Measuring Efficiency Through PUE
PUE is the ratio of total amount of power used by a computer data center facility to the power delivered to computing equipment.
Recent studies show wide range of PUE values for data centers, but the overall average tends to be around 1.8. Data centers focusing on efficiency are achieving PUE values of 1.2 or less. When the ESIF building was conceived, NREL set an aggressive requirement that the HPC data center achieve an annualized average PUE of 1.06 or better. For 2016, the NREL HPC data center achieved an annualized PUE rating of 1.04
How We Calculate It
NREL calculates instantaneous PUE using the following components:
Lights & Plugs are the lighting and utility plugs associated with the data center and dedicated mechanical room. The crank-case heater for the emergency standby generator is also captured as light & plug load.
Cooling captures the power used by the fans and pipe trace heaters associated with outdoor cooling equipment that cool data center cooling water. The dedicated tower filter pump power is also captures as cooling load.
Pumps captures the power used by the pumps that move water in the data center Energy Recover Water loop and the Tower Water loops. It also captures power used by the boost pumps that circulate water through the fan walls.
HVAC captures fan power used by the fan walls, fan coils that support the datacenter electrical rooms, and the make-up air unit.
IT equipment captures power used by the IT equipment on the data center floor.
All measurements points mentioned above are measured with electrical power meters except for the following two points:
- Generator heat is calculated as a percentage of total generator heat power since the emergency generator is shared with the whole ESIF facility
- The tower filter pump runs constantly to filter water from the data center cooling tower system, so 2.67 kW is attributed for this pump.