28 total posts
Some of this isn't rocket science
but just common sense. Put an electric car and one with an internal combustion engine side by side rolling down the highway and measure the carbon output. Of course, for the electric car, that measurement is zero...impressive, isn't it. The magic is in where the measurement takes place. For the electric car, the carbon emissions have already occurred...far away at the power plant...and possibly even more pollution was created in developing the electricity needed for the vehicle. It's all in where the measurements take place but, "out of sight, out of mind".
Dirty little secret
is that the electricity for the "clean cars" would come from dirty coal !!!!
Or, in the case of France, nuclear...
A lot of truth there, but a couple of points
First, not regarding total world carbon emissions. I can see pollution being "removed" by several miles or more being a plus in cities that the exhaust pollution is trapped by geography or meteorological conditions to build up to dangerous levels.
Second, while I can't address carbon emissions from personal knowledge, I do know from doing E&I maintenance work in the power department of a plant producing a lot of steam and most of our electrical demands, that every year, the standards for emissions after scrubbing seem to go up. Some older boilers are grandfathered as far as what they permit, but when it comes time to do overhauls past a certain degree on the scrubber systems, they have to be updated.
I suspect per watt, most power plants emit no more and probably less carbon than individual automobiles.
That doesn't mean everyone should drive electric cars. But I can see where it is possible or even probable that an electric one does produce less carbon emissions than a strictly internal combustion engine model.
But that there are other matters to be debated, battery disposal and/or recycling etc.
The devil is in the details ...
I don't doubt that stationary power plants are more efficient than the automobile's internal combustion engine. Unfortunately that does not necessarily mean that use of electric cars inevitably reduces CO2 emissions. In addition to the battery disposal issues you mentioned, there are questions related to battery efficiency. Assume the automobile generates 100% more CO2 than the power plant (a WAG, but my impression is that coal plants run <40% efficiency and automobiles <20%). Assume the battery is only 45% efficient at storing/retrieving electricity (counting losses in power transmission, limitations in battery technology, loss of charge while not in use, ...). Efficiency varies by type of battery, and frequently efficiency for either rechargeable batteries or fuel cells is fairly low. In this scenario it is not at all clear whether the electric car increases or decreases net energy expenditure.
The situation is further complicated by the fact that different energy sources produce varying amounts of CO2, ranging from relatively low (nuclear or hydroelectric) to relatively high (fossil fuels)
Something got seriously messed up in that post ...
For some reason the post got truncated:
Assume the battery is only 45% efficient at storing and retrieving electricity (counting transmission losses and intrinsic losses in the battery or fuel cell). In that case it is not at all clear whether the battery powered electric vehicle actually decreases energy use.
I would at this point say the most need for electrical cars in regard to emissions are in thick city traffic where the overall pollution and local concentrations of it is a larger issue than the carbon output and global warming.
One huge downside of electric cars I see is how many employer parking lots are going to have connection points so a car can recharge while you're at work?
We had a couple of people make halfway joking remarks they'd buy an electric car if the company would provide free charging while at work.
But even if metered and charge somehow, it would be a huge project to wire parking lots and parking buildings/garages with an outlet at every slot. And almost certain not to happen in my lifetime, even if they doubled efficiency and recyclability of the batteries tomorrow.
Why do you think this is polically inconvenient?
No voter would object to a 50% lower fuel bill, I think. And it would certainly fit the target of a 20% reduction in CO2 in 2020.
Another inconvenient truth about electric cars
There are 1.3x10^8 joules of energy per gallon of gasoline which equates to just over 36 Kwh per gallon. This means that pumping 10 gallons of gas in 5 minutes time is the same as transferring 4,320 kwh of electricity in 5 minutes time. This is roughly 14.8 million BTUs. According to the U.S. Department of Energy the average household energy consumption is approximately 95 million BTUs per year. That means a 10 gallon fill up is nearly 2 month's of household energy pumped into a car in 5 minutes time (or less). If the power grid now suffers rolling blackouts during peak usage times imagine what will happen when you start connecting millions of cars to it everyday. Electric cars will not be feasible until the power grid is significantly upgraded or we build mini nuke plants for each filling station.
Not sure I follow...
I'm not sure that I follow those figures. In the U.S., the average Annual household electricity use is 10,660 kwh / household. Can you produce 10,660 kwh of electricity from 10 gallons of gasoline?
10 Gallons is roughly 360kwh
At 3413 BTUs per kwh that's 1,228,680 BTUs. Remember as well that we're talking about transferring that much energy in 5 minutes or less, what it takes to fill a car now, not an overnight charge. This means transferring 12 times that amount in an hour, thus a rate of 4320kWh per hour. Google "joules per gallon of gasoline" to work it out in pure units of energy.
BTW, I don't know where your number comes from but according to the U.S. Department of Energy consumption report for 2005 the average energy consumption per household in the U.S. is 95,000,000 BTUs annually. At 3413 BTUs per kWh that's about 28,000 kWh annually.
Did you notice that both of our figures....
come from the same site. I used 2005 information while yours is 2001 but I find it hard to believe it more than doubled in 4 years. At any rate, 10 gallons of gas contains a lot of energy to try and transfer to a vehicle electrically in 5 minutes time or less.
Are you sure about the figures?
I have not researched the numbers, but given the amount of air conditioning/heating energy used by many households and given the limited amount of power that a portable generator can produce from a couple of gallons of gasoline the figures don't make sense.
Your original point, that use of electric vehicles might put a significant strain on the power grid, may well be correct but I'd like to see more information about the figures you posted.
Here's a handy list of conversions
Convert gasoline to joules and joules back to KWH to see a comparative value. Part of the reason you see so little effective energy from a gallon of gasoline is because of the truly inefficient combustion engine. This does mean that you really only need to try transferring about 40% of the energy in a gallon in unit time but it is still way beyond what the grid can handle now considering that it currently gets overloaded with no cars connected. Millions of cars requires a lot more energy than most people realize when you convert it to electrical units.
OK, so ...
When the Governator gets his Tesla Roadster he is actually contributing to the summer time brownouts in California? And it's all in the name of 'Green'?
Sounds like it's time to recall the Governator.
Yep, the reality is....
That a car here and there is not going to cause a noticeable difference but advocating a wholesale switch to electric transportation has real technical obstacles that many people don't realize.
http://www.diyelectriccar.com/blogs/2007/11/six-major-preproduction-electric-vehicles-compared.html shows peak power, continuous power and recharge time for 6 cars.
Now some calculations. Please correct me if I'm wrong.
Say an electric car is used 1 hour a day and uses 50 kW on the average, that's 50 kWh a day (by the definition of kWh). With 300 days in a year that's 15,000 kWh a year per car. If a household has 2 cars on the average, that's 30,000 kWh a year per household. If the current use is 10,000 kWh a year per household, that means a tripling of the electricity use. My estimate for electricity use of households versus other consumers (transport, industry, offices) is that households use 20% of all electricity. So all in all that would mean 40% more use of electricity (80+20 = 100, 80+3*20=140). That would be a sizable, but not impossible, change of the infrastructure.
No one I know has said it would be impossible
RE: No one said it would be impossible
or we build mini nuke plants for each filling station.
Does that sound "possible"?
Can you support a claim that option would be totally impossible? Such plants would not necessarily be reactors. Maybe they could be powered by some type of nuclear batteries.
Such plants would not necessarily be reactors. Maybe they could be powered by some type of nuclear batteries.
Why build a plant powered by nuclear batteries to provide electricity to power electric cars?
Why not just power the car with nuclear batteries?
Then a hazmat licencse would be needed for cars
RE: hazmat license...No problem
I'd prefer a positronic battery.
Positrons worked very well in Isaac Asimov's robots. And it would add some intelligence to the cars and probably make traffic much safer.
Aaahhhh! I see!
We're talking Science Fiction here. That was the general thrust of Critic's original post I think. Glad you guys are now on board!
That has been discussed here some time ago.
This is the link: http://www.hyperionpowergeneration.com/
If such a thing supports 20.000 households, it would support 5.000 households including 2 electric cars per household, if my above calculations are right.
With some 100.000.000 households in the USA, you would only need 20.000 of them to cover the whole USA.