MIT students adapt regenerative braking principles to shock absorbers

[PaperclipGod]

Originally posted by: Harvey

Originally posted by: PaperclipGod

How is this an improvement over simply stiffening the suspension, then? Less energy stolen by a cushy spring = more energy left to the cars momentum.

"Simply stiffening the suspension" is not the objective. It's intended to soften the ride for the passengers. If the system produces more energy than it uses, and it can store that excess energy for later use, the system is producing a net gain in efficiency.

Right, I understand the purpose of suspension. My confusion stemmed from thinking that the way the MIT guys achieved this energy recovery was by replacing the resistance of the spring with the resistance of their hydraulic energy recovery device. If you had an exactly tuned replacement of the spring with the hydraulic system, the ride comfort would be the same. But as soon as you begin increasing the resistance of the hydraulic system (to produce recoverable energy), you also decrease the ride comfort. Instead, the way I now understand it, this hydraulic system sits on top of the spring, in place of the damper. This works because the spring is still able to fully absorb the shock of hitting a bump, which also displaces the damper. As the hydraulic damper attempts to re-attain equilibrium, the hydraulic fluid flowing throw the impeller recovers energy that would otherwise be lost as heat.

Originally posted by: Harvey

Originally posted by: PaperclipGod
That's not what the MIT guys designed, though. They're not re-using waste heat, they're using the actual force of hydraulic fluid through an impeller to "recover" energy. Yes, if they were actually using waste heat to recover energy, I'd agree with you... but I'd also say they'd have better luck using the engine block.

So they're not going through the wasteful transition from mechanical energy to heat. It's still using the energy that would otherwise be wasted as heat to drive their system. If it's not used, that same energy would otherwise eventually be wasted as dissipated heat.

Think of it in more macro terms. Roads are not infinitely smooth so a car travelling down a road WILL produce mechanical shock energy. This shock absorbing system extracts more energy from the vibration than it requires to operate, and converts the excess to a usable, storable form.

It's a law of physics know as the law of conservation of energy.

Conservation of energy

The law of conservation of energy states that the total amount of energy in an isolated system remains constant. A consequence of this law is that energy cannot be created or destroyed. The only thing that can happen with energy in an isolated system is that it can change form, that is to say for instance kinetic energy can become thermal energy. Because energy is associated with mass in the Einstein's theory of relativity, the conservation of energy also implies the conservation of mass in isolated systems (that is, the mass of a system cannot change, so long as energy is not permitted to enter or leave the system).

Another consequence of this law is that perpetual motion machines can only work if they deliver no energy to their surroundings, and also that devices that produce more energy than is put into them without losing mass (and thus eventually disappearing), are impossible.

Einstein's theory of relativity expands the concept to address the equivalency of mass and energy.

Right... that's exactly why I was perplexed as to how this system was working, which i initially understood to use the mechanical energy of the spring itself (or its MIT counterpart) to "recover" energy, which would mean (thanks to the law you just taught me) that the suspension was just stealing energy from the cars own momentum. It'd be like using a generator to power a fan to blow air through a windmill, and then celebrating the energy recovery.

 

[kylebisme]

Originally posted by: frostedflakes
That's probably the big thing. Will the extra cost of the system be worth a 10% increase in fuel economy. I can only assume that it isn't, or else this technology would probably already be used in hybrid vehicles. I mean it's not a radical idea, I can't believe that somebody wouldn't have thought of and tried to implement something like this already.

Sure, if it was any good then someone would have done it already, that kind of thinking has done much for society.

 

[StageLeft]

10% seems really optimistic to me. Much of the energy in shocks when the car compresses goes back out to pushing the car back up afterward, so as the efficiency there gets closer to perfect, the benefits from this would become more negligible. The hybrid from brakes braking works because brakes only slow and never accelerate a car, so it makes perfect sense to take that completely wasted energy and do something with it.

 

[Fern]

The regenerative shock absorbers developed by the students use a hydraulics system to smooth the ride and capture the lost energy by forcing hydraulic fluid through a turbine that generates electrical power.

It's not clear to me how using the shocks to generate electricity increase gas mileage, unless they're claiming it somehow reduces the load from the alternator. I.e., the electricity generated from the shocks means less horsepower used to turn the alternator, resulting in better gas mileage.

I wasn't aware the alternator had such a large impact on gas mileage?

Fern

 

[CallMeJoe]

Originally posted by: Fern

The regenerative shock absorbers developed by the students use a hydraulics system to smooth the ride and capture the lost energy by forcing hydraulic fluid through a turbine that generates electrical power.

It's not clear to me how using the shocks to generate electricity increase gas mileage, unless they're claiming it somehow reduces the load from the alternator. I.e., the electricity generated from the shocks means less horsepower used to turn the alternator, resulting in better gas mileage.
I wasn't aware the alternator had such a large impact on gas mileage?

Fern

They're using the system to recharge the battery pack on a hybrid vehicle...

 

[kylebisme]

You mean there are cars which run off partially off electricity, WTF?

 

[Harvey]

Originally posted by: PaperclipGod

It'd be like using a generator to power a fan to blow air through a windmill, and then celebrating the energy recovery.

Not at all. You're not applying the engine's power for the purpose of creating the vibration. When you drive, you're already applying power to the drive wheels to put the car in motion, some of which is applied in a way that causes the car to interact with the road surface in undesirable ways, resulting in the vibration that has to be countered by the shock absorber system. In other words, the undesired vibrational energy is a waste biproduct of moving the car.

The object is to redirect more of that inertial energy through a system that harvests it instead of wasting it into the environment as heat.

Originally posted by: TheSnowman

Sure, if it was any good then someone would have done it already, that kind of thinking has done much for society.

I don't know the source, but I believe the Chinese proverb says...

"Those who say it can?t be done should get out of the way of those doing it."

True story -- A high ranking engineer at a major semiconductor manufacturer once told my late co-inventor and me that the specs we claimed for our invention were theoretically impossible. I had the pleasure of handing him our circuit while replying, "That's nice. You've got theory. We've got hardware. Measure this, and tell us again about your theory." :laugh:

Originally posted by: Skoorb

Much of the energy in shocks when the car compresses goes back out to pushing the car back up afterward, so as the efficiency there gets closer to perfect, the benefits from this would become more negligible.

That's why we invented rectifiers that allow current to flow in one direction while blocking any counter-flowing current that would negate the harvested power.

 

[frostedflakes]

Originally posted by: TheSnowman

Originally posted by: frostedflakes
That's probably the big thing. Will the extra cost of the system be worth a 10% increase in fuel economy. I can only assume that it isn't, or else this technology would probably already be used in hybrid vehicles. I mean it's not a radical idea, I can't believe that somebody wouldn't have thought of and tried to implement something like this already.

Sure, if it was any good then someone would have done it already, that kind of thinking has done much for society.

Just saying, I'm sure we'd see this already on hybrids if the fuel savings were worth the cost.

Found this site that says the MIT students aren't the first to try to commercialize this idea, another company is doing something similar (except with a linear generator). So far it sounds like most of the interest is from manufacturers of large vehicles. Perhaps the shocks in consumer vehicles aren't numerous or large enough to harvest any meaningful amount of energy.

http://www.greencarcongress.co...2/mit-students-de.html

 

[PaperclipGod]

Originally posted by: Harvey

Originally posted by: PaperclipGod

It'd be like using a generator to power a fan to blow air through a windmill, and then celebrating the energy recovery.

Not at all. You're not applying the engine's power for the purpose of creating the vibration. When you drive, you're already applying power to the drive wheels to put the car in motion, some of which is applied in a way that causes the car to interact with the road surface in undesirable ways, resulting in the vibration that has to be countered by the shock absorber system. In other words, the undesired vibrational energy is a waste biproduct of moving the car.

The object is to redirect more of that inertial energy through a system that harvests it, instead of wasting it into the environment as heat.

Yes, I get it, what you quoted was an example of what I first thought the MIT guys were doing. I said that to illustrate why I was so initially so incredulous.

 

[kylebisme]

Originally posted by: frostedflakes
Just saying, I'm sure we'd see this already on hybrids if the fuel savings were worth the cost.

Found this site that says the MIT students aren't the first to try to commercialize this idea, another company is doing something similar (except with a linear generator). So far it sounds like most of the interest is from manufacturers of large vehicles. Perhaps the shocks in consumer vehicles aren't numerous or large enough to harvest any meaningful amount of energy.

http://www.greencarcongress.co...2/mit-students-de.html

Sure, I imagined they weren't the first, I had considered such a system myself back before we had commercial cars which could run on electricity. What I was getting at is that though advancements in efficiency one can turn what is impossible or impractical into what would be absurd to go without, as can be demonstrated throughout our history, there is no reason to stop now.

 

[Oceandevi]

I think using any kinetic energy laying around is a good thing. I love this new market of harnessing waste energy. Its badass.

 

[Freshgeardude]

Originally posted by: DrPizza

Originally posted by: senseamp
Do they not teach physics in school anymore?

They do at MIT. However, it's not a requirement for posting in P&N.

unfortunately

 

[PaperclipGod]

So... any of you bandwagon-jumpers feel like telling me where my understanding of physics is flawed...?

 

[CADsortaGUY]

Originally posted by: PaperclipGod
So... any of you bandwagon-jumpers feel like telling me where my understanding of physics is flawed...?

So you still don't understand? What part seems to still be confusing you? I thought you "got it" when thinking of shocks as a "damper"? What else is there to get? The springs still smooth the ride but instead of the shocks just compressing and releasing - the turbine uses that flow of fluid(hydraulic) during compression(and likely releasing) to turn a generator producing electricity. There is no extra input from the car's engine for this to work - it just takes the normal but undesirable vertical movement and harnessing it instead of wasting it. The resistance provided by the turbine would act similarly to the compression of a gas charged shock(damper).


I wept while reading this thread.... one reason is because I nodded in agreement with Harvey, and the other was because I hit myself too hard due face-palm...

 

[frostedflakes]

Yeah, I still don't understand why you think energy lost in the suspension comes from the car's engine.

 

[CADsortaGUY]

Originally posted by: frostedflakes
Yeah, I still don't understand why you think energy lost in the suspension comes from the car's engine.

Well, it does in a way as it's misdirected energy. Energy that was meant for horizontal movement but gets directed vertical due to bumps. However, this is recovering that misdirected energy.

 

[frostedflakes]

Yeah actually thinking about it more, I think you guys are right. Sorry PaperclipGod.

 

[TastesLikeChicken]

Originally posted by: PaperclipGod
So... any of you bandwagon-jumpers feel like telling me where my understanding of physics is flawed...?

It's not necessarily your understanding of physics that is flawed. It's more an engineering issue.

As already explained, shocks are dampers, specifically hydraulic dampers. The hydraulic pressure deviations in a shock can be harnessed to generate electricity. I don't know how the MIT guys did it, but a small accumulator, a couple of ports, a pair of check valves, and an impellor/generator could harness the energy from the pressure flow in a shock to generate electricity on a simple mechanical level. Their electronic controls no doubt helps to maximize the regenerative output.

 

[Moonbeam]

Let's take two basket balls and put them on a table side by side.

Now let's get a pipe of that diameter that we can just fit a baseball inside, but instead of a baseball we use a cylindar of the same diameter that is going function as a piston inside the pipe.

Now imagine the piston is a magnet and the pipe is surrounded by coils such that if the piston moves back and forth in the pipe an electric current will be generated. Now lets put an elbow on each end of the pipe cylindar and put it under the basket balls under the table.

Then we drill though the table and into our basket balls and with more pipe connect the basket balls and the elbows on each end of the cylindar. We now have an airtight U shaped affair with a cylindar at the bottom of the U and the Balls at each end of the U.

Next we pump oil into each of the basket balls with a basketball pump until the oil fills each side of the piston and say half the basket balls. Then we pump air into each ball with equal pressure.

Now the air pressure is pushing against each side of the piston and holding it stationary.

Now we can turn the table on it's side and sort of make a C.

Now imagine that we cut out a length wise slot in the pipe cylinder. The oil won't leak out because under the slot is the wall of the piston.

Lastly, though the slot we drill in a bolt directly into the piston.

If we grab the bolt now we can push the cylindar back and forth up and down the length of the slot, but the forced needed to do so will depend on the air pressure in each of out basket balls.

Now we could attach a car wheel to the bolt just like it were an axle. We could put some rubber at each end of the slot to dampen preventing the piston from traveling too far in either direction.

Now every time the wheel hit a bump it would move generating electricity and causing greater pressure in one basketball and less in the other. The piston would thus be sent shooting back by the pressure and relative vacuum in the two balls causing more electricity to be generated.

If you follow this you can see that nowhere has this anything to do with heat or loss of heat or anything to do with heat at all. Heat will be created in the pressurized chamber and cold in the other relatively speaking. No waste heat is captured or used. Heat, here, has nothing to do with anything anymore than when you compress a spring. A spring stores and releases energy.

The car engine supplies the energy. Energy that is not used in a normal spring suspension will be captured by the spring suspension system I just described. The rigidity of the system will be determined by the volume of air in the basket balls, the elastic properties of the balls themselves, and by the pressure of the air in the system. By varying the volume of air and or the pressure the rigidity of the suspension system can be altered.

The piston I described could be replaced by a propeller, etc. I would think my example would be more efficient.

 

[PaperclipGod]

Originally posted by: CADsortaGUY

Originally posted by: PaperclipGod
So... any of you bandwagon-jumpers feel like telling me where my understanding of physics is flawed...?

So you still don't understand? What part seems to still be confusing you? I thought you "got it" when thinking of shocks as a "damper"? What else is there to get? The springs still smooth the ride but instead of the shocks just compressing and releasing - the turbine uses that flow of fluid(hydraulic) during compression(and likely releasing) to turn a generator producing electricity. There is no extra input from the car's engine for this to work - it just takes the normal but undesirable vertical movement and harnessing it instead of wasting it. The resistance provided by the turbine would act similarly to the compression of a gas charged shock(damper).


I wept while reading this thread.... one reason is because I nodded in agreement with Harvey, and the other was because I hit myself too hard due face-palm...

Right, I do understand how the system works, now. What I asked was where my understanding of physics was flawed, not my understanding of how a cars suspension system is designed.

Do you understand the difference...?

 

[PaperclipGod]

Originally posted by: Moonbeam
Let's take two basket balls and put them on a table side by side.

Now let's get a pipe of that diameter that we can just fit a baseball inside, but instead of a baseball we use a cylindar of the same diameter that is going function as a piston inside the pipe.

Now imagine the piston is a magnet and the pipe is surrounded by coils such that if the piston moves back and forth in the pipe an electric current will be generated. Now lets put an elbow on each end of the pipe cylindar and put it under the basket balls under the table.

Then we drill though the table and into our basket balls and with more pipe connect the basket balls and the elbows on each end of the cylindar. We now have an airtight U shaped affair with a cylindar at the bottom of the U and the Balls at each end of the U.

Next we pump oil into each of the basket balls with a basketball pump until the oil fills each side of the piston and say half the basket balls. Then we pump air into each ball with equal pressure.

Now the air pressure is pushing against each side of the piston and holding it stationary.

Now we can turn the table on it's side and sort of make a C.

Now imagine that we cut out a length wise slot in the pipe cylinder. The oil won't leak out because under the slot is the wall of the piston.

Lastly, though the slot we drill in a bolt directly into the piston.

If we grab the bolt now we can push the cylindar back and forth up and down the length of the slot, but the forced needed to do so will depend on the air pressure in each of out basket balls.

Now we could attach a car wheel to the bolt just like it were an axle. We could put some rubber at each end of the slot to dampen preventing the piston from traveling too far in either direction.

Now every time the wheel hit a bump it would move generating electricity and causing greater pressure in one basketball and less in the other. The piston would thus be sent shooting back by the pressure and relative vacuum in the two balls causing more electricity to be generated.

If you follow this you can see that nowhere has this anything to do with heat or loss of heat or anything to do with heat at all. Heat will be created in the pressurized chamber and cold in the other relatively speaking. No waste heat is captured or used. Heat, here, has nothing to do with anything anymore than when you compress a spring. A spring stores and releases energy.

The car engine supplies the energy. Energy that is not used in a normal spring suspension will be captured by the spring suspension system I just described. The rigidity of the system will be determined by the volume of air in the basket balls, the elastic properties of the balls themselves, and by the pressure of the air in the system. By varying the volume of air and or the pressure the rigidity of the suspension system can be altered.

The piston I described could be replaced by a propeller, etc. I would think my example would be more efficient.

Whoa, awesome explanation, thanks a ton for going step by step like that!

That makes a lot more sense to me now.

 

[CADsortaGUY]

Originally posted by: PaperclipGod

Originally posted by: CADsortaGUY

Originally posted by: PaperclipGod
So... any of you bandwagon-jumpers feel like telling me where my understanding of physics is flawed...?

So you still don't understand? What part seems to still be confusing you? I thought you "got it" when thinking of shocks as a "damper"? What else is there to get? The springs still smooth the ride but instead of the shocks just compressing and releasing - the turbine uses that flow of fluid(hydraulic) during compression(and likely releasing) to turn a generator producing electricity. There is no extra input from the car's engine for this to work - it just takes the normal but undesirable vertical movement and harnessing it instead of wasting it. The resistance provided by the turbine would act similarly to the compression of a gas charged shock(damper).


I wept while reading this thread.... one reason is because I nodded in agreement with Harvey, and the other was because I hit myself too hard due face-palm...

Right, I do understand how the system works, now. What I asked was where my understanding of physics was flawed, not my understanding of how a cars suspension system is designed.

Do you understand the difference...?

So where is the issue then? I don't see why "bandwagon-jumpers" are getting called out when you were the one confused.

 

[Moonbeam]

Furthermore, all the kinetic energy created in a normal suspension system is created by burning fuel to make the car move and is not recaptured. Instead, electricity to charge the battery is generated by an alternator that uses around 1 to 2 HP. Eliminating the alternator and capturing the energy currently wasted in the suspension saves the fuel needed to produce that HP. Capturing energy via breaking would create additional recharging power as would a solar cell skin on the car.

 

[TheSlamma]

Depends on how the roads are in your city.

The turn lane into my work could recharge a 747 in one pass.

 

[Fern]

Originally posted by: CallMeJoe

Originally posted by: Fern

The regenerative shock absorbers developed by the students use a hydraulics system to smooth the ride and capture the lost energy by forcing hydraulic fluid through a turbine that generates electrical power.

It's not clear to me how using the shocks to generate electricity increase gas mileage, unless they're claiming it somehow reduces the load from the alternator. I.e., the electricity generated from the shocks means less horsepower used to turn the alternator, resulting in better gas mileage.
I wasn't aware the alternator had such a large impact on gas mileage?

Fern

They're using the system to recharge the battery pack on a hybrid vehicle...

That's not what the article says, at least the way I read it.

Looks like they're saying all vehicles.

I still think my alternator question is valid...

Fern