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Old 12-29-2012, 07:11 PM   #15 (permalink)
In the fasting lane
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Location: Nieuwegein, the Netherlands
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Red Devil - '11 Honda Insight Elegance
Team Honda
90 day: 48 mpg (US)

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I have an issue with the fossil fuel/electricity conversion in general.
I take it that you're comparing the caloric value of both, not the actually produced power on the road.
Gasoline engines are hopelessly inefficient, converting only a small part of all the energy into movement. EV's on the other hand use almost all of it.

So I enter a real world comparison; My Insight II will do 5 l/100 km @ 120km/h under good conditions. According to the tool that's 443.25 Wh/km; in an hour it will need 53190.56 Wh/ slashing the hour away, a constant power consumption of over 53 kiloWatt.

At first this seems strange. This is very close to the max power output of the engine. how can it be then that the top speed of my car is over 180 km/h?
Then I realise that the 53 kW is the car's power consumption, not production. When it produces its max 66 kW or so it will use over 250 kW worth of gasoline, wasting almost 200 kW to heat.
And yes, the tool mentions consumption not production. It does what it is supposed to do.

However, to search out how much kWh I'd need to get an acceptable range on an EV by comparing the gas FC for a comparable car, or how much gas I'd save by converting all my lights to HID and LED, I must base my calculations on output power production.
To convert fuel per distance to output power you need to estimate the efficiency of the conversion, what type of fuel is used, what th driving conditions are and the engine load; as lightly loaded engines burn inefficiently, even while attaining good mpg at the same time.

In the case of HID and LED conversion I even have to account for losses by the alternator, as that provides the electricity from the output power of the gas engine.
My estimate was that every kWh of electrity usage reduction would yield at least half a liter of fuel savings. Electricity produced by a gas powered car is way more expensive than electricity from the wall. If it weren't then EV's would have no right of existence.

Of course, real world figures show that an EV's power consuption costs per mile are just a fraction of that of their gas powered cousins.

Having said all this, it is possible to take all these factors into account recalculating them on the result.
In the LED conversion case I even just need the table.
So to save 1 litre fo fuel burnt at 20% efficiency (running partial load) and converted to electricity by a 70% alternator it takes just 14% of the 8.87 kWh specified in the table so just below 1.25 kWh.

When I drive my HID kit and license plate etc. LEDs will be always on (for safety), a 50 W reduction to the original lighting. In 25 hours of running that will save me a litre.
I do about 60 km/h average speed overall and achieve about 5 l/100 km so I use 3 l/h.
This conversion wil reduce my FC by 1/75th or about 1.333 %
Just running LED DRL's would double the gain: - 100 W or -2.666 % FC.

In Holland gas is more expensive than Heineken (per volume, supermarket prices).
I will earn back my investment within a few years.
2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut.
lifetime FE over 0.17 Gmeter or 0.1 Mmile.

“We all know that light travels faster than sound. That's why certain people appear bright until you hear them speak.” ― Albert Einstein
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