Electric cars are a pipe dream

[DaS Energy]

Hello Billy T
Tthanks for that, I am well aware of who Carnot was and what Carnot means in the mechanical world. A battery is the closest thing to defeating Carnot. Allmost no heat loss.

Cheers peter

 

[billvon]

Should it be that a radiator or expansion chamber not be defined as a cooler reseviour then the law is wrong not the workings.

?? If you have a warm reservoir and a cooler reservoir then your heat engine can work as long as that differential is maintained against the heat that your engine is transferring into the cold reservoir. This is basic thermo.

If you imagine you can dump the heat into the reservoir and then magically remove it, then you have a Type 2 perpetual motion machine.

See "Einstein" Ammonia absorption fridge.

It is a refrigerator that gains its energy by using a heat source (like a flame) that transfers heat to a heat sink (the environment.) As long as you maintain that temperature differential it works. If the environment ever rises to the temperature of the flame, it ceases operation.

The Wikipedia article is a good overview, and includes this note:

"The absorber works by removing ammonia vapor by dissolving it in water. As this happens, the gas mixture flows to maintain the nearly constant pressure Psys, and as a consequence, the partial pressure of the refrigerant, Prfr, can approach Psys. At this higher partial pressure, it can condense and deliver heat to an external heat sink, as in a conventional refrigerator."

That "external heat sink" is the critical part, and is the reason that your device will not work.

 

[Aqueous Id]

Question. On what premise do you base all ectric cars need a battery. Electricity does not need be stored but may taken direct from alternator to electric motor. There be no reason electricity why electricity need first be passed to a battery. Electricity need be generated somewhere so why not under the hood. This can be simply done 24/7, no museum technology needed.
Cheers Peter

It's not whether the technology is in a museum or not. It's whether it works. Batteries and motors are museum pieces, as are electric cars. But running a motor from an alternator is ludicrous. The losses will eat you alive. Besides, a standard alternator won't come close to developing enough electricity. What's the point?

 

[DaS Energy]

Hello Aqueous Id,

I take your point on museum peices. All electric motors are driven from a alternator/generator somewhere. Standard alternator?

Cheers Peter

 

[DaS Energy]

Hello billvon,

Ammonia is very old refrigerant, CO2 is not. CO2/R744 does not need a water bath to condense back to liquid.
The grill you find at the back of all fridges is in fact a cooler. The Ammonia/water tank on the absorption fridge is not.

Cheers Peter

 

[billvon]

Ammonia is very old refrigerant, CO2 is not. CO2/R744 does not need a water bath to condense back to liquid.

Most refrigerants do not need a water bath to condense back to liquid. They just need a heat sink.

The grill you find at the back of all fridges is in fact a cooler. The Ammonia/water tank on the absorption fridge is not.

?? It's not a "cooler," it's a condenser. It dumps heat into the environment and allows the working fluid to condense.

 

[Billy T]

Most refrigerants do not need a water bath to condense back to liquid. They just need a heat sink. ... ?? It's not a "cooler," it's a condenser. It dumps heat into the environment and allows the working fluid to condense.

Yes all true. There is a lot DaS Energy is confused about, but main reason I post is to tell about a natural ~4 degree heat sink that is used near Cornell University (at least years ago when I went there as an under grad.)

Cornell over looks Lake Cayuga, one of the five "Finger Lakes" in central NY state. It is very deep so during winter some of the most dense cold water sinks to the bottom making a large body of ~4C water. Many years before I went there, a power company with most of it customers in Pennsylvania concluded it should haul PA coal up to power plant on lake Cayuga to condense it steam (with smaller condenser and greater Carnot efficiency, and did so) even though most of the electricity would go back to PA. After I was long gone from Cornell, I read in an alumni magazine that Cornell was also taking the cold bottom water up to the campus to make their summer air conditioning more efficient and economical too.

 

[Gravage]

Who says electric cars are a pipe dream?
http://www.rimac-automobili.com/press/the-concept_one-world-debut-at-frankfurt-motor-show-p4
http://uk.autoblog.com/2011/09/15/new-rimac-electric-supercar-stuns-frankfurt/
http://wheels.blogs.nytimes.com/2011/09/07/rimac-an-e-v-dark-horse-heads-to-frankfurt/

 

[DaS Energy]

Hello billvon,

Fridges have external heat sink.

Times have moved on since "Einstein", R744 (CO2) now replaces Ammonia and water. A very small heat differential now maintanes a very high pressure differential. That differential of pressure may be even greater in some gasses, but CO2 is a refrigerant readily self cooling.
Example CO2 at 32*C has 64 bar of pressure/force at 100*C it has over 7,000 bar force. Steam on the other hand has 1 bar prressure/force at 100*C and 175 bar pressure /force at 550*C. Steam turbines engage external heat sinks which is why they work!

Cheers Peter

 

[DaS Energy]

Hello billvon,

Have I posted anything that requires water to assist with cooling?

Cheers Peter

 

[DaS Energy]

Hello billvon,

A cooler cools a substance be it gas, liquid or solid. A cooler cooling gas to temperature where it remains gas is a cooler. Should a cooler cool the gas to a temperature where it becomes liquid may be called a condenser. However a cooler it still remains. Gas can be condensed to liquid by actualy adding heat, or just by sheer force. To use the word condenser leaves so much unexplained, the word cooler being engaged to signify nothing other than heat loss is occuring to obtain condensation.

Cheers Peter

 

[billvon]

To use the word condenser leaves so much unexplained, the word cooler being engaged to signify nothing other than heat loss is occuring to obtain condensation.

Condensers condense gases to liquids. Coolers cool things. That process may include condensation (as in the case of a heat exchanger) _or_ evaporation (as in the case of a cooling tower.)

Steam turbines engage external heat sinks which is why they work!

So does any turbine. Without external supplies of energy (in the form of combustion heat, heat flow across a steady temperature differential, mass flow across a steady pressure differential etc) no turbine will run.

 

[Billy T]

Replying to DaS Energy´s "Steam turbines engage external heat sinks which is why they work! " you said:

... So does any turbine. Without external supplies of energy (in the form of combustion heat, heat flow across a steady temperature differential, mass flow across a steady pressure differential etc) no turbine will run.

That needs the qualifier "closed cycle turbine" as I´m sure you know, but just did not state. There are thousands of turbines (that drive same shaft air compressors) flying at any time. BTW most of the jet´s power is used to drive these air compressors, not put into the exhaust jet.

One of the big advantage of IC engines is they just dump the waste heat - are "open cycle." To make a closed cycle car with the user expected performance, is essentially impossible as the air drag of the condenser would consume at least 90% of the power produced.

 

[billvon]

That needs the qualifier "closed cycle turbine" as I´m sure you know, but just did not state.

"Open cycle" turbines use combustion heat to generate the increase in pressure/temperature required for their operation.

One of the big advantage of IC engines is they just dump the waste heat - are "open cycle." To make a closed cycle car with the user expected performance, is essentially impossible as the air drag of the condenser would consume at least 90% of the power produced.

I bet you could do a pretty good job by keeping temperatures high and streamlining the heck out of it.

 

[Billy T]

... I bet you could do a pretty good job by keeping temperatures high and streamlining the heck out of it.

Yes but if you keep the {condenser} temperature high* the Carnot limit efficiency will make you burn a lot of fuel. The streamlined condenser will have much less air flow thru it (unless you add some big energy consuming fans) so will weight more than the rest of the car without the fans.

But I conservatively said "essentially impossible" to make a closed cycle car with the user expected performance. I guess if cars owner is happy with something like 1 MPG fuel economy and peak acceleration (due the being very heavy with only a few horse power delivered to the wheels) of about 0.03 G it is "possible."

* Also if high enough to burn some kid or melt some wind blown plastic on him, your insurance cost will be very high too.

 

[billvon]

Yes but if you keep the {condenser} temperature high* the Carnot limit efficiency will make you burn a lot of fuel. The streamlined condenser will have much less air flow thru it

Agreed.

(unless you add some big energy consuming fans) so will weight more than the rest of the car without the fans.

That's an unsupportable statement.

But I conservatively said "essentially impossible" to make a closed cycle car with the user expected performance. I guess if cars owner is happy with something like 1 MPG fuel economy and peak acceleration (due the being very heavy with only a few horse power delivered to the wheels) of about 0.03 G it is "possible."

That's also unsupportable. Indeed there is evidence that it is NOT true.

Early steam engines were open cycle. They exhausted their working fluid (steam) into the air, which is where the traditional "chuff chuff" noise associated with steam engines comes from. This limited their range; early engines had to stop every 10 miles or so, with later engines being able to travel 100 miles or so by more efficient use of water and larger storage tanks. (Which BTW is why there are suspiciously regular towns along rail lines in the West; the towns began as water-and-fuel stops for steam locomotives.)

As demand for longer range increased - especially in areas where water was not present - locomotives began to move to closed cycle operation. They used condensers to condense the water so it could be re-used. Contrary to your claim, these locomotives were not lower in performance; indeed, they improved their performance (in terms of total power, top speed and fuel economy) as condensers became more common. Note that this was not due to any advantage the condenser conferred - indeed there was some decrease in performance - but rather the steady advancement of engine technology. If going closed loop were as performance-limiting as you claim, there would have been massive and crippling degradations in performance of condensing steam locomotives, to match the 50:1 performance reductions you claim above.

 

[Billy T]

...
Early steam engines were open cycle. ... This limited their range; early engines had to stop every 10 miles or so, with later engines being able to travel 100 miles or so by more efficient use of water and larger storage tanks. (Which BTW is why there are suspiciously regular towns along rail lines in the West; the towns began as water-and-fuel stops for steam locomotives.). ...

that ~100 mile town spacing is an interesting observation that never occurred to me. What fraction of the 100 mile open cycle steam train´s weight was the water filled tank? As trains have very gradual hills to climb compared to cars, they could support more a greater fraction of the motor being the water tank.

You are probably right - instead of "essentially impossible" I should have said: "closed cycle car is not very practical" and certainly water or air are the only "working fluids" cheap enough to discard in an open cycle car. All IC cars are open cycle and discharging chemically changed air, and as I have noted in a few posts, can be more powerful and efficient it they discharge some H2O* also but not much if the weight of it is a significant fraction of the car. Probably the "Stanly Steamer" car was open cycle too - it held the world speed record for quite a few years - do you know?

* Injected as a fine mist that becomes steam in final half of the down stroke to keep more pressure on the piston. - less useful heat dumped with the exhaust, more used for power.

 

[billvon]

that ~100 mile town spacing is an interesting observation that never occurred to me. What fraction of the 100 mile open cycle steam train´s weight was the water filled tank?

Depends on the locomotive. "Tank locomotives" carry their water in tanks, but as range increased water storage moved to the tender. In general ratios were around 14 tons of coal per 10,000 gallons of water, so you can calculate backwards once you know the range and coal consumption of the locomotive. The Chicago & North Western 4-8-4 locomotives (late model steam locomotives used through about 1960) carried 18,000 gallons, but I don't know what their range was.

One way of extending the range of locomotives interestingly was a "track pan" - a pan full of water between the tracks that the locomotive would scoop water out of.

You are probably right - instead of "essentially impossible" I should have said: "closed cycle car is not very practical"

Several have been built. The NASA MODII project converted a 1985 Chevrolet Celebrity Notchback to a Stirling engine, and significantly improved gas mileage (went from 40 to 58mpg) with no appreciable change in vehicle weight. The radiator was a stock Chevy radiator with another fan added. The project never went anywhere primarily due to long startup times and long lag times as power was ramped up and down, making driving in traffic difficult. (Note that this would not be a problem with a series-parallel hybrid such as a Prius.)

Probably the "Stanly Steamer" car was open cycle too - it held the world speed record for quite a few years - do you know?

Stanley Steamers used condensers on their cars starting around 1915. I think the speed record was set before that though.

 

[Billy T]

To billvon:
You are either some transportation buff or one hell of a good searcher - I have so much stuff stuffed in memory that I rarely search, and am not very good at it.

 

[billvon]

To billvon:
You are either some transportation buff or one hell of a good searcher - I have so much stuff stuffed in memory that I rarely search, and am not very good at it.

Really just a nerd who finds things like steam trains interesting. (And Wikipedia is great as a way to restore all the not-insignificant gaps in my memory.)