Experts in data centre power & cooling - Company Message
RSS

Recent Posts

DC Power
powered by

My Blog

DC Power

Write your post here.
HVDC power for data-centres?  Not for Europe, please?
There has been a lot of talk for time now about adopting DC power for data-centres to improve their energy efficiency and, recently, ABB has purchased the sole vendor and the marketing money has stirred the debate even further.   The underlying argument is that converting the AC power to DC and back-again cant be efficient but, to my mind, seems to ignore the fact that we have >10kV AC coming in and consume at 0.4VDC at the chip – so somewhere we have to transform downwards and convert, why not at the load?  It also ignores the fact that a growing number of UPS are line-interactive and actually don’t convert the supply to DC and back-again!  Of course the debate is now centred around High Voltage DC (HVDC) because we can’t use LV (e.g. like -48VDC in telecom) due to the high currents (and loads of copper) associated with the high power found in data-centres.  By ‘high’ we are talking about the range 380-600V DC.  Anyway, in March 2012, The Green Grid met in the USA to debate the AC/DC issue and I hear that the conclusion was in favour of retaining AC despite the fact that I had hoped that someone would be there to speak up for Europe since we have a different perspective on HVDC, and here is why:
There is no doubt that the North American legacy practice of 460V/208V UPS that has isolation transformers front and back with 3-wire distribution to a 208/120V PDU transformer feeding 120V 1ph servers is very inefficient – typically <87% from MV facility input to load input as a maximum, really poor partial load efficiency and low SMPS (Switched Mode Power Supply) efficiency in the 120V IT load.  On the other hand there are good arguments that it is a very robust and, particularly in the presence of harmonics, a very stable power platform with good earth/grounding and low Neutral-Earth voltages.  So if someone in the USA wanted to do some research into energy saving no one should be surprised.
A few years back Lawrence Berkley National Labs (LBNL) did exactly that.  However they decided to test a new pared-down 380V DC system with a legacy 460/208/120V AC system.  The UPS was not new even then and was a prime example of worst-practice.  Not surprisingly they came to a conclusion that you could save a lot of energy if ‘you’ (USA) switched to HVDC.
However, following the European solution might have been a better, or third, option:  400/400V UPS, 4-wire distribution, transformer-less UPS and PDU and 230V servers – along now with a wide acceptance of line-interactive topology and a growing interest in eco-mode.  Even double-conversion UPS in Europe (from American OEMs!) gets you to 96% efficiency and well over 92% at 40% load (although the same OEMs don’t try to sell it in USA!).  Unfortunately they didn’t test the third option – the European transformer-less 4-wire.  IF they had done that they would have reached the interesting conclusion that we in Europe had already achieved the same energy saving without going away from AC.
OK, for each geography/region, there are code/regulation/standards issues, safety stuff (if you have ever worked with HVDC you will appreciate the arcing-display with disconnection), the idea of IT technicians getting arc-blindness etc – but all those practical barriers are nothing that couldn’t be got around if HVDC was in fact more energy efficient.  For ‘us’, in EMEA, the saving in energy is within 1% for dual-bus (Tier IV) and it is actually less efficient for single-bus (Tier III, active/passive path). 
That brings up one important point; ALL HVDC systems will have to be dual-bus 2N even if you want Tier II or Tier III.  Why?  just think about the ‘UPS’ bypass; with AC you can put the load onto the genset or the utility – something you cant do with HVDC unless you have the second active bus and that means that you have to have two DC power plants.  Another point that has always bothered me is the ‘fiddle’ that LBNL used to demo the higher HVDC efficiency: They (very correctly) used 2N dual-bus but one path was just a rectifier without any energy storage and the other path had a single flywheel with a fixed DC output.  Flywheels are less popular than batteries (and with two OEMs gone bust due to lack of sales and another losing $20M/year for the past few years, and probably not ‘growing’ in popularity) so if you put battery support onto both of the two buses you need a DC:DC regulator to cope with the +10%-20% battery voltage (float to deep-discharge) – so the losses increase!  If the DC version of the server can accept +10-20% then why don’t the AC versions do the same?
I think that the covers most concerns in EMEA but behind it all is our big problem; all the ICT vendors are US/Asia based and we don’t have any in Europe so we often we have to ‘follow’ what our American cousins give us – and in this case, if we follow a change to HVDC, we go backwards.

21 Comments to DC Power:

Comments RSS
Charter a bus to DC on 01 May 2013 11:11
Thanks for taking this opportunity to talk about this, I feel fervently about this and I enjoy learning about this topic. Please, as you gain facts, please update this blog with more information. I have found it enormously useful.
Reply to comment
 
Machine Exporter on 20 March 2015 07:16
I found your website perfect for my needs. Thanks for sharing the great ideas.


Truman Gudinas on 31 October 2013 02:05
Self- assembly
Reply to comment


na-praingam on 05 December 2013 02:15
Thank you so much for your kind words. I appreciate you following me and I will try to keep posting good content.
Reply to comment


Powerpoint Polling on 21 May 2014 14:01
Undeniably believe that which you said. Your favorite reason seemed to be on the net the simplest thing to be aware of. I say to you, I certainly get annoyed while people think about worries that they plainly don’t know about. You managed to hit the nail upon the top and defined out the whole thing without having side-effects , people could take a signal. Will probably be back to get more. Thanks Youre so cool! I dont suppose Ive read anything like this before. So nice to search out someone with some authentic ideas on this subject. realy thanks for starting this up. this website is something that’s wanted on the web, somebody with a little bit originality. helpful job for bringing something new to the internet!
Reply to comment


electricians Falcon on 18 June 2014 03:58
Sounds good. Your shared post about DC power and all its facts and necessity seems to me wonderful though I'm very much pleased by getting a chance to read about it. Thanks
Reply to comment


link on 15 July 2014 23:28
hallway are additionally not even uncommon?
Reply to comment


Martin on 16 July 2014 09:10
products really don't fulfill your main needs?
Reply to comment


livewetten on 16 July 2014 13:38
Wahlquotenwetten
Reply to comment


supermanicure.beep.com on 06 August 2014 13:34
his accommodation and even consult?
Reply to comment


Olisade on 08 August 2014 14:41
you should really go for?
Reply to comment


witryna on 11 August 2014 13:53
take benefit for the?
Reply to comment


Sportwetten on 13 August 2014 15:14
Haben sie zahlen berappen die Gesamt Summe schnell und durch Verwendung einer mindestens Aufhebens oder sie neigen sie dazu, sie eine Tendenz haben ziehen oder noch schlimmer noch doch ; ausgeben aus in keiner Weise ?Buchmacher - das Sportwetten ist einer der gehoert zu den Schwergewichten in der Offshore-und Wettangebot fuer Praesentation good tolle Boni.
Reply to comment


Sport Wettquoten on 13 August 2014 21:23
erstellt die Notwendigkeit fuer fuer nur eine Safe Wetten Technik ueber Casinos und Buchmacher.Es ist nicht Sache keinen Unterschied machen, die Leichtathletik Sie bis Wette auf.
Reply to comment


mgm Sportwetten Quoten on 13 August 2014 23:42
Loeschen Materialize.Die sehr wirklich zuerst World Wide Web Macher festgelegt die Muse fuer diese Struktur und wie Unternehmen sollte wirklich funktionieren work.
Reply to comment


jobs in canada on 14 October 2014 11:30
Loeschen Materialize.Die sehr wirklich zuerst World Wide Web Macher festgelegt die Muse fuer diese Struktur und wie Unternehmen sollte wirklich funktionieren work.
Reply to comment


telicando marafecco on 30 October 2014 22:45
Seien Sie Zweck. Unterschiedliche Arten von Wetten ist in der Regel jedem jeder einzelne Sportwetten, und dies die Vorteile vor allem, weil Sie umschauen fuer Art Wette Sie sollten zusammen mit dem groessten erhaeltlich diesem spezifischen Spiel oder Gelegenheit .
Reply to comment


réplicas de relojes on 29 November 2014 14:25
Der Wett sie Set Displays zeigt die Wett-oeffentlichkeiten Wahrnehmung mit den Kraft mit den Gruppen. réplicas de relojes http://www.replicarelojesrapido.com réplicas de relojes
Reply to comment


zwrot podatku z francji on 23 December 2014 18:01
especially on these?
Reply to comment


Hobbart007 on 21 December 2019 08:29
I am really happy to read this blog Jason Clay
Reply to comment


stem cell treatment for knee replacement on 13 March 2020 12:03
While marketing can be tricky, it is the content that makes the site important. If you provide informative content that serves the needs of your visitors, word will spread. Chicago Stem Cell Therapy
Reply to comment

Add a Comment

Your Name:
Email Address: (Required)
Website:
Comment:
Make your text bigger, bold, italic and more with HTML tags. We'll show you how.
Post Comment