Judging by the triple-digit temperatures recorded recently out
of our Georgetown, Texas plant, you'd be hard-pressed to imagine
the official start of summer is still a week or so away. But sure
enough, all around the country, things are heating up - and when
things heat up, fan use kicks into high gear.
Of course, here in the data center world, we aren't talking
about your usual fan box propped up in a brownstone window - we're
talking server fans, industrial sized CRACs, CRAHs and every other
kind of swirling, whirling apparatus designed to keep our data
processing at a comfortable temperature - even as the outside world
bakes and broils.
To that end,
fan affinity laws can provide a simple yet effective way to
help reduce power consumption in the data center when it comes to
the operating set points of your cooling equipment. Take this
explanation into consideration:
If you have a data center that needs 10,000 CFM of cooling, you
might have an air conditioner that provides 10,000 CFM at 100
percent load, and another one just like it turned off for
redundancy. The fan affinity law here essentially operates like the
cube effect - instead of running one A/C at 100 percent capacity,
you could run them both at 50 percent load. This means that you'd
still have the necessary 10,000 CFM with each A/C providing 5,000
CFM. Logically, it would seem that running one at 50% would reduce
the energy in half, right? That's where the fan affinity law comes
further into play. Instead of X .5, it becomes .5 X .5 X .5 = .125
or 1/8. So with each running at 50 percent load, instead of using
50 percent of the energy, we're only using 25 percent of the energy
it takes to run one A/C at full capacity! For you math
enthusiasts out there, it breaks down like this:
(Q1/Q2) =
(N1/N2)3 whereas
(P1/P2) =
(N1/N2)3
Get it? Got it. Good!
When you realize that most traditional data centers may be over
provisioned for two to three times normal demand, fan affinity laws
begin to look like an awfully attractive solution - especially when
you couple this idea with
CPI's Passive Cooling® Solutions. With passive cooling, you
only need to provide what your demand is 1X. So while there's
always savings to be had, with fan affinity laws working hand in
hand with passive cooling, there is considerably more efficiency
taking place - possibly resulting in paying as little as 25% of 1/3
of what your current A/C costs are!
We'd say savings like that go a long way towards making summer
extra cool. Jeff Cihocki, eContent Specialist
and Fernando Reyna, RCDD & Senior Technical Support
Specialist