Tesla Motors claims 114% efficiency

[Phrak]

Tesla Motors claims a "well-to-wheel" efficiency of 1.14

http://www.teslamotors.com/efficiency/well_to_wheel.php"

What in the blue blazes are they talking about?

 

[Dale]

Look at the units. That is 1.14 km/MJ efficiency, not 114% efficiency.

 

[Ivan Seeking]

They certainly aren't including the cradle to grave energy costs.

How much energy does it take to make 900 Lbs of Li ion batteries, and how are they recycled.

 

[Fabius]

They certainly aren't including the cradle to grave energy costs.

How much energy does it take to make 900 Lbs of Li ion batteries, and how are they recycled.

The energy cost of production of the system isn't part of the system efficiency calculation, it never is.
The well to wheel efficiency is a measure of how much of the available energy contained in whatever raw material used for fuel actually makes it to the driving wheels of the car.

... and Tesla published a blog about receycling of the Li-Ion cells: http://www.teslamotors.com/blog4/?p=66

 

[Phrak]

Look at the units. That is 1.14 km/MJ efficiency, not 114% efficiency.

Thanks, DaleSpam. Blind spots, you know.

Something else is a bit odd. They quote a "Source Fuel" of natural gas, while 49-51% of US electricity is generated with coal. However, they are located on the west coast, in California with electricity generated from

Natural Gas 45.2%
Nuclear 14.8%
Large Hydro 11.7%
Coal 16.6%
Renewable 11.8%

A minor swindle, I suppose.

 

[Fabius]

Thanks, DaleSpam. Blind spots, you know.

Something else is a bit odd. They quote a "Source Fuel" of natural gas, while 49-51% of US electricity is generated with coal. However, they are located on the west coast, in California with electricity generated from

Natural Gas 45.2%
Nuclear 14.8%
Large Hydro 11.7%
Coal 16.6%
Renewable 11.8%

A minor swindle, I suppose.

Hmmm.. using figures for the fuel source predominant in their major market... scandalous! Of course they should be making their figures look as bad as possible like every other car maker, right?

 

[Ivan Seeking]

The energy cost of production of the system isn't part of the system efficiency calculation, it never is.
The well to wheel efficiency is a measure of how much of the available energy contained in whatever raw material used for fuel actually makes it to the driving wheels of the car.

... and Tesla published a blog about receycling of the Li-Ion cells: http://www.teslamotors.com/blog4/?p=66

Yes, I realize that. My implicit point was that these must also be considered when comparing technologies. There are hidden energy and evironmental costs for every option to petro. Cherry-picking specific data can be very misleading.

Tesla was also claiming something like a 100,000 miles lifespan for the batteries, which is ridiculous. Shelf life alone makes that claim impossible for most drivers. And I don't know about you, but with heavy use, I need a new battery for my laptop about once a year. There is still battery life, but I need more than 30% or 40% capacity.

 

[Phrak]

Hmmm.. using figures for the fuel source predominant in their major market... scandalous! Of course they should be making their figures look as bad as possible like every other car maker, right?

Those of us who are objectively intested in these things would prefer facts over fiction. So what, you don't care or you prefer the fiction?

The source of electricity when you plug-in your electric car is the elecrical grid. That source is not exclusively natural gas, and unlikely so if you live in the eastern United States. Unless I've missed yet another point, to claim a souce of power such as natural gas is somewhat incredulous.

 

[kmarinas86]

Tesla Motors claims 1.14 kilometers/megajoule performance

Those of us who are objectively intested in these things would prefer facts over fiction. So what, you don't care or you prefer the fiction?

The source of electricity when you plug-in your electric car is the elecrical grid. That source is not exclusively natural gas, and unlikely so if you live in the eastern United States. Unless I've missed yet another point, to claim a souce of power such as natural gas is somewhat incredulous.

If you look at the table on the webpage (http://www.teslamotors.com/efficiency/well_to_wheel.php ), the last two rows show cars whose source fuel is natural gas. The wheel-to-well ratio decreases as you go down the table. The table suggests that the selected natural gas burning cars provide less efficiency than the selected gasoline burning cars while having slightly less well-to-station efficiency. The well-to-station efficency for the Tesla roadster is the lowest of all in the list, yet the car itself is remarkably more efficent than the other cars. That's no surprise either, because the Tesla roadster is electric.

 

[Phrak]

If you look at the table on the webpage (http://www.teslamotors.com/efficiency/well_to_wheel.php ), the last two rows show cars whose source fuel is natural gas. The wheel-to-well ratio decreases as you go down the table. The table suggests that the selected natural gas burning cars provide less efficiency than the selected gasoline burning cars while having slightly less well-to-station efficiency. [\quote]

Apparently the 86% well-to-station efficiency for the Honda CNG is energy cost for transportation and compression before it arrives at the dealer. Then the 81% number for gasoline is the energy lost in refining and delivery.

The well-to-station efficency for the Tesla roadster is the lowest of all in the list, yet the car itself is remarkably more efficent than the other cars. That's no surprise either, because the Tesla roadster is electric.

This number of 52.2% efficiency for "well to station efficiency" is actually another one that should be suspect. It suggests a 52% efficiency in generating, transporting and converting electricity from natural gas to where it arrives to charge the car. I think this number is only realistic if the waste heat from the turbine is utilized for heating. Waste heat utilization is represtented in only a small fraction of electric power generation plants.

Overall, 30% to 35% is closer to the delivered energy efficiency of power generated via a heat engine. If they insist upon quoting natural gas, sources such as hydroelectric and atomic power shouldn't enter into the calculation.