I have just read an article about CO2 emissions of the Tesla Model S.
I am not stating anything about the article, nor about the author which is well-known in this forum.
My question is about a comment on the article.

In the comment, the question is raised if the solar panels can actually provide the electricity. They question the statement of Elon that the solar panels will provide more electricity to the grid than used for charging. The comment seems logical, but is it true ?

mrspaghetti | 2012年10月10日

Elon's statement speaks for itself.

It is a waste of time to read anything written by Petersen, or the comments by his readers at the end of his articles. Seriously, it adds nothing to any intelligent discussion and I wish people would stop posting links to his idiotic articles.

Shelmire | 2012年10月10日

The question "Is it true" is a legitimate one.

Vawlkus | 2012年10月10日

It is a legitamite question............. But not from that particular source as his biases are well documented.

mrspaghetti | 2012年10月10日

The question "Is it true" is a legitimate one.

Ok, and that question would be legitimate about virtually any statement by anyone about anything. It adds nothing to the discussion.

(Wait, is that true?...)

danielccc | 2012年10月10日

So there are a couple of things you need to know about the seeking alpha piece.
One is that it references a study "published by the Journal of Industrial Ecology", though it never names who put the study together. The reason for that, I suspect, is that the study was written by a group in NTNU, the Norwegian University of Science and Technology, Trondheim. Norway is the Western Europe's #1 oil and gas producer and exporter. The industry is about a quarter of Norway's GDP.
Trondheim is sited right next to Norway's offshore fields. It turns out that NTNU Trondheim has deep links with Statoil, sharing a research center (SINTEF) with 750 people. The head of the department that produced the study won a USD $35,000 award from Statoil last year, and this year NTNU celebrated "Statoil Day 2012" (I am not making this up) to mark the 40th anniversary of the company. Statoil is a major recruiter on campus, as one would expect.
It does not sound like an environment conducive to objective research on the benefits of EVs.
The second thing you need to know is that the study itself uses a number of tricks to skew the numbers, but the main one is that it assumes a high percentage of coal input to electricity generation, by using the European average, which includes former Eastern European countries, like Poland, most of which rely heavily on coal. This not only affects CO2, but also water toxification (from coal tailings), and other parameters.
Having said all that, we don't know what Elon is calculating, since AFAIC Tesla has published no reference design spec for the supercharger stations, or estimated average use load. Being Elon, I am sure these numbers are in some neuron of his somewhere, but I am going to guess they are order of magnitude estimates, since there are a couple of major unknowns at this point:
o How many 60 and 85kWh Model S cars will Tesla eventually sell?
o How many times per year will Tesla Model S owners use supercharging on average?
There isn't a soul on Earth outside of Tesla who can say that the solar panels can or cannot provide the electricity, because without specs or the numbers above they have no data on which to base such an assertion.
Tesla, on the other hand can make adjustments at any time should the capacity of the stations fall short of actual needs. Ultimately it comes down to whether you trust Elon's intent and ability to execute on it.
I think he's shown both characteristics so far. Not to mention, Tesla has an incentive to drive their aggregate net electric cost to zero (though obviously some stations will be net producers and others net consumers).

Schlermie | 2012年10月10日

At the time Elon made that statement, it's definitely true, because there are so few Model S making roadtrips today, those solar panels are spending nearly all their time providing power to the grid and very little time is spent supercharging. Someday, the reverse may be true and his comment may no longer be valid at that time.

Brian H | 2012年10月10日

If you listen to and parse Elon's launch statement, the installations will be de facto designed, built, and run by Solar City. SC will pay the grid charges, and sell back whatever power it generates. This is only profitable if it has excess to sell. In fact, Elon said there will be (net, net) across the n/w enough capacity to run the charging units 24/7. All of them.

Remember, from SC's POV the stations are sites where it can set up as many revenue-generating arrays as necessary to make it worthwhile (using the most convenient, productive, lucrative locations to "carry" any stations not having arrays).

Brian H | 2012年10月10日

by "installations" above, I mean the solar arrays. TM builds the charge units, but the power transactions are Solar City's.

DouglasR | 2012年10月10日

I suspect the solar stations are profitable for Solar City only if TM foots the capital cost of the panels. Otherwise, why would Solar City need to connect the solar farms to charging stations at all? They could simply build solar generating stations. But if you include the capital cost, solar is still more expensive than conventional forms of fuel, say natural gas or coal.

And as we discussed in another thread, I do not believe there is any way the solar arrays on the charging station canopies could generate enough power to run all the units 24/7. The solar panels would need to be sized to cover a supermarket parking lot, not just the canopies on the charging stations.

Brian H | 2012年10月10日

DouglasR +½

Elon: "We're sizing the arrays, with Solar City, to put more power into the system than the cars use, over the course of a year." 6:40 mark, et seq.
So you're right about the 24/7 bit; don't know where I picked that up.
But the stations are "really cheap"; the chargers themselves are all Elon suggests TM is concerned with.
SC is a "sister company", and I would wager Elon arranged the financial setup so that the solar imposes zero pressure on TM. After all, if a homeowner can make installation and net power savings pay over a decade or so, SC can do even better "selling to itself".

DouglasR | 2012年10月10日

Brian H,

When a solar company installs a residential system, the capital cost may be recouped in a decade or so. But the company does not bear the upfront cost of the system, the homeowner does (along with some governmental incentives). The energy is then sold back to the utility, sometimes at an artificially high price. At least that's how they do it where I live. I have to believe that the upfront costs here are being borne by TM, with Solar City doing the installation and management of the system perhaps in exchange for getting title to the excess energy. I think Elon was saying the stations are "really cheap" because, compared to building cars, they are really cheap. Even if the cost is $50k per station, it would still be a great value because of the benefit the network brings to owning a Model S and what that will do for sales.

evanstumpges | 2012年10月10日

While offer PV solar installations at select Supercharger stations is a very welcome gesture from Tesla & Solar City, it is important to realize that once the stations start getting used regularly, it is unlikely that solar energy will be able to offset the charging demands without vastly expanding the array sizes.

To illustrate this point, consider that in San Diego, the average solar insolation for a fixed south facing solar array tilted at latitude had an average solar insolation of 5.7kWh/m^2/day. This is according to NREL data found here:

Over a 24 hour day, 5.7kWh/m^2/day averages out to an insolation of 0.2375kW/m^2. Let's say the solar array efficiency is 20% (this is an optimistic number unless Solar City is using SunPower panels). The usable continuous electrical power produced is only 0.0475kW/m^2. For the sake of argument, I'll assume that the combined inverter and charging efficiency is 90%, which is also an optimistic estimate. This results in 0.04275kW of energy delivered to the car battery per m^2 of solar array area averaged over the course of the year.

Tesla states that each Supercharger provide 90kW of charging power. To meet this demand continuously, a 2,105m^2 solar array would be required (according to the location and specs assumed above). This is over half an acre of solar panels for one Supercharger. To be fair, the actual charging power required should be somewhat less than 90kW since it probably tapers off as the batter gets closer to full. Nonetheless, if these charging stations were ever to be used continuously like gas stations, it would require a lot of area for solar panels to offset a significant portion of their use, let alone 100%. That said, if the Superchargers ever approach 100% continuous utilization, this is a long way off.

To shed a little light on this scenario, this theoretical half acre solar array would be offsetting a lot of driving miles per year! 90kW of continuous power is 2,160kWh of energy per day. The Model S is rated at 2.63mi/kWh according to the EPA. Hence, the solar energy would be enabling 5,680 miles per day (over 2 million miles per year!) of carbon dioxide free driving. Another way to look at this is, it would require about 10m^2 (108ft^2) of solar array area in San Diego to offset 10,000 miles of annual driving.

In my opinion, the best way for EV owners to offset their electricity is to install an appropriately sized solar array at the home or garage.

In the near term, even if a solar powered Supercharger in San Diego were only used once per day, it would need need over 80m^2 (861ft^2) of solar panels. Short story is that it's hard to imagine that Supercharge usage won't rise much faster than solar installations to the point that the solar energy will only be producing a small fraction of the energy supplied...

Sorry for all the technical info and numbers, but this stuff is always interesting to me and perhaps it will be to someone else. If anyone wants to check my numbers or question my methodology, feel free to do so. I'd be glad to explain anything in more detail if it was not presented clearly...

Brian H | 2012年10月11日

Over the life of the installation, or whatever is suitable in each case, the homeowner plans to recoup his capital cost, too. SC would be in the same situation, except with lower capital costs.

The solar "contribution" is not on a per-station basis, but the whole network, over the course of a year. That is EM's assertion. Network demand will be exceeded by total generated power.

TikiMan | 2012年10月11日

If anyone is a member of this idiots web blog, please post this for me... (I love F'ing with these hypocrites)


So you are admitting that man-made CO2 emissions are slowly destroying our planet, via global warming?

Because oil companies, the Republican Party, most conservative Christians, and free-market anti-government regulation groups, disagree with you.

I just want to make sure you realize who you are citing with.



dtesla | 2012年10月11日

Both comments are correct. They are saying different things.

Petersen is correct because the supercharging solar PV will not generate enough instantaneous power to charge your car. So his statement is true, but irreverent.

Elon is correct because when nobody is charging Model S the solar electricity generated is pumped into the grid. The meter runs backward (I have grid-tie solar PV and the meter really runs backward). Someone else uses the instantaneous power. When you need to charge the meter will run forward. In effect Tesla is using the grid as a battery. Elon is saying the [net] will provide more electricity to the grid. To learn more search grid-tie solar.

Brian H | 2012年10月12日

But Peterson's irreverence is irrelevant.

Volker.Berlin | 2012年10月12日