ICE's and EV's-energy use breakdown (hint: EV's win)

EV Small Talk
1

Hi, I’m new to this forum but would like to say hi and get some feedback about a little project I’m working on.

I have recently been compiling a comparison of energy use for EV’s compared to ICE’s under real world conditions. This would be more than just a comparison of the cars themselves, but of the real cost in energy, from getting the fuel from the ground to putting the car in motion. It is based on current technologies and the current system of extraction and refinement, as well as the generation of electricity needed to power EV’s using the equipment we currently employ to generate it.

It has nothing to do with the cost in dollars, but the cost in energy (BTU’s). I’m using statistics for the US and empirical data from testing of actual vehicles where I can find it. Most numbers are national averages whenever possible to account for things like varying octanes of gas, formulations, driving habits, and seasonal & temperature effects on gas & electrical systems.

In order to do this I am breaking everything down to a common unit of energy (BTU’s) and making certain assumptions that most, if not all, are commonly accepted. Here they are for the skeptics:

-1kWh=3,412 BTU
-1 Gallon Gasoline=125,000 BTU
-US Population=303.7 million people
-Avg. miles driven/person/year=13,000 miles
-Avg. gallons consumed/person/year=500 gallons
-Avg. MPG US car=17 MPG
-Number of cars operating in the US=239 million

The story of the ICE can pretty much be extracted from those numbers alone in terms of the cost in BTU to operate a nation of ICE’s [I]once the gas is in the car[/I]. It translates to about [B]18.9 quadrillion BTU’s[/B] annually in the US.

I’ll deal with the cost in BTU’s to produce a BTU of gasoline energy later.

To get a sense of the cost in BTU of an electric vehicle I’m using test data for 4 RAV-4’s tested under normal driving conditions for 3 years and around 100k miles each. The data gleaned from this follows:

-0.4 AC Kwh/mile=avg. fuel economy
-Using average driving miles/person/year=5,200 AC Kwh/person/year or 1.6 trillion AC kWh would be consumed if all vehicles in the US were RAV-4’s.
-In BTU’s, this amounts to [B]5.4 quadrillion[/B] BTU’s anually.

So this means that if you ignore the cost in BTU’s to get the power (gas or electricity) to the vehicle itself, a nation of EV’s would consume 28.39% of the energy in BTU’s that are currently consumed by our ICE’s, or that we would immediately consume just over a quarter the amount of energy driving RAV-4’s (or similar EV’s), assuming my calculations are correct.

As for the production of fuel sources, gas for ICE’s and electricity for EV’s:

-For every 1 BTU expended in the generation of electricity, 33.42% is turned into electricity
-Transmitting the electricity has an efficiency of 92.8%
-Converting the electricity to power at the drive train of the vehicle is 88% efficient, for a total efficiency of [B]27.29%[/B].

The same calculations for gasoline, curiously much harder to find, look like this:
-Extraction: I can’t find this number so have to assume it uses 0 energy to extract oil from the ground. Maybe someone here knows.
-Refinement: 92% efficient
-Delivery (refinery to pumps): Also can’t find so have to assume 100% efficient.
-Converting gasoline to power at the drive train: 18% (the rest is heat and exhaust).
-Total efficiency of a typical ICE: [B]16.56%[/B]

So comparatively speaking and giving the gasoline folks every benefit of the doubt when I don’t have data, a nation of electric cars consumes a little less than half the amount of total BTU’s, or overall energy. I know this will only go up when I find the data because the energy to transport those tankers and run those truck to fill up those gas stations, not to mention the cost of drilling and pumping must be significant.

If anyone can help fill in some blanks, I would appreciate it.

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Thanks for the info, very interesting post. I don’t know how much this helps, but as far as moving fuel from the refinery to the pump, a gas tanker hauling 10,000 gallons of gas gets around 4-5 mpg. So, to haul a gallon of gas 100 miles it takes roughly .02 gallons of diesel.

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“a gas tanker hauling 10,000 gallons of gas gets around 4-5 mpg. So, to haul a gallon of gas 100 miles it takes roughly .02 gallons of diesel.”

I don’t claim to be a math whiz, but hauling a gallon of gas 100 miles @ 5mpg would be 20 gals.

Whether you haul 1 gallon or 10,000 gallons in a tanker, driving 100 miles you will still burn about the same amount of fuel.

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This is very true. What an astute observation. :wink: I could be way off here, but I’m guessing that the gas companies fill the tankers with as much gas as they can hold when they haul it from the refinery to the station. I suppose they could haul it 1 gallon at a time, but I think it’s a safe assumption that tankers leave the refinery completely full…

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Thanks for your thoughts.

I’m pretty certain a loaded truck will require more fuel/mile to drive, but what I need for the sake of my calculations is a real-world number like a national average fuel spent delivering fuel. There’s no doubt the industry has this number down to the penny, and tracks it yearly monthly, and probably daily. But I can’t find it anywhere.

The other number is the cost to extract, and take the crude to the refineries themselves. The fact that this happens in other countries for the majority of the oil produced doesn’t matter because, in terms of BTU’s used, the “cost” is the same anywhere, even if the dollar amount isn’t. It must require vast amounts of energy to ship oil tankers around the world and how about those oil platforms? There is an aggregate number out there for all of this, but I can’t seem to find it.

The more refined my calculations the better I can compare the real cost to the environment for the 2 technologies. This is the only way I think the green community can make it’s argument really stick. Otherwise it’s easy for the other side to poke holes in the argument (pollution shifting, etc.), and obfuscate the true cost of our petro-centric world.

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Bear in mind that 50% of the energy generated in centralised power stations is lost in transmission.

If you averge out the efficiency of average electricity generation (fossil fuels in a simple/combined cycle mode) it’s about 40% efficient. Halve that for distribution losses and you have 20% efficiency from the wellhead to the battery of the EV. Then factor in the EV losses.

It’s not a pretty picture this energy efficiency debate!!

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These calcs assume that the fuel to generate electricity magically appears at the electric generating station. The cost (ie btu expenditure) of mining and hauling and pulverizing coal, or producing and transporting natural gas and compressing it at the powerplant need to be considered if you’re comparing against a gasoline value chain that includes refining and trucking. And before anyone says RENEWABLES to power the cars, please acknowledge that there aren’t enough renewable resources to power the country and the cars. So to keep the math fair, you can include 0 fuel cost renewables as long as we include all the cost and btu’s we’d need to spend to build a bunch of new renewable generation capacity. Which will take a LOT of energy to construct. Plus require construction of the transmission lines to get it to market: (http://www.puc.nh.gov/Transmission%20Commission/20101109Meeting/News%20Article%20-%20The%20Great%20Transmission%20Heist.pdf) PLUS the btus expended to build the electric cars themselves while we throw away the (still working) stock of ICE cars… EV’s are a worthwhile technology, but not an efficiency slam dunk.