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Part 4: In Data Centers, Simplicity of Design, Commissioning Saves Energy
By James McEnteggart
February 2012 -
Energy efficiency and simplicity do not have to be mutually exclusive. None of the systems described are inherently complicated to operate. Unfortunately, many projects are over-designed to the point that data center staff find them difficult to operate. So they save a lot of energy on paper, but not in practice.
Commissioning is a simple measure to prevent this problem. Commissioning not only verifies that mechanical and electrical systems are installed and operate as designed. When the commissioning agent is involved at the inception of design, the project team can find ways to simplify design and operation of these systems while achieving the same project goals. The commissioning agent offers the benefit of practical operating experience with these types of systems. In a sense, the commissioning professional acts as the operator's advocate for simplicity as well as energy efficiency. And that's a real win-win.
James McEnteggart, PE, is vice president of Primary Integration Solutions LLC, a national mission critical commissioning firm headquartered in Charlotte, N.C. He has more than 20 years of experience in MEP design and commissioning for mission-critical and health care facilities. Reach him at JMcEnteggart@primaryintegration.com.
"We started a project at Facebook a little over a year ago with a pretty big goal: to build one of the most efficient computing infrastructures at the lowest possible cost," begins the introduction at the Open Compute Project's website (opencompute.org). "The result is a data center full of vanity free servers which is 38 percent more efficient and 24 percent less expensive to build and run than other state-of-the-art data centers."
How did they do it? The new facility in Prineville, Ore., uses 100 percent airside economization with an evaporative cooling system, and an electrical system with a 48V DC UPS system integrated with a 277V AC server power supply. They are sharing their experience and detailed specs on the Open Compute Project's website.
On the mechanical side, the use of 100 percent airside economization with evaporative cooling means that Facebook avoided buying, designing and installing a conventional chiller system. Instead, fans and spray arrays spray mist into the air to cool it down when needed. Then they take the hot air generated by their data center and use it to heat the office area in the winter.
The electrical design — a 277V AC power supply on one power supply and a 48V DC support on the other power supply — means they are taking straight utility power at 480V wye, reducing it to 277V, and feeding it to the computer supply. For every six racks, a computer with batteries at 48V DC feeds the racks DC power. The power supplies are designed so that if the voltage on the AC utility power starts to drop, the electrical system automatically switches to DC power. The batteries feed the computer until the generator starts, feeding 277V AC power to the servers until the utility power is back on. As a result, Facebook eliminated several pieces of equipment and several steps in the process — and every time a voltage conversion or change from AC to DC is avoided, there is less energy lost.
— James McEnteggart
Part 1: PUE is One of Many Metrics for Data Center Energy Performance
Part 2: Free Air, Water-Cooled Servers Increase Data Center Energy Efficiency
Part 3: UPS Energy Saver Mode, High Voltage DC Power Cut Data Center Energy Use