Protection from power loss is a common characteristic of datacenter facilities. Such protection comes at a significant first cost price, and also carries a continuous power usage cost that can be reduced through careful design and selection.
 

Objective 1: Design UPS system for efficiency. The electrical design impacts the load on and the ultimate efficiency achieved by the UPS. (See chart illustrating typical power flows in data centers.)  Strategies:  Maximize Unit Loading. When using battery based UPSs, design the system to maximize the load factor on operating UPSs. Use of multiple smaller units can provide the same level of redundancy while still maintaining higher load factors, where UPS systems operate most efficiently.

Metric: Average UPS loading. Battery based UPSs should be loaded to 50% or greater in actual operation.

  Objective 2: Select most efficient UPS possible. UPS efficiencies vary, not only across different types of topographies, but also within the same type of system between different models.  Strategies:  Specify Minimum Unit Efficiency at Expected Load Points. There are a wide variety of UPSs offered by a number of manufacturers at a wide range of efficiencies. Include minimum efficiencies at a number of typical load points when specifying UPSs. Compare offerings from a number of vendors to determine the best efficiency option for a given UPS topography and feature set.

Evaluate UPS Technologies for Most Efficient. New UPS technologies that offer the potential for higher efficiencies and lower maintenance costs are in the process of being commercialized. Consider the use of systems such as flywheel or fuel cell UPSs when searching for efficient UPS options.

Do Not Overspecify Power Conditioning Requirements. In general, the greater the level of power conditioning used, the lower the system efficiency. Consider line-reactive UPSs for standard server equipment that does not require the higher level of power conditioning offered by double-conversion units. Some manufacturers offer UPS systems that can operate in both single and double conversion mode, allowing for flexibility to deal with unanticipated future equipment or power conditions. Do not use additional power conditioning in the PDU if it is not required.

  Metric: UPS Efficiency. UPS efficiency should exceed 90% at full load and 86% at half load. See chart for range of UPS found on the market today.

Objective 3: Use self-generation for large installation. For large facilities, a self-generation plant designed to capture and utilize waste heat can achieve very high total efficiency as well as offering great control over power reliability and quality.  Strategies:  Eliminate Standby Generator. Standby generators are typically specified with jacket and oil warmers that use electricity to maintain the system in standby at all times, so even if (especially if) they are never used they are a constant energy waste. Eliminate of a standby generator requires proper engineering of the system, but will reduce energy use as well as save first and maintenance costs. Standby generator heaters (many operating hours) use more electricity than the generator will ever produce (few operating hours).

Recover Waste Heat for Local Heating Uses. If the datacenter is physically near a commercial or industrial heat load, use the waste heat directly to serve the load. Use of the waste heat directly for heating is the most efficient way to optimize total self-generation system fuel efficiency.

Recover Waste Heat for Datacenter Cooling Use. Waste heat can be used to drive absorption or adsorption chillers, maximizing the utilization of the fuel used to power the generator system.

Eliminate UPS Systems. With careful design, UPS systems can be replaced by self-generation equipment. Combined with recovering waste heat, such a system combines high efficiency with no UPS efficiency losses.

  Metric: Utilized Electricity and Heat / Input Fuel Btus Include electricity use and legitimate uses of waste heat. Include electricity use and legitimate uses of waste heat.