Toyota Describes Combustion Engine That Generates Electricity Directly

cartechboy writes: "While electric cars are now more available than ever, combustion engines will remain for decades to come. Now auto engineers are working to refine combustion power as part of cars that are increasingly electrified, including plug-in hybrids. Toyota's new 'Free Piston Engine Linear Generator' (or FPEG) shows us one potential way. Linear engines eliminate the rotating crankshaft of conventional engines in favor of a single chamber, in which a piston moves forward and backward. A linear engine has no crankshaft, nor connecting rods. In their place is a gas-filled chamber, the compression of which functions like a spring — returning the piston after the expansion / combustion phases of a typical combustion cycle. This back-and-forth motion can be turned into energy, when you haven't got a crankshaft and the mechanically-useful rotation it produces. While linear engines are far from new, and Toyota's test units are only 10 kW (13 horsepower), a pair of them can still produce enough electricity for a Yaris- or Corolla-sized vehicle to cruise on the highway at 75 mph."

Comments

Efficiency?

[Dan East]

The real question is how efficient is it? The article doesn't say. It might be simpler mechanically than using a crankshaft to generate rotational energy, but that doesn't mean it is more efficient than an alternator / generator method of producing electricity.

Re:Efficiency?

[kimvette]

The real question is actually, will the car be safe? with 13hp*2, 0-60 will likely be in the high 20s. Not very good for merging, or crossing traffic, or going uphill, or even hauling groceries. Think sub-VW Beetle performance, considering that a Beetle weighed in at less than half the weight of today's nannystate-mandated safety features.

Re:Efficiency?

[kimvette]

Okay anonymous coward, tell me this: what happens when you have a very long incline for miles, such as found on I-84, I-76, I-80, I-70, etc. and your batteries run down? Granted most of it isn't steep, but very long distances. Also, what happens when the cells have worn out? The generator has got to provide enough power to drive the electric motors directly in order for the car to be streetworthy. Also, is 75mph the top speed? Speed limits are now 70 or even 80 or 85 on more and more American highways, and the minimum is usually 10mph under the posted limit. Again, on long inclines, when the batteries have drained, will the generator provide enough current to keep the car moving at legal highway speeds?

Now, it's time to turn your snark around against yourself.

Re:Efficiency?

[Blaskowicz]

Nobody has used them because they need some high tech. From what I've read free-piston engines need to be computer-controlled at a very high rate, else the technology is unworkable. Something like an Intel 8051 wouldn't keep up, so for that reason alone it was not invented 30 years ago.
Writing the firmware must be hard, as hinted by the wikipedia article's end. Maybe that requires a lot of computer simulations, which is easier to do in the 2000s and 2010s to say the least.

I do agree a portable generator would nice, or a lightweight vehicle that doubles as a power plant. 10 kilowatts would be pretty good for audio gear, lighting and an ice machine to keep the beer cool.

Re:Efficiency?

[Crayz9000]

Effectively?
Mechanical losses are a major issue with cars, particularly when dealing with power losses through differentials. Friction will quickly make you its bitch, which is why everything must be kept well-lubricated, and even then you have to keep the viscosity to an absolute minimum to avoid fluid load.
A completely electric drivetrain, if done right, can eliminate almost all of the moving parts that contribute to power loss. Electricity, wires, and motors. It doesn't get much simpler than that.

The vibration must suck

[drinkypoo]

So you're gonna need at least two cylinders. But they'll have to be opposed and they'll have to fire in time, because otherwise they're not going to help you. I don't have any trouble believing they can synchronize them, but this makes the engine a lot longer, and you might as well just build a boxer. If the gas seal on the chamber on the other side of the piston fails, your engine will fail spectacularly. Seals fail all the time. Meh.

Why use the gas chamber?

[140Mandak262Jamuna]

The description talks about using a gas chamber as a spring to push the piston back to starting position. Why? There is no crank shaft on the other side? We could imagine a dual acting piston with a combustion chamber on both sides. In a regular IC engine there is a flywheel to do the intake, compression and exhaust strokes soaking up the energy from the power stroke. Even with a dual acting piston, there is an issue there.

The linear generator is also a motor. We should be able to use the magnetic fields to move the piston back and forth. Mechanical complexity of cams, crankshafts and flywheels and clutches replaced by the electrical complexity. Easier to handle and more reliable too. But still don't see any reason to believe it is going to be more efficient.

Most? Hardly

[the_humeister]

I bought a ScanGauge II back in 2008 and use it to this day. Plug it into the OBD II port to read data. One of the data points is engine torque, which can be converted to power. My previous car, a 2008 VW Jetta with the 2.5 L engine needed 35 hp to maintain 75 mph on a flat road. 26 hp is about right for my wife's 2011 Prius at 75 mph.

Re:10 kw

[ShanghaiBill]

10 kw is an interesting number for another reason, too -- 10 kwh is about the size of the average US home electrical draw.

For stationary residential use, you could run the thing on cheap natural gas (rather than expensive gasoline) and use the waste heat to warm your house. It would be personalized cogeneration.

Disclaimer: Yes, I realize that outside North America, natural gas isn't cheap.