View Full Version : Tesla -vs- Insight high-score (1 kWh = 2.32 oz gas)
Saw a segment on the Tesla and was truly awestruck, want one bad, but need to win the lottery first. But it dawned on me that all the tire screeching stuff didn't interest me in the least, just that huge Lithium pack. So I began a mental exercise as to whether the worst Tesla hot-rod lead foot would really end up causing more GHG than a prudent Insight driver.
Rough calculations lead to the gas powered cars causing 5-10 times more GHG than EVs.
Here's the math.
1 kWh coal (worst case) = 2.117 lbs CO2 <ref1>
Average energy efficiency of EV = 262 Wh/mi <ref2>
EV GHG based efficientcy = 1.8 MPP (miles-per-pound-of-CO2)
1 lb gasoline = 19 lb of CO2 (mole math)
1 gallon of gasoline weights 6.15 lbs <ref3>
70 mpg = fair guess of an insight driver even remotely trying.
GHG based efficiency of insight = 0.6 MPP
So what's the break even point? Well at about 117 mpg the Insight is ticking along at about 1.0 MPP. At about 470 Wh/mi the Tesla is also ticking along at 1.0 MPP.
So we have pretty good data on what an insight is capable of, the question is: "How inefficient can an EV (Tesla) driver be?" As far as I know EVs 470 Wh/mi is pretty darned inefficient, but I don't really know EVs that well.
Reference 1: http://www.eia.doe.gov/cneaf/electricity/page/co2_report/co2emiss.pdf
Reference 2: http://www.calcars.org/conversions-factsheet.pdf
Reference 3: http://en.wikipedia.org/wiki/Gasoline
09-24-2007, 05:17 AM
Theres a fairly good whitepaper on the tesla site.
there is also some info on Darell-D ev site, about 180Wh/m for the RAV4 L EV
How about stuck in traffic with the AC on full blast? Not sure of the power rating for the AC.
Might be able to get 400Wh/m if barely moving.
09-24-2007, 10:11 AM
And I think is safe to say that by 2020, we are going to have around 15-20% of power from renewables, bringing worse case for Tesla to 2.25 MMP. Personally, I'm hoping by 2030, those numbers will grow far more, but by then, we may all have an PHEV, EV, or better in our driveway.
Revised GREET metric assuming the absolute worse possible coal fired electricity using to most egregious mining efforts:
1 kWh = 9 oz gasoline
Well did a bit more reading. Apparently there is a lot more GHG contributions in mining coal. Original figures just calculated the GHG contributions from the power plant. Throwing in the GHG contributions from the mining operations the MPP for the Tesla drops to about 0.95 MPP and the Insight to about 0.75 MPP. This puts the cross-over point a lot closer than before. Close enough to say that a hypermiling Insight driver has a foot print as small as an oblivious Tesla driver.
Now that said, throw in renewables and it isn't even close. But it is interesting that coal is really that dirty. So I guess once we get all the gas powered cars replaced with battery powered ones, we better make darn sure we continue to build out our nuclear power infrastructure and fix our 100 year old power-to-ground electric grid.
Reference 1: http://www.transportation.anl.gov/software/GREET/pdfs/esd_bv2.pdf
___Currently, there is ~ 19.6 #’s of CO2 released from the tail-pipe while consuming a gallon of fuel at stoich (RFG, E10, Boutique fuels not segregated – better or worse). Gasoline itself also has an additional CO2 production emissions quotient of ~ 9.5 #’s and that number is getting higher as it becomes more energy intense to pump the black gold from ever more remote locations.
___As it stands, the CO2 output and the energy needed to create a gallon of gasoline is more then what an EV based Prius would use from the energy alone minus the gasoline in the first place. Gasoline is now just an energy carrier just like H2 as far as I am concerned. A cruel joke on all of humanity imho :ccry:
___Currently, there is ~ 19.6 #’s of CO2 released from the tail-pipe while consuming a gallon of fuel at stoich (RFG, E10, Boutique fuels not segregated – better or worse). Gasoline itself also has an additional CO2 production emissions quotient of ~ 9.5 #’s and that number is getting higher as it becomes more energy intense to pump the black gold from ever more remote locations.Good data, thanks!
Any guess on what the 1 kWh = ? oz gasoline metric might be (GHG-wise)? It's hard to guesstimate these figures since energy can be renewable or dirty. 1 kWh = 9 oz may be a bit overkill, and 1 kWh = 2.32 oz may still be high.
OK.. think I have a finalized number here. Looking at our second favorite site... FuelEconomy.gov. Turns out they've published all their data for the 2000-2003 EV models. The two of interest are the RAV4 EV and the Ford Explorer EV. These both have conventional models to compare against should you need to.
The basic info is buried in the GHG score for the vehicle along with the annual fuel costs. From that you can calculate lbs GHG per gallon and lbs GHG per kWh. Here goes:
2001 RAV4 (gasoline)
1827 = annual gas cost @ $2.80/gal
652.5 = gal per year assuming 15000 mi year.
8.0 = tons of GHG from said gas.
16,000 = lbs of GHG from said gas.
24.5 = lbs of GHG per gal of gas.
0.19 = lbs of GHG per oz of gas.
2001 RAV 4 (EV)
391 = annual elect cost @ $0.08 / kWh
4887.5 = kWh per year assuming 15000 mi year.
4.2 = tons of GHG from said elect.
8,400 = lbs of GHG from said elect.
1.7 = lbs of GHG per kWh of elect.
So from that we can deduce that 8.88 oz gas production and consumption produces the same amount of GHG (1.7 lbs) as the production and consumption of 1 kWh
So the metric is 1 kWh = 8.88 oz gasoline GHG-wise according to the EPA. Since the electricity was calculated on national averages, some states will be greener (1kWh = 7 oz) and some will be blacker (1 kWh = 10 oz). Since Texas is on the dirty side, I'll probably settle on 1 kWh = 9 oz for my calcs.
So looking at the RAV4 example, someone meeting EPA estimates of 326 Wh / mile would have as small a GHG footprint as someone pulling 44 mpg out of that gas version. That's some serious hypermiling, specifically 170% of 2007 EPA.
So a non-hypermiling EV driver is doing as good as an Uber-hypermiler pulling down 170% of 2007 EPA estimates.
I'm a believer... Where's them batteries?
Sites: U.S. Department of Energy's GREET model, version 1.7
___Nice detective work and I will buy those figures …
___Let us remember that a PHEV can possibly be pushed even harder then the numbers would suggest? I remember reading that the Prius was a 250Wh/mile vehicle over at EVWorld 2 years or so ago. I was doing some similar math after the Prius marathon and thought the numbers would be more like 125 – 135 Wh/mile range at a decent suburban clip with a 25 – 30 mph average. The cool thing is that driving an EV is always driving near the max abilities of a good hypermiler because that is the way EV’s work. You apply the pedal and only the amount of power needed is allowed to propel whereas you apply the accelerator and even a Prius is pulling 10 mpg for some of the accel. You let off in a PHEV/BEV and it is either Regen or pure glide depending on the algorithms. Somebody that owned a RAV4EV told me it had a switch to remove Regen. Oh how I would dig that little feature ;) Watching the Accord in the 3 – 7 mpg range in the beginning phase of a pulse is sickening compared to how efficient an EV would be at those slower speed launches. Just too much garbage spinning around and not going anywhere in all phases of ICE operation. I have the feeling many of us here are going to become great Insight - DWL like drivers once we get behind the wheel of a PHEV of our own. That is the way the Insight worked on the highway and I suspect PHEV’s will have very similar attributes to minimize power output for a given accel or steady state speed and expected distance.
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