Electric Shocks to charge batteries

Post by **Mr Camouflage** » Fri, 13 Feb 2009, 20:48

Saw this on Wired

http://blog.wired.com/cars/2009/02/students-at-the.html

"The regenerative shock absorber uses the oscillations of a vehicle's suspension to generate electricity. Its inventors claim a heavy-duty truck using six of their GenShock shock absorbers can produce enough power to displace the alternator, thereby increasing engine efficiency and fuel economy."

Could have uses in electric vehicle applications.

Post by **fuzzy-hair-man** » Fri, 13 Feb 2009, 21:45

The students developed a shock absorber that forces hydraulic fluid through a turbine attached to a generator. It is controlled by an active electronic system that optimizes damping to provide a smoother ride while generating electricity to recharge the battery or operate electrical equipment. Should the electronics fail for any reason, GenShock works just like a regular shock absorber.

It's hydrolastic suspension just 40 years later

except hydrolastic suspension replaces the shock absorber AND the spring with a single unit capable of lasting something like 40 years or more!

Man that's hilarious!! right I'm off to find some little turbines to hook up to the hydro lines on my mini!

Post by **acmotor** » Fri, 13 Feb 2009, 21:54

Sorry to pour water on it but the energy numbers just don't add up.

The efficiency of a hydraulic pump driving a turbine driving a generator all linked up with hoses and control valves is very poor.
Let me suggest less than 50%, could be more like 30% from experience.
The added weight of the modified shock absorbers and the tray of hyraulics would help increase the energy available though !

There is no question that there is energy to recover, but it would need to be done without adding weight and wasting power in itself.

"The amount of energy available in the suspension is on par with the energy coming out of the alternator," Avadhany said. "It's 6 to 10 kilowatts for a heavy truck and 3 to 4 kilowatts for a passenger car."

My dirty great Landrover has a 130A alternator. So that is around 1.5kW and most smaller cars have 40 to 60A alternators (500 to 750W).
Where did the idea of 3 to 4 kW come into it ? It doesn't add up.

You would be better off replacing globes and headlights with LED/HID if you wanted to save power. Electrical aircond. e.g. prius etc would also save considerable energy over the standard mechanical systems. Toyota have a study on this.

The spin off is active shock absorbers but then that has been done for years. e.g. citroen

Don't get me wrong. I'm into anything electric and pure EV. Just not hydraulic, compressed air or hybrid (if I can help it).

Make the shocks push amps directly and I'm interested !

Post by **Electrocycle** » Fri, 13 Feb 2009, 22:08

yeah there's no reason you couldn't have magnets and coils in the shocks and generate power from them that way.

Of course then it means you can use it as a linear motor and have active damping, but that'll use up all the power you generate (and more!)

Post by **Johny** » Fri, 13 Feb 2009, 22:13

Or feed the car stereo into them for that real SUB-SUB woofer!

Post by **Thalass** » Fri, 13 Feb 2009, 23:34

I've heard of electromagnetic shock absorbers, I think replacing the gas struts with aluminium with strong magnets inside. I suppose you could have plastic struts with wire wound around it for the whole length. It might work but probably wouldn't be worth the effort!

Post by **a4x4kiwi** » Sat, 14 Feb 2009, 01:35

you might be thinking of the Bose suspension.

http://www.youtube.com/watch?v=eSi6J-QK1lw

Post by **Mark T** » Sat, 14 Feb 2009, 14:21

There will be an Electric shock article in the next EV News.

Post by **bga** » Sun, 15 Feb 2009, 19:26

I like the flimsy wires coming off the shock. My guess is that a shock absorber can produce pulses of up to 50kW per wheel (500kg corner, 100mm travel in 0.1 second), maybe more. A capable battery or capacitors are needed to absorb this energy.

The 'Wired' drawing looks like a linear version of a brushless PM DC motor. Hmm, could rectify the 3PHAC and dump it in a resistor - some products may be let-down for any ideas of active suspension.

They mention fuel efficiency, although I think that with good roads, this will be mimimal:

The 2004 fuel efficiency report from EAPA/Eurobitume indicates:
Uneven roads may indicrease fuel consumption by up to 12% (really rough and uneven) and a rough macrotexture (eg cobblestones) by up to 7%, compared to a very smooth road.
I have an associate who is a pavement specialist, he indicates that indicates that the common Australian macadamised country road accounts for a few percent (2-3, I think) of additional fuel consumption.
Most of this produces noise and tyre/sidewall heating and is not recoverable in an electric shock absorber.

The real bonus has to be from ride quality and reduction of suspension components (no sway bars). For light weight vehicles, active suspension could make the car ride a lot better than would otherwise be.
The BOSE body roll and hump demonstration was particularly impressive.

Post by **acmotor** » Sun, 15 Feb 2009, 22:29

bga,

Just to keep that energy number in perspective.
50kW for 0.1 second (both serious overestimates likely to rip the body apart) actually gives around 0.1 Watt hour if you were to extract the energy. The truth is that the suspension needs to be pushed down again after the bump/corner and the system needs to remain fairly elastic with damping only. Shock absorbers are quite mis-named. They are dampers and not absorbers !
Given that a typical EV may have 20 or more kWh battery then the road would have to be very rough for that 1 in 200,000 bump to make a difference !
The road roughness issue results more in tyre energy losses than suspension loss.

Agreed, as I have already noted. The bonus is the ride quality and it is likely that the potentially small energy recovery will be used up in the active suspension function.

Post by **juk** » Mon, 16 Feb 2009, 10:49

"Shock absorbers are quite mis-named. They are dampers and not absorbers ! "

I agree and disagree. Clearly they dampen, but where does the energy go? It goes into the damper, thus the damper adsorbs it, therefor they should be named damper-adsorbers.