List:
Daytime running lights on cars and trucks consume 15,000 MW of electricity as
related by some letter writer in ME magazine. 15,000 MW is enough to power
most of New York state. When I told this to a group, I got arguments that the
lights were "free" if you were driving the car anyway. But you still need to
burn gasoline to power the lights.
Given 100 watts needed to power the daytime running lights on one vehicle and
assuming 150 million cars and trucks, you get 15,000 MW.
The alternator/battery "turn-around" efficiency which is comprised of the
alternator efficiency (high by itself), conversion from AC to DC, storage in
the battery, and discharge of the battery, is about 30% when all this stuff is
considered. However, since at least part of the time the electricity goes
directly to the headlamps without being cycled through the battery, I will
neglect the "turn-around" efficiency (or inefficiency).
Assume a 20% efficiency for conversion of gasoline to alternator electrical
output. Also assume the daytime running lights operate for an average of 2
hours per day (including commercial vehicles)
So then: 15,000 MW x 2 hrs/0.2 = 150,000 MW-HRS per day which is 513 x 10^9
Btu per day.
Since gasoline is 125,000 Btu/gallon, operating the daytime running lights
consume 4 million gallons of gasoline per day.
Or 1.1% of the total gasoline consumed in the U.S. (360 million gal/day).
Four million gallons of gasoline is about 98,000 "barrels", So, if we get only
about 20% (wild ass guess) of gasoline from refining a barrel of crude oil,
then the daytime running lights "consume" about 500,000 barrels of imported
oil per day. So, are the daytime running lights worth this cost?
Why am I wasting time on this? Because this kind of mental exercise is
supposed to ward off Alzheimer's and I can't have any real fun until after
dark anyway.
Lance
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