The Oil Drum

146 comments on Tuesday Open Thread

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Gets IT on March 8, 2006 - 9:10am

Hard to see it. Seems much more valuable to use the heat as hot air space heating as I do. GB's A/C load at this time of year is zero and minimal, except for 1 month, the rest of the year.

3412 Btu/h = 1 kW @ 100% heat transfer efficiency
reasonable heat transfer @ 60% efficiency
1 kW = 2047 Btu/h

10 computers @ 100 W/ea = 3600 W
@ 60% efficiency = 2160/h Btu useable heat transfer
2160 Btu/h /3412 Btu/h/kW = 0.63 kW saved/hr
@ 0.125 $/kWh
savings rate = 0.07875 $/h

$500.00 material cost
add
$500.00 Labour Cost (unless you DIY as a hobbby or labour of love)
$1000.00 Total Cost

@ 0.07875 $/h = 12698 hrs
12698 hrs/8h/d = 1587 Work days
260 WD/yr = 6 years (@ i=0%)

Evaluating Alternatives
$1000.00 invested @ 5% simple interest/yr
$1000.00 invested in PC water heat X-changer

Even allowing for a fuel cost escallation factor of 25%/yr

Net Values won't be equal for about 10 years.

Even if you install it for free, it takes 8 years.

Problem is; Who keeps a PC for more than 3 years?
At end of 3 years, you must remove cooler and replace it in the new equipment. Another 500.00 every 3 yrs to do that.

Every 5 years? Needs running the PC for 11 yrs.

I haven't seen a 8 yr old PC anywhere, although there is a 5 year old one over in the corner that hasn't been turned on for 2 years now. I don't think I'll turn it into a water X-changer anytime soon. Do they make good air heaters?

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TrueKaiser on March 8, 2006 - 6:30pm

Problem is; Who keeps a PC for more than 3 years?

more then you realize.
contrary to popular belief the vast majority of pc users(all the non-gamers) keep their machines as long as possible.
the parents of a friend of mine still use their amd-k6 350mhz machine.

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Gets IT on March 9, 2006 - 6:50am

You're probably right. I do a lot of CFD work, but did buy a game about a month ago. The first game I bought since CivII 5 years ago. I was intending to put it on a 450 mHz I've had sitting in a dark corner waiting to become dinner for a canibal. Needless to say, it would hardly run the intro screen.