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February 9, 2009 2:52 PM PST

Shocks turn a jolt into a volt

by Wayne Cunningham

MIT shock absorber

This shock forces hydraulic fluid through a turbine to generate electricity.

(Credit: M.I.T.)

Every time your car hits a bump in the road, it could be generating electricity. That is, if it were equipped with a new type of shock absorber designed by a group of M.I.T. undergraduates. Whenever this shock absorber prototype gets compressed, it pushes its hydraulic fluid through a turbine, generating electricity. The shock absorber also has a control unit that delivers a smoother ride than conventional shock absorbers, according to the M.I.T. group.

The students came across the idea for the shock absorber after looking at areas where cars waste energy. As regenerative braking is an idea already in use, the students noticed the energy being absorbed by the shocks, and devised a means to capture it. Heavy vehicles generate the most energy at the shocks, and the students have found they can generate one kilowatt per shock from a six-shock heavy truck traveling on a typical paved road.

AM General has shown an interest in the shock-absorber technology for use in the military HMMWV, or Humvee, it is developing. These shocks could also be used on hybrid vehicles to help keep the batteries charged.

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by epross February 9, 2009 3:34 PM PST
Logging trucks would really benefit from this technology. Those logging roads are very bumpy :-)

Sounds like a great idea, if it can be produced cheaply enough.
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by tm_anon February 9, 2009 6:02 PM PST
Put these together with the regenerative braking tech, pop a couple solar panels on top and the electric car is now a possibility for more than just 200 mile round trips. It also would help big rigs become hybridized by equipping the trailer wheels with these and even by making miniature versions and placing them underneath the load. Make massive versions and put them underneath buildings to help earthquake proof them, but also to use the earthquake to help produce more energy (thinking California could benefit from the earthquakes more than the losses caused by them). Add these underneath major highways and it's yet another way to produce cheap electricity without burning fossil fuels.
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by sroussey February 9, 2009 6:31 PM PST
Could be useful to the EPA/UPS hydrolic hybrid:

http://edition.cnn.com/2008/TECH/biztech/10/28/ups.hybrid.trucks/index.html
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by tech_crazy February 10, 2009 1:41 AM PST
Wow, 1kW for 1 sec. Let's see ... that's a whopping 0.3WHr! And at what cost?

For something to be used as a source of energy, the total energy output needs to be considered, and also the cost, not just the instantaneous power. Even mosquito hums are theoretically convertible to electrical energy but nobody uses those. Not every source of energy is sustainable and feasible.
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by JaquesLenoir February 10, 2009 6:31 AM PST
Could you explain your findings? (1kW for 1 sec = 0.3WHr). As far as I know there are 3600 seconds in one hour. So if you produce 1kW in one second you should get, unless I'm wrong, 3.6 MWHr.
by Penguinisto February 10, 2009 6:42 AM PST
He goofed his sources and his math.

It was "1kW per shock from a six shock heavy truck" This means 6kW per bounce... but it'd be one hell of a bump, so I doubt you'd get one per second unless you were in Moab and off-road. Also, unless you had capacitors on board (and I mean some damned big ones), there's nowhere you'd be able to store it for later use.
by freemarket--2008 February 10, 2009 7:33 AM PST
No capacitor is needed. Hydraulic fluid can be pressurized by each shock, even small ones and drawn off slowly to drive the turbine.
by wcunning February 10, 2009 10:30 AM PST
As it was explained to me by one of the team members, as each shock can produce one kilowatt, driving for an hour would produce one kilowatt hour (kwh) of electricity.
by February 10, 2009 1:44 PM PST
The article says "one kilowatt per shock from a six-shock heavy truck traveling on a typical paved road". I understand this to mean that as the truck is constantly traveling along the road, the shock is constantly delivering 1 kW. This incredible!

Power (Watts) is calculated by multiplying the voltage by the current. Therefore if you have 1000 Watts (1kW) at 12 volts, the current should be ~83 amps. (12 * 83.33 = 1000)

83 amps constantly coming from one shock, or even all 6 put together, by constant driving along a regular paved road is very impressive. My mind boogles at all the possible uses for a free 83 amps in a truck.

If the numbers are correct, the patent holder could become very rich.
by February 10, 2009 2:38 AM PST
I'm wondering when someone is going to improve the axle so you can attach extra generators to charge the batteries. It's just so obvious.
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by Penguinisto February 10, 2009 6:46 AM PST
Not really feasible for constant generation - most of your raw power lurks in the engine, where the alternator gets its source... by the time the engine power gets to the axle, there's only something like 3-5% of the original power pool left... and adding generators to that would only induce drag on the axle.

OTOH, there is something similar in place right now, called regenerative braking... where you're braking, you're trying to dump off extra power anyway, so regenerative braking pushes that towards generating juice. :)
by February 10, 2009 8:24 AM PST
I am aware of the drag it would cause but, the the axles are going to to be turning regardless so you might as well use them besides there are plenty of intelligent people out there who could make it would and not just slam after a few minutes for thought.
by RainCaster February 10, 2009 10:10 AM PST
That would be called "regenerative braking", and is already being done on most hybrid and electric vehicles. Are you talking about doing a retro-fit onto existing vehicles perhaps?
by drewu February 10, 2009 12:09 PM PST
To generate power off the axle, you'd have to input more power to go the same speed, defeating the purpose. This is pretty basic thermodynamics.
by Quality_Engineer February 11, 2009 9:55 AM PST
drewu is right about the input vs speed, but it's not thermodynamics, it's the "law of conservation of energy." In physics, 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. And it is basic for those with an engineering background.
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