[mythtv-users] Cooling data centres (Was: raid array spin down possible?)

[Simon Hobson]

Ian Clark wrote:

>I wonder how much energy would be saved if the worlds datacenters just
>operated a few degrees hotter.

Actually, I doubt that either would make a significant difference.

Whilst cooling systems would be very slightly more efficient (higher 
Energy Efficiency Ratio) running at a slightly higher indoor 
temperature, I don't think this is a particularly great effect in the 
grand scheme of things.

Where huge savings can be made is by not "cooling" the datacentre at 
all - but instead just use outside air at whatever temperature it 
comes in at. In relative terms, blowing outside air in (through 
filters) is very cheap compared with active cooling.

We do the latter at work. Our load is about 8kW, and to cool that 
with refrigerant based cooling would need something in the order of 2 
to 2.5kW to run the chillers. We actually use about 1/10 of that to 
run a couple of fans.

>(and stopped cooling dead underfloor
>space, but that's another issue.)

Again, unless you have some very poor insulation it's unlikely to be 
an issue. The space under the floors is a convenient and large duct - 
so it's really easy to stuff a large volume of air through it. Once 
you've cooled down the stuff that's in there (floor supports, 
underlying concrete slab, the floor itself), then it doesn't take any 
more energy to keep it cool.

As an analogy, if you go and stuff a load of unfrozen food in your 
freezer then it takes a lot of effort to get it frozen. Once it is 
fully frozen through, then the only energy input need to keep it like 
that is to deal with the heat that leaks in through the imperfect 
insulation.
-- 
Simon Hobson

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