Installing multiple modular UPS units in a manual or automated variable module management system (VMMS) in place of a single unit to increase part-load efficiency.
Uninterruptable power supplies (UPS) deliver instant power to data centers and/or end-use equipment during power supply interruptions. UPS equipment is designed to temporarily provide power to operate data center equipment until emergency power generation comes online or the equipment can be properly shut down.
Conventional design of data center power systems includes a single large legacy UPS to deliver reliable power to the data center. Because of equipment oversizing and fluctuating IT loads, these larger UPS operate at about 38% of full load (LBNL, 2005), which has a lower efficiency than if the UPS was fully loaded. A more optimal approach is the focus of this ET – install multiple modular UPS units and operate them with a variable module management system (VMMS) control strategy.
Once modular UPS units are in place, they should be configured on a VMMS that automatically loads fewer UPS units to maximize loading and efficiency. In addition to optimizing efficiency on UPS units that are loaded more heavily, with a VMMS system, unnecessary redundant UPS units can be taken offline completely, saving additional energy.
Major energy efficiency losses in data centers occur due to oversized and redundant systems. UPS system energy efficiency, as described in this measure, can improve from approximately 80% in a legacy system baseline (in a 2N redundancy) case up to 97% in a modular, streamlined and properly sized system (in a 1N zero-redundancy) case. (APC, 2013)
Status:
Baseline Description: Standard Double Conversion Mode UPS (about 40 kVA) Baseline Energy Use: 118240 kWh per year per unit
The efficiency of double-conversion UPS topologies varies with load. At 25% load, efficiency ranges from 81% to 93%. At 50% load, it improves to a range of 85% to 94%. Efficiency at 75% to 100% load is in the range of 85% to 95%. Efficiency at the high end is associated with larger UPS kVA ratings. Smaller ratings have diminished efficiency.
Studies have shown that the average load factor for UPS units tested in the field is 37.8% with an efficiency at this load point of 85.2% (LBNL, 2005). Note that the stock of installed units is fairly small in kVA ratings: LBNL indicates that in 2004 114,431 units (51% of the national data center/IT sector population) is in the 5.1 to 20 kVA range. An additional 20% is in the 20.1 to 50 kVA size range while 20% more is in the 50.1 to 200 kVA range. An average served load of 38 kVA x 0.8 power factor x 38% load or 11.5 kW will be taken for the small double conversion UPS units that are appropriate for this module management technology. Annual energy use for a "typical" small UPS is estimated at (11.5 kW /0.852) x 8760 hours/year = 118,239 kWh/year.
Energy efficiency will be assumed to improve from a base of 85.2% up to 94.5% through "right sizing" of modules and only energizing modules needed to meet total load requirements at a high load factor. Expected annual energy savings per unit are thus 118,239 kWh/year x (1 - 85.2/94.5) = 0.098 x 118,239 = 11,590 kWh/year (approximately 10% of the baseline energy use).
Note: UPS units at larger data centers are much larger and assumed to be much more efficient. Savings for these large UPS units may be on the order of 1% to 3%.
"Typical" Savings: 10% Savings Range: From 3% to 17%
"Typical" Savings: 10% Energy Savings Reliability: 3 - Limited Assessment
Energy efficiency will be assumed to improve from a base of 85.2% at the operational load point up to 94.5% through "right sizing" of modules and only energizing modules needed to meet total load requirements at a high load factor. Expected annual energy savings per unit are thus 118,239 kWh/year x (1 - 85.2/94.5) = 0.098 x 118,239 = 11,590 kWh/year (approximately 10% of the baseline energy use).
Energy Use of an Emerging Technology is based upon the following algorithm. Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
A summary of UPS stock (circa 2004) indicates a nationwide total of 226,309 installed units. See Table 1 in (LBNL, 2005). While the number of large data centers has certainly increased in the Northwest, a population-based prorated estimation of 4% of the nationwide total of data centers will be assumed to reside in the Northwest. This equates to 0.04 x 226,309 = 9,052 total units.
Regional Technical Potential of an Emerging Technology is calculated as follows: Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): N/A
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
LBNL, 01/01/2005. High Performance Buildings: Data Centers Uninterruptible Power Supplies (UPS) Lawrence Berkeley National Lab
APC, 10/11/2013. Making Large UPS Systems More Efficient Schneider Electric
Emerson Power, 01/01/2011. The Quest for Energy Efficiency Emerson Power
Eaton, 01/01/2013. VMMS - Variable Module Management System Eaton
Eaton, 10/11/2013. UPS for Efficient Data Centers Eaton Corporation
Eaton Power Quality, 04/01/2010. Variable Module Management System Technology - Maximizing UPS Efficiency Without Compromising Reliability Eaton
Technical Advisory Group: 2013 Information Technology TAG (#8) TAG Ranking: 21 out of 57 Average TAG Rating: 3 out of 5 TAG Ranking Date: 10/25/2013 TAG Rating Commentary: No data this is more efficient - modular can use more energy in total, since they are sized for max demand and are rarely turned off. Nice theory on paper, not used that way in real word (not emerging). Available and a great idea to get load up to achieve peak efficiency. Especially viable for smaller data centers. But, not new! I like the battery pack option better. Not an ET.