Greening the data center: Choose your weapon.


I’ve been reading the article Green Grid Enters AC VS DC Power Debate and I thought some of their conclusions could use a different take. In this post, I’ll discuss voltage choices.

First off, let me state, as I’ve written in previous posts and articles, I’m a strong proponent of standard 48V DC power for data centers. 48V DC provides the best efficiency gains vs standardization. In this post, I’m going to examine the Green Grid’s findings in reference to AC power choices.

The Green Grid considered 600, 480, 400Y230, and 277V AC power. To start, I’m not aware of any data center equipment that will use the Canadian standard 600V AC directly, not to mention that this voltage would require a major infrastructure change (this voltage would exceed standard wire insulation rating, panel board rating, and breaker ratings). Not using the voltage directly requires use of a step down transformer, negating any efficiency gains and adding heat to the data center. Scratch 600V.

Next we’ll consider 480V AC. This is probably the most standard industrial voltage found in the US. Since it is that common, there isn’t any issue with using standard (read as less expensive) infrastructure components with it.On the down side, only the largest of data center equipment is set up to use this voltage directly (DC power plants tend to be the exception to this), so we’re back to step down transformers again. Scratch 480V for all except the big boys.

Now we’ll examine 400Y230. This is European format “wye” power (400V is the 3 phase component, 230V is the single phase component). 400V offers zero advantage over the standard 480V, scratch that. 230V fits into the range of standard universal equipment power supplies so no step down transformers are required. If it wasn’t for the requirement to acquire European format transformers to supply it, this would be an ok option.

Finally, from the Green Grid’s list, we’ll examine 277V. This voltage is the single phase component of 480Y277. On the plus side, this is a standard industrial voltage in the US. On the minus side, this is outside the range of universal power supplies and no data center equipment is designed to use it directly. As a side note, 277V is use almost exclusively for lighting in industrial plants. Scratch 277V.

So what is the best option here? The Green Grid left out one older power format still commonly found in industrial/commercial settings in the US: 240D (240V delta 3 phase). This is a standard power, still widely found, and it fits perfectly with almost all universal power supplies found in data center equipment. It provides the best efficiency and the most simplicity, since it uses all standard equipment and infrastructure, as well as not requiring any step down transformers.

Like many other of the green techniques I’ve discussed, some of the best steps to the future can be found by looking to the past!

Vern, SwiftWater Telecom
Datacenter, telecom, and engineering services

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