Tesla Turning the Corner

My Volt's battery pack capacity is around 16 kW-hrs I can get about 70 miles range in combined driving off a full charge during the summer no problem so something wrong there.

We're both correct: The miles per gallon gasoline equivalent is based on the energy content of gasoline. The energy obtainable from burning one US gallon of gasoline is 115,000 BTU, 33.70 kWh, or 121.3 MJ.

That's 33.7 kW-hr for one gallon of gas. That's 33.7 kW-hr for 1 gallon of gas *OR* 33.7 kW-hr for 100 miles if the EV gets 100 MPG-e. Same thing, methinks.

I was trying to avoid miles traveled in the calcs and did it by using gallons instead of miles. I never mentioned miles anywhere in my calcs. Therefore, I used the following, where I substituted 33.70 kW-hrs for 1 gallon of gasoline: 1 MPG-e = 1 mile / gallon(electric) = 1 mile / 33.70 kW-hrs or if you invert all the terms: 1 gallon(electric) / mile = 33.7 kW-hrs / mile

Guilt of guessing(tm) as charged. As I mentioned: Let's do the math, using some rather overly simplistic over simplifications

The problem was that I wanted numbers for annual consumption, production, and such. All I had were the daily graphs for today's consumption from CAISO. So, I eyeball averaged the various graphs, contrived a suitable guess(tm) for the average daily consumption, and multipled by 365 days/year to get the annual consumption, production, and such. While such averages will vary radically throughout the year, I think I can ignore those variations since I'm only interested in an appoximation to within +/- an order of magnitude. I'm sure better numbers can be found or calculated. I just didn't want to burn the time doing it for a back of the envelope estimate.

Drivel: Frankenstein Tesla salvage rebuilds: Rich Rebuilds channel:

Maintaining ~65 mph on level ground in a ~0.3 drag coefficient 3500 lb car doesn't require more than around 12-14 kW, or about 15 horsepower.

The problem with the calculations is that most of the energy content of the ~16 billion gallons of gasoline burned is wasted in the intrinsic inefficiency of the fuel -> combustion -> mechanical transmission -> energy transmitted to the wheels to overcome drag and rolling resistance of a moving vehicle-process.

The reports I've read say 5x the generation and distribution capacity would be needed.

The back of the envelope calculation is pretty straightforward the tank-to-wheel efficiency of an average ICE car is 15% the battery pack to wheel efficiency of an average electric car is 80-90%. Use the first percentage to estimate what amount of the 15 billion gallons of fuel burned accomplishes nothing useful but producing waste heat, throw it away, and then work with the figures you have left.

ONly lefty asshats who have no life have a problem.

Because there is no need, asshat.

My back of the envelope calculation shows it would require about 35 billion kWh per year to replace all the gas cars in California with electric. By comparison residential lighting in CA consumes about that amount per year, it's around 8% of total residential energy consumption.

That is to say if charging was done primarily at night when the grid is under-utilized it would probably barely notice.

I beg to differ. The MPG-e number is designed to directly compare a gasoline burner with an electric vehicle. As I understand it, if you replace the gasoline burning engine and gas tank, with an electric motor and battery, the distance traveled will be identical at a ratio of 33.7 kw-hr of battery energy to 1 gallon of gasoline. Miles per gallon gasoline equivalent (MPGe or MPGge) is a measure of the average distance traveled per unit of energy consumed.

In other words, all the inefficiencies are built into the ratio. If you want to add something like aerodynamic efficiency into the equation, you have to apply it equally to the gasoline burner and the EV resulting in the same 33.7 kw-hr/gallon ratio.

Actually, the equivalence of gasoline power and EV power is equally political as it is technical. If you go through the history of MPG-e, you'll find that it has changed 5(?) times in the last 30 years. When GGE (gasoline gallon equivalent): enters the picture, I'm lost. At least the conversion factor is close. The NIST uses 33.40 kW-hr/gallon possibly because the addition of alcohol has reduced the energy content of gasoline.

Duz the 5x mean that the US would need to add 5 times todays grid capacity for a total of 6x todays capacity, or that it needs to increase the capacity by 5 times, for a total of 5x todays capacity? Are you sure that the report said "capacity" and not "production"?

One might suspect that my 44,000x number is a bit off. However, I'm not so sure (unless I screwed up somewhere). My 44,000x number is based on how much additional capacity would need to be added to the existing grid. I also suspect that the 2x and 5x figures are based on the assumption that the grid can handle a 2x or 5x increase continuously as in 24x7 and thus ignoring any peaks caused by usage patterns. I also did the numbers only for California, not the entire US. Also note that generating capacity means adding up all the maximum outputs of all the generating facilities that might be online, possibly ignoring generators that are down for repairs or on standby because of lack of demand.

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tation in the US. Not all of that is for cars which could be powered by el ectricity. But I'll use that number. Using 26.4 mpg (2008 average) that i s 3,775.2 billion miles (10^9).

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sing 0.33 kWHr/mi that would be 12,411.3 trillion miles (10^12). Seems to be a rather large discrepancy... about a factor of 3300 times more electri city than gasoline.

out 1,258.4 billion kWh or 0.03% of the currently generated electricity. T his is a very useful statistic to know when people start talking about over loading the electric grid.

I can't say exactly what is wrong with the calculations, but using the GGE does not seem to factor in an adequate comparison to electric car usage and gasoline car usage. A gallon of gas gets you about 25 miles. Those same miles require about 8 kWh of electricity. That is from real cars on real r oads. The Teslas (and several other cars) have a range of 300 miles on 100 kWh of battery.

I asked you to check my math. Introducing another conversion factor that i s not for this same purpose is not helpful. By this factor the 100 kWh bat ter in the Tesla longer range autos is equivalent to a 3 gallon gas tank!

That said, I confused watts with kwatts making my mileage of the electrical grid wrong by a factor of 1000. It should be 12,411.3 billion miles (10^9 ) or about three times all the gasoline used in ground transportation.

Rick C.

Then why is the number wrong? A gallon of gas will give you around 25 mile s of range. 33.7 kwh will give you about 100 miles range in a Tesla. Clea rly these are *not* comparable. What I read in Wikipedia is that the GGE i s intended to compare the *energy content* of fuels, not the mileage. If y ou factor in the 20% efficiency of the gas engine the numbers are more alik e.

Nonsense. It is off by a factor of about 4. Alcohol isn't that bad.

I know nothing of how they come up with the GGE, but I know 100 kWh battery in the Tesla gets you around 300 miles of range equivalent to about 12 gal lons of gas.

Rick C.

The range on Tesla's vehicles is so good that the most common way I see them parked at public charging stations around here is sort of sideways blocking both the spots and not even plugged in.

IIRC, it was 5x current capacity but the numbers should scale. The point is that it's not feasible, particularly in today's political climate. Lefties would never allow it, though they would be the ones demanding it. Lefties are like that.

No. That would have to scale, as well.

Not to mention those plants on hot standby and those on PF correction duty.

I get about 2x assuming that everybody drives tiny wimpy electrics and charges at home all night every night.

If you convert current gas consumption to electricity, it would be a lot more.

You taking into account that ballpark 85% of the gas burned in combustion engines does nothing useful but produce waste heat? The tank to wheel efficiency of an ICE vehicle is pretty terrible.

That's what an ICE car's radiator and coolant loop is for, after all. It's a money to high entropy waste heat conversion machine designed for the sole purpose of ejecting your dollars out to heat the Universe

Thermal electric power plants in the US average roughly 40% efficiency. Distribution loses about 5%. Then for an electric car, there is charger efficiency and battery charge/discharge efficiency, and finally motor efficiency. Power plants do get fuel cheap, like gas and coal, neither of which needs refining.

Auto engines run 25 to as much as 50% efficient. Toyota has a gas engine that's 38.

Tiny wimpy gas cars don't use much fuel.