Here's the setup from last night. More on that adventure as soon as I make some sense out of the results.
Tentative Success
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About Powering Down
This page contains a single entry by Rachel VanCott published on January 16, 2009 12:11 PM.
In Which Things Get Complicated was the previous entry in this blog.
The Results From Thursday is the next entry in this blog.
Check back daily and follow my attempt to measure and reduce my energy use.
About Powering Down
This page contains a single entry by Rachel VanCott published on January 16, 2009 12:11 PM.
In Which Things Get Complicated was the previous entry in this blog.
The Results From Thursday is the next entry in this blog.
Check back daily and follow my attempt to measure and reduce my energy use.
Rachel VanCott's account is inspiring. It is also educational, and I hope others will try some first-hand learning in the same way she is now doing.
I would like to comment on my experience with automobile fuel-economy. In 1991, I bought a Chevrolet Geo Metro XFI from a local dealer who tried very hard to sell me a big luxury model with lots of horsepower. I had planned to trade this car in on a later model with the same performance in about 3 or 4 years, but GM permanently dropped this line of vehicles just 2 or 3 years later. I still use my Metro XFI, which has always delivered 60 to 65 miles per gallon, and starts instantly, winter or summer. It cruises smoothly at any legal speed I have encountered, and has only needed a new thermostat, spark plugs, oil changes, and new tires up to now. When GM sent me a questionnaire asking what model I would buy next time, I said that I would not consider any of their big inefficient cars, and would only buy another Metro XFI
AC power calculations differ from DC power calculations. DC power is indeed volts times amps. For AC circuits, one also needs to know the phase angle between the voltage and current.
In AC, apparent power is equal to volts times amps and is labeled volt-amps (VA). Real power is VA times the cosine of the phase angle between the voltage and current.
From wikipedia:
http://en.wikipedia.org/wiki/Power_factor
In a purely resistive AC circuit, voltage and current waveforms are in step (or in phase), changing polarity at the same instant in each cycle. Where reactive loads are present, such as with capacitors or inductors, energy storage in the loads result in a time difference between the current and voltage waveforms. This stored energy returns to the source and is not available to do work at the load. Thus, a circuit with a low power factor will have higher currents to transfer a given quantity of real power than a circuit with a high power factor. A linear load does not change the shape of the waveform of the current, but may change the relative timing (phase) between voltage and current.
Circuits containing purely resistive heating elements (filament lamps, strip heaters, cooking stoves, etc.) have a power factor of 1.0. Circuits containing inductive or capacitive elements (lamp ballasts, motors, etc.) often have a power factor below 1.0.