Road Emissions Dominate Long-Term Global Transport Climate Impact
EMA Says Engine Manufacturers Good to Go for 2010 Heavy-Duty Engine Regs

Electric Truck Exclusively Options Regenerative Magnetic Shock Absorber Technology from Tufts

Electric Truck, LLC (ET) has exclusively optioned commercial rights to a technology from Tufts University that can recharge the batteries of any hybrid electric and electric-powered vehicle while it is driven. The regenerative electromagnetic shock absorber technology was developed by Tufts engineering professor emeritus Ronald Goldner and colleague Peter Zerigian within the School of Engineering and received additional support in subsequent years from Argonne National Laboratory.

At the SAE Government/Industry Meeting in Washington in 2001, Goldner, Zerigian and J.R. Hull from Argonne presented a paper estimating that the percentage of recoverable power/energy for a 2,500 lb vehicle that employs four optimized design regenerative magnetic shock absorbers and whose average speed is 20 meters/s (45 mph) on a typical US highway is likely to be between 20% and 70%.

This result indicates that, with regenerative brakes and regenerative magnetic shock absorbers, electric vehicles might have significantly improved “charge-mileage”. Clearly, this would be a desirable result, especially if the shock absorbers could be manufactured economically.

—Goldner et al. (2001)

The shock absorber uses an electromagnetic linear generator to convert variable frequency, repetitive intermittent linear displacement motion to useful electrical power. The Goldner device uses superposition of radial components of the magnetic flux density from a plurality of adjacent magnets to produce a maximum average radial magnetic flux density within a coil winding array.

Due to the vector superposition of the magnetic fields and magnetic flux from a plurality of magnets, a nearly four-fold increase in magnetic flux density is achieved over conventional electromagnetic generator designs with a potential sixteen-fold increase in power generating capacity. As a regenerative shock absorber, the disclosed device is capable of converting parasitic displacement motion and vibrations encountered under normal urban driving conditions to a useful electrical energy for powering vehicles and accessories or charging batteries in electric and fossil fuel powered vehicles.

—Goldner et al. Patent# 6,952,060

The linear generator comprises an assembly of magnet arrays, high magnetic permeability spacers and coil winding arrays with an innovative magnet-spacer-coil configuration and geometry which uniquely provides for vector superposition of the magnetic fields.

Unlike conventional devices, such as a linear motion generator, a regenerative shock absorber, or a reciprocating linear motor, the Goldner device provides substantially more uniform and higher average radial magnetic flux density throughout coil winding volumes, according to the inventors, resulting in the increase in electrical power regeneration.

In their patent filing, the inventors claim that the regenerative electromagnetic shock absorber system is capable of peak power generating capacity of between about 2 to 17 kW, average power generating capacity ranging from about 1 to 6 kW, and power contribution efficiencies ranging from 8-44% for passenger vehicles traveling at relatively moderate speeds on typical roads encountered under normal urban driving conditions.

For rough roads with bump slopes as high as 0.10 and displacement velocities greater than 1.0 m/s, they claim that the system may generate nearly 50 kW of peak power and nearly 16 kW of average power with a power contribution efficiency approaching 70%.

It is anticipated that, with devices fabricated with high permeability materials having a saturation magnetization of greater than 2.5 Tesla, even greater peak and average power outputs and power contribution efficiencies may be realized from additional increases in radial magnetic flux density in the coil windings.

—Goldner et al. Patent# 6,952,060

Since the technology actively uses the weight of a vehicle for energy recovery, it could help speed the expansion of the hybrid and battery electric vehicle market from cars to vehicles of greater size, weight and payloads, such as SUVs, pickup and delivery trucks, mail trucks, school and city buses and other light and medium duty trucks.

Prof. Goldner and Mr. Zerigian were passionate about the need to lower greenhouse gas emissions and provide some relief to individuals and industry from the expensive and unpredictable costs of gasoline and diesel fuels. They were innovators who came up with this idea more than a decade ago and were truly ahead of their time.

—Martin Son, Associate Director Tufts’ Office for Technology Licensing and Industry Collaboration (OTL&IC)

ET is a privately held licensing and technology development firm headquartered in Greenwich, CT, USA. ET designs, develops, and markets alternative energy technology solutions for the transportation industry, and is seeking a $3 million round of funding, along with sponsors for its Progressive Insurance Automotive X PRIZE entry.




This could be an excellent way to reduce fuel (imported oil) consumption on hybrids and extend e-range of PHEVs and BEVs. With a potential energy saving of 10% to 15% a subsidy would be justified to offset part of the upgrade cost.

Our very rough badly maintained street and roads would offer even more pentential energy savings.

Americans have the knowhow and creativity to develop more efficient machines. What is needed is appropriate leadership for mass production and diffusion.


This could be an excellent way to reduce fuel (imported oil) consumption on hybrids and extend e-range of PHEVs and BEVs. With a potential energy saving of 10% to 15% a subsidy would be justified to offset part of the upgrade cost.

Our very rough badly maintained street and roads would offer even more pentential energy savings.

Americans have the knowhow and creativity to develop more efficient machines. What is needed is appropriate leadership for mass production and diffusion.

Yosef M.

HarveyD, bad roads aren't so great, and here's why: The efficiency of the regeneration may be higher, but it is the efficiency of the power needed to move forward *and* the power needed to overcome the bumps. On a bumpier road you'll recover more but you'll also expend more. So accourding to their own table, for the relatively smooth road you get ~1900 W out of ~9,600 invested, and in the bumpier road you get 17,400 out of 25,000 invested (approx.), which means you still wasted the same 7600 W.

You can't beat the 2nd law of common sense*: Energy can't be generated by wasting it.

Still, getting back all that energy is even better than regenerative breaking, as it's a constant increase in efficiency - wasting the same 7600 W is obviously better than wasting the full 25,000. It only remains to be seen if it can be made economically.

* derived from the second law of thermodynamics, of course:


I was going to mention the second law....

It seems that in order to maintain proper response (equal response times and forces both in the upward and downward direction) this system would actually operate at net energy loss.


I'm sceptic about the figures quoted. If 16 kW of power is absorbed by the shock absorbers - worst case - in a 2500 lb (1130 kg) car they would burn and fall off. That's a very small car, if you include some luggage and passengers in the weight. Imagine the size of the shocks.


And then we can also put wind turbines on the front of the cars and get even more energy back!!!

Just kidding.... This looks interesting. But with all these wound magnetic coils I wonder how heavy it is. With regenerative braking the losses from stopping and starting all that extra weight could be reduced but I wonder if they factored that into the equation.


"It seems that in order to maintain proper response (equal response times and forces both in the upward and downward direction) this system would actually operate at net energy loss."

Could you explain that? Why wouldn't they just generate power in both directions?

GreenPlease, every shock absorber has a component that takes energy out of it - usually a hydraulic restrainer or something. Consider it a low-pass filter that removes all the high frequencies (shocks) and leaves the low frequencies (road going up and down). If it were an electronic filter, there would be a resistoe taking a way some of the energy.

The way I understand their system, it uses the energy that you need to remove from the system anyway - instead of dissipating it as heat, it turns some of it into electricity. This is why it's not operating at a loss - you're using energy you'd have thrown away otherwise - just like in regen breaking.

Yosef M.

That was me, sorry.


Gosh, if you listen to the jailhouse rock thermodynamics lawyers, you would think none of them ever had a suspension system wear out.


Some comments - a: it sounds too good to be true.

b: If we really are loosing that much energy in shock absorbing, why not try to optimize the shocks for fuel economy (rather than ride comfort [ or whatever they are optimized for now] ), or at least put fuel economy in as a parameter (or make it switchable) - sport, comfort - economy.

c: It sounds like it needs independent verification - just how much can you save on normal roads in normal driving.
They may have slanted the figures for the benefit of investors.

Nonetheless, it is an interesting problem to look at, and it can be applied to any drivetrain, so it could be useful.

It would be interesting to see a full "energy diagram" for a typical car to show all the losses.


While we are on it, what ever happened to the Bose suspension system?


The part of this that I have a problem with is that these and many professors, most likely with government money, created a widgit and then sell an exclusive license to a private party. What ever happened to the tax payers having at least a partial ownership in the things they funded? Why not make that widgit available to anyone and everyone? I believe this would increase the likelihood that it becomes available at a reasonable, non monopolistic price.

I want one under my bed.



I will bet that these same professors have a plan up their sleves to create long stretches of washboard and pot-holed roads just to charge batteries.



The shocks should also be able to be used in reverse, to lean the car into the turns. Or with road monitoring anticipate the road surface for an absolutely smooth ride.


Listen to all these rocket scientist!
Regen shock are so logical I've been tempted to experiment myself. A common garden variety hydraulic shock absorber simply converts resisting spring movement into heat. Rally cars have remote reservoirs to help dissipate some of this heat to prevent shock failure. As all the above rocket scientists know heat and energy are directly related so there is power there to be harvested.
This has ENORMOUS potential in motorsport where shock absorbers could be constantly variable. An electromagnetic shock could be tuned to respond to virtually any input. Hook the system up to an on-chip gyro and a 4 shock system can be variable via a microprocessor according vehicle to pitch and yaw.
Bose have been working on a similar system of linear motor shocks since the mid 80s but I think they went too far in deleted the springs making it a fully active suspension system. Linear motors as just ‘shock absorbers’ are a much cheaper idea with more regenerative potential.


Electric shockers sound a lot like wave power.

Lots of spikes, that can be turned into pressure & run through a hydraulic motor?

The linear electric wave buouys have so far not delivered - compared to pressure hydraulics.

We love pot holes.

Jim from Virginia USA

This is a great thread to post this question which has been burning under my skin for quite a while. Are there any metallurgists or electrical engineers out there who can answer it?

I love the idea of improving efficiency in the manner described; however, I see two problems. 1.) The amount of copper used in these coils would be huge, and thus they would be very heavy. 2.) There is a limited amount of copper than can be mined, and between explosive growth of hybrids, and the economies of the BRIC nations, I see copper availability becoming a severe bottleneck in a few years.

Thus, my question: Would it be possible to use aluminum wiring for the windings, or perhaps an aluminum-brass alloy? Al would reduce the weight, and it's quite a bit cheaper than Cu, and it is abundant relative to Cu. Al wiring in USA homes in the 1960/70's was a disaster, but perhaps this application would work. Then again, I've never seen an electric motor with coils made from anything other than Cu. I suppose Cu's great electrical conductivity is critical.

Any experts care to comment, especially about Al-brass alloys (like the 50 Euro cent coins)?

Alex Kovnat

The regenerative magnetic shock absorber sounds to me like an electromechanical active suspension. If you feed energy into this device in the right manner, it can counter unwanted body motion. But then, energy can flow in either direction so you can use it as a shock absorber, which regenerates body motion energy rather than just converting it into heat like a conventional shock absorber.

But I would rather have a smooth road than a bumpy one. Its better not to set the sprung mass into up-and-down motion in the first place, than regenerate body motion once it starts. Unfortunately, perfectly smooth roads are not always possible.


@Jim from Virginia,

At a given weight per meter, aluminium has a lower resistance than copper, therefore utilities like to use it:

I believe aluminium wire is also used in speakers. Google for "aluminium voice coil".

The alloy used for the 10, 20 and 50 eurocent coils is called 'Nordic gold', which is:
89% Koper
5% Aluminium
5% Zink
1% Tin

So that won't save you a lot of copper.

I can see a case for using aluminium wire where weight is important. In-wheel motors for example.

No need to wait with burning questions: I found all answers in 5 minutes thanks to Google.

Yosef M.

@Jim from Virginia (Although I'm only a mech. eng., not a metalurgist):
To answer your first question, the relevant mass in that matter is that of the entire vehicle sitting on the suspension, so the coils' mass is negligible.

The second question is more a question of economics: the cost of energy vs. the cost of materials. This changes over time, so you might see tomorrow's cars having copper-windings, and the cars of 2050 having aluminum-powder or any other cheap and efficient tech of the day. Let the producers worry about that :)


It could replace both springs and shock absorbers (weight savings), and you get an active generate some electricity.. what is there not to like?

You could even lower the car at hwy speeds and reduce drag.

The comments to this entry are closed.