Free-piston engines could be alternative energy alternative
Long ago (last month for example) when fuel prices were high and looked likely to get even higher, it seemed everyone had an idea to improve fuel economy and reduce emissions. While some aftermarket companies played with magnets, it looked like the major OEMs were looking at some form of electric propulsion. Toyota has taken a mostly hybrid route, while GM looks to be investing in plug-in, rechargeable vehicles and Honda likes hydrogen fuel cells. In the end, they're all different ways to create electricity.
But none of those methods are as efficient as an engine design invented in 1928. It's called a free-piston engine, and until now it's been less than ideal for transportation use but could prove to be 50% more efficient than fuel cells at generating electricity.
Basically the engine is two opposed pistons pushing each other back and forth. One past use of the design was as an air compressor where each piston was connected to a compressor cylinder.
But researchers at the Sandia National Laboratory have come up with a new use for this decades-old tech. They have attached magnets to the two opposing pistons that move back and forth past metal coils, thereby creating electricity. The researches claim the free-piston design can easily be modified to run on almost any liquid fuel including hydrogen, ethanol and diesel.
One major problem they'll need to tackle to make the design successful, though, is how very loud the engine operates. The engine also will require a computerized, active control system to keep the piston movement in check.
Trust us, it's explained much better and in much more detail here as well as in a PDF here.
[Source: Technology Review]
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Reader Comments (Page 1 of 2)
hatchbacks are cool 10:17AM (10/17/2008)
It sounds great . But dose it need any coal ? Oh Peak oil is said to happen by 2040 .
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tankd0g 12:30PM (10/17/2008)
Peak oil is said to happen by 1989.
Rocketboy 1:07PM (10/17/2008)
I don't think it would need to be dosed at all. I'm not sure what your question even is.
Yago Bal 10:48AM (10/17/2008)
The OScar project has been working on that concept for a long time, already!
Check it at wikipedia or theoscarproject.org
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Braden 11:26AM (10/17/2008)
One thing I don't get: why aren't all cars "hybrid" in that they use the motor only to generate DC power and then use DC to drive motors in one or more wheels? I always thought that wires were more efficient at transporting power than driveshafts and mechanical linkages are - with wires you should really only have a single loss (during the conversion from mechanical to electrical energy) with very minimal losses due to wire resistance (given appropriately sized wires).
Or do the physics behind the mechanical linkages in a car still waste less energy than the mechanical -> DC conversion would? I didn't pay a ton of attention in physics as the professor was a bit scatterbrained, and I haven't had physics for 8-10 years now...
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Farris 12:02PM (10/17/2008)
Braden - Part of the problem is that you have to go from mechanical energy (generating power) to electrical energy (transmitting the power to the motors) BACK to mechanical energy (turning the wheels). There are losses at each step of the process.
tankd0g 12:30PM (10/17/2008)
Electric motors have drive shafts.
Hamm Sammich 1:34PM (10/17/2008)
When you run an ICE powered vehicle, it is converting the stored chemical energy of the Gasoline into mechanical energy to power the car. However, at specific times in driving a car (such as deceleration and idle) most of the converted power is wasted. A paralell hybrid works relatively efficiently, because it is theoretically using that wasted energy to create some electrical energy, which is then stored chemically in batteries to be used later to assist in propelling the vehicle - by converting the chemical energy to electricity, and then to mechanical energy. Obviously, due to inefficiences, every time you change the state of energy you lose some. Notably a series hybrid converts the stored chemical energy in gasoline in to mechanical energy then into electrical energy, (and some back into chemical energy for the batteries) and then back into mechanical energy to propel the car. The largest benefit of a series hybrid is that the ICE can operate constantly at the most efficient speed (RPM's).
@ Ian - I believe there is some engineering work going on w/ Mazda to use Wankel's in a Series hybrid which could be of benefit due to the rotary's excellent power to weight ratio, and would also allow the engines to operate more efficiently. Another benefit of such a setup is already realized in the Dual Fuel RX-8's in Japan - with minimal mods you can power them on Hydrogen or Gas interchangibly.
John P. 11:38AM (10/17/2008)
This design does indeed look very interesting. Maybe with some noise canceling technology it could be made to sound more quiet.
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Sonny Crocket 11:58AM (10/17/2008)
I sent Autoblog a tip about this, like 3 weeks ago. I first read about it on Kneeslider
http://thekneeslider.com/archives/2008/09/30/free-piston-engine-as-efficient-as-fuel-cells/
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Farris 12:06PM (10/17/2008)
The thing I don't understand with free piston engines is timing. How do you know when to send a spark? How do you know when to open valves?
If the timing was off just a little bit, wouldn't you basically be rocketing your piston(s) through one of the heads? Or, if it was off the other way, you would only ever get one firing at a time.
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tankd0g 12:30PM (10/17/2008)
Hence the need for computer control. I have no idea how the design worked without it, but some sort of tripped timing mechanism was probably used, making the piston not completely "free".
thePeterN 1:47PM (10/17/2008)
Yeah, I don't get how they'd deal with that problem either. But maybe it's an opportunity with the right technology? It might work really well in a Diesel application, or maybe even a Diesel two-stroke application? I guess the problem would still be there when you go to stop the engine.
Ian 12:17PM (10/17/2008)
Don't the Subaro boxed sengine designs exhibit some of the mechanical advantages seeing as the pistons oppose each other in 2 separate banks?
Also why go in this direction given the enherent smoothness and efficiency of the rotary engine design which also works super well off CNG which is 50%+ cleaner than gasoline.
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tankd0g 12:30PM (10/17/2008)
Efficient is not really a word that comes to mind with rotaries.
Ian 4:14PM (10/17/2008)
The actual cc size of a rotary means it produces 2x as much power as a piston engine. For a secondary motor to produce electricity for a hybrid it's a fantastice engine. Efficient in CCs, efficient in physical size/weight, relatively inexpensive to manufacture and ideal for CNG use. Running at a consitent speed of engine the rotary is et.supremely efficient and smoot and quiet
Smeagle 6:48PM (10/17/2008)
Ian, cc's are irrelevent unless you are after bragging rights. When you look at the rate of fuel burned to achieve a certain amount of power, rotary engines are very inefficient when compared to piston driven ICE's.
Richard 1:58PM (10/17/2008)
The engine as represented by the illustration will not work or at least not work very well. An electrical emf (voltage) is generated when the magnetic flux changes through a coil. This is to say that electricity is generated when the magnet enters or leaves the interior of the solenoid wound around the combustion cylinder. In order to maximize its electricity production, the engine should have a short coil on either each side of the engine.It should have at least two magnets--one for each side which passes back and forth through the coil on its respective side.
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1970Dodge 3:12PM (10/17/2008)
Or better yet a whole laminated stack of small disc shaped magnets to improve magnetic flux. and Multiple coils the whole length to maximize power generation, then all you need is a 3(or more)-phase rectifier at the end of that and you have a decent DC power.
I like the idea, even if their PDF says they have a lot of challenges ahead, hopefully they'll figure them out. Seems promising, even though its not completely thought through yet.
Noah 2:17PM (10/17/2008)
Cool idea, would like to see their cooling solution to keep the magnets cool (heat destroys the magnetic property).
However, alternative engine designs have never taken off, save for the Rotary. I think its just b/c nobody wants to learn how to fix a new type of engine.
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