Directory:Power-Generating Shock Absorber

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The Power-Generating Shock Absorber (PGSA) converts kinetic energy into electricity through the use of a Directory:Linear Motion Electromagnetic Systems (LMES).

There are at least two entities who have spent time/resources developing this concept: Goldner et al. and Oxenreider.

Most of the following information was derived from: Emhart/Tech Briefs Contest Winners 2005 - Entry Power Generating Shock Absorber.

Official Website

None found yet.


Image:Power-Generating Shock Absorber 500.jpg

click to enlarge

Graphic by Oxenreider


No U.S. patent found in Oxenreider's name. He referred us to another entity's patent that he discovered after developing the idea first himself.

U.S. 6,952,060 'Electromagnetic linear generator and shock absorber' Inventors: Ronald B. Goldner (Lexington, MA), Peter Zerigian (Arlington, MA) Assignee: Trustees of Tufts College (Medford, MA) October 4, 2005.

Abstract : An electromagnetic linear generator and regenerative electromagnetic shock absorber is disclosed which converts variable frequency, repetitive intermittent linear displacement motion to useful electrical power. The innovative device provides for 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. The disclosed device is capable of high power generation capacity and energy conversion efficiency with minimal weight penalty for improved fuel efficiency.

How it Works

A conventional automotive shock absorber dampens suspension movement to produce a controlled action that keeps the tire firmly on the road. This is done by converting the kinetic energy into heat energy, which is then absorbed by the shock’s oil.

The Power-Generating Shock Absorber (PGSA) converts this kinetic energy into electricity instead of heat through the use of a Linear Motion Electromagnetic System (LMES). The LMES uses a dense permanent magnet stack embedded in the main piston, a switchable series of stator coil windings, a rectifier, and an electronic control system to manage the varying electrical output and dampening load.

The bottom shaft of the PGSA mounts to the moving suspension member and forces the magnet stack to reciprocate within the annular array of stator windings, producing alternating current electricity. That electricity is then converted into direct current through a full-wave rectifier and stored in the vehicle’s batteries.

The electricity generated by each PGSA can then be combined with electricity from other power generation systems (e.g. regenerative braking) and stored in the vehicle’s batteries.


The PGSA is the same basic size and shape, and mounts in the same way, as a standard shock absorber or strut cartridge.

Adjustable Dampening

An electronic control system monitors the requirements of each individual road wheel’s suspension and varies the dampening by quickly switching on or off individual stator coil rings. With all stator coil rings switched on the PGSA produces a strong dampening force which can then be varied for disparate road conditions by switching coils on and off as needed. This provides an added level of benefits in allowing the shock to be very soft in cruising situations (small, high-frequency movements) and instantly change to a sport shock in aggressive cornering situations (longer, lower-frequency movements). Further, the rebound and compression strokes can have different dampening values and application curves depending on performance requirements.

This application could conceivably produce over twenty watts per wheel in normal operation. City driving, with its varying road surface characteristics, as well as stop and go traffic’s font-to-back loading, will generate more power than driving on smooth roads at consistent speeds.

Manufacturing Considerations

Manufacture of the Power-Generating Shock Absorber will require a machined main shaft with embedded permanent magnet stack, a strong air-gap cylinder housing, high quality stator windings, and robust slide bearings. Other systems, such as microprocessor-controlled voltage, current, and dampening regulation, external casing, protective bellows, etc. will also need to be designed and tested.


LMES technology is already finding its place in ocean power generating systems. Its introduction into the automotive world is the next logical step. This technology can be applied to any type of vehicle that employs movable suspension technology and uses electricity in some form as its fuel.


Emhart/Tech Briefs Contest Winners 2005 - Entry Power Generating Shock Absorber

Inventor A: David Oxenreider

David Oxenreider of Boiling Springs, PA, was recently awarded Second Prize in the 2005 Emhart "Create the Future" Design Contest for his Power-Generating Shock Absorber (PGSA).

We received the following by email from David Oxenreider on June 12, 2006.

: While this design idea, application concept, and diagram description are 100% my idea, it seems after doing a patent search to begin the patenting process, I found almost the identical idea has already been patented by Goldner & Zerigian of Tufts College last year. Their idea was originally submitted in 2001, with the patent being awarded in October of 2005. I've had this idea since I saw the first hybrid car at the Detroit Auto Show years ago, but never did anything with it.

: So, even though I came up with this on my own, the old adage is true "he who holds the patent is the inventor". I think it would only be right to put a link to this patent on your site. It's obvious that your very comprehensive site is a clearinghouse for information on new energy systems, and including this link would allow companies interested in developing this idea to know who to contact for licensing.

: If you are interested, my background is actually in artistic design primarily computer graphics and animation. I have a tiny company based around this called Singularity Arts. I am essentially a self-taught mechanical and optical engineer and have designed several laser graphics projectors over the years for the planetarium and science center communities. All my engineering work is done in 3-D CAD and uses solid-modeling techniques. I guess I should have developed this idea long ago, instead of playing with lasers...

: David A. Oxenreider, Visual Design & Animation



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Regenerative shock absorbers developed by team at MIT - A team of undergrads at MIT - led by Shakeel Avadhany and Zack Anderson - has produced a prototype of a shock absorber for vehicles which can harness and generate electricity back into the vehicle. The team claims that their prototype increases a vehicle's fuel-efficiency by up to 10 percent by using a "hydraulic system that forces fluid through a turbine attached to a generator." (Engadget Feb. 10, 2009)

In the News

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. (Green Car Congress Nov. 23, 2008)


See Talk:Directory:Power-Generating Shock Absorber

"This has been done many, many times...Purdue University did it, BYU did it, Tufts University (as another poster noted) and countless other individuals. Everything from extracting energy from the hydraulics to adding magnetic coils....been there, done that. Engineers have been messing with this tech for years...and years....and years." (solipsist61 @ Feb 10th 2009 11:52PM on "Engadget")

NEC Assessment

New Energy Congress member, Congress:Member:Kenneth M. Rauen, gave the following assessment on June 9, 2006.

: With millions of cars on the roads, it will be a noteable "source." Since shock absorbers use hydraulic/pneumatic dissipation of vertical motion, why not capture it and return it?

Related Technologies

Image:Levant Power shock absorber 95x95.jpg
Directory:Fuel Efficiency > Directory:Recuperated Energy > Directory:Power-Generating Shock Absorber > Electricity-Generating Shock Absorbers - Shock absorbers that generate electricity, which are being developed by Cambridge, MA-based Levant Power, can lower fuel consumption by 1.5 to 6 percent, depending on the vehicle and driving conditions. The system can also improve vehicle handling. (MIT Technology Review May 10, 2010)

See also

Image:Autoroute pause222.JPG

Directory:Linear Motion Electromagnetic Systems

Directory:Ocean Wave Energy

Directory:Sea Wave Energy

Directory:Recuperated Energy - Converting the mechanical energy of road transporation (e.g. off ramps) into electrical energy.

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Directory:Fuel Efficiency Retrofits


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