PG&E on data centre cooling..

Sun Apr 1 14:43:19 UTC 2007

Myth Busters proved that turning the lights off is more cost efficient than 
leaving them on.

-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com

----- Original Message ----- 
From: "Robert Bonomi" <bonomi at mail.r-bonomi.com>
To: <nanog at merit.edu>
Sent: Saturday, March 31, 2007 11:41 PM
Subject: Re: PG&E on data centre cooling..

>
>
>> Date: Sat, 31 Mar 2007 19:31:53 -0700
>> From: Jay Hennigan <jay at west.net>
>> Subject: Re: PG&E on data centre cooling..
>>
>>
>> John Kinsella wrote:
>>
>> > I sorta wonder why the default is lights on, actually...I used to 
>> > always
>> > love walking into dark datacenters and seeing the banks of GSRs (always
>> > thought they had good Blink) and friends happily blinking away.
>>
>> Consider the power consumption per square foot of the gear in a typical
>> data center, then add in the power needed to keep it cool.  I suspect
>> that the cost of energy to keep the lights on will be down in the noise.
>
> In addition,
>   1) if the lighting is 'already there', figure the cost of re-wiring
>      to 'sensor-based' switching.  The parts aren't terribly expensive,
>      but consider the amount of labor required.  Particularly if the 
> desired
>      switched lighting 'zones' don't match the existing circuit wiring.
>      Don't forget the maintenance costs, either.  You're probably going
>      to have to replace bulbs more frequently -- on/off cycles _are_ added
>      'stress' on bulbs.
>   2) if it is new construction, figure the differential cost in parts,
>      labor, *and* maintenance, of sensor-based lighting switching.  This
>      is lower than 1), but still 'non-trivial'.
>
> Now, estimate how much energy will be saved, and how long it will take for
> that savings to pay back the cost of the investment.
>
> "Secondary" savings from reduction in HVAC load?   How many KW/sq.ft. does
> the gear eat?    vs. how many watts/sq.ft for lighting?  ['Office grade'
> lighting is under 2 watts/sq.ft. (and may be significantly less) using
> conventional fluorscents, high-intensity halogen can be lower. 
> 'Residential
> level' general lighting can easily be under 1 watt/sq.ft.]
>
> It's not like you're going to reduce the load enough to shut down one of
> the chillers. :)
>
>
> 