Organic Rankine Cycle
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Just because the switch says “OFF” doesn’t mean a device is not consuming electric power. Many modern appliances contain clocks, memories, remote controls, microprocessors, and instant-on features that consume electricity whenever they are plugged in. That’s 24 hours a day, 7 days a week.... While these Phantom Loads are often small, their power consumption really adds up. Some Phantom Loads are easy to spot — clocks and and timers have displays. Other Phantom Loads are truly hidden: the appliance seems off when it is switched off, but it really isn’t.
My introduction to the phantoms...
I first became aware of the impact of phantom loads about five years ago. At the time I was working as an installing dealer of RE systems. I had a call from a customer complaining that his brand new batteries weren’t working. Immediately after installation, the family went
on vacation for three weeks
and returned to fully
discharged batteries. I made
a service call to the site and
investigated. After questioning,
it was apparent that the family
had mistakenly left their inverter
up and operating during their
vacation. But since all the
appliances were switched off, this
couldn’t explain where the two kilowatt-
hours of daily PV energy went. I
questioned the family further, “Did you add any
new appliances to the system?” “Yes,” they replied, “we bought two new TV sets and a new stove with electronic ignition.” And the hunt was on!
While the two 21-inch color TVs looked great, both were equipped with remote controls and “instant-on” picture tubes. A quick measurement determined that each TV was consuming 28 watts even when switched off. Most of this power was keeping the filaments in the picture tube warm 24 hours a day. A quick go with the calculator gave us a total inoperative TV power consumption of 1300 watt-hours daily. Measurement of the stove showed that the power supply driving the electronic ignition was operating 24 hours a day and consuming 14 watts. So the stove was consuming about 330 watt-hours daily, even when no one was cooking. Since all these appliances were powered via an inverter, the actual power consumption was even higher due to inverter inefficiency. I figured that the two TVs and the stove were consuming about 1,900 watt- hours of power daily. And they weren’t even being used!
Obvious Phantom Loads
Consider a clock. Many microwave ovens, washing machines, stoves, VCRs, and other appliances contain a clock or timer. The electronic clock/timer and its display consume very little (≈0.5 Watts). However, there is a power supply in the appliance that converts 120 vac into low voltage DC for the clock/timer. This power
supply is very inefficient at low power, consuming many times the power actually used by the clock. This power supply consumes between 4 and 8 Watts or about 100 to 200 Watt-hours daily — enough to run a compact fluorescent light
for about ten hours.
Sneaky Phantom Loads
Some Phantom Loads appear to be truly OFF when switched off. There are no lights or indicators showing power consumption, but the device is still using electricity. Offenders in this category include instant-on TVs, stereos, VCRs, computers, calculators, computer printers, satellite TV systems, and any device powered by a “wall cube”. Wall cubes are power supplies in plastic boxes that plug into 120 vac outlets. Let’s visit a few of these
Phantoms where they lurk.
The Primary is Alive!
Many 120 vac appliances contain power supplies. These convert 120 vac, either inverter or grid produced, into low voltage DC for the appliance’s electronics. On
46 Home Power #37 • October / November 1993
Image | Phantom Loads
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