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Old 06-05-2016, 04:34 PM   #21
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Then again, consider how the three hybrid hypercars went about it. Wouldn't it be better to use electric motors driving the wheels directly to overcome boost lag/low rpm issues on the high power engines? Kind of cuts out any inefficiencies of using electric power to first supplement a compressor which then supplements an engine.
Depends. F1 uses the recovery system on the turbo, because otherwise once boost pressure is reached, that energy would be wasted through the wastegate vs the energy being recovered by the TERS and sent to the battery pack. Even then not all of it is recovered and some goes through the wastegate. That's largely a factor of the rules and how much energy they are allowed to recover per lap.
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Old 06-05-2016, 07:38 PM   #22
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Depends. F1 uses the recovery system on the turbo, because otherwise once boost pressure is reached, that energy would be wasted through the wastegate vs the energy being recovered by the TERS and sent to the battery pack. Even then not all of it is recovered and some goes through the wastegate. That's largely a factor of the rules and how much energy they are allowed to recover per lap.
TERS can either send energy to the battery pack, or use it to keep the compressor spooled. But you kind of rely on the turbo making more boost than necessary, cases where the waste gate would have to open. When you're goal is to be full throttle as often as possible, then I can see it being useful, both in maintaining boost between off-throttle conditions and storing unused energy that would normally bypass the turbine. Keeping boost up makes more sense than supplementing low-rpm acceleration since you're keeping the engine in the powerband anyway.

Something like KERS, or regenerative braking makes more sense for everything else. You only rely on momentum, and can use what normally would be heat energy escaping while braking. You don't need to be making full boost to regain the energy. You gotta imagine how much more energy is used to stop a car than is used to make it accelerate. If you use some of it to turn a generator/motor, you have the ability to store way more energy than if you were using what excess energy would have escaped past a wastegate.
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Old 06-05-2016, 07:49 PM   #23
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You gotta imagine how much more energy is used to stop a car than is used to make it accelerate.
The exact same amount.....
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Old 06-05-2016, 07:50 PM   #24
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You gotta imagine how much more energy is used to stop a car than is used to make it accelerate
I usually try to avoid nit-picking, but are you stupid?

In the real world, slightly more energy changes form in order to accelerate the car than to stop it. If you were to eliminate air resistance and surface friction from the equation, than the energy expended in accelerating the car would exactly equal the energy liberated in stopping it.


What, precisely, is the point which you were attempting to convey in the above?
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Old 06-05-2016, 08:30 PM   #25
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The exact same amount.....
Sorry, bad wording. You gotta imagine how much more energy potential the brakes have than the engine does. The brakes almost always can slow a car down from a certain speed to a stop faster than the engine can accelerate it to that speed from a stop.
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Old 06-05-2016, 08:55 PM   #26
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Sorry, bad wording. You gotta imagine how much more energy potential the brakes have than the engine does. The brakes almost always can slow a car down from a certain speed to a stop faster than the engine can accelerate it to that speed from a stop.
Ok, I think we are all familiar with the fact that hydraulic disc brakes can slow most cars more quickly than most engines can accelerate most cars.

Have you figured out a way to capture electrical energy from the action of a hydraulic friction brake?

I'm really confused as to what the point of this is. Does the action of a friction brake somehow relate to electric brake regen in your mind?
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Old 06-05-2016, 09:20 PM   #27
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Ok, I think we are all familiar with the fact that hydraulic disc brakes can slow most cars more quickly than most engines can accelerate most cars.

Have you figured out a way to capture electrical energy from the action of a hydraulic friction brake?

I'm really confused as to what the point of this is. Does the action of a friction brake somehow relate to electric brake regen in your mind?
Interestingly, several years ago Ford was testing a hydraulic braking system in which pumps driven by the wheels were used to pressurize an accumulator in the vehicle to store energy when braking. By design this system can capture energy at a high rate, where most electrical regen systems are limited. I'm not aware of it ever being put in a production vehicle, not surprised though. I bet it was heavy, expensive, and not reliable.
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Old 06-05-2016, 09:32 PM   #28
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Ok, I think we are all familiar with the fact that hydraulic disc brakes can slow most cars more quickly than most engines can accelerate most cars.

Have you figured out a way to capture electrical energy from the action of a hydraulic friction brake?

I'm really confused as to what the point of this is. Does the action of a friction brake somehow relate to electric brake regen in your mind?
Already what most hybrids do while coasting/braking. You can slow a car down via magnetic resistance from a motor-generator, and charge the battery from the energy produced from that. Ideally, you're only really limited by how quickly you want to stop and the grip of the tires. You can modulate how much resistance the motor-generator will provide, use it as an "engine brake", to the point where the standard brakes have to do little or none of the work. There's a lot more energy you can use here than would be drawing anything extra lost from the engine, like how TERS uses excess boost pressure for energy recovery.

This goes back to the hybrid drive vs TERS style turbocharger. IMHO it would make more sense to have a hybrid drive providing power where a boosted engine wouldn't be spooling, instead of a TERS style turbocharger.

I'm going way beyond the e-supercharger discussion, should have kept it on track.
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Old 06-05-2016, 10:11 PM   #29
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Already what most hybrids do while coasting/braking. You can slow a car down via magnetic resistance from a motor-generator, and charge the battery from the energy produced from that. Ideally, you're only really limited by how quickly you want to stop and the grip of the tires. You can modulate how much resistance the motor-generator will provide, use it as an "engine brake", to the point where the standard brakes have to do little or none of the work. There's a lot more energy you can use here than would be drawing anything extra lost from the engine, like how TERS uses excess boost pressure for energy recovery.

This goes back to the hybrid drive vs TERS style turbocharger. IMHO it would make more sense to have a hybrid drive providing power where a boosted engine wouldn't be spooling, instead of a TERS style turbocharger.

I'm going way beyond the e-supercharger discussion, should have kept it on track.
The problem is that the only way this is true (regen doing all or most of the braking) is during light braking, because the batteries in the hybrid can't accept a charge at a rate fast enough to do moderate or heavy braking. Even with ultra capacitors, you run into limits with the electronics being able to carry that much power. Making this work gets expensive and heavy, which undo the benefits of the hybrid system.
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Old 06-05-2016, 10:12 PM   #30
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Originally Posted by Flak View Post
Already what most hybrids do while coasting/braking. You can slow a car down via magnetic resistance from a motor-generator, and charge the battery from the energy produced from that. Ideally, you're only really limited by how quickly you want to stop and the grip of the tires. You can modulate how much resistance the motor-generator will provide, use it as an "engine brake", to the point where the standard brakes have to do little or none of the work. There's a lot more energy you can use here than would be drawing anything extra lost from the engine, like how TERS uses excess boost pressure for energy recovery.
So, to paraphrase, the entire point which you're attempting to convey is "brake regen is a thing."


In what way is the magnitude of the force exerted by a hydraulic disc brake directly relevant to the amount of energy which is capable of being absorbed by an electrical generator?


Or, put another way: "Hydraulic disc brakes are capable of absorbing huge amounts of energy quickly. Re-capturing energy with an electrical generator in lieu of dissipating it as heat is a strategy for improving efficiency. These two concepts are not directly related."
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Old 06-05-2016, 10:46 PM   #31
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Old 06-05-2016, 11:06 PM   #32
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So, to paraphrase, the entire point which you're attempting to convey is "brake regen is a thing."


In what way is the magnitude of the force exerted by a hydraulic disc brake directly relevant to the amount of energy which is capable of being absorbed by an electrical generator?


Or, put another way: "Hydraulic disc brakes are capable of absorbing huge amounts of energy quickly. Re-capturing energy with an electrical generator in lieu of dissipating it as heat is a strategy for improving efficiency. These two concepts are not directly related."
You're right, they're not. Keeping this going draws away from the point of this thread. I shouldn't have brought it up.

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Originally Posted by patsmx5 View Post
The problem is that the only way this is true (regen doing all or most of the braking) is during light braking, because the batteries in the hybrid can't accept a charge at a rate fast enough to do moderate or heavy braking. Even with ultra capacitors, you run into limits with the electronics being able to carry that much power. Making this work gets expensive and heavy, which undo the benefits of the hybrid system.
For now, it's not possible. Hopefully the trend in battery tech continues to the point where it is.
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