Data Centers are power guzzlers. Therefore, it is very important that the Data Centers are designed to reduce the energy losses. This involves use of energy efficient equipment/ devices and properly designed facility. Let’s observe closely what is required in a Data Center environment and the factors that determine the energy efficiency of the Data Center, the standards used and the ways of improving the PUE.
Compelling Requirements in a Data Center Environment
Facility power for the Data Center comprises of the electrical power requirements to the Data Center IT equipment, HVAC (Heating, Ventilation and Air Conditioning) system, Lighting system and Safety & Security systems. Utility power is normally the prime source of power to the Data
Centers. Electrical power generators are used for the Data Center to ensure that even on disruption of the utility power, the Data Center is still functional. UPS Systems are used for providing the clean and uninterrupted power to the IT equipment of the Data Center.
IT equipment dissipates heat when operational. To maintain the optimum operating temperature within the equipment, built-in cooling fans are used for forced cooling. Precision Air Conditioners (PAC)/Precision Air Handling Units (PAHU) are used to cool the environment in the server room. Cooling systems are also required for maintaining the required environment conditions in the rooms, such as Telco, Staging, Electrical and UPS.
Fire Safety and Physical Security systems are provided for the Data Center. Building Management System is provided for monitoring/controlling the Data Center Facility.
Facts about Efficient Data Centers
As per BS ISO/IEC 30134-2:2016 standard and popular metrics, Power Usage Effectiveness (PUE) is a measure to quantify the efficiency of the Data Center in the form of electricity.
PUE is the ratio of total power drawn by a Data Center facility to the amount of power solely used by the IT equipment.
PUE = Total Facility power/IT Equipment power
PUE is normally calculated as an annualized value and this value of <1.6 is considered efficient.
Data Center infrastructure Efficiency (DCiE) is another metric to measure the energy efficiency of the Data Center. DCiE is the inverse of PUE and is expressed as a percentage value.
Power requirement for the cooling system is a major component of the facility load that impacts the PUE. Geographical location and its ambient temperature are important factors that determine the Data Center’s PUE.
Measuring Data Center Efficiency
Total Facility Power is measured in kWh at main power distribution panel for the Data Center. This could be metered at the output of the ATS (Automatic Transfer Switch) wherein the Utility power or the Generator power gets distributed to the total Data Center Facility. IT Equipment Power in kWh can be measured directly from the
output of the USP System that provides the power to the IT load. Based on the Total Facility Power and IT Equipment Power, PUE or DCiE is calculated.
Data Center Facility Electrical Panel Load Meters and UPS Systems are normally integrated to the Building Management System (BMS). PUE can be directly displayed in the BMS based on the measured kWh values of Data Center Facility Electrical Panel Load Meters and UPS Systems (that provides the power to the IT load). PUE should be measured regularly and is calculated over a 12-month period.
Improving the Data Center Efficiency
Cooling system consumes about 30% of the Facility power. Increasing the efficiency of the cooling system results in having lesser PUE and substantial saving in the operating costs of the Data Center.
Cooling system efficiency can be improved by considering the following:
- Optimum designing of the cooling system
- Use of energy efficient cooling system
- Providing cold/hot aisle containment
- Use of free cooling (depending upon average year-round outside air temperature ranges)
Electrical System efficiency can be improved by designing the Data Center using energy efficient UPS Systems, transformers, PDUs and lighting systems.
Technologies to be considered for Electrical Systems for improving the efficiency are:
- UPS with Eco-mode
- Modular UPS with Variable Module Management System
Improving the Data Center’s Efficiency—An Example
Let’s see how to improve cooling efficiency using aisle containment.
Let’s assume that the Data Center IT load is 200kW and the total facility power is 320kW resulting in the PUE of 1.6. Now, considering 30% as the cooling load for the facility, the power consumption for cooling is 96kW. Using cold/hot aisle containment, 10% cooling efficiency is achieved. This will result in the power saving of 9.6kW and the PUE would reduce to 1.552.
Annual power saving in kWh = 9.6kW x 24 hours x 365 days = 84,096 units.
Assuming US$ 0.13 per unit as the electricity charges payable to the electrical power distribution company, the saving would be: 84,096 x 0.13 = US$10,932
Though it appears, as if there is only a marginal power saving or fractional improvement in the Data Center PUE by using efficient equipment/design, however, the sum of these marginal improvements make a significant saving in the annual run-time cost of the Data Center.