Self sustainable vehicle

[david]

I just had a random thought, couldn't they make a self sustaining electric vehicle by using the momentum of the spinning wheels to generate electricity to charge the battery?

[nvllsvm]

What you essentially describe is a perpetual motion machine which the law of conservation does not allow for. However, Toyota Prius's use it's braking system to help recharge it's battery. As for how that works, I'm not sure.

[Stephen Veteran]

your car already does this. its the reason why if you jump start a car, the battery is charged after leaving it running for a while.

it can never be 100% efficient though

[david]

What you essentially describe is a perpetual motion machine which the law of conservation does not allow for. However, Toyota Prius's use it's braking system to help recharge it's battery. As for how that works, I'm not sure.

So you couldn't have a vehicle that has been fully charged at your home, and drive around with having the spinning wheels create energy to keep the the battery charged. I may be dumb, but can someone explain to me in a way I could understand why it wouldn't work.

[david]

your car already does this. its the reason why if you jump start a car, the battery is charged after leaving it running for a while.

it can never be 100% efficient though

The alternator. So basically this idea is debunked because it couldn't generate enough energy to keep the car running?

[Stephen Veteran]

So you couldn't have a vehicle that has been fully charged at your home, and drive around with having the spinning wheels create energy to keep the the battery charged. I may be dumb, but can someone explain to me in a way I could understand why it wouldn't work.

as you will loose energy through sound/vibrations etc of the motor

[laycat]

1/. Energy transfer is never fully efficient, there are always losses through atmospheric heating, noise production etc.

2/. By introducing a method of charging into the wheels you increase the load on the wheels, therefore you're just increasing the rate of energy transfer needlessly incurring additional loss though inefficiency.

[Stephen Veteran]

The alternator. So basically this idea is debunked because it couldn't generate enough energy to keep the car running?

basically yeah.

[laycat]

The alternator. So basically this idea is debunked because it couldn't generate enough energy to keep the car running?

This is actually slightly different. Yes the car does generate energy from the motor running to charge the battery, but it is not energy recuperation, just transfer. The only reason it does this it to charge the battery, it's an inefficient addition of a process in reality.

As previously stated there are research methods into other recuperation methods with a focus on breaking, where the aim is to transfer the energy into say a flywheel instead of just transferring to heat in the break pads. Off the top of my head, doesn't KERS in F1 do this?

[Stetson]

I just had a random thought, couldn't they make a self sustaining electric vehicle by using the momentum of the spinning wheels to generate electricity to charge the battery?

You can't take energy from a spinning wheel without slowing that wheel down some. It's why generators have to have an engine running to keep the generator part spinning while it's making electricity.

If you take energy out of the battery, use it to spin the wheels, and then take the energy back out of the wheels and put it back in the battery, you will have slowed the car back down. You will also not get 100% of the energy you put into the wheels back out of them because of losses from the wire and friction etc.

Basically, the only way to gain net energy from a spinning object is to slow that object down.

Electric cars and hybrid cars already do this, it's called regenerative braking. When you hit the brakes it puts energy into the battery by slowing down the wheels/car. When you hit the gas again it puts that energy back into the motion of the wheels and car, but as said above it loses some percentage in both directions.

Trying to keep a car going the same speed with an electric motor at the same time that you try to generate power back from the wheels with a generator will actually slow the car down more than if you just let it coast. You are taking energy from the motion of the car, converting it to electrical energy, converting it back to motion, and putting it back to the same wheels you took it out of, losing energy to heat and friction all the way.

[david]

Energy from coasting wouldn't work? I'm just too dumb to understand why something has to be slowed down for this to work lol. Oh well

[Stetson]

Energy from coasting wouldn't work? I'm just too dumb to understand why something has to be slowed down for this to work lol. Oh well

Because you can't get energy for free. You can't make energy, only move it or convert it to a different form. If you take energy from a spinning wheel, the spinning wheel no longer has as much energy as it used to.

http://en.wikipedia....ation_of_energy

If you've ever used a generator (like gas or diesel powered), if you plug in something that uses a lot of power to it you will actually hear the engine load down and have to work harder. The more energy you try to pull from a generator, the more energy you have to spend to turn it. It doesn't make energy, it just converts it from gasoline, to spinning motion, and then to electricity.

Here's another way to think about it:

A car could go down the road at a fixed speed without using any energy at all if there were no friction in the bearings, no friction of the wheels on the road, and no air resistance to slow the car down. Those things do actually all exist though, so if you shut the engine off while going down the road the car will slow down and eventually stop.

Since a car is therefore always losing energy (it is escaping from the car, mostly as heat, from the bearings, tires, and from air resistance), you have to keep putting energy back into it to keep it going the same speed.

[david]

Thoughts on this? Self sustaining roller coaster

EDIT:

Nevermind, it was removed. But it was a old Toyota commercial talking about a self sustaining roller coaster a couple years back.

[Stetson]

Thoughts on this? Self sustaining roller coaster

It says the video is private. I will bet though that there is some sort of energy input into the roller coaster at some point. There has to be, because of the friction of the wheels and the friction from the air: http://en.wikipedia....erpetual_motion

Nevermind, it was removed. But it was a old Toyota commercial talking about a self sustaining roller coaster a couple years back.

Maybe they meant 'self sustaining' as in using 'green' renewable energy to power it, like wind or solar.

[david]

Couldn't wind capturing systems work?

or

Using different sets of batteries. Have the the energy from the moving car charge the dead batteries while the car uses the batteries that powers the car.

[Stetson]

Couldn't wind capturing systems work?

If you mean a stationary wind turbine that sends power the roller coaster or charges the battery of a parked car, then yes.

If you mean mounting a wind turbine on a car, then no. Just like with the generator, you will get less energy out of the wind turbine than it takes to move it through the air.

http://www.lghs.net/...PoweredSail.mov

[cacoe]

I'd love to see this car :shifty:

The best option at the moment for propelling anything is solar panels on light high flying aircraft which can fly high enough to get a constant supply of sunlight, and where air resistance is thinner.

Everything else loses energy. You only start with so much fuel with a full tank of petrol. When you start to move, some of it is converted to kinetic energy, causing the car to move. When it's used, that's it, it's lost. Well it isn't exactly, there are many ways it's let off, for example the wind caused by the car moving, the heat generated by the engine. Yes, you can capture some of it and charge a battery for a while but ever wonder why a car with a battery needs to be running for the battery to keep working? It's because it can only hold so much power and you're actually using some of that fuel to power the battery, even though it's being captured from the function of the engine in the first place.

[NitramX9X]

If i remember correctly, an electric generator consists of two parts, one part the rotor which is spinning (because connected to the tires, wind turbine,...) and has a magnet attached on it and it creates and changing magnetic field, and a second part the stator which consists of a copper coil. The changing magnetic field creates an electric charge in the copper coil and that's how you get electricity . The thing is that electric current flowing thru a wire or coil creates a magnetic field the same way that a changing magnetic field creates electricity in a wire or coil and in case of a generator that new magnetic field is opposite of the first one and causes the rotor to slow down. That's why you won't get any surplus energy when you connect an motor to an generator, and only have an energy transfer minus the losses.

[Stetson]

If i remember correctly, an electric generator consists of two parts, one part the rotor which is spinning (because connected to the tires, wind turbine,...) and has a magnet attached on it and it creates and changing magnetic field, and a second part the stator which consists of a copper coil. The changing magnetic field creates an electric charge in the copper coil and that's how you get electricity . The thing is that electric current flowing thru a wire or coil creates a magnetic field the same way that a changing magnetic field creates electricity in a wire or coil and in case of a generator that new magnetic field is opposite of the first one and causes the rotor to slow down. That's why you won't get any surplus energy when you connect an motor to an generator, and only have an energy transfer minus the losses.

Yep, that's right.

If you took away the car part completely and had an electric motor hooked to a generator with the motor draining from a battery and the generator charging the same battery, it would run if you started it with the battery at full charge but the battery would eventually drain down and the motor would stop.

[Stetson]

Couldn't wind capturing systems work?

or

Using different sets of batteries. Have the the energy from the moving car charge the dead batteries while the car uses the batteries that powers the car.

The dead batteries would recharge at a slower rate than the motor would drain the other batteries. You would end up with less energy than you started with.

The difference between how much energy was in the motor batteries at the start and how much was in the generator batteries at the end would be equal to the amount of energy lost due to friction etc.