Item ID: 496
Right-Size Data Center Power Equipment
Data Center Power Equipment: Right-Sized vs. Over-Sized
Avoiding over-sizing power equipment to reduce power conversion losses.
Many factors contribute to power equipment sizing decisions, including codes, reliability, and anticipation of load growth. One of increasing interest is energy efficiency.
One example of this is with uninterruptible power supplies (UPS). According to a study by Lawrence Berkeley national Laboratory, energy efficiency drops an average of 4% for most UPS systems when a UPS system load drops from 100% to 25%. (LBNL, 2005 Pg 1-2)
Prior to 2002, the efficiency “sweet spot” for transformers was 80-100%. Since then, transformers have been manufactured to be most energy-efficient at about 35% load. For a 75 kVA transofmer, typical losses are 1,000W or 1.3% at 35% load but 3,000 W for linear loads and 4,000 W for non-linear loads (such as computer servers); 4-9.3% respectively. (Lovorne, 2013)
A third power component where size matters is power distribution wiring. Energy losses are a function of current and resistance of the wiring, so increasing the wire size above the minimum required will decrease losses. For a single-phase, 15-amp load operating continuously with a 100-foot wire, increasing the wire size from 12-gage to 10-gage will increase wire and conduit cost by about $6.75 but decrease the value of energy losses by about $25/year, resulting in an attractive payback of about 3 months. (CDA, 2013)
So to optimize facility efficiency, minimize UPS oversizing, instead adding modular UPS as load grows. Try to keep transformers at 30-50% load, and consider upsizing power wiring by one size to minimize losses. Unfortunately, these goals can be conflicting; if the transformer has a 35% load, it's hard not to have a UPS with a 35% load.
Energy Savings: 3%
Energy Savings Rating:
Concept validated: What's this?
|1||Concept not validated||Claims of energy savings may not be credible due to lack of documentation or validation by unbiased experts.|
|2||Concept validated:||An unbiased expert has validated efficiency concepts through technical review and calculations based on engineering principles.|
|3||Limited assessment||An unbiased expert has measured technology characteristics and factors of energy use through one or more tests in typical applications with a clear baseline. |
|4||Extensive assessment||Additional testing in relevant applications and environments has increased knowledge of performance across a broad range of products, applications, and system conditions. |
|5||Comprehensive analysis||Results of lab and field tests have been used to develop methods for reliable prediction of performance across the range of intended applications.|
|6||Approved measure||Protocols for technology application are established and approved.|