me RemoveThis @privacy.net wrote:
> Well they announced a 40 percent increase in local
> electricity rates here locally today.
>
> Having said that..... what could a person do to either
> buy or build a "green" low energy use PC? Something
> that one would not be afraid to leave on 24/7?
>
> Uses would be for typical Internet stuff as well as
> word processing, maybe voice recognition software even.
>
> What make a PC a power hog anyway? If you have a big
> power supply say 500 watts.... but it is only being
> used to power say 200 watts worth of equipment in the
> box ...does that mean the PC is STIL using 500 watts
> energy?
>
> And what could a person do if wanting to build a home
> server type machine where it would in fact be on 24/7
> and recording TV programs off air, etc? How to keep it
> low power?
>
> Or.... can I just BUY something already low power out
> there?
The first thing to do, would be to work out what it
costs to run a device, 24/7. But to do that, you need
to know exactly what it is using.
To start, purchase a Kill-a-Watt meter. This will allow
you to measure the actual system consumption. You can go
around the house, and monitor other things, as well as
your computer.
http://www.amazon.com/P3-International-Kill-Electricity-Monitor/dp/B00009MDBU
I have one additional trick. I have a clamp-on ammeter, and
have used that to measure larger devices in the house. One
power loss I discovered in my house, was my central air
conditioner wasting ~70W for an internal heater. Now I
open the breaker when the summer is finished. For years,
during the winter, that damn thing was wasting electricity.
You'd be surprised what some devices do behind your back.
I discovered this, when doing maintenance
on the central air.
A 500W ATX supply doesn't draw 500W. It has a 500W total output
limit. If the computer draws 100W, the supply delivers 100W.
So the computer components are the determining factor, not
the size of the supply.
Say the computer uses $100 of electricity per year. Then,
if you replaced the box with a new design, how many years
would it take for the electrical savings, to pay back the
capital cost ? Remembering, that the new box also uses
electricity, so we're talking about the difference between the
new and old box, in electrical usage.
To make a recording device, that uses minimal electricity -
1) Capture device or information source, already in a
compressed mode. In other words, for the computer part
of recording, you want the processor to not have to
do anything to the data, but write it to disk. If
you can achieve that, you could then use a Conroe-L 35W
processor, which is a single core. For example, some
capture cards record in some MPEG format, so the data is
already compressed.
2) Storage devices. A 3 1/2" drive runs constantly and
power use varies a bit from product to product. For
power calcs, I assume 5V @ 1A, and 12V @ 0.6A, but you
can usually look up a drive and get a more recent number.
2.5" laptop drives use about 5V @ 500mA or less. They
may also operate incrementally, spinning down when not
being used. For recording applications, you'd save power,
but I don't know how long a laptop drive would last, if
it is constantly spinning down and spinning up again.
SSD drives based on flash, can have power usage less than
those figures. But they also cost a lot of money, to get
a large drive. If using an SSD for the task, you'd want to
wake another system a few times a day, and "dump" recordings
to a HDD based computer of some sort.
3) Computers come with Cool N' Quiet or with EIST. Those are
schemes, where the core speed and core voltage, are adjusted
to meet the computing load. That helps keep the power low.
There are even lower power states, but it would be pretty
hard to tell if you were achieving them, unless you have
your Kill-a-Watt handy. Lower power states are only possible,
if the computer isn't doing anything.
4) Power supply choice. The cheapest power supplies have an internal
efficiency of 68%. A good supply may manage 85%. The efficiency
depends on the loading as well, so the 85% supply doesn't give
85% at low load. But certainly the 85% supply will help trim
the wastage. Good 85% efficient supplies might range around $100.
Cheap 68% supplies might cost $20. You get what you pay for.
Going to this much trouble, usually pays off for applications
which are "off the grid". If you use batteries, have solar, or
wind power, or water power, then every watt counts. It may then be
worthwhile wasting thousands, to develop just the right solution
for your application. But when the grid is present, the
payback might take a while. Especially when you consider the
number of hours you spent building and researching just the
right solution.
Say you install a 4GHz processor in a computer. Then you write
a piece of C code, that polls a device on the bus. The CPU spins
in a loop, and ends up running at full power. Instantly,
with your Kill-a-Watt meter, you see the computer drawing 100W
more electricity. If the program was more carefully written, to
be triggered by hardware interrupts, the power drops down quite
a bit. For example, my processor only draws 13.2W measured, when
sitting idle in Linux or Win2K, due to the Idle loop using the
HLT (halt) instruction. If the HLT instruction is not used, the
power jumps up to like 50W or so. The Kill-a-Watt meter makes
it easy to monitor for stuff like that. At least you can keep
track of the progress you're making. For example, you can
boot a Linux LiveCD, like Ubuntu or Knoppix, measure the computer
power with the Kill-a-Watt. Then, boot into Windows. If you
haven't buggered your Windows install, Windows can match the
power performance of Linux. I get the same processor power
consumption for all of those OS options. When my antivirus
software is installed in Windows, that is when Windows becomes
more of a pig. So even innocent looking software additions,
can upset your power saving plans.
But you'll learn more about this, the more that you use your
new Kill-a-Watt.
My area is getting "time of day" billing. My power meter has
already been replaced with a digital meter. All the meters
have wireless transmission, but the wireless part isn't running
yet. Some day, the power usage every 15 minutes, will be reported
to the power company, via the "pico net" concept. And I'll be billed
a different fee, between 8AM and 5PM, than the rest of the
day. At that point, the central air will be running all night,
and switched off during the day. By 5PM, I'll be good and
sweaty, thanks to the coming new policy. Welcome to the
future.
Paul
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