Monday, March 17, 2008

Hybrid Vehicles

By Edward Smallwood

I fully expect to be misquoted on this at some later date. I’m going to do my best to make that difficult. Here's the statement that will most likely be misquoted: I am not happy with the design of any production hybrid vehicle available today. Most of my reasons for disliking the designs are fairly technical, but I will attempt to make them understandable.

Current production hybrid vehicles all have the same thing in common under the hood. They have an electric motor powered by batteries built into an internal combustion engine. Essentially, they are gas-powered vehicles with really big starter motors and a big battery. There are several problems with this, some of which can be addressed after you buy one by modifying it, but some are inherent to the design and can't be changed easily.

No current production hybrid vehicle can be plugged into a wall and have the battery recharged. All of them must use gasoline to recharge the battery unless modified, voiding the warranty. Some people are modifying the Prius so that it has a larger battery and built-in recharger so that you can recharge the battery when you get home or to work. This can increase fuel economy of the Prius to about 100MPG for normal around-town driving. But what this design decision made by the auto makers means is that every mile you run your hybrid car, even if you are running off of battery power only, is being powered by gasoline.

I’m going to digress and discuss the differences between electric motors and internal combustion engines for a moment. Please trust me that I will try to keep it understandable. Electric motors basically use strong magnetic fields to move either a set of coils or a metal cage in a circular motion. The only point of friction (force that takes energy instead of using that energy to move the car) is the bearings at either end of the motor (and a little bit due to air circulation within the motor.) In most internal combustion engines used today, gasoline mixed with air is exploded in a little chamber. This explosion forces a piston to move in a straight line away from the explosion, and then a part called a crank-shaft changes that straight line motion into a circular motion used to drive the engine. The piston has to overcome friction along the walls of the chamber the explosion happens in, as well as that in the bearings in the crank-shaft. In addition to providing the force to move the car, this energy is used to move valves, water to cool the engine, circulate the oil, and many other parts in the engine that do not add power to the system.

This may not be terribly interesting until you realize that every Hybrid vehicle has both of these kinds of engines by definition. Now, imagine that the electric motor of the Hybrid car is hooked directly to the internal combustion engine. Even when you are running on electricity only, your electric motor is turning the internal combustion engine. You suddenly gain an enormous amount of friction that is not part of an electric motor simply by turning the internal combustion engine. So you lose some of the natural efficiency of the electric motor there.

Electric motors are more efficient at more speeds in general than internal combustion engines. This is why we need a transmission in most cars. If you look at the old Saturn electric car it did not have a transmission. It was able to go from a standstill to highway speeds directly from the electric motor. A transmission is made up of gears changing the speed of the motor into a useful turning of the wheels, at least in cars with internal combustion engines. Since an electric car has no need of all of these gears, all adding friction to the system, throwing a transmission into a production electric car would not be a good idea. It would cut into the efficiency of the electric motor. However, all current production Hybrid cars have this system.

There are so many different factors sapping power in these cars that I wondered how they actually compared to much older cars, as far as Mileage was concerned. I went to the government web site to check current mileages, and when I compared a 2008 Prius to a 1989 Geo Metro, I discovered that they get exactly the same combined mileage. Yes, both come out at 46MPG combined city and highway. A car built 19 years ago by an American company got the same mileage as the best we can do today. At least, that's what Toyota wants us to believe.

Most people are unaware that we have a better Hybrid system available today that is being used throughout the world. The fact is that internal combustion engines can be wonderfully efficient power plants in a narrow range of speeds. Current battery technology actually isn't as efficient as a well-tuned internal combustion engine directly connected to an electric generator. This is why all modern diesel-electric trains use a system where a diesel engine turns an electric generator, which powers the electric motors that move the train. I have heard that an American company is planning to make a production Hybrid car that uses a system like this, with a battery thrown in. If they add the ability to plug this thing into the wall to charge up the battery, I can't fault this design. I see no reason they could not make the generator an option, or a module that could be replaced. This would allow most users to simply replace the generator with an extra battery for general home-to-work commuting, and replace that battery with the generator for long-haul vacations and road-trips when you may actually need that kind of range.

I would like to see a car with this kind of power system, and if it actually got better mileage than a 1989 Geo Metro, I would feel good buying an American designed and built car for the first time in my adult life.

I might briefly add ad this point that I do not see Hydrogen as a reasonable alternative to gasoline. It doesn’t matter if we directly burn it in an internal combustion engine, or if we use it to produce electricity in fuel-cells. Most hydrogen used today is produced directly from oil, and since it takes more energy to produce it than it provides, it is not a fuel, but rather an energy storage medium much like a battery. The same will be true even if we use electricity to break hydrogen out of water. Since it is very difficult to store safely in any useful amounts, it will take much longer for it to be useful to us in any way, if it ever does, than simply switching to a hybrid as outlined above. Also, we have yet to completely analyze the effects of wide-spread hydrogen use on the environment. Some preliminary analyses suggest that escaping hydrogen gas could have drastic effects on the environment if we switch to a hydrogen economy.

In addition, I do not see ethanol as a long-term solution. Right now in this country we are seeing corn prices increasing as our food is being consumed to make fuel. This is already having an impact on movie theaters as wholesale popcorn prices increase. Expect your snacks to have a price increase very shortly. Cellulosic ethanol made from corn stalks or switchgrass is still too difficult to make in industrial amounts to make a significant dent in our oil use in this country. Do not expect alternative fuels to change the way we drive.

So, Detroit, the ball is now firmly in your court. Can you meet the challenge? We’re all depending on you.

1 comment:

Ed Smallwood said...

Right now you can make a difference in California. The California Air Resources Board (CARB) is going to vote on changes to the Zero Emissions Vehicle regulation. Car manufacturers are pressuring them to drop requirements to produce Zero Emissions Vehicles. Plug-In America has a webpage where you can make your voice heard on this subject to both CARB and the Governor. Check it out now at