Understanding the New ASHRAE 90.4 Standard

Renewable Energy

The American Society of Heating, Refrigerating, and Air-conditioning Engineers, more commonly known as ASHRAE, has finally put forth the finished version of the data center efficiency and energy usage standards.  According to ASHRAE, the purpose of the 90.4 Standard is “to establish the minimum energy efficiency requirements of Data Centers for: the design, construction, and a plan for operation and maintenance, and utilization of on-site or off-site renewable energy resources.” The ASHRAE Standard takes into consideration that most existing data centers pass the requirements set under the standard, going with an 80/20 approach. This means that only the data centers that are the most energy inefficient are the ones that will fail to comply. The standard also takes into consideration the constant innovation and progress that takes place in the IT world and subsequently affects data centers.

Part of Standard 90.4 focuses on the efficiency of the use of on and off site renewable energy resources. Instead of opting for the unit of PUE or Power Usage Effectiveness to measure the efficiency of a data center, 90.4 divides it into two parts: Mechanical Load Component (MLC), a merit to measure the minimum energy efficiency of all mechanical cooling systems specified for a variety of different climate zones, and Electrical Loss Component (ELC). The values are calculated and compared to the specified limits for each unique climate zone. The Standard requires that the calculated values be lower than the set limits in order that the goal of the standard to be achieved.

An alternative path also allows data centers to perform tradeoffs between the two: MLC and ELC, if required in the case either of the systems compensates for the inefficiency of the other.

The older 90.1 Standard was implemented for almost all kinds of buildings, but the 90.4 Standard is built to ensure that it covers the design and structure of data centers specifically. ASHRAE now looks to shift the compliance from the previous version of the Standard to the new recommendation for the efficient functioning of a data center sites as well as efficient energy usage.

Jeffrey Dorf is the Editor of The Data Center Blog, President of the Global Data Center Alliance, and oversees the Mission Critical Practice for the M+W Group

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