Daytime Headlights and Greenhouse Gases

Hello,

I found the following discussion interesting but possibly misleading... From the HowStuffWorks website....

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This page discusses the energy demand of running headlights in the daytime. It calculates the extra gasoline required to run headlights for several hours per day and scales this at the US national level per annum. It then goes on to show how much extra CO2 this represents in a slant towards the environmental impact of daytime running lights!

My question is in regards to the calculations, which are based on the notion of "extra" energy demand from the alternator. I'm not an expert in auto electrical systems, but I thought a typical alternator normally generated power in excess of what the system demands? Am I incorrect in this thinking? If not, then the author(s) of the discussion has made quite a misleading argument.

Interested to find out what the truth is on this subject.

Cheers

Reply to
EF
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Dear EF:

No.

Yes. The belt tension increases as load on the alternator is increased. The current through the alternator (proportional to power consumed) creates the counter-torque the belt friction must overcome.

David A. Smith

Reply to
N:dlzc D:aol T:com (dlzc)

Thanks for the quick reply Mr. Smith.

So, in essence then, the more electrical power you demand of the system, the engine must provide for this thru increased power and thus more fuel burn. Correct?

Thx again EF

Reply to
EF

Two 100 watt headlights for 2 hours per day = 344 kcal. In comparison active people eat 1500 - 3000 kcal/day.

A more effective solution would be to get rid of active people, not headlights.

Bret Cahill

Reply to
Bret Cahill

Yes. Even if you run off the battery for a while, you'll end up (hopefully) restoring the charge on the battery. Any power drawn from the engine compartment is supplied by burned fuel. There are no "free" sources of energy there, that won't bathe you with radioactive particles ( ;>) ).

And as Bret points out, daytime headlights aren't a whole lot of additional power. Even if they do look silly.

David A. Smith

Reply to
N:dlzc D:aol T:com (dlzc)

Checking...

2 X 100 X 2 X 60 X 60 = 1.44 MJ = 343 C .....yep, you're right!

Brian W

Reply to
Brian Whatcott

Doesn't this neglect the conversion efficiencies of the engine (gasoline to crankshaft power) and alternator ? The net fuel consumption and CO2 output is based on the overall efficiency.

---------- Ed Ruf Lifetime AMA# 344007 ( snipped-for-privacy@EdwardG.Ruf.com)

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Reply to
Ed Ruf

To be fussy, it could be argued that the heat used to warm the car's passenger compartment is free energy from the engine compartment, because otherwise it is transferred to the atmosphere through the radiator. :-D

Chris

Reply to
Christopher Tidy

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