Why Electric Motors Are 3X - 4X More Efficient Than Internal

When it comes to converting one form of energy one way to mechanical
work only a Pelton wheel can approach an electric motor's 95+%
efficiency.

In sharp contrast all single cycle high compression ratio ICE small
enough to be hauled down a road tops off at 40% efficiency with
vehicle size spark ignition ICE generally running below 30%. That's a
well tuned engine running on it's "sweet spot" rpm.

Why can't anyone do much about the sorry efficiency of 99.9% of the
prime movers on the planet?

Far and away the biggest problem comes from the basic thermocycles of
adiabatic engines, i. e., gas turbines (Brayton/Joule/Ericsson I),
diesel (Diesel) and spark ignition (Otto).

The machinery dictates the processes and the shape of the thermocycle
and even the idealized [read: fantasy] adiabatic cycle doesn't fill a
Carnot or other isothermalized parallelogram cycle -- the
thermodynamic limit of heat engines -- very well. Materials
temperature limits reduce the Carnot limit below 100%, so maybe a
little over 50% Carnot for most ideal adiabatic cycles.

The real cycle, however, looks more like a paramecium. The nice
sharply defined corners of the ideal have been rounded reducing
efficiency still more.

Toss in incomplete combustion and other parasitical losses and
electric motors start to look pretty.


Bret Cahill

 

[John Larkin]

On Fri, 15 Aug 2008 08:04:21 -0700 (PDT), BretCahill@peoplepc.com
wrote:

When it comes to converting one form of energy one way to mechanical
work only a Pelton wheel can approach an electric motor's 95+%
efficiency.

In sharp contrast all single cycle high compression ratio ICE small
enough to be hauled down a road tops off at 40% efficiency with
vehicle size spark ignition ICE generally running below 30%. That's a
well tuned engine running on it's "sweet spot" rpm.

Why can't anyone do much about the sorry efficiency of 99.9% of the
prime movers on the planet?

Far and away the biggest problem comes from the basic thermocycles of
adiabatic engines, i. e., gas turbines (Brayton/Joule/Ericsson I),
diesel (Diesel) and spark ignition (Otto).

The machinery dictates the processes and the shape of the thermocycle
and even the idealized [read: fantasy] adiabatic cycle doesn't fill a
Carnot or other isothermalized parallelogram cycle -- the
thermodynamic limit of heat engines -- very well. Materials
temperature limits reduce the Carnot limit below 100%, so maybe a
little over 50% Carnot for most ideal adiabatic cycles.

The real cycle, however, looks more like a paramecium. The nice
sharply defined corners of the ideal have been rounded reducing
efficiency still more.

Toss in incomplete combustion and other parasitical losses and
electric motors start to look pretty.

Sure, but where does the electricity come from?

An electric motor is efficient because it's not a heat engine. Their
practical efficiency can approach 100%. Transformers can approach 100%
too. Neither can turn fuel into work.

And electricity is hard to transport and store.

John

Bret Cahill

 

[Eeyore]

BretCahill@peoplepc.com wrote:

When it comes to converting one form of energy one way to mechanical
work only a Pelton wheel can approach an electric motor's 95+%
efficiency.

In sharp contrast all single cycle high compression ratio ICE small
enough to be hauled down a road tops off at 40% efficiency with
vehicle size spark ignition ICE generally running below 30%.

One word. Carnot.
http://en.wikipedia.org/wiki/Carnot's_theorem_(thermodynamics)

etc etc. And there's more.

Graham

 

[bud--]

BretCahill@peoplepc.com wrote:

Far and away the biggest problem comes from the basic thermocycles of
adiabatic engines, i. e., gas turbines (Brayton/Joule/Ericsson I),
diesel (Diesel) and spark ignition (Otto).

The Prius uses a 4 stroke Atkinson cycle engine. Like a conventional
Otto engine, the air-fuel mix is optimum. But like a diesel there is no
throttle plate. Not pumping air past a throttle plate is supposed to be
one reason Atkinson has a higher efficiency. The effective compression
ratio (and power) are controlled by intake valve timing.

http://en.wikipedia.org/wiki/Atkinson_cycle

--
bud--

 

[Michael A. Terrell]

"Daniel T." wrote:

Really? Do you know of any city in the industrialized world that
*doesn't* have an electricity transportation system already in place?

Do you know of any built entirely with superconductors to eliminate
all I/R losses? Do you know ANYTHING about electricity, other than not
to stick your tongue in a light socket, the second time?



--
http://improve-usenet.org/index.html

If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm


There are two kinds of people on this earth:

The crazy, and the insane.

The first sign of insanity is denying that you're crazy.

 

Far and away the biggest problem comes from the basic thermocycles of
adiabatic engines, i. e., gas turbines (Brayton/Joule/Ericsson I),
diesel (Diesel) and spark ignition (Otto).

The Prius uses a 4 stroke Atkinson cycle engine. Like a conventional
Otto engine, the air-fuel mix is optimum. But like a diesel there is no
throttle plate. Not pumping air past a throttle plate is supposed to be
one reason Atkinson has a higher efficiency. The effective compression
ratio (and power) are controlled by intake valve timing.

http://en.wikipedia.org/wiki/Atkinson_cycle

Good point. Without a turbo or other scheme there is an additional
loss from incomplete expansion.


Bret Cahill

 

arne't you smart!

You haven't done much in law or politics have you?


Bret Cahill

news:f5554356-f802-4096-9fad-cb1d0e313253@26g2000hsk.googlegroups.com...



When it comes to converting one form of energy one way to mechanical
work only a Pelton wheel can approach an electric motor's 95+%
efficiency.

In sharp contrast all single cycle high compression ratio ICE small
enough to be hauled down a road tops off at 40% efficiency with
vehicle size spark ignition ICE generally running below 30%. �That's a
well tuned engine running on it's "sweet spot" rpm.

Why can't anyone do much about the sorry efficiency of 99.9% of the
prime movers on the planet?

Far and away the biggest problem comes from the basic thermocycles of
adiabatic engines, i. e., gas turbines (Brayton/Joule/Ericsson I),
diesel (Diesel) and spark ignition (Otto).

The machinery dictates the processes and the shape of the thermocycle
and even the idealized [read: fantasy] adiabatic cycle doesn't fill a
Carnot or other isothermalized parallelogram cycle -- the
thermodynamic limit of heat engines -- very well. ďż˝ Materials
temperature limits reduce the Carnot limit below 100%, so maybe a
little over 50% Carnot for most ideal adiabatic cycles.

The real cycle, however, looks more like a paramecium. �The nice
sharply defined corners of the ideal have been rounded reducing
efficiency still more.

Toss in incomplete combustion and other parasitical losses and
electric motors start to look pretty.

 

[Eeyore]

Publius wrote:

BretCahill@peoplepc.com wrote

When it comes to converting one form of energy one way to mechanical
work only a Pelton wheel can approach an electric motor's 95+%
efficiency.

Yup. But the gas/oil/coal-fired power plants needed to generate the
electricty do not. Then you have the line losses transmitting it to point-
of-use.

Overall typical thermal efficiency is in the 30-40% region. No free lunch.

Graham

 

[Eeyore]

"Daniel T." wrote:

John Larkin wrote:

Sure, but where does the electricity come from?

Power plants that run at much higher efficiency

Not that great actually.

(and much cleaner per kilowatt of energy produced) than any automobile
engine

How do you reckon they're cleaner ?

could ever hope to do.

Overall thermal efficiency from typical power plant to power socket is in
the 30-40% region.

A very large marine diesel can and does EXCEED 50% thermal efficiency. Only
now are combined cycle gas turbine generators coming on line that can beat
that but you still have transmission losses.

Graham

 

[Eeyore]

"Michael A. Terrell" wrote:

"Daniel T." wrote:

Really? Do you know of any city in the industrialized world that
*doesn't* have an electricity transportation system already in place?

Do you know of any built entirely with superconductors to eliminate
all I/R losses? Do you know ANYTHING about electricity, other than not
to stick your tongue in a light socket, the second time?

The myths about electricity and how it can be used and how good it is 'for
the environment' never fail to amaze me.

Graham

 

[RLDeboni]

Eeyore wrote:

A very large marine diesel can and does EXCEED 50% thermal efficiency. Only
now are combined cycle gas turbine generators coming on line that can beat
that but you still have transmission losses.

On one side:
- an oil terminal
- at 1 km from the oil terminal, a 50MWe marine diesel, fueled with that
oil at 50% efficiency
- an electric network that takes the electricity to 10'000 homes
- in each home an electric car that makes 100 km daily, no warming need,
no motor testing, only start and go

On the other side:
- an oil terminal
- at 1 km from the oil terminal, a refinery
- a dozen of gas stations
- a couple of gas trucks to refill the gas stations
- 10'000 cars, that at least weekley make a stop at the gas station
- 10'000 cars, that in winter need a warming phase before actual drive
- 10'000 cars, that at every traffic light, burn fuel waiting green

Transmission losses ?
Surely. Oil and fuel have to travel. A gas truck takes 8'000-12'000
gallons. If that trucks does 100 km, what are the transmission losses ?
And the refinery efficiency ? Some how it as to go in the ICE motor
calculations.

R.L.Deboni

 

[John]

(and much cleaner per kilowatt of energy produced) than any automobile
engine

How do you reckon they're cleaner ?

How can a water turbine generator pollute more than a coal fired turbine
of the same output?

 

[Eeyore]

RLDeboni wrote:

Eeyore wrote:

A very large marine diesel can and does EXCEED 50% thermal efficiency. Only
now are combined cycle gas turbine generators coming on line that can beat
that but you still have transmission losses.

On one side:
- an oil terminal
- at 1 km from the oil terminal, a 50MWe marine diesel, fueled with that
oil at 50% efficiency

An interesting concept.

- an electric network that takes the electricity to 10'000 homes
- in each home an electric car that makes 100 km daily, no warming need,
no motor testing,

testing ?

only start and go

On the other side:
- an oil terminal
- at 1 km from the oil terminal, a refinery
- a dozen of gas stations
- a couple of gas trucks to refill the gas stations
- 10'000 cars, that at least weekley make a stop at the gas station
- 10'000 cars, that in winter need a warming phase before actual drive

That is not the correct way to drive a car from cold AIUI.

- 10'000 cars, that at every traffic light, burn fuel waiting green

Build roundabouts like in Europe. You see relatively few lights here.

Transmission losses ?

Low.

Surely. Oil and fuel have to travel. A gas truck takes 8'000-12'000
gallons. If that trucks does 100 km, what are the transmission losses ?

Pretty minimal I expect.

And the refinery efficiency ? Some how it as to go in the ICE motor
calculations.

Refining petroleum is ~ 75% efficient IIRC but you also get other saleable and
very useful by-products.

Graham

 

[Eeyore]

John wrote:

(and much cleaner per kilowatt of energy produced) than any automobile
engine

How do you reckon they're cleaner ?

How can a water turbine generator pollute more than a coal fired turbine
of the same output?

You mean hydro ? Most suitable locations are already in use.

Graham

 

[Eeyore]

Rod Speed wrote:

John <nohj@droffats.ten> wrote:

(and much cleaner per kilowatt of energy produced) than any automobile engine

How do you reckon they're cleaner ?

How can a water turbine generator pollute more than a coal fired turbine of the same output?

Trouble is that only a tiny percentage of electricity is generated that way.

Norway is lucky that way.

Graham

 

[John Larkin]

On Sat, 16 Aug 2008 00:33:51 +0200, RLDeboni
<robertodeboni@deboni.name> wrote:

Eeyore wrote:

A very large marine diesel can and does EXCEED 50% thermal efficiency. Only
now are combined cycle gas turbine generators coming on line that can beat
that but you still have transmission losses.

On one side:
- an oil terminal
- at 1 km from the oil terminal, a 50MWe marine diesel, fueled with that
oil at 50% efficiency
- an electric network that takes the electricity to 10'000 homes
- in each home an electric car that makes 100 km daily, no warming need,
no motor testing, only start and go

On the other side:
- an oil terminal
- at 1 km from the oil terminal, a refinery
- a dozen of gas stations
- a couple of gas trucks to refill the gas stations
- 10'000 cars, that at least weekley make a stop at the gas station
- 10'000 cars, that in winter need a warming phase before actual drive
- 10'000 cars, that at every traffic light, burn fuel waiting green

Transmission losses ?
Surely. Oil and fuel have to travel. A gas truck takes 8'000-12'000
gallons. If that trucks does 100 km, what are the transmission losses ?
And the refinery efficiency ? Some how it as to go in the ICE motor
calculations.

R.L.Deboni

5PM, I'm in a hotel in Santa Barbara. We had a late breakfast in San
Francisco. We stopped for gas once, for about 5 minutes, and ran 75-80
MPH most of the way. And we climbed some serious hills towards the
end.

There weren't many traffic lights.

Do you warm up your car? It's not good for it.

Does your car need "motor testing" every day?


John

 

[Sevenhundred Elves]

On Sat, 16 Aug 2008 10:08:59 +1000, "Rod Speed"
<rod.speed.aaa@gmail.com> wrote:

John <nohj@droffats.ten> wrote:

(and much cleaner per kilowatt of energy produced) than any automobile engine

How do you reckon they're cleaner ?

How can a water turbine generator pollute more than a coal fired turbine of the same output?

Trouble is that only a tiny percentage of electricity is generated that way.

World-wide, it's 16% hydro and 15% nuclear. Together, they constitute
almost a third of the world's electricity generation.

Coal is 40%,
gas 20%,
oil 7%,
and "other" is 2%.

S.

 

[rlbell.nsuid@gmail.com]

On Aug 15, 3:05 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
wrote:

Publius wrote:
BretCah...@peoplepc.com wrote

When it comes to converting one form of energy one way to mechanical
work only a Pelton wheel can approach an electric motor's 95+%
efficiency.

Yup. But the gas/oil/coal-fired power plants needed to generate the
electricty do not. Then you have the line losses transmitting it to point-
of-use.

Overall typical thermal efficiency is in the 30-40% region. No free lunch.

Graham

Transmission losses can be between 1 and 2 percent. Even a really bad
grid should be able to keep the transmission losses to under 5% .

GE will sell you a 60% thermally efficient combined cycle unit (H1).
It definitely will run on natural gas. It may run on oil. Using it
to burn pulverised coal will drastically shorten its service life.

Nuclear plants should be able to achieve gobsmacking efficiencies if
we can conquer the psychological and engineering barriers of designing
the reactor pile to be a thoroughly contained, ball of radioactive,
incandescent gas. The reactor is based on the gaseous cored, nuclear
thermal rocket engine (check out The Atomic Rockets Homepage
http://www.projectrho.com/rocket/index.html), driving a magneto-
hydrodynamic generator (which has a theoretically high efficiency, but
only at obscene temperatures), with the gas circulated (and energy
recovered) by a closed-cycle gas turbine. Before passing through the
compressor and returning to the reactor, the working fluid exhausted
by the turbine is used to raise steam. I consider this to be a rather
harebrained scheme I concocted after looking up MHD's and remembering
the NTR-gas, but stranger things have happened.

 

[rlbell.nsuid@gmail.com]

On Aug 15, 6:42 pm, John Larkin
<jjSNIPlar...@highTHISlandtechnology.com> wrote:

On Sat, 16 Aug 2008 00:33:51 +0200, RLDeboni



robertodeb...@deboni.name> wrote:
Eeyore wrote:

A very large marine diesel can and does EXCEED 50% thermal efficiency. Only
now are combined cycle gas turbine generators coming on line that can beat
that but you still have transmission losses.

On one side:
- an oil terminal
- at 1 km from the oil terminal, a 50MWe marine diesel, fueled with that
oil at 50% efficiency
- an electric network that takes the electricity to 10'000 homes
- in each home an electric car that makes 100 km daily, no warming need,
no motor testing, only start and go

On the other side:
- an oil terminal
- at 1 km from the oil terminal, a refinery
- a dozen of gas stations
- a couple of gas trucks to refill the gas stations
- 10'000 cars, that at least weekley make a stop at the gas station
- 10'000 cars, that in winter need a warming phase before actual drive
- 10'000 cars, that at every traffic light, burn fuel waiting green

Transmission losses ?
Surely. Oil and fuel have to travel. A gas truck takes 8'000-12'000
gallons. If that trucks does 100 km, what are the transmission losses ?
And the refinery efficiency ? Some how it as to go in the ICE motor
calculations.

R.L.Deboni

5PM, I'm in a hotel in Santa Barbara. We had a late breakfast in San
Francisco. We stopped for gas once, for about 5 minutes, and ran 75-80
MPH most of the way. And we climbed some serious hills towards the
end.

There weren't many traffic lights.

Do you warm up your car? It's not good for it.

Does your car need "motor testing" every day?

John

If you are afflicted with that horrid bugbear from ancient times named
'the carburator', there are instances where warming up is a necessary
evil. I had a '76 T-bird that would flood with the least provocation
in cold weather and losing the power assist to the steering of that
nose-heavy land yacht, in a turn, threatened to break your thumbs as
the steering wheel spins along with the castering front wheels. I let
the car warm up, after that.

 

[RLDeboni]

John Larkin wrote:

5PM, I'm in a hotel in Santa Barbara. We had a late breakfast in San
Francisco.

It's a long trip for an electric car ...
I am thinking about commuting, about 50 km range.

We stopped for gas once, for about 5 minutes, and ran 75-80
MPH most of the way. And we climbed some serious hills towards the
end.

NiMh or Li-ion batteries and new electronics for energy recovering, will
take all "serious" hills with a breeze.

There weren't many traffic lights.

R.L.Deboni