Can someone please explane to me

and what, exactly, would you use as the source of the energy to drive the alternator? the battery? drain down the battery to charge it ? you'd get nowhere. actually, you'd run down the battery , nothing is 100% efficient.

you can't create energy out of nothing.

a gas car uses the energy in gasoline to run the alternator.

 

Just design it for us, we'll test it out, then we'll proclaim it a "Perpetual Energy Device (brother to the Perpetual Motion Machine), and you'll be instantly and fabuously well known and rich.

Circular thinking will get you everywhere.

ZC1

 

In simple terms: "There is no such thing as a free lunch."
If this were possible, we would have the first perpetual motion machine (a physical impossibility). The alternator on a conventional ICE car is driven by a belt, which is driven by the engine. Some of the mechanical energy created by burning fuel in the engine is used to turn the alternator, thus that energy is not free but is factored into the total fuel consumption of the vehicle. If an alternator was installed on an electric car, the electric motor would have to spin it. So, in a perfect conversion, the energy drawn from the battery to spin the alternator would be replaced by the energy generated by the alternator resulting in a net gain of zero. Compounding the problem is the fact that energy conversion can never achieve 100%, so some of the battery's energy would be wasted in the process, resulting in a negative net charge. A physical model for this would be a tank filled with water (i.e the battery). Out of one side of this tank you have a pipe where water drains out and spins a waterwheel and then drains off into the environment (i.e. the electric motor driven wheels of the car). An alternator would be the equivalent of another pipe on the other side of the tank with water pouring out of it. You could stand there with a bucket (i.e. alternator) catching this water as it spills out and returning it to the tank. Not only would some water spill on the ground while you emptied the bucket back into the tank (conversion inefficiency), but you would not be adding any water to the tank that was not already in it.

 

Energy IS created out of nothing, it's just WE can't do it.

ZC1

 

Ron C,
Here's a good graphic example of your question.
Think of the water in the picture as the generated electricity you describe.

Do you see anything interesting here?

ZC1

 

i think what he's driving at (unless it really is asking why we dont have perpetual motion machines) is why we dont use a system like the prius does with regenerative breaking, just with an all electric car, that obviously wouldnt run the motor to recharge the battery thats...running the motor.

unless they already have that.

 

Uh, yeah. The Rav's definitely already have that. FAR superior to the Prius system. I hope you're right that regen is what is being asked about. Generous of you to consider that!

Unfortuantely, he is talking about "charging while driving." I'm afraid we really are talking about perpetual motion.

 

Because the alternator is powered by the engine. And the alternator doesn't power the car's movement, it only powers the electronics.

 

The second law of thermal dynamics: entropy always increases.

The engine converts about 1/3d of the gas energy into power of which most goes to the wheels to keep the car rolling. The battery has a net energy change of zero, it adds or subtracts as needed to keep the engine in the most efficient power range.

The electric car battery has to provide power to the wheels to keep it running. To simplify the math, treat this as the 100% efficient path.

If has to also turn an alternator, only about 92-95% of the alternator turning power comes back out as electrical power. This electrical power then has to either go to the wheels (if you are lucky) or into the battery with about 90-92% efficiency. So this worst case means:

.95*.92 ~= 87% efficiency with about 13% being lost as heat
95% if the alternator power goes to the wheels with a 5% loss
100% if the alternator is never involved
​

Your choice.

Bob Wilson

 

Giant magnet to the back of a truck is a WAY better idea.

 

To the OP, get into a small car, one with a 1200cc engine or less, drive it until the engine is warm and it is idling nice and smooth, now go to a quiet place, not a park because there are too many birds, try a car-park after hours in a quiet suburb.
Now with the engine idling I want you to turn the headlights on high beam and listen to the engine. You might need to turn them on and off a few times. You will hear the engine load up a little bit, that is because the electrical system places a load on the engine via the alternator, it doesn't just free spin but it requires real energy input, that is revolutions and effort to generate electricity. This shows there is a small cost in petrol for driving with your lights on.

Now for safety I want you to turn off the engine and open the bonnet of the car. Using a torch (yanks call it a flashlight) find the alternator under the bonnet. Now feel the alternator and you will feel it is warm, now feel the battery and note that is also warm although not as warm as the alternator, this heat is energy which has escaped from the system, there is also heat loss in the wires and motors. You may also notice the heat lost from the radiator to the air from that internal combustion engine, one of the reasons it is only 20% efficient.

So you can see that if we put energy into an alternator you get less usable energy out because some is lost as heat, and you could hear that the energy required to turn the alternator increases with electrical load and comes from the engine.

So you can now see that you can't get out what you haven't put in, if you could we wouldn't have an energy crisis.

 

I hope Bob's happy with his new sunroof, which was created after said truck hit the brakes.

 

This is just like those who think burning 'clean' fuels will be the cure for global warming. There really is no such thing as a free lunch. Burning anything in oxygen converts that fuel and oxygen into carbon dioxide. You can't convert the chemical potential energy in a battery into mechanical energy and back again without losing some (inefficiency) nor can you avoid burning fuel to charge that battery in the first place. We're prisoners of the laws of thermodynamics- that's why we call them laws.

 

You can burn hydrogen in oxygen and you don't get any carbon dioxide.
You can recharge a battery using solar or nuclear power without burning any fuel and without making any carbon dixoide.

 

To obtain hydrogen you need to put energy into it which most likely came from carbon.

Yes but you need to put energy in from somewhere, I think that is the point being made.

I disagree that using biofuel isn't clean energy, you capture carbon from the atmosphere then burn it and release it into the atmosphere then capture it in a plant then burn ... can you see a pattern?

 

You are just talking about the Prius here, I assume? The OP is talking about EVs... and you certainly don't have to burn any fuel to charge the batteries of a real battery car. I sure don't.

 

Someone's gotta burn some fuel to ship those solar panels to your house. Some power plant has to burn some fuel to provide power to the solar panel factories.

But yeah, your right. You don't have to burn any fuel. And like they say in risk management: "Transfer" the risk of burning fuel

 

You're being kind of silly with this point. If you want to play this sort of game we can always look at the option of manufacturing and shipping the panels with clean energy, perhaps even more solar.

Tom

 

What will you use to power the alternator?