With the cost of energy increasing, whether at the pump or in terms of cooling your home this summer, or using devices to reduce your energy consumption, here are some factors consumers should keep in mind. Let’s look at two types of products. The first is called the “radiant barrier.”
Radiant barriers may be “reflective foil, reflective metal roof shingles, reflective laminated roof sheathing, and even reflective chips, which can be applied over loose-fill insulation. The reflective material, usually aluminum, is applied to one or both sides of a number of substrate materials. Substrate materials include kraft paper, plastic films, and cardboard, oriented strand board.”
These barriers are then installed in the attics of homes. In some cases, homeowners are told that they may be able to save a lot of money. Some savings claims range from 20 to 30 percent while others state even greater savings on utility bills.
According to information from the Dept. of Energy, “Some studies show that radiant barriers can lower cooling costs between 5%–10% when used in a warm, sunny climate. The reduced heat gain may even allow for a smaller air conditioning system. But in cool climates, it’s usually more cost effective to install more than the minimum recommended level of insulation rather than a radiant barrier.”
The second product uses what’s called “power factor conversion.” With this unit, claims are made that consumers could save approximately 30% on their utility bills.
According to information from the National Institute of Standards and Technology’s website:
If you’ve seen an Internet ad for capacitor-type power factor correction devices, you might be led to believe that using one can save you money on your residential electricity bill. However, a team including specialists at the National Institute of Standards and Technology (NIST) have recently explained why the devices actually provide no savings by discussing the underlying physics.
(1) Power factor correction devices have no effect on a typical household electric bill. Activating the device reduces the current drawn from a power line but simultaneously increases the power factor. Electric bills are based on the product of the two, which remains the same.
(2) Power factor correction in operation, how it works. Current from the power line is reduced by introducing a charge, on a capacitor and creating an oscillating charge or current, between the capacitor and the inductive load, such as a refrigerator.
These devices, sometimes referred to as Amp Reduction Units or KVARs, are touted as good investments because they reduce the amount of current drawn from power lines while simultaneously providing the necessary amount of current to appliances inside the house. Though engineers elsewhere have discredited the devices for use in typical residences already, NIST physicist Martin Misakian and two of his colleagues decided to write a brief primer describing the devices’ inner workings for readers who are not power engineers, but who still have some technical background.
“One of the important functions of our primer is to remove the mystery of how current from the power line can decrease while at the same time current going to an appliance remains the same,” says Misakian. The nine-page Technical Note explains this result in terms that might interest readers with knowledge of college-level physical sciences. It shows that although the devices can indeed reduce current flow from the power line, it is not just the current flowing from the power line that determines your electric bill, but the product of the power factor and the current. Though current decreases with a power factor correction device, the power factor increases correspondingly, meaning the product of the two remains the same with or without the device. Because a residential electric bill is proportional to this product, the cost remains unchanged.”
To explain this mathematically, let’s use an example of a small motor whose current is five amperes. If the input amperage is five amperes, and the power factor is one, then product of the two would be five, (5 * 1 = 5). With the KVAR unit in place, the current going to the motor is reduced to 1.4 amperes, which the power factor would need to be raised correspondingly, 5/1.4 = 3.571428571428571, which means that you multiply the power factor of 3.571428571428571. So when the power factor is multiplied by the amperage of 1.4, the resulting product is 5.
Another thing to consider is that residential customers pay for kilowatt usage, and not solely on current usage.
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