[Palio_2005]

Hi,

Pardon me for an absolute noob question. Mods please delete or merge the thread is not relevant. The question I had is why is it not possible to generate electricity when the EV is in motion? Can’t the kinetic energy of the motion of wheels be converted to electric and recharge the battery?

[torquecurve]

It’s actually a good question which a lot of people do have. Of course you can generate ‘some’ energy when you are just rolling along on a slightly downward sloped road, where your battery energy is not being used but the car is maintaining speed and the regeneration is happening. This however is a very low number, and you will not get the same energy you are putting in to climb the same slope.

However, if you are talking about regenerating while driving itself, then nope, it can’t happen as it goes against the basic law of Thermodynamics.

To achieve the kinetic energy of motion, you are using the potential energy of the battery. But the equation is not exact, meaning PE=/= KE. This is because there are energy losses in heat, friction, etc. For example, some PE is used to overcome the inertia of the tyre and the friction that is there between the tyre and road, the same PE cannot be recovered.

In fact, if you want the motor to act as a generator (which is what happens in regen mode), you have a resistance that the generator creates, which slows the vehicle. If you have an additional generator for the wheels, you will have to overcome the resistance of the generator also with additional power from your motor.

So net net, you will not be able to regenerate on the move - and overall, will not recover the energy you put in. In fact, this is why EVs use low rolling resistance tyres as it makes differences to the range

[dhanushs]

Well, the primary function of the electric motor is to propel the wheels (in a most efficient way) and not generate electricity. Regeneration makes sense only when used as an alternative to any other energy applied to the wheels. Like brakes.

So, the idea of generating electricity while propelling the wheels would be like using an electric motor to power a dynamo which in turn, powers the motor back.

[androdev]

We are in the early days of EV technology. I am sure we will see more optimisations in the future (of course, to the extent that is permissible by thermodynamics and economics). ICE saw similar evolution involving fuel injection, water cooled, higher compression, turbo charging, hybrid technology, etc.

Software will play a much bigger role in EV optimisation which would mean faster evolution compared to ICE. I don’t think regeneration would be the main focus compared to superior battery technology, more efficient motors/generators and algorithm improvements.

It’s the same electric machine that acts as both motor and generator - there is no problem with switching modes, just that there should be decent regeneration potential to harvest. Simultaneous propulsion and regeneration doesn’t have a strong case.

[arpanjha]

Actually for the sake of argument, it is possible to generate electricity while moving considering the basic concept of basic dynamo & alternator route as cited by @anjanc sir. But as pointed out by @torquecurve there will be a net net zero effect. Even if you setup a separate motor and battery unit to charge via the wheels, the car as a whole unit will end up using more than generating.
But you never know, product development life cycle starts with wild ideas. Thanks for sharing this idea on this platform.

[padmrajravi]

Originally Posted by Palio_2005

Hi,

Pardon me for an absolute noob question. Mods please delete or merge the thread is not relevant. The question I had is why is it not possible to generate electricity when the EV is in motion? Can’t the kinetic energy of the motion of wheels be converted to electric and recharge the battery?

Well, If that was possible, all of world's energy problems will be solved. Google the term Perpetual Motion Machines and you will understand the fallacy of that thought. There will always be loss of energy from heat, friction etc and the net will always be negative.

[GutsyGibbon]

More than 65% of energy of an EV is spent on wind resistance and rolling resistance.
https://fueleconomy.gov/feg/atv-ev.shtml

The numbers are much worse for an ICE car.

[mohanphadnis]

Energy can neither be created, nor be destroyed, it can just be changed from one form to another, unless you go nuclear, but let us not go into that realm at this point.
Plus everytime the energy changes form, some will be lost to heat, unless you are changing the energy to heat itself. In which case some is always lost as light .

Moral of the story, regen braking already does what you asked for, but then it slows down the vehicle. With dynamos on cycles, there was an engine (human) continuously pedalling. Just because everything else is inefficient, we did not figure out the extra effort we had to put to run that additional dynamo.

[Torq]

Originally Posted by padmrajravi

Perpetual Motion Machines

Bang on! Running a motor and then using same to generate electricity to charge the same battery that is running the said motor, It's a paradox. Where's the energy loss accounted for? If this would've worked, all the world's energy crisis would be solved!

But, hear me out. What if we utilise a wind turbine generator? How much would it increase the already high wind resistance?
And, can it be coupled to battery to charge while on the go?

[saket77]

The additional amount of drag created by an extra generator will not be equal to the energy produced. So, net-net it may will be further loss.

This is my thinking but members here may substantiate it with more facts and math.

[padmrajravi]

Originally Posted by Torq

But, hear me out. What if we utilise a wind turbine generator? How much would it increase the already high wind resistance?
And, can it be coupled to battery to charge while on the go?

It is the same. The energy generated will always be less than the energy lost in wind resistance while operating the turbine.

[roy_libran]

Ki + Ui = Kf + Uf where:
i = initial & f = final
K = Kinetic energy & U - potential energy

You can't outrun this guys, so where are we going with this thread?

[speed79]

When the concept of motors and generators was introduced in school (grade 11th or 12th), I always used to wonder why we can not use a small motor to drive a big dynamo and generate electricity, and that would give us an inifinite amount of energy created at a low cost (as against the law of conservation of energy which states that the energy can neither be created nor destroyed. It can change from one form to another.)

With this question in mind, I went on to one of the best Engineering colleges of India and got admitted for B.Tech. in Electrical Engineering, and my query was answered as I learnt more and more about motors and generators. To drive a dynamo, one needs torque. Bigger capacity the generator is, larger is the torque needed to turn the dynamo.

So if you try to run the dynamo using rotation of moving wheel of a car, you would effectively be putting on brakes, as the torque used for turning the dynamo is taken away from the wheel. That is what regenerative braking does. When we apply brakes in an EV, it causes dynamos to be turned by the wheels, applying torque in direction opposite to rotation of wheel, thereby charging some battery.

PS. I am not an Electrical Engineer by profession, just by degree.

[SKC-auto]

Let me try to explain in a simple example:

Normal Nexon EV range: 200kms
Nexon EV range with this setup: <135kms( as shown by GutsyGibbon wind takes 65% energy)

Normal NEV: 1 motor + 1 battery
New setup NEV: 2 motors + 2 batteries(one set for running the car, other set for capturing power)

Remember, the same motor and battery switch as power source and storage in the case of regenerative braking.

[locusjag]

Originally Posted by Torq

What if we utilise a wind turbine generator? How much would it increase the already high wind resistance?
And, can it be coupled to battery to charge while on the go?

Aircraft have Ram Air Turbines (RATs), working on the same principle.

And then, I found myself raising my eyebrows at some of the things I read on Wikipedia on RATs. It turns out that some aircraft from the past and present use RATs as more than just a hail-mary fail-safe option.

https://en.wikipedia.org/wiki/Ram_air_turbine

A ram air turbine (RAT) is a small wind turbine that is connected to a hydraulic pump, or electrical generator, installed in an aircraft and used as a power source. The RAT generates power from the airstream by ram pressure due to the speed of the aircraft.

In some early aircraft (including airships), small RATs were permanently mounted and operated a small electrical generator or fuel pump. Some constant-speed propellers, such as those of the Argus As 410 engines used in the Focke-Wulf Fw 189, used a propeller turbine on the spinner to power a self-contained pitch governor controlling this constant speed.

MILITARY USE
RATs are common in military aircraft which must be capable of surviving sudden and complete loss of power.

In other military uses, pod-fitted systems such as the M61A1 Vulcan cannon or high-powered electronics such as the AN/ALQ-99 jamming system can be powered by a RAT in standard operation. This allows their installation on a standard hardpoint, without requiring a pod-specific power supply. Also, some free-fall nuclear weapons, such as the British Yellow Sun and Red Beard, used RATs to power radar altimeters and firing circuits; these were a more reliable alternative to batteries.

CIVILIAN USE
The Airbus A380 has the largest RAT in the world at 1.63 metres (64 in) in diameter, but around 80 centimetres (31 in) is more common. A typical large RAT on a commercial aircraft can be capable of producing 5 to 70 kW, depending on the generator.

RATs have also been used to power centrifugal pumps to pressurize the spray systems on aircraft that are used as crop dusters to deliver liquid agents to cropland. The major reason for choosing a RAT is safety; using a RAT in the United States allows an FAA-certified engine and power systems on the aircraft to remain unmodified. There is no need to use an engine power takeoff to drive the pump, as the pump can be placed low or below the exterior of the airframe, greatly simplifying plumbing. Being the lowest point in the plumbing, it will have gravity feed from the spray tanks and never need to be primed. In the event of a pump failure that could result in seizure, there is no effect on the flying ability of the aircraft or its systems apart from the fact that the spray systems are non-functional.