97 percent, so deploying newer PDUs can add another two or more efficiency points at the PDU itself.
Upping UPS Utilization Rate
In addition to updating equipment, changing the power infrastructure design provides important benefits. These include improving asset performance, saving capital costs and gaining the ability to add capacity quickly and easily.
In legacy enterprise data centers with 2N or 2N+1 redundancy, UPS efficiency is actually even lower than the 91 to 92 percent at 100 percent load previously mentioned, since the dual-bus power architecture typically chosen in enterprise applications reduces UPS utilization. This is because to ensure safe operating conditions when one bus is carrying the full load, power system components on each bus are typically sized at 110 percent of the load.
With overprovisioning, UPS utilization under normal operating conditions falls below 45 percent. In a legacy data center with 45 to 50 percent utilization, efficiency is 83 to 86 percent at 100 percent load after accounting for losses from the low utilization rates.
To avoid the higher costs of 2N or 2N+1 redundancy, some enterprise data centers and most colocation data centers today employ “reserve” power system architectures. Reserve architectures offer comparable availability, greater efficiency and scalability, and higher resource utilization at lower cost than dual-bus architectures. Switching to a reserve architecture can raise your UPS system utilization to approximately 75 percent, and some data centers have deployed reserve architectures that check in at better than 85 percent utilization.
Adding It All Up
With energy costs at .10/kWh, a 1 percent efficiency improvement for a single 1 MW UPS translates into approximately $10,000 in annual savings. Upgrading to a modern $250,000 UPS system will reduce losses at the UPS itself by 4 to 5 percent, yielding a $40,000 to $50,000 annual savings and a five-year ROI.
For more information please visit www.emersonnetworkpower.com