Corvet said:
Can this 18KW Power Energy saver useful for energy saving? (for desktop
PC, 250W power supply)
http://eecrest.com/enjoy24hours/278-1.jpg
http://eecrest.com/enjoy24hours/278-2.jpg
"It uses a state of the art electrical technology to actively monitor
and improve the power factor of electrical appliances, suit for
household or office.
The technology optimizes the voltage and current demands to reduce the
active power demands, reduce electricity bills by up to 35%."
There is a note: "Note: Please make sure that it is installed as close
as possible to the point of entry of your electricity supply in order to
detect all loads before the meter and adjust the power factor
accordingly". Can be connected to one Saver a few electrical
devices(PC, TV, with total power less than 18KW) via multi socket
extension lead?
Does anyone have experience with such a device and if so what kind /
brand do you use?
If you want a PC power supply to waste less power, get one with
a good rating. The "80 Plus" system rates supplies to help
identify ones that are more efficient at power conversion.
http://www.newegg.com/Product/Product.aspx?Item=N82E16817121080
Efficiency of that unit is 90% from 111W to 448W (in other words,
that design is noteworthy for achieving good results over a wide
range).
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story2&reid=219
Regular ATX supplies are 68% efficient, which means the interior
of the power supply generates a fair amount of heat. An 80% to
90% efficient ATX supply, can reduce that kind of waste. The
Kingwin power supply can leave its fan turned off, a lot of
the time.
You then have to consider the pay back period, for such an ATX
supply upgrade. If the Kingwin supply costs $149 USD, it would take
years for the power savings to pay off.
*******
The efficiency of a supply internally, is to some extent independent
of the power factor issue. (In other words, buying a new supply could
well save a higher percentage, than any PFC scheme might.) Power factor
correction is mandated on ATX supplies now, in the interests of the
utility companies, rather than for the home consumer. In a business
setting, ATX supplies with power factor correction makes sense (because
they're billed on kVA), while for home consumers this is largely a
"don't care" consideration. So the inclusion of PFC in ATX supplies in
North America, is to help large business installations. For example,
my former employer had a 30 megawatt feed, powering lots and lots of
computers (so many computers, that the heat from the computers provided
the heating for the buildings). In such a situation, a person purchasing
equipment, will be looking for PFC due to the size of the loads involved.
For a home consumer, with one 150W PC, this isn't an issue that needs to be
addressed. Home heating and cooling are much larger loads in North America
(central air conditioning or heating systems), compared to the 150W idling PC.
Your original question, may have to do with a "power factor correction"
type device. An example of information on such a solution is
described here. In some countries, they may bill kVA as well as kW,
while as far as I know, my meter only measures kW (kW-hours).
I pay a total price right now of around $0.17 per kWh. My 150W
PC costs me about 3 cents per hour, while it is running.
http://www.reliableplant.com/Read/13339/power-factor-correction
The paragraph "Why correct the power factor?" here, helps explain
all it is doing is reducing the drop in the distribution wires "Rline".
In my house, that drop in voltage is pretty damn small.
http://home.earthlink.net/~jimlux/hv/pfc.htm
If your PC ATX supply already has passive PFC or active PFC in it,
that little box from eecrest.com will do nothing. Similarly,
if you're running an incandescent light bulb, the eecrest.com
box will do nothing. It might even waste a few watts itself.
In the past, if you compared an ATX supply with active PFC,
versus one without active PFC, the PFC circuit itself wastes
a bit of power. But in the larger picture, it helps the utility company,
and means the size of conductors between the power poles, can be
reduced a bit. Not all of the current that flows in the transmission
lines, is "billable" current.
Paul
