Tag Archives: dc power plant

Data center DC power, power backup runtime, and free air cooling, a greener shade of green.


I’ve written previously here about the green, energy saving benefits of DC power in the data center, the reliability follies of super short run time power backup, and, of course, the well recognized benefits of free air cooling. In this post, I’m going to discuss making the best green use of all three of these together in the data center.

The “classic” data center power backup system is the double conversion UPS. In this scenario, commercial AC power is rectified to DC for the backup batteries and then inverted back to AC to supply the data center equipment. This configuration actually has three points of efficiency loss, the rectifiers for the AC to DC, the inverters for DC to AC, and the load power supplies for AC to DC again. The data center DC power plant does away with 2/3 of the efficiency loss by eliminating the DC to AC inverter and the AC to DC power supply in the load equipment.

The second part of this equation is the backup power itself. The trend to incredibly short run time backup power (such as flywheels with only 15 seconds of run time) is a foolish gamble that fallible generators are going to work perfectly every time. If there’s even a small issue that could easily be dealt with, there simply is no time and the facility is going down hard.

The third part is the free air cooling. It really goes without saying that using cooler outside air for cooling is far more efficient than any type of traditional data center air cooling.

So, how do these three things tie together to make the data center even greener than any one separately? Many data centers use load shifting to save power costs (such as freezing water at night when power is cheaper to cool with during the day). I call this technique heat shifting.

My data center is equipped with an 800A 48VDC modular power plant equipped N+1, a battery string capable of 8 hours of run time, and free air cooling. The idea is to simply pick the hottest part of the day (usually early afternoon) and remove heat load from the free air cooling by shutting down the rectifiers and running the facility from the battery string for 2 hours.

This shifts that part of the heat load of the data center to times when the free air cooling is operating more efficiently, allowing the free air cooling the elbow room to support more productive equipment load. Additionally, you have the side effect of exercising the batteries regularly, avoiding the ills that can plague idle batteries, such as stratification and sulfation.

As if there weren’t already enough great reasons to use green DC power, long run backup, and free air cooling in the data center, here’s another one.

Email or call me or visit the SwiftWater Telecom web site for green data center services today.

Vern

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Monday data center tidbits. #cloudcomputing rants, #datacenter DC power


First up is reading a rant about losing data in “the cloud” and how cloud computing is unreliable. I’ve got two pieces of news: banks have been screwing up customer’s online accounts and transactions long before cloud computing came along and there’s no indication (and it’s quite unlikely) that a bank is using any form of cloud computing for customer accounts and financial transactions. Blaming an obviously human error on “the cloud” and cloud computing is just silly cloudwashing.

Next up is reading about DC power distribution in the data center. The idea of “standardizing” on 380VDC for the voltage is a curious one. Presuming you’re going to float a battery string on this for backup as is standard practice, and that most batteries are built as multiples of 6 cells, you’d expect to want a voltage divisible by 6 (12/24/48VDC etc). Unless you’re planning to build your battery string from individual 2VDC cells, skip this turkey.

Email or call me or visit the SwiftWater Telecom web site for sensible green data center DC power engineering!

Vern

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Monday data center tidbits.


The “duh” award for most obvious statement of the day comes from this article about the next steps for green IT:

“That capability could save energy because a computer that’s off, most experts agree, is more efficient than one that’s in sleep mode ..”

Um, DUH! I’m glad we had experts to reveal this.

From the same article, we get duh #2, the idea that data center servers that will accept high AC voltages such as 480VAC are more efficient. Until they make chips that use 500V, the voltage STILL has to be stepped down. All you’re doing with the scenario is moving the inefficiency (and all the heat load) inside the server, the last place in the world that you want it.

If you want to get rid of the transformer penalties of AC, go DC in the data center and forget shuffling the penalty around.

Email or call me or visit the SwiftWater Telecom web site for green data center DC power services!

Vern

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Lightning and the data center (GNAX goes boom).


Sounds like a bad sitcom, doesn’t it? I don’t think it’s close to what the folks who are affected by the lightning related GNAX data center outage are saying.

This is one area that doesn’t get talked about where the data center DC power plant really shines. When the classic power protection technology of surge suppressors and lightning arrestors aren’t enough, the data center DC power plant helps to isolate the server loads from bad things that happen on the AC main power. Couple that with the ability of the DC power plant battery string to absorb spikes and improve power quality and you have an optimal environment for your equipment that’s difficult to match (compare this to a modern “eco mode” AC UPS that ties your servers directly to the commercial AC power most of the time).

Add in the ability to easily replace DC power plant equipment without interruption power to the server loads and you can sleep easy the next time it rumbles out.

Email or call me or visit the SwiftWater Telecom web site for green and reliable data center DC power engineering, construction, and operation.

Vern

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Friday data center tidbits.


First up today is yet another story about data center AC vs DC power efficiency, with the usual sprinkling of BS. Required cable size is based on voltage vs current, not whether the power is AC or DC. Higher voltage means lower current means smaller conductors. AC or DC power isn’t a factor. The idea that larger cables used in lower voltage DC power are more susceptible to arcing because of their size is ridiculous. Any well designed data center DC power plant will be just as safe as any AC power system.

Second up is the story about Horizon Data Center Solution’s new expansion. The tidbit here is not that they’re expanding, but that they’re measuring the facility in megawatts worth of space, not square feet worth of space. Physical space in the data center is becoming a very secondary measurement, it’s all about the power now.

Email or call me or visit the SwiftWater Telecom web site for green data center DC power engineering, construction, and operation that saves money without the hype.

Vern

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More green data center DC power myths.


I’ve just been reading about the value of DC power in the data center. in this post, I’m going to correct some of the strange myths and egregious errors that are spread about DC power.

“But the downside is that DC power can require much larger wires to carry the current, thus creating power buildup and arcing that can endanger IT equipment and staff.”

Where do I start on this one. Power does not “build up” in the large conductors of DC power systems, any more than power “builds up” at your unused AC outlet. Not using the DC power doesn’t mean it’s going to build up, over flow, and arc. Mark this one as completely ridiculous.

“.. added that moderately high-voltage DC power poses some safety concerns, where the power can build up and arc.”

Once again, DC power doesn’t “build up”. Any high voltage distribution system that’s inadequately insulated has the potential to do this whether it’s AC or DC. I’ve seen catastrophic failures in common 240VAC and 480VAC circuits that resulted in melted bus bars, holes burned in armored cable, and total destruction of equipment (look at the Fisher Plaza fire where they destroyed 4000A aluminum bus bars).

What does affect the tendency to arc is jacking the voltage up and that’s just the same whether it’s AC or DC, there’s no great mystery to that. There’s a tendency to want to use high voltages to reduce wire size (higher voltage=less current=smaller wire). I myself much prefer to use long time industry standard 48VDC power, which is touch safe and has an extremely small arc over distance.

“”Four-hundred volts DC may be more dangerous than 400-volts AC,” he said.”

In a properly constructed DC power system, there’s no appreciable difference in safety between AC and DC, expect for some possible difference in coming in contact with the energized conductors. This point is really moot since you do NOT want to be coming in contact with either live 400VDC or 400VAC. Either way, someone is getting hurt.

Is there any safety hazard in the DC power plant? Yes, the battery string (exactly the same hazard that a battery equipped AC UPS has as well). Short the unfused battery leads or drop an uninsulated tool into the bus bars and you’re going to be missing some wire or a tool, completely. Batteries can put out 9,000+ amps of current in a fraction of a second in a short condition.

Finally, there’s the efficiency issue. Comparing a DC power plant to a conventional double conversion (or “online”) UPS is not in doubt. The UPS systems that fare better against DC are the type with “eco mode” (the old “standby” UPS). In normal operation, the eco mode UPS powers the load directly from the AC power, so it doesn’t use the power hogging inverter. Of course, this means the data center equipment has to stand the switch over to battery and the efficiency looks just as bad as a double conversion UPS when it’s running from battery.

Call or email me or visit the SwiftWater Telecom web site today and we’ll design a green DC power plant for your data center that will be SAFE and EFFICIENT!

Vern

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The great data center power debate.


After commenting on the Navisite San Jose data center outage (original here), I had a number of different viewpoints presented to me on the data center power reliability subject. I thought I’d take a few minutes to expand on where I believe data centers are really going wrong.

It used to be a tenet of data center operations that if the facility went down, someone’s head was going to roll. It was a rare thing that a data center went down and it usually because of a large scale disaster. However, in 2008, 2009 and so far in 2010, there have been rampant power failures in major data centers that have taken all or large parts of facilities down.

It seems that data center operators have developed a much greater tolerance to the pain of having their data center go down uncontrolled in the name of saving money up front. Short run battery systems and incredibly short run options such as flywheel depend on the most fallible piece of equipment in the data center, the generator. I hope the hit team from CAT and Generac don’t come knocking on my door, but starting a generator is like rolling the dice. Stake your entire facility on it working perfectly in the 15 second run time of flywheel and it’s just a matter of when it’s going to let you down.

It’s certainly true that batteries, such as the ones I use for green DC power plants, can fail you, there’s almost nothing that can happen with batteries that will let you down totally and most battery issues are very easy to spot with minor maintenance. On the other hand, failure to transfer, generator failure to start, or generator failure while operating is catastrophic. You’re not going to be operating degraded, you’re going down hard.

This issue is becoming even more important with the use of other green data center technologies, such as cloud computing. Now instead of just one angry customer, you have 10 times (or more) the amount of angry customers for the same amount of failure. Couple that with data loss, fixing screwed up hard drives, time and money to straighten the mess out, and monetary loss to the customers and this doesn’t make any sense to me at all.

Keep your reputation intact, keep your customers happy, and avoid becoming a trending topic on Twitter (the bad way). Stop skimping on the power protection.

If you’re looking for highly reliable cloud computing services or data center green DC power plant engineering, installation, and maintenance, drop me an email, give me a call, or visit our site at SwiftWater Telecom today!

Vern

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