Plug In Cars: How Many "Miles Per Gallon" Do They Achieve?

My literary agent directed me to an article in the New York Times this past week, Plug-In Cars Pose Riddle for E.P.A., which discussed how to measure the mileage of these cars. First, there are no gallons becase there is no gasoline to burn in a plug in electric car. So let's try to sort this out. We can make them equivalent to compare them.

The plug-in Nissan Leaf was described in the NYT article, so I'd like to use this vehicle as an example. Let's assume it takes 50 kilowatt-hours to charge this car during an 8 hour overnight charge. The car is designed to go an average of 100 miles on that charge, but speed, acceleration, weather, using the heater or the air conditioner, as well as the other options, will affect the range.

So how much energy is this and how does it equate to miles per gallon? 50 kilowatt-hours will require about 510,000 Btus (10,200 Btus/KwH)  to be burned at a far-off power plant to deliver that electricity to the Leaf's charger though an electrical outlet. That's the amount of energy in about 4.4 gallons of gasoline. If you travel 100 miles, you've received 22.7 miles per gallon. Not much different than a gasoline powered vehicle, with one exception: The gasoline powered vehicle will take you 400 miles on a tank of gas, rather than 100 miles on a charge.

What about cost? Residential electricity prices can range from around 6 cents per kilowatt-hour in Idaho to 30 cents in Hawaii. The current average price of gasoline in the U.S. is about $2.82 per gallon. This is a little difficult because the price of gasoline across the U.S. is in a tighter range than electricity. Let's assume the average price of electricity in the U.S. is about 12 cents per kilowatt-hour. 4.4 gallons of gasoline will cost you about $12.41. And 50 kilowatt-hours of electricity will cost you only about $6.00, on average, or $3.00 in Idaho and $15.00 in Hawaii.

Why? Why is an electric car, of similar energy efficiency to a gasoline driven internal combustion engine, less costly to run? It's because power plant fuel, coal, natural gas and uranium, are much less expensive on the basis of cost per million Btus than the gasoline you and I purchase at the pump. In a recent post, I reported that at $3.00 per gallon, gasoline cost $26.00 per million Btus. Currently natural gas is $3.42 per MMBtu at the well head and coal will cost an average of $2.26 per MMBtu in 2010 at the mine mouth. One has to add the cost of transport to make the comparison, however, it will not increase the cost by an order of magnitude.

How Many Windmills Does It Take?

In the last post, we estimated that the U.S. would need to double (more or less) the electric generating capacity, 1,000,000MW, in order to power a fleet of 135,000,000 electric cars. Remember, we left out trucks and buses.

Currently, at the end of 2007 there was about 15,600MW of wind generating capacity. Let's estimate, for argument's sake, that at the end of 2008 there was 20,000MW of wind capacity in the U.S. So how many windmills would it take to charge 135,000,000 automobiles?

Let's orient ourselves with some criteria. There are a number of wind turbine sizes available from manufacturers but for our purposes let's assume that we use the largest size--2.5MW. We also assume that each of these wind turbines is running full tilt (no pun intended) during the six hours we're charging the fleet. The fleet is charged at the same time of day, let's say overnight, and that there is sufficient wind to run the turbines at maximum output. None of this is realistic but we're trying to estimate an order of magnitude.

So, how many? Simplistically: 1,000,000MW divided by 2.5MW per turbine results in 400,000 new wind turbines. If we assume our existing fleet were composed of 2.5MW turbines (which it is not), we would have approximately 8000 wind turbines (20,000 divided by 2.5). There are more wind turbine units in the country because the original sizes were smaller, so it could be 2 or 3 times that number. A truly national study of the number of units required might be significantly larger to account for all of the changing variables.

The point is this: there is no time soon or possibly ever that the U.S. will increase the number of wind turbine units by one or two orders of magnitude. Not feasible.

Of course, one could argue that wind turbines are only one source of renewable energy that could be used, and I concede that. But we could make similar calculations for all of the renewable energy sources combined--and as much as we all would like it to--it's just not going to get us there. Moreover, as I argued in a previous post, electric cars are too inefficient and the infrastructure to support them too capital intensive to pursue this ill advised course. It's not sustainable.

The realistic solution in a future post.

Electric Cars: The Electric Infrastructure Required

My literary agent passes on articles to me (She's really helpful.) from time to time and I like to comment on them here. I do this to illustrate and quantify people's qualitative assessments. Back in February I wrote a post about electric cars and suggested that the electric generating infrastructure required should be examined very carefully. So let's do a little quantitative examination of the infrastructure required.

First, let's establish some facts. There are 17,342 electric generators in the U.S. and they have a nameplate capacity of approximately 1,000,000 Megawatts. A Megawatt equals 1,000,000 Watts or 1000 kilowatts. There are 244 Million motor vehicles in the U.S., 135 Million cars and the rest are trucks and buses.

Let's set some design criteria to size our infrastructure. First, I want my infrastructure to be built in phases. So I'm only going to design and build enough power plants, transmission lines and distribution lines to charge and power 135 Million automobiles. We'll deal with the trucks and buses later. In addition, let's size the electric car's motor and let's be realistic. A Honda Civic has a 140 horsepower engine which amounts to a 104kW electric motor. That's realistic. Phoenix Motorcars of Ontario, California provides its SUT/SUV vehicle specifications that I think are realistic. The top speed is 95 miles per hour; it can travel 100+ miles per charge; in can go 0-60 in less than 10 seconds and it requires 6.6 kilowatts for a five to six hour charge. The motor is 147 horsepower or 110 kW. Torque is 369 ft-lbs.

So how much additional power would the U.S. require to instantaneously power all of these vehicles. The utilities that provide electricity to each of us must design and build enough power stations to supply the peak load plus a reserve or capacity margin. The margin is an amount of oversupply in case power plants have an unanticipated outage and avoids blackouts. It's why power in the country is available virtually continuously.

Let's calculate the instantaneous additional power required:

135,000,000 x 6.6 kilowatts = 891,000,000 kilowatts or 891,000 Megawatts.

When one adds a 15% capacity margin, the figure increases to 1,024,650 Megawatts, doubling existing electric generating capacity in the U.S. I have personal, hands-on experience as an engineer and a banker in the construction of power plants. It is a vastly massive undertaking. The people who do it routinely in this country are unknown and unsung . . . except by me, of course, and I have high respect for them and high regard for their skill.

Of course this is an instantaneous figure. It assumes we're all plugged in at the same time. It does not account for time zones, different driving characteristics, different characteristics of the many utility service territories in the country, different size vehicles, different battery technology, and the current overall utilization rate of existing power plants, etc., but it is in the ballpark. One can argue one way or another that it's three quarters of that figure or 50% greater. But it is huge. It is extremely costly. And I haven't begun a discussion of the transmission lines, and the opposition to building them, that would be required as well.

In the next post, we'll take a look at how many power plants would be required and how much electricity renewable energy would need to generate to power the theoretical electric vehicle fleet of the future.

Electric Car Charging in San Francisco

There is an article (http://www.physorg.com/news154288469.html) encouraging the use of electric charging stations in San Francisco as a way of cleaning up inner city air. My first thought is that I spend time in San Francisco occasionally and I find the city to be very clean, without any intrusion on my senses. Moreover, I work in New York City each day and I have spent my entire life in that city, having been born, raised and employed there and no where else. NYC is light years better in terms of air quality than it was when I was a boy.

But let's look at electric cars realistically. From the standpoint of efficiency, they're not better than the traditional internal combustion engine. Each car must be charged with electricity generated at a central station power plant. The average steam electric generating station in the U.S. is about 33% efficient. So two thirds of the energy used to generate a Kilowatt-hour is gone before it leaves the plant. In addition, losses on the transmission and distribution system (the wires that carry power) amount to up to 10% and the drive train of the vehicle, motors, electric power quality, etc. will likely reduce efficiency by a similar amount. Those additional reduction in efficiency, another 20%, reduces the electric car efficiency to around 26%. This is not much better than the internal combustion engine.

One can argue that we are reducing pollution. But are we? Or are we really displacing pollution. Every fossil-fuel burning power plant emits pollution of various kinds and amounts depending on the fuel used. What we do not endure from a tail pipe we still endure from a power plant stack. One can also argue that it's easier to control pollution from thousands of power plants rather than millions of cars and with that I agree. But is displacing the emissions from your vehicles to another community for the sake of your own air really fair?

Before the U.S. embarks on an all out electric car phase, the amount of infrastructure both in terms of power plants and millions, tens of millions, of charging stations should be examined very, very carefully. There has to be a benefit associated with the huge cost, not just the illusion of pollution reduction. Plus, if there's a black out, especially an extended one like the 2003 blackout of a large swath of the U.S., how will cars be charged? Is this potentially a national security issue?

There is a better way at this. One that is more efficient and ultimately pollution free. But that's for a future blog post.