<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; color: rgb(0, 0, 0); font-size: 14px; font-family: Calibri, sans-serif; "><div>Lots of interesting talk on PUE – but from what my own research told me in the past, it was not a metric that could be used to compare facilities that were not completely alike.</div><div><br></div><div>One example:</div><div><a href="http://notesfromtheconsultantsjungle.com/2010/12/20/pue-hype-and-setting-realistic-expectations/">http://notesfromtheconsultantsjungle.com/2010/12/20/pue-hype-and-setting-realistic-expectations/</a></div><div><br></div><div>Another example was an article I can't find right now which mentioned that data centre operators may cut corners (compromised redundancy etc) to reduce power consumption. It'll improve their PUE, but the risk of failure inside the facility is greatly increased.</div><div><br></div><div>It isn't a metric that can be used by itself, but something that should be taken into consideration with all other factors IMO.</div><div><br></div><div>Macca</div><div><br></div><div><br></div><span id="OLK_SRC_BODY_SECTION"><div style="font-family:Calibri; font-size:11pt; text-align:left; color:black; BORDER-BOTTOM: medium none; BORDER-LEFT: medium none; PADDING-BOTTOM: 0in; PADDING-LEFT: 0in; PADDING-RIGHT: 0in; BORDER-TOP: #b5c4df 1pt solid; BORDER-RIGHT: medium none; PADDING-TOP: 3pt"><span style="font-weight:bold">From: </span> Tony de Francesco <<a href="mailto:tonyd@pue.com.au">tonyd@pue.com.au</a>><br><span style="font-weight:bold">Date: </span> Thu, 5 Jan 2012 11:48:25 +1100<br><span style="font-weight:bold">To: </span> 'Luke Smith' <<a href="mailto:luke@smith.name">luke@smith.name</a>><br><span style="font-weight:bold">Cc: </span> <<a href="mailto:ausnog@ausnog.net">ausnog@ausnog.net</a>><br><span style="font-weight:bold">Subject: </span> Re: [AusNOG] Data Suburb<br></div><div><br></div><div xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:st1="urn:schemas-microsoft-com:office:smarttags" xmlns="http://www.w3.org/TR/REC-html40"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-7"><meta name="Generator" content="Microsoft Word 11 (filtered medium)"><!--[if !mso]>
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</o:shapelayout></xml><![endif]--><div lang="EN-AU" link="blue" vlink="purple"><div class="Section1"><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:black">Thanks very much for that analogy as it precisely
highlights one of the reasons why the “reduced efficiency at part load”
argument gets so much traction with people, i.e. people think they understand
the technology and find over simplified examples to justify their position.<o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:black"><o:p> </o:p></span></font></p><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:black">If you will allow me, let me educate on
how an air conditioning system (and not a V8 engine) responds to part load
operation:<o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:black"><o:p> </o:p></span></font></p><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:black">Let’s look at an air conditioning
unit that is designed for 1000kW of cooling, but is delivering only 200kW of
cooling:<o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:black"><o:p> </o:p></span></font></p><p class="MsoNormal" style="margin-left:36.0pt;text-indent:-18.0pt;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;
color:black"><span style="mso-list:Ignore">a)<font size="1" face="Times New Roman"><span style="font:7.0pt "Times New Roman""> </span></font></span></span></font><!--[endif]--><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;
color:black">Firstly when operating at a full 1000kWs of Load:<o:p></o:p></span></font></p><p class="MsoNormal" style="margin-left:72.0pt;text-indent:-18.0pt;mso-list:l0 level2 lfo1"><!--[if !supportLists]--><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;
color:black"><span style="mso-list:Ignore">a.<font size="1" face="Times New Roman"><span style="font:7.0pt "Times New Roman""> </span></font></span></span></font><!--[endif]--><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;
color:black">Refrigeration System Power Use: EER of 3.5, equating to
around 286kW of absorbed power<o:p></o:p></span></font></p><p class="MsoNormal" style="margin-left:72.0pt;text-indent:-18.0pt;mso-list:l0 level2 lfo1"><!--[if !supportLists]--><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;
color:black"><span style="mso-list:Ignore">b.<font size="1" face="Times New Roman"><span style="font:7.0pt "Times New Roman""> </span></font></span></span></font><!--[endif]--><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;
color:black">Air handling System Power Use: (relates to 69,000m©ø/s
of supply air based on an equipment ¥ÄT of 12¡ÆC) equating to around 60kW of fan
power<o:p></o:p></span></font></p><p class="MsoNormal" style="margin-left:54.0pt"><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:black">TOTAL =
346kW of power use or a pPUE of 1.346<o:p></o:p></span></font></p><p class="MsoNormal" style="margin-left:54.0pt"><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:black"><o:p> </o:p></span></font></p><p class="MsoNormal" style="margin-left:36.0pt;text-indent:-18.0pt;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;
color:black"><span style="mso-list:Ignore">b)<font size="1" face="Times New Roman"><span style="font:7.0pt "Times New Roman""> </span></font></span></span></font><!--[endif]--><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;
color:black">The same system at 200kW of Load:<o:p></o:p></span></font></p><p class="MsoNormal" style="margin-left:72.0pt;text-indent:-18.0pt;mso-list:l0 level2 lfo1"><!--[if !supportLists]--><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;
color:black"><span style="mso-list:Ignore">a.<font size="1" face="Times New Roman"><span style="font:7.0pt "Times New Roman""> </span></font></span></span></font><!--[endif]--><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;
color:black">Refrigeration System Power Use: EER of 8 (as the
refrigeration COP improves at part load), equating to around 25kW of absorbed power<o:p></o:p></span></font></p><p class="MsoNormal" style="margin-left:72.0pt;text-indent:-18.0pt;mso-list:l0 level2 lfo1"><!--[if !supportLists]--><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;
color:black"><span style="mso-list:Ignore">b.<font size="1" face="Times New Roman"><span style="font:7.0pt "Times New Roman""> </span></font></span></span></font><!--[endif]--><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;
color:black">Air handling System Power Use: (relates to 14,000m©ø/s
of supply air based on an equipment ¥ÄT of 12¡ÆC) equating to around 1kW of fan
power (as per the fan laws). <o:p></o:p></span></font></p><p class="MsoNormal" style="margin-left:54.0pt"><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:black">TOTAL =
26kW of power use or a pPUE of 1.130<o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:black"><o:p> </o:p></span></font></p><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:black">So you can see in this example at 20%load utilisation, the pPUE (i.e. cooling system PUE) should be around 1.130 and
increase to 1.346 as the load approaches 100%.<o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:black"><o:p> </o:p></span></font></p><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:black">This correlation is often not the case
with electrical systems, such as static UPS and DRUPS units, which tend to have
lower efficiency at part load and better efficiency at full load (as per your
V8 analogy).<o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:black"><o:p> </o:p></span></font></p><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:black">However, the improvement in the cooling
system PUE at part load generally offsets the reduction in electrical system
PUE at part load and so the overall facility PUE remains static over the load
utilisation range.<o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:black"><o:p> </o:p></span></font></p><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:black">Hope this helps your understanding
although please feel free to email me on or off list if you would like me to
explain any of this in further detail. <o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy"><o:p> </o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy"><o:p> </o:p></span></font></p><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy"><o:p> </o:p></span></font></p><div><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:black">Kind Regards</span></font><font size="2" color="#0f2b5f" face="Arial"><span style="font-size:10.0pt;font-family:Arial;
color:#0F2B5F"><o:p></o:p></span></font></p><p class="MsoNormal"><font size="3" color="#0f2b5f" face="Arial"><span style="font-size:12.0pt;font-family:Arial;color:#0F2B5F"><o:p> </o:p></span></font></p><p class="MsoNormal" style="margin-bottom:12.0pt"><font size="2" color="black" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:black">Tony de
Francesco<br>
Technical Director</span></font><font size="2" color="navy" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:navy"><o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:black">email: <st1:personname w:st="on"><a href="mailto:tonyd@pue.com.au">tonyd@pue.com.au</a></st1:personname><o:p></o:p></span></font></p><p class="MsoNormal"><font size="2" color="black" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:black">mob: +61 (0) 457 701 179<o:p></o:p></span></font></p><p class="MsoNormal"><font size="1" color="black" face="Arial"><span style="font-size:
8.0pt;font-family:Arial;color:black">.....................................................<o:p></o:p></span></font></p><p class="MsoNormal"><font size="3" color="navy" face="Arial"><span style="font-size:
12.0pt;font-family:Arial;color:navy"><img width="140" height="86" id="_x0000_i1026" src="cid:image001.jpg@01CCCB9F.EF0347F0"></span></font><font color="navy"><span style="color:navy"> </span></font><o:p></o:p></p></div><div><div class="MsoNormal" align="center" style="text-align:center"><font size="3" face="Times New Roman"><span lang="EN-US" style="font-size:12.0pt"><hr size="2" width="100%" align="center" tabindex="-1"></span></font></div><p class="MsoNormal"><b><font size="2" face="Tahoma"><span lang="EN-US" style="font-size:10.0pt;font-family:Tahoma;font-weight:bold">From:</span></font></b><font size="2" face="Tahoma"><span lang="EN-US" style="font-size:10.0pt;font-family:Tahoma">
<a href="mailto:ausnog-bounces@lists.ausnog.net">ausnog-bounces@lists.ausnog.net</a> [<a href="mailto:ausnog-bounces@lists.ausnog.net">mailto:ausnog-bounces@lists.ausnog.net</a>] <b><span style="font-weight:bold">On Behalf Of </span></b>Luke Smith<br><b><span style="font-weight:bold">Sent:</span></b> Thursday, 5 January 2012
11:16 AM<br><b><span style="font-weight:bold">To:</span></b> <a href="mailto:ausnog@ausnog.net">ausnog@ausnog.net</a><br><b><span style="font-weight:bold">Subject:</span></b> Re: [AusNOG] Data Suburb</span></font><span lang="EN-US"><o:p></o:p></span></p></div><p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:
12.0pt"><o:p> </o:p></span></font></p><div><div><p class="MsoNormal" style="margin-bottom:12.0pt"><font size="3" face="Times New Roman"><span style="font-size:12.0pt">> This
statement has permeated the industry and led to people accepting lower levels
of efficiency at part load in the hope that their PUE will improve as the load
increases. There is no technical reason why PUE has to suffer at part utilization,
other than people accepting a facility design that allows this. <o:p></o:p></span></font></p></div><p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:
12.0pt">Applying an analogy... if this were the case then you should also
expect the same economy from a 6.0l V8 as you get from a 2.0l four in the same
car. But the world doesn't work like that.<o:p></o:p></span></font></p><div><div><p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:
12.0pt"><o:p> </o:p></span></font></p></div><div><p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:
12.0pt">Unless its *very* modular and you can totally turn off the bits you are
not using then you simply can't expect a half used facility to have the same
efficiency as a fully utilised one half the size. Going back to the analogymodern V8s have cylinder deactivation that saves some of the overhead, but they
still waste energy spinning a few extra cranks and pistons about that they
don't need 99% of the time.<o:p></o:p></span></font></p></div></div></div><p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:
12.0pt">-- <br>
Cheers,<br><br>
Luke Smith<br>
0419 671 006<o:p></o:p></span></font></p></div></div></o:smarttagtype></div>
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