Re: engine efficiencies

It is significant that we *have* to speculate. The only hard number I am aware of is for a rather low-specific-power air-breathing PEM cell that converts, to DC electricity, a little less than 33 percent of HHV .

Run that through a 75-percent-efficient EV powertrain and you would have 24.5 percent; but an EV needs higher specific power (More kW per fuel cell kg), so we can't be certain today's hydrogen FCEVs are reaching 20 percent, tank-to-wheel.

With regard to 50 percent diesels, you have to be careful. They sometimes say "An ideal Carnot cycle between this diesel's two temperatures would be 76 percent efficient, and it really does 38, so that's half. 50 percent! Go us!"

ISTR big marine diesels achieve a no-fooling 45 percent.

--- Graham Cowan

--fireproof fuel, real-car range, no emissions

Surely the power problem is solved by a combination battery/UltraCap?

The advantage of EV drives is that they are highly energy efficient at a wide range of load and speed (>95% for good motors).

This is in stark contrast to the efficiency of ICE engines, whether spark ignition or compression ignition (typically less than 15% in typical urban use).

ICE engines are only achieve close to specified efficiency in a very limited load and speed range.

Car engines are a closed shop. Nobody can innovate a car engine, without significant lifetime commitment to the corporate ladder of a major automobile company.

Since technical ability and political acumen are highly negatively corrolated, ther is almost no chance of a car running a turbine engine, regardless of the merits.

Yep, watch out for 'Carnot' or 'Theoretical' efficiency, vs. energy efficiency (actually the former two are more appropriate in any situation - look up exergy)

Exactly. Marine engines typically run at a single speed and load regime, for periods of up to months.

Commuter traffic is an entirely different problem space.

Roland

They managed a 45% efficient diesel for an aircraft, in the fifties, but it was killed by the rise of the jet engine. It was called the Napier Nomad, and its turbocharger produced more mechanical power than was needed to drive the compressor (the rest was delivered to the crankshaft). It looked like a bizarre mating of a piston and jet engine, as its turbocharger had an axial flow, multistage compressor and turbine, with the option of reheating the diesel exhaust for extra power at the turbine.

Many aero-engine manufacturers experimented with turbocompounding, but only the Wright Cyclone R3350 flew in significant numbers as a TC engine. Aero engines boosted power/displacement ratios by supercharging low compression ratio engines (the R3350 had a CR of 4, the Nomad had 3.5), so there was a great deal of recoverable energy in the exhaust.

As opposed to a freakin' *belt*?

I dunno...._maybe_ complexity.

Yes, there is a good reason not to use a belt. A 50A alternator robs about

1KW from the engine. Generating steam from the engine block does not.

Your idea is theoretically possible. It does not violate any laws of thermodynamics. That puts you way ahead of a lot of crackpot dreamers. It does not mean your idea is practical.

Your turbine powered alternator will need.

1. steam turbine.
2. steam generator tubing wrapped around the exhaust manifold.

3 Steam condesor. This is a large radiator looking device. 4 Feed water pump to pressurise the condensate back up to boiler pressure.

You could do without 3 and 4 but then you would need to refill the water tank every couple of hours just like an old steam locomotive.

Also, the alternator would not put out any power until the water started to boil. That puts a huge drain on the battery. It must power the car until it warms up. That means you will need a larger battery.

Or you could use 1 belt and 2 pulleys.

Erich good luck and let us know when you have it working.

"Eric Gisin"

Or maybe a small stirling engine or thermal diode?

We could. But exhaust temperatures aren't going to provide high carnot efficiency to the steam engine. The added weight and complexity of a small steam engine to turn an alternator would decrease vehicle performance in the bargain. If one instead used thermo-electric diodes they could directly convert exhaust and waste engine heat to electricity with no need for an alternator or steam engine. With proper design you could even eliminate the need for a battery while being compact and light weight itself.

Nope :).

Well, the belt doesn't recycle any waste energy. It just robs power from the motor. Belts frequently slip and stretch, creating inefficiencies. Doing something with the lower temperature waste heat of the engine is a better idea.

If you want to reduce mechanical complexity then all electrical cars are the way to go :).

What is thermal diode?

Regards,

Boris Mohar

Got Knock? - see: Viatrack Printed Circuit Designs

Ontario

The latter is definitely preferable. Stirlings are fairly expensive and mechanically tempermental. Plus, you'd still need to link it to an alternator somehow. The only real issues would be whether you could achieve high enough temperatures to get the thermal diodes to output reasonable amounts of energy and how economical this would be.

It also might be interesting to try using piezo materials in the engine mounts and elsewhere in the car, though I don't think that these alone would deliver all the necessary power.

"Boris Mohar"

Something like thermo couple or peltier element, only with better efficiency. It produces electricity directly from temperature difference.

More details:

How about the H2O2/C12H26 IRRCE

I'm thinking 15+kw/kg and the engine itself at not more than 0.1kg/kw.

I guess I'm still the village idiot that's thinking way outside the box, though as for our going back to the moon (if ever) may have to be for robots, not for mankind. At least not until we have obtained a pilot documented and thus working lander of sufficient shielding as for radiation as well as for fending off all those pesky micro meteorites. Venus on the other hand has lots of energy, more than you can shake a flaming stick at.

LSE-CM/ISS (Lunar Space Elevator plus Counter Mass and new ISS) or GMDE (Guth Moon Dirt Express), plus there's lots of other related energy stuff, with more on the way;

Regards, Brad Guth / IEIS~GASA

By the way, how about a fireplace which would produce both heat and electricity? All that is needed is to connect a thermal diode between the inner part of a fireplace and under-floor heating pipes.

This "hybride-fireplace" could supplement ordinary solar panels; solar panels are most effective in summer, a fireplace is used mostly during winter.

Honey, start a fire. I need to send some email.