[6155] in Release_7.7_team
Re: Putting display to sleep on Athena
daemon@ATHENA.MIT.EDU (Jonathon Weiss)
Mon Jan 12 18:00:55 2009
Message-Id: <200901122300.n0CN0G7I004930@speaker-for-the-dead.mit.edu>
From: Jonathon Weiss <jweiss@MIT.EDU>
To: lrao@MIT.EDU
cc: Jonathon Weiss <jweiss@MIT.EDU>, Greg Hudson <ghudson@MIT.EDU>,
release-team@MIT.EDU, wdc@MIT.EDU
In-reply-to: Your message of "Tue, 23 Sep 2008 17:07:30 EDT."
<D1F9D050-D817-4F5A-BC6F-E63505E98E28@MIT.EDU>
Date: Mon, 12 Jan 2009 18:00:16 -0500
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Laxmi,
To followup on our hallway conversation this afternoon... Below is
some of the resarch and details of the numbers we worked through to
estimate the cost savings of sleeping the displays on idle Athena
machines (both in clusters and private offices). However the short
form is:
Assume 25W/monitor savings (conservative)
Assume 1000 workstations (actually 956 according to Dec. stats)
Assume 10 sleeping hours per day (conservative and easy to multiply)
Assume 365 days per year :-)
Estimated power savings: 91.25MWh
Using your (conservative) blended average cost to MIT of $0.11/kWh
Estimated cost savings: $10037.05/year
Of course, we really only have 1-2 significant digits, but we can
reasonably say $10K/year!
If we assume 35W, and an average cost of $0.15 we're up ot $19K/year.
Jonathon
> To follow up, I looked at the Dell and HP data sheets on the 3 common
> Athena video monitors for power consumption:
>
> This year's: Dell 2009W: Max: 35w, Minimum (displaying msdos prompt):
> 19.4w, Active-Off: .6w
> Last year's: Dell 2007WFP: Max: 75w, Typical (routine task): 55w, Off
> (still plugged in.): .85w
> Older HP 1702: Max: 40w, Typical: 28.5w, Power Save: 2w.
>
> I don't really want to do a weighted sum of monitors and power
> usage. I think going with telling people "25 watts saved per monitor
> as a conservative estimate", or "roughly 100 MWH per year,
> conservatively", is the right thing.
>
> -wdc
>
>
>
> On Jul 29, 2008, at 4:38 PM, Jonathon Weiss wrote:
>
> >
> > This got me to thinking "this will probably save enough power to
> > actually be interesting, won't it?" to answer that question for
> > myself and other's I present some numbers.
> >
> > Assume you can save 25W by sleeping an average Athena LCD monitor (I
> > beleive this is a conservative estimate, and the actual number will be
> > more like 30 or 35).
> >
> > Multiply by 1000 Athena workstations (Actually 984 in the July status
> > report, but 1000 is really easy to multiply): 25kW
> >
> > Assume that the average monitor will be sleeping 10 hours a day/night
> > (I think this is very conservative, especially since it assumes
> > weekends are regular days, but again it is easy to multiply): 250kWH
> >
> > 365 days/year: 91.25 MWH/year.
> >
> > http://cogen.mit.edu/powermit/ estimates that N* bills MIT $58.77/MWH
> > (though this number appears to be 5 years old, and is probably a
> > low-ball estimate now): $5363/year
> >
> > If we assume 35W savings and 14 hours a day of sleeping monitors
> > (which is certainly more agressive, but not unbelievable):
> > 490kWH/day
> > 178.85MWH/year
> > $10511/year
> >
> > Realistically, I'd guess that we'll fall between the two. Either way,
> > it seems worth pursuing.
> >
> > Jonathon
> >
>
