With the advent of the Tesla Roadster, a new generation of 100% battery powered car is upon us. It’s about time. But hybrids with extra battery packs, known as “strong hybrids,” and their counterparts, hybrids that you can plug in to recharge, appropriately known as “plug-in hybrids,” are moving out of the hands of tinkerers and into the mainstream.
An interesting study from CalCars.org, entitled “100+ MPG Hybrids” makes the case that cars powered by electricity from the power grid can get over 100 miles to the gallon. This is somewhat misleading - because cars powered from the grid, to the extent they’re using grid electricity stored on-board, are not getting miles per gallon, they’re getting miles per kilowatt-hour.
Assume a car is a strong hybrid, with range on a battery charge sufficient to fulfill a normal daily commute cycle, and assume that the car is a plug-in hybrid, getting recharged at night from the power grid so no gasoline energy whatsoever is used in its daily functions. This is not a huge assumption - these cars are here today, and soon they will make it out of the tinkerer’s garages and onto the dealer’s showroom floors. How much per mile does it cost to drive these cars?
The math isn’t all that challenging if you are really interested in knowing the answer. First of all, assume a gas powered car gets 30 MPG, and gas costs $3.00. This means a gas car costs $.10 per mile to drive.
Next assume a gasoline powered car has an engine that converts the energy in gasoline into mechanical energy at an efficiency of 25%. This is typical; the rest of the energy is lost in extraneous motion, friction and heat. This means that if a gasoline engine were 100% efficient, that same car could go 120 miles on a gallon instead of only 30 miles per gallon.
Here’s where it gets interesting. A battery will recharge and discharge kilowatt-hours from the power grid at an efficiency of 90%. An electric motor will convert electricity into mechanical energy at an efficiency that is also about 90% (the larger the engine the better the efficiency). This means a battery powered electric car will convert kilowatt-hours from the power grid into mechanical energy at an efficiency of over 80% (90% times 90%).
For this reason, a battery powered car can take that same one gallon of gasoline, using the equivalent amount in kilowatt-hours, and go 96 miles, more than three times what a gasoline powered car can do.
The rest is simple. There are 32.91 kilowatt-hours of energy in a gallon of gas, and the market cost consumers pay for kilowatt-hours is about $.10 (this varies widely, but for recharging at night during off-peak rates $.10 is probably on the high side), which means for $3.29 you can drive an electric car 96 miles. That equates to 2.9 miles per kilowatt-hour, or 3.4 cents per mile. Compared to gasoline powered cars, all-electric cars use far less energy to drive the same distance, and consequently cost far less to fuel.
This is why we will see strong hybrids, plug-in hybrids, and 100% battery powered cars on the roads within a few short years. For references and more in-depth explanations of these formulas, read “The Battery Powered Car.”
September 2nd, 2006 at 7:40 am
The major costs for an electric car is not the electricity it uses.
Those who have ever bought a small toy car know that it’s the batteries that cost a fortune. That Tesla you mention uses 6,871 lithion ion cells batteris. Total cost (wholesale) is around $20,000. Life expectency is 4 to 5 years, making battery yearly costs more than $4,000 plus electricity costs of somewhere around $300. A 25 MPG gasoline car driven 12,000 miles has gasoline costs of less than $1,500 for $3 gallon gasoline. Electric cars are EXPENSIVE to own. It has nothing to do with the costs of a kilowatt hour.
And an electric car loses at least 20% of its capacity by the 4th year. Because of its short range, time required for recharging and lack of recharging stations, no electric car can satisfy a person’s driving requirements. It can only function as a second car. A VERY expensive grocery getter.
September 2nd, 2006 at 8:48 am
You are absolutely right in the points you make regarding the cost of lithium ion batteries. They have other problems, such as with heat management, and Tesla is banking on a lot of improvements in battery safety and cost in order for a car car like that to become viable for the rest of us.
It’s interesting, the point you are making about the cost of the car itself (as opposed to the cost of operating it) is the same point we make with respect to fuel cell powered cars (of course they cost a lot to operate as well, but that’s another story) in our post http://www.ecoworld.com/blog/2006/05/23/the-hydrogen-hoax/
On the other hand, nickel metal hydride batteries are now down to $3,000 per pack in hybrid cars, maybe double that to make a pack sufficient for a 100% battery powered car (and the EV-1 used modified lead acid batteries, actually). I think a serial hybrid car, where a constant RPM diesel powers an onboard generator to recharge the batteries that power an electric motor - but isn’t itself (the diesel) connected to the drive train - is a less complex way to build a hybrid car, and potentially more viable.
I believe we are getting close to seeing electric cars that are affordable for commute cycles - where they have a daily range requirement of 100 miles or less. At least the Tesla puts to rest the notion that electric cars have no power.
September 3rd, 2006 at 8:56 am
Remember when Bill Gates said that computers would never need more than 640K of RAM? The statement made complete sense at the time but the trends were all against him, just like they against gasoline cars today. The gorgeous electric Xebra PK pickup truck costs only 10,000 even when produced in tiny numbers. Yes it’d be nice to have a little more speed and range, but the writing is on the wall. Batteries are improving in leaps and bounds while gasoline prices won’t be stopping at 3,4,5, or even 6 bucks a gallon. To forecast the future, ignore the small obstacles and pay attention to the overall trend.
September 3rd, 2006 at 7:05 pm
As far as price - Maybe it is $20,000 for batteries, but if you look at the Mitsubishi Miev electric prototype, you will notice that there is no cooling system, no drive train, no differential and no transmission. All of that stuff costs money to produce initially, and all break down a lot more than a modern battery. Today’s lithium-ion batteries don’t go bad after 4 years, and the NiMH batteries in the 1999 Prius have yet to fail or lose charge.
September 4th, 2006 at 12:24 am
Regarding the Tesla and battery cost. When you buy a Ferrari, the cost of the vehicle is what it is because of what the vehicle can do. To over simplify the Tesla by speaking in terms of battery cost is missing the point. Battery cost will come down with supply and demand.
September 4th, 2006 at 8:57 am
Actually the Generation II EV1 had NiMh batteries, But in a larger format than is being used in current hybrids. Allot of the problems associated with Lithium batteries are chemistry specific. Lithium cobalt has a tendency to catch fire, slip into a condition called thermal runaway, or explode. This is due to the fact that the chemical reaction of cobalt releases oxygen during a fire..which fuels the fire. Lithium phosphate chemistries do not exhibit this tendency…In short they are inherently much safer. Unfortunately this safety comes at the sacrifice of some energy density. But it is a trade off we can live with. Nanotechnology is bringing improvements in battery technology and Lithiums in the pipeline are now capable of much higher charge/discharge rates…ultimately this will lead to smaller packs and some reduced costs.
Other improvements can be found in changing the way cars are built too….composite materials can be cost effective and competitive with steel, but the manufacturing requirements are different. extensive use of plastics though has some hiddn advantages such as reduced parts count. A part that was traditional made up of several pieces of steel can be molded in a single piece, cutting costs and assembly times. Colors can molded directly into the part, avoiding the need to paint the car.
September 4th, 2006 at 9:29 am
Not all electric cars are the same. I have less than $7000 in my
25 year old conversion, including $1300 for new Lead Acid batteries. My gas bill went from $298 in May to ZERO in July and August.
My solar roof-top system pays for all the electricity.
Maintenance? Tires, Brakes, suspension. I calculate my 1981
Ford Electrica is good for another 25 years. Simple. Reliable, easy
to maintain. My 2nd car, a Chevy 3500 van gets about 11 miles per gallon.
True, I gave up a lot, but I gained much more!
September 5th, 2006 at 12:50 am
“And an electric car loses at least 20% of its capacity by the 4th year.”
A minor problem with this apodictic statement is that the NiCd batteries in my ‘95 Renault Express are so ignorant about this “fact”, that they still have more than rated capacity (147 instead of 136 Ah) after 11 years.
And those people who already drove >60k miles in a Think city, >50k miles with a Twike, or >150k miles with RAV4 EVs without replacing the batteries, must all be aliens from a parallel universe.
The biggest problem with EVs are uninformed and clueless people completely ignoring facts, and not willing to learn.
September 20th, 2006 at 12:14 pm
I never understand why people think there is a lack of charging stations for electric cars. Almost every garage in the country has a 110v outlet. I’ve kept a driving record for many years and have found that I drive more than 200 miles in a day approximately 5 times a year. If I had an electric car my “fuel tank” would be full every morning - I wouldn’t need charging stations scattered all over town.
September 22nd, 2006 at 5:10 pm
The laws of thermodynamics that limit internal combustion engine efficiency are also acting on power plants as well. You’ve entirely neglected the waste heat that’s part of the combustion cycle at the power plant. A high quality combined cycle gas turbine might yield a maximum of 60% efficiency if you’re doing electricity only. Applying that factor to your equation gives a result of about 50% efficiency, i.e. 80% x 60%=48%. That would get you about 60 MPG equivalent. Not bad, but it’s not 96.
October 2nd, 2006 at 4:56 pm
60% Efficiency at the power plant x 80% at the car is valid. So let’s add drilling, refining, and truck transport to gasoline. While pipeline is comparable to transmission lines in efficiency, they don’t go to every home like power lines do. So, considering refining, drilling and trucking, gasoline would likewise drop to around 15 MPG equivalent under this scenario.
Hey, if you’re gonna count production and distribution against the electric car, you should charge it against the gasoline car as well.
October 31st, 2006 at 3:44 pm
“Hey, if you’re gonna count production and distribution against the electric car, you should charge it against the gasoline car as well.”
The important thing is to start at the same starting place and measure the cost from there. Start from a gallon of gasoline. Then use it either to power a conventional automobile, or, alternatively, to fuel an electric power plant and eventually power an EV.
Both require the same starting point. The upstream petroleum production costs accrue to both.
To make the EV vs IC powered behicle comparison by basing the electric vehicle cost on energy in electrical form, while basing the ICE vehicle cost on energy in petroleum form isn’t quite legitimate, in my opinion.
One could make the argument that electricity to power an EV need not be based on a petroleum product if one is considering nuclear, hydroelectric, or coal sources for electricity production.
April 2nd, 2007 at 6:52 am
hi i am a engineering student and would like to give a seminar on nuclear powered car so can you give any information so that i can give this seminar thanking you
June 24th, 2007 at 12:54 am
Well, since most of the salient points where addressed in the above discussion I’ll only add that it’s nice (and more efficient) to have an IC vehicle during cold weather because the waste heat can be used to keep ones feet warm. This is called co-generation and it is very efficient if used correctly.
My idea of an ideal vehicle would be a plug-able diesel hybrid. It would get about 70 mpg on the highway and 80 mpg in city driving when it’s off the grid.
June 25th, 2008 at 4:05 pm
I am no engineer or expert on any of this, but i would think that if we can have transportation modules using electricity made from coal, hydro, solar, wind, or other sources, as well as hydrogen fuel cells, IC petroleum engines, and anything else that develops, our resources across the world will be better utilized and meet more needs for particular vehicles.