Re: [MBZ] electric cars - was Cash for clunkers hits home

[Redghost]

A Tesla drove past me yesterday.  Somebody in the neighborhood has too  
much free cash



clay

On Aug 27, 2009, at 10:04 PM, Craig McCluskey wrote:


On Thu, 27 Aug 2009 23:19:05 -0400 Rich Thomas
 wrote:


How many kJ in a 100 volt, 1 farad capacitor?


U = 0.5 C V^2

= 0.5 x 1 x 100^2

= 5000 J = 5 kJ


 


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Re: [MBZ] electric cars - was Cash for clunkers hits home

[Craig McCluskey]

On Thu, 27 Aug 2009 23:19:05 -0400 Rich Thomas
 wrote:

> >>> How many kJ in a 100 volt, 1 farad capacitor?
> >>>   
> >> U = 0.5 C V^2
> >>
> >>  = 0.5 x 1 x 100^2
> >>
> >>  = 5000 J = 5 kJ
>
> That would get your attention.

In my lab in graduate school, we had a discharge chamber that had high
voltage power supplies to charge up several (small) high voltage
capacitors before they were dumped in series into the chamber, many times
per second.

The capacitors for the discharge were too small and the power supplies
charged them up too fast to see if the power supplies were working
properly. So, I had a 100 microfarad, 10 kilovolt capacitor (= 5 kJ) that
I used as a load to test out the power supplies. It took the supplies
several seconds to charge up that capacitor, which gave enough time to
observe that all the lights that were supposed to be flashing in a
specific order actually did so.

One evening, something went wrong with one of the power supplies. I
connected the supply up to the big capacitor and ran it and found that the
supply was indeed malfunctioning.

I then took the discharge sticks to discharge the capacitor. These were 1"
diameter plexiglas rods with 1/2" copper electrodes in their ends. Between
the electrodes a pack of resistors were wired to dissipate the energy in a
controlled fashion. At least they were supposed to.

It turns out, unbeknownst to me, that the person who had built the
resistor pack had used ADJUSTABLE wirewound resistors. Those resistors
have a stripe down one side where there is NO insulation on the windings
(to provide a way to adjust the resistance). Also unbeknownst to me, the
malfunctioning power supply had charged the big capacitor up to much more
voltage than I was accustomed to using. When I went to discharge it, the
extra voltage arced across the bare windings of the resistor pack and
discharged the capacitor VERY rapidly. At most milliseconds kind of
rapidly. With a VERY loud BANG! My ears were ringing 2 hours after the
incident. In addition, the parts of the resistors and the connecting wire
(12 gauge stranded) were all over the lab, more than 20 feet away from the
site of the calamity. People came running in from other labs to see if I
was OK.

I called my advisor, told him what happened, and went home, more than a
little shaken.


Craig

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Re: [MBZ] electric cars - was Cash for clunkers hits home

[Rich Thomas]

That would get your attention.

--R

OK Don wrote:

Cool - thanks.

On Thu, Aug 27, 2009 at 9:41 PM, Craig McCluskey wrote:

  

On Thu, 27 Aug 2009 13:02:25 -0500 OK Don  wrote:



How many kJ in a 100 volt, 1 farad capacitor?
  

U = 0.5 C V^2

 = 0.5 x 1 x 100^2

 = 5000 J = 5 kJ


Craig

--
OK Don
Pair of W124 300D 2.5 Turbos




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Re: [MBZ] electric cars - was Cash for clunkers hits home

[OK Don]

Cool - thanks.

On Thu, Aug 27, 2009 at 9:41 PM, Craig McCluskey wrote:

> On Thu, 27 Aug 2009 13:02:25 -0500 OK Don  wrote:
>
> > How many kJ in a 100 volt, 1 farad capacitor?
>
> U = 0.5 C V^2
>
>  = 0.5 x 1 x 100^2
>
>  = 5000 J = 5 kJ
>
>
> Craig
>
> --
> OK Don
> Pair of W124 300D 2.5 Turbos
>
>
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Re: [MBZ] electric cars - was Cash for clunkers hits home

[Craig McCluskey]

On Thu, 27 Aug 2009 13:02:25 -0500 OK Don  wrote:

> How many kJ in a 100 volt, 1 farad capacitor?

U = 0.5 C V^2

  = 0.5 x 1 x 100^2

  = 5000 J = 5 kJ


Craig

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Re: [MBZ] electric cars - was Cash for clunkers hits home

[OK Don]

How many kJ in a 100 volt, 1 farad capacitor?

On Wed, Aug 26, 2009 at 11:25 PM, Craig McCluskey wrote:

> On Wed, 26 Aug 2009 23:26:34 -0400 Allan Streib 
> wrote:
>
> > Craig McCluskey  writes:
> >
> > > Jim's comment about how much momentum a moving freight train has is
> > > indicative of the size of flywheel you would need. It wouldn't fit on
> > > the train and couldn't fit through tunnels and across bridges.
> >
> > I'm imagining some kind of giant, box-car sized capacitors that would
> > absorb energy during braking and release it back to the motors during
> > acceleration.  Again, probably impractical or they'd be doing it.
>
> Well, there have been recent improvements in capacitors that allow them to
> store more energy, but I don't remember the energy storage density.
>
> To get an idea of how much energy one would need to store, consider a
> locomotive accelerating a train from stop to some speed. Say, for example,
> we have a 4000 horsepower locomotive that runs for 10 minutes to get the
> train moving. That's
>746 watt  60 seconds
>  4000 horsepower x -- x 10 minutes x 
>   horsepower   minute
>
>  = 1.79 x 10^9 watt-seconds = 1.79 x 10^9 Joules = 1.79 x 10^6 kiloJoules
>
>
> If the energy storage density is 10 kJ / cubic foot (not too far off, I
> think) the volume of the capacitor would be 100,000 cubic feet. If the
> energy storage density is 100 kJ / cubic foot, the volume of the capacitor
> would be only 10,000 cubic feet.
>
>
> Craig
>
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-- 
OK Don
Pair of W124 300D 2.5 Turbos
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Re: [MBZ] electric cars - was Cash for clunkers hits home

[Craig McCluskey]

On Wed, 26 Aug 2009 23:26:34 -0400 Allan Streib 
wrote:

> Craig McCluskey  writes:
> 
> > Jim's comment about how much momentum a moving freight train has is
> > indicative of the size of flywheel you would need. It wouldn't fit on
> > the train and couldn't fit through tunnels and across bridges.
> 
> I'm imagining some kind of giant, box-car sized capacitors that would
> absorb energy during braking and release it back to the motors during
> acceleration.  Again, probably impractical or they'd be doing it.

Well, there have been recent improvements in capacitors that allow them to
store more energy, but I don't remember the energy storage density.

To get an idea of how much energy one would need to store, consider a
locomotive accelerating a train from stop to some speed. Say, for example,
we have a 4000 horsepower locomotive that runs for 10 minutes to get the
train moving. That's
746 watt  60 seconds
 4000 horsepower x -- x 10 minutes x  
   horsepower   minute

 = 1.79 x 10^9 watt-seconds = 1.79 x 10^9 Joules = 1.79 x 10^6 kiloJoules


If the energy storage density is 10 kJ / cubic foot (not too far off, I
think) the volume of the capacitor would be 100,000 cubic feet. If the
energy storage density is 100 kJ / cubic foot, the volume of the capacitor
would be only 10,000 cubic feet.


Craig

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Re: [MBZ] electric cars - was Cash for clunkers hits home

[Allan Streib]

Craig McCluskey  writes:

> Jim's comment about how much momentum a moving freight train has is
> indicative of the size of flywheel you would need. It wouldn't fit on
> the train and couldn't fit through tunnels and across bridges.

I'm imagining some kind of giant, box-car sized capacitors that would
absorb energy during braking and release it back to the motors during
acceleration.  Again, probably impractical or they'd be doing it.

Allan
-- 
1983 300D

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Re: [MBZ] electric cars - was Cash for clunkers hits home

[Craig McCluskey]

On Wed, 26 Aug 2009 15:05:03 -0500 Fmiser  wrote:

> > WILTON wrote:
> >
> > Pity; doesn't seem to "regen" anything, then, does it?  Well,
> > 'cept heat. What a waste.
> 
> Yeah. But think of the quantity of electricity generated. Not
> very practical to store that in batteries.  
> 
> Maybe the "spare" electricity could generate hydrogen - except
> the main diesel engine can't run on hydrogen.
> 
> A flywheel? Could use an electric motor and regenerative
> "braking" using the flywheel to store the energy.

Jim's comment about how much momentum a moving freight train has is
indicative of the size of flywheel you would need. It wouldn't fit on the
train and couldn't fit through tunnels and across bridges.


Craig

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Re: [MBZ] electric cars - was Cash for clunkers hits home

[Fmiser]

> > > LWB250  writes:
> > >
> > > That is regenerative braking, and it's exactly what the
> > > resistor banks on the tops of the locomotives are for.
> > > They use regenerative power from the traction motors and
> > > dump it into the resistors as required to place a load on
> > > the traction motors when braking or slowing the train down
> > > grades.

> > Allan wrote:
> >
> > What I meant was, they don't recover the energy for later
> > use.  They blow it off as heat.

> WILTON wrote:
>
> Pity; doesn't seem to "regen" anything, then, does it?  Well,
> 'cept heat. What a waste.

Yeah. But think of the quantity of electricity generated. Not
very practical to store that in batteries.  

Maybe the "spare" electricity could generate hydrogen - except
the main diesel engine can't run on hydrogen.

A flywheel? Could use an electric motor and regenerative
"braking" using the flywheel to store the energy.

--  Philip

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Re: [MBZ] electric cars - was Cash for clunkers hits home

[WILTON]

Pity; doesn't seem to "regen" anything, then, does it?  Well, 'cept heat. 
What a waste.


Wilton

- Original Message - 
From: "Allan Streib" 

To: "Mercedes Discussion List" 
Sent: Wednesday, August 26, 2009 1:38 AM
Subject: Re: [MBZ] electric cars - was Cash for clunkers hits home



LWB250  writes:


That is regenerative braking, and it's exactly what the resistor banks
on the tops of the locomotives are for.  They use regenerative power
from the traction motors and dump it into the resistors as required to
place a load on the traction motors when braking or slowing the train
down grades.


What I meant was, they don't recover the energy for later use.  They
blow it off as heat.

Allan
--
1983 300D

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Re: [MBZ] electric cars - was Cash for clunkers hits home

[LWB250]

Gotcha.  And heat it does.  Was working in the Beech Grove (IN) AMTRAK yards 
some years back and saw some guy cooking hot dogs over a fan during a dyno test 
on a GE locomotive.  It was the result of a bet with the new kid (sort of like 
sending them out to get a bucket of "prop wash".)

Dan

--- On Wed, 8/26/09, Allan Streib  wrote:

> From: Allan Streib 
> Subject: Re: [MBZ] electric cars - was Cash for clunkers hits home
> To: "Mercedes Discussion List" 
> Date: Wednesday, August 26, 2009, 1:38 AM
> LWB250 
> writes:
> 
> > That is regenerative braking, and it's exactly what
> the resistor banks
> > on the tops of the locomotives are for.  They use
> regenerative power
> > from the traction motors and dump it into the
> resistors as required to
> > place a load on the traction motors when braking or
> slowing the train
> > down grades.
> 
> What I meant was, they don't recover the energy for later
> use.  They
> blow it off as heat.
> 
> Allan
> -- 
> 1983 300D
> 
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Re: [MBZ] electric cars - was Cash for clunkers hits home

[Allan Streib]

LWB250  writes:

> That is regenerative braking, and it's exactly what the resistor banks
> on the tops of the locomotives are for.  They use regenerative power
> from the traction motors and dump it into the resistors as required to
> place a load on the traction motors when braking or slowing the train
> down grades.

What I meant was, they don't recover the energy for later use.  They
blow it off as heat.

Allan
-- 
1983 300D

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Re: [MBZ] electric cars - was Cash for clunkers hits home

[LWB250]

That is regenerative braking, and it's exactly what the resistor banks on the 
tops of the locomotives are for.  They use regenerative power from the traction 
motors and dump it into the resistors as required to place a load on the 
traction motors when braking or slowing the train down grades.

If you look closely at a diesel electric locomotive next time it passes you at 
a grade crossing, you'll see the fan shrouds on the roof of the locomotive.  
These are for both the engine cooling system radiators which are mounted 
horizontally as well as the resistor banks that are usually below the radiators.


Dan


--- On Tue, 8/25/09, Allan Streib  wrote:

> I don't know a whole lot about locomotives but a couple of
> advantages
> spring to mind, one is that the diesels can run at optimum
> RPM to drive
> the generators, also the electric traction motors eliminate
> the need for
> a transmission.  They will apply torque to the wheels
> at 0 RPM.
> 
> They can also serve as brakes, though I think locomotives
> just have a
> bunch of huge resistors they do not have any form of
> regenerative
> braking.
> 
> Allan
> -- 
> 1983 300D
> 
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Re: [MBZ] electric cars - was Cash for clunkers hits home

[Allan Streib]

pm7...@comcast.net writes:

> I doubt that. I believe that Diesel/Electric trains allow a much
> smoother transition of power. I can think of no other drive train that
> would allow what they do.

I don't know a whole lot about locomotives but a couple of advantages
spring to mind, one is that the diesels can run at optimum RPM to drive
the generators, also the electric traction motors eliminate the need for
a transmission.  They will apply torque to the wheels at 0 RPM.

They can also serve as brakes, though I think locomotives just have a
bunch of huge resistors they do not have any form of regenerative
braking.

Allan
-- 
1983 300D

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Re: [MBZ] electric cars - was Cash for clunkers hits home

[pm7088]

Electric drivetrains are more efficient. That's why hybrids get 
better mileage even though they have a quarter-ton-plus more 
equipment. Also why diesel trains run generators and use electric 
motors. 


I doubt that. I believe that Diesel/Electric trains allow a much smoother 
transition of power. I can think of no other drive train that would allow what 
they do. 

Pete 
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Re: [MBZ] electric cars - was Cash for clunkers hits home

[Tim C]

Yes, it's over 10 days old, I'm slow. :)

On Fri, Aug 14, 2009 at 4:42 PM, Fmiser wrote:
>> R A Bennell wrote:
>
>> No one seems to make any comments on these issues. It is all
>> about the environment and the utopian dream that we can carry
>> on without polluting anything. Nothing practical ever
>> mentioned.
>
> Unless the electric generating is pollution-free, the pollution
> is just moved.  Now, in the LA CA bowl, there is some merit to

Electric drivetrains are more efficient.  That's why hybrids get
better mileage even though they have a quarter-ton-plus more
equipment.  Also why diesel trains run generators and use electric
motors.

> that. Otherwise, the typical modern automobile engine is way
> cleaner than the coal fired electric plant.

I don't believe that at all.  Even the nuclear plants have diesel
backups, if it was really cleaner (= better efficiency) they'd be
using them all the time.  Coal scrubbers are pretty sophisticated, and
if you are producing a lot of power in a single area you can afford
much better filtration equipment than you can if you have a lot of
small spots to clean.  I think catalytic converters are a good idea,
but I don't think it makes the exhaust anywhere close to what a modern
coal plant outputs, much less nuclear.  Diesel by that logic is out of
the picture, I won't go there...

Random geeks, via Google, seem to agree with my WAG, though not quite
so overwhelmingly as I'd expected:
http://forums.treehugger.com/viewtopic.php?t=1034
Only comparing CO2, a quick scan found a mention of other pollutants
but it appears they are practically nothing after power generating.

> Now if we could get some fusion plants online

Agree, the more the merrier.  Here in NC we still have a glut of
capacity, if you need it bring cash. :)

-Tim

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Re: [MBZ] electric cars - was Cash for clunkers hits home

[Fmiser]

> R A Bennell wrote:

> No one seems to make any comments on these issues. It is all
> about the environment and the utopian dream that we can carry
> on without polluting anything. Nothing practical ever
> mentioned.

Unless the electric generating is pollution-free, the pollution
is just moved.  Now, in the LA CA bowl, there is some merit to
that. Otherwise, the typical modern automobile engine is way
cleaner than the coal fired electric plant.

Now if we could get some fusion plants online

> Also have to wonder what happens when a couple of hundred
> thousand people plug their car in at night. Does the power go
> off all over or just in some areas? Do you have to shut off
> your house AC so you can charge up the family buggy?

Actually, if there are only plugged in a night, it could be
_helpful_.  One of the challenges of electric generating is
coping with peak load.  It takes days for a coal-fired plant to
turn on. That is of no use when we need more generating capacity
for the 6PM peak.  Nuclear fission is even slower, I think..
(Don't know about fusion - still very new). Natural gas can come
on line in a hour, as I recall.  So coal and fission are used
for baseline.  Wind is - well, variable. But I'd guess that if
you really had more capacity than load those windmill generators
can turn on and off fairly quickly.

Anyway, if we can shift _any_ energy use to the deep off-peak
time, then more of the higher-efficiency, slow-start generators
can supply the power.

Out here in the country, the electric company gives away
dusk-to-dawn lights (but the user pays for the electricity) to
help create some load during the night. I'm guessing it's less
important now than when the program started in the days before
air-conditioning. 

--Philip

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