The problem with gasoline engines is that their torque, speed characteristics aren't suitable to use in an automobile.
Well I would not say "not suitable" as they have been used quite successfully in cars for 100+ years but not ideal for sure. And they have acquired quite a few flotsam and jetsam of technology to help them in that task over the years and gasoline itself needed to be improved - first with Tetraethyllead, then without it to increase the octane number and many more.
Diesel engines are even worse.
Indeed. As I mentioned before, while diesel engines have more torque and better mileage their usable rpm band is narrower than on gas engines. That is even worse on big rigs which is the reason why they have many gears - 18 or even more.
In fact gas and diesel engines run the most efficiently at a single speed, the exact opposite of the requirements of a car.
As Loren said, that makes pure ICE generators coupled with electric motors so potentially attractive.
You have to have a large engine with a lot of horsepower to compensate for the short comings of the engine.
Well if you add enough horsepower you can do with fewer gears and vice versa.
Electric motors have none of these disadvantages. Electrical motors used in vehicles are designed to provide maximum torque at zero speed. You don't have to oversize the electrical motor to gain torque at disadvantageous speeds like you do for the gas engine. You can size the motors for the maximum power required cruising at the highest speeds. Electric motors can easily provide two to three times torque for short periods to accelerate the car. Electric vehicles in fact have to be designed with torque limiting to keep from damaging the mechanical parts of the car, wheels, tires, etc.
All true. The biggest drawback of the electric car has always been the battery.
Electric motors can be designed to provide torque over the entire speed range of the wheel. This means that you don't need gearboxes.This means that you don't have to shift gears.
Well, most still use a single speed gearbox but that is a lot simpler than even a conventional manual gearbox. You don't even need a reverse gear because you can reverse the motor. That said, a car like Tesla Roadster would have benefited from a second gear because its top speed was a rather limited 125 mph (even a Golf GTI makes it to almost 150).
We are now to the point that we can design motors that fit in the wheel of a car, in the wheel hub. The rotor of the motor is held stationary in relation to the car and the housing of the motor rotates around it as the wheel hub. Think of an old fashioned drum brake. The shaft of the motor is the wheel spindle.
I wonder why they are not used more. I guess it's because a) it's difficult to integrate any reducing gears and b) they increase your unsprung mass considerably.
And talking about brakes, the electric motors act as the main brakes for the car. The motors are turned into generators when you have to brake. The kinetic energy of the car mass moving is converted into electrical power that is returned to the batteries. You only need a combination emergency/ parking mechanical brake, it requires electrical power to use the motors as a parking brakee
Regenerative braking is great because you get some of the energy back. I think you will still need standard friction braking for quick stops though.
The reason gasoline became the fuel of choice and dominated all automotive technology for more than a century is quite simple. It was the only liquid hydrocarbon which could be used anywhere on the planet, any time of year. Gasoline will ignite at temperatures far below freezing and remain a liquid at any ambient temperature. This alone was such an advantage, engineers worked tirelessly to overcome all the other inherent short comings of the gasoline engine.
Yes, in addition to other disadvantages diesel fuel starts solidifying at much higher temperatures.
Another big advantage is it's energy density, and cheap price and ubiquity of oil (well up until recently at least).
Yup. I think in not too long we will be seeing the second generation of hybrids--gasoline-electric or diesel-electric designs.There will be an engine but it won't be connected to the wheels, only to an alternator. A battery pack will act as a buffer.
Not pretty soon but right now. BMW's i3's optional range extender acts that way.
The engine will have only two speeds--idle and producing power. (And I'm not sure that idle speed is even needed.)
And if you design the engine for a single speed (instead of taking one off the shelf) you can make it much simpler and lighter. Alas on the i3 it's a motorcycle engine and I do not know how much redesign (simplification) they did.
For maximum efficiency we would use a turbine. Lots of power, small, quiet, very few moving parts, efficient at speed. They're not used much now because they have truly abysmal idle/low power performance but for an engine that only will be running at it's good speed that doesn't matter.
There is a sort of inverse relationship between good as prime mover and good as generator. Turbines run best at very high rpm, which makes them bad for driving wheels but very good in producing a lot of power efficiently and in a small package. And if you already have an electric motor and batteries you don't want to be adding a clunky ICE as well so this is perfect.
And there have been concepts, everything from a futuristic
Jaguar sports car (which also uses SimpleDon's hub motors) to
Walmart semi truck but alas, nothing in production just yet that I know of.
Another thing to look for is hydrogen fuel cells that I think especially Honda is keen on. You basically have an electric car with power produced from combining hydrogen and oxygen through a membrane rather than having a battery. Biggest advantage is obviously the refueling time since no charging is necessary. A hybrid of sorts would be possible where you can recharge limited battery capacity very cheap at home/work when you have time but fuel up with hydrogen on longer trips.
