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Iron-Chromium Flow Battery Aims to Replace Gas Plants

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  Iron-Chromium Flow Battery Aims to Replace Gas Plants Rich <rich@example.invalid> - 2014-06-02 10:44 +0000
    Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Sylvia Else <sylvia@not.at.this.address> - 2014-06-02 23:47 +1000
      Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Whiskers <catwheezel@operamail.com> - 2014-06-03 15:20 +0100
        Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Sylvia Else <sylvia@not.at.this.address> - 2014-06-05 22:14 +1000
          Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Whiskers <catwheezel@operamail.com> - 2014-06-05 20:58 +0100
            Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Sylvia Else <sylvia@not.at.this.address> - 2014-06-06 11:57 +1000
              Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Whiskers <catwheezel@operamail.com> - 2014-06-06 21:14 +0100
                Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Sylvia Else <sylvia@not.at.this.address> - 2014-06-07 13:24 +1000
                  Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Will Honea <whonea@whonea.net> - 2014-06-06 22:49 -0600
                    Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Paul Sture <nospam@sture.ch> - 2014-06-07 08:33 +0200
                    Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Sylvia Else <sylvia@not.at.this.address> - 2014-06-07 16:44 +1000
    Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Bruce Horrocks <07.013@scorecrow.com> - 2014-06-07 22:02 +0100
    Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Oregonian Haruspex <bob_davis_retired@yahoo.com> - 2014-06-09 19:42 +0000
      Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Tim Streater <timstreater@greenbee.net> - 2014-06-09 22:37 +0100
        Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Oregonian Haruspex <bob_davis_retired@yahoo.com> - 2014-06-09 15:19 -0700
          Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Tim Streater <timstreater@greenbee.net> - 2014-06-09 23:26 +0100
            Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Oregonian Haruspex <bob_davis_retired@yahoo.com> - 2014-06-09 15:36 -0700
              Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Tim Streater <timstreater@greenbee.net> - 2014-06-09 23:40 +0100
                Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Oregonian Haruspex <bob_davis_retired@yahoo.com> - 2014-06-09 16:12 -0700
          Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Marko Rauhamaa <marko@pacujo.net> - 2014-06-10 07:44 +0300
            Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Oregonian Haruspex <bob_davis_retired@yahoo.com> - 2014-06-10 18:47 +0000
              Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Marko Rauhamaa <marko@pacujo.net> - 2014-06-10 23:43 +0300
                Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Oregonian Haruspex <bob_davis_retired@yahoo.com> - 2014-06-11 17:12 +0000
                  Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Marko Rauhamaa <marko@pacujo.net> - 2014-06-11 21:58 +0300
                    Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Oregonian Haruspex <bob_davis_retired@yahoo.com> - 2014-06-18 12:44 -0700
            Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Oregonian Haruspex <bob_davis_retired@yahoo.com> - 2014-06-11 17:20 +0000
              Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Marko Rauhamaa <marko@pacujo.net> - 2014-06-11 22:05 +0300
                Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Oregonian Haruspex <bob_davis_retired@yahoo.com> - 2014-06-11 20:52 +0000
                  Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Marko Rauhamaa <marko@pacujo.net> - 2014-06-12 00:14 +0300
                    Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Oregonian Haruspex <bob_davis_retired@yahoo.com> - 2014-06-11 15:12 -0700
                      Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Marko Rauhamaa <marko@pacujo.net> - 2014-06-12 09:18 +0300
                      Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Tim Streater <timstreater@greenbee.net> - 2014-06-12 09:31 +0100
                        Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Marko Rauhamaa <marko@pacujo.net> - 2014-06-12 12:34 +0300
                          Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Paul Sture <nospam@sture.ch> - 2014-06-12 12:37 +0200
                          Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Rich <rich@example.invalid> - 2014-06-12 10:39 +0000
                            Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Marko Rauhamaa <marko@pacujo.net> - 2014-06-12 13:56 +0300
                              Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Rich <rich@example.invalid> - 2014-06-12 12:10 +0000
                                Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Marko Rauhamaa <marko@pacujo.net> - 2014-06-12 15:32 +0300
                                  Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Rich <rich@example.invalid> - 2014-06-13 12:37 +0000
                                    Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Tim Streater <timstreater@greenbee.net> - 2014-06-13 14:13 +0100
                      Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Rich <rich@example.invalid> - 2014-06-12 10:30 +0000
                        Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Huge <Huge@nowhere.much.invalid> - 2014-06-12 10:59 +0000
                          Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Rich <rich@example.invalid> - 2014-06-12 12:12 +0000
      Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Sylvia Else <sylvia@not.at.this.address> - 2014-06-10 20:42 +1000
        Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Tim Streater <timstreater@greenbee.net> - 2014-06-10 15:55 +0100
        Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Oregonian Haruspex <bob_davis_retired@yahoo.com> - 2014-06-10 18:47 +0000
          Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Marko Rauhamaa <marko@pacujo.net> - 2014-06-10 23:50 +0300
            Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Oregonian Haruspex <bob_davis_retired@yahoo.com> - 2014-06-11 17:13 +0000
            Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Randy Westlund <Vorzakir@invalid.invalid> - 2014-06-11 17:23 +0000
              Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Marko Rauhamaa <marko@pacujo.net> - 2014-06-11 22:13 +0300
                Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Randy Westlund <Vorzakir@invalid.invalid> - 2014-06-11 19:22 +0000
                  Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Marko Rauhamaa <marko@pacujo.net> - 2014-06-11 22:39 +0300
                    Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Randy Westlund <Vorzakir@invalid.invalid> - 2014-06-11 19:54 +0000
              Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Tim Streater <timstreater@greenbee.net> - 2014-06-11 22:26 +0100
              Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Rich <rich@example.invalid> - 2014-06-12 00:47 +0000
          Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Sylvia Else <sylvia@not.at.this.address> - 2014-06-11 11:57 +1000
            Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Oregonian Haruspex <bob_davis_retired@yahoo.com> - 2014-06-11 17:12 +0000
          Re: Iron-Chromium Flow Battery Aims to Replace Gas Plants Johny B Good <johnny-b-good@invalid.ntlworld.com> - 2014-06-11 19:21 +0100

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#3635

Oregonian Haruspex <bob_davis_retired@yahoo.com> wrote:
> On 2014-06-11 21:14:21 +0000, Marko Rauhamaa said:

> > Oregonian Haruspex <bob_davis_retired@yahoo.com>:
> > 
> >> So it IS your contention that cells "burn" things in tiny furnaces?
> > 
> > Yes, oxidizing being one of the basic meanings of burning.

> So when rain causes iron to rust underwater it's really burning?

At a chemical reaction level, there is no difference.  What we humans
"see" as "burning" is simply fast oxidation of a chemical in the
presence of oxygen.

The only thing that separates the "burning" of methane in oxygen vs.
the "burning" of iron in oxygen is the speed at which energy is
released in the process.  The methane/oxygen reaction occurs quickly,
so we see flames, light, and significant heat due to the quick release
of energy.  The iron/oxygen reaction occurs slowly, so there is no
measurable (on a human senses level of measurable) heat (typically),
therefore no flame, and no light.

I say "typically" above because you can get iron to "burn", you just
have to start with a large surface area (i.e., steel wool) and apply a
fair amount of starting heat (use a torch), but you can get iron to
visibly "burn".

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#3639

On 2014-06-12, Rich <rich@example.invalid> wrote:

> I say "typically" above because you can get iron to "burn", you just
> have to start with a large surface area (i.e., steel wool) and apply a
> fair amount of starting heat (use a torch), 

Just press the terminals of a PP3 (do Merkins call them that? The 9V battery
with 2 press terminals on the top) into a wad of "fluffed up" wire wool. It
burns quite well.

-- 
Today is Pungenday, the 17th day of Confusion in the YOLD 3180
"I do not believe in revealed religion — I will have nothing to do with your
immortality; we are miserable enough in this life, without speculating on
another." Lord Byron, 1778-1824, letter to Rev. Francis Hodgson, 1811

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#3642

Huge <Huge@nowhere.much.invalid> wrote:
> On 2014-06-12, Rich <rich@example.invalid> wrote:

> > I say "typically" above because you can get iron to "burn", you
> > just have to start with a large surface area (i.e., steel wool) and
> > apply a fair amount of starting heat (use a torch),

> Just press the terminals of a PP3 (do Merkins call them that? The 9V
> battery with 2 press terminals on the top) into a wad of "fluffed up"
> wire wool. It burns quite well.

Here in the USA we call them 9V batteries (or at least that's all I've
ever heard them called).  YMMV.

You can get the same effect with some aluminum foil and a 6V lantern
cell as well.  And aluminum, once you get it to burn, burns about as
brightly as magnesium (which is significantly easier to ignite).

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#3603

On 10/06/2014 5:42 AM, Oregonian Haruspex wrote:
> Rich <rich@example.invalid> wrote:
>> http://spectrum.ieee.org/energywise/energy/the-smarter-grid/new-flow-battery-aims-to-replace-gas-plants
>>
>> "Startup EnerVault will unveil tomorrow what it says is the largest
>> iron-chromium flow battery ever made. Installed in Turlock, Calif., the
>> four-hour, 250-kilowatt battery will be charged by a solar array and
>> power an irrigation system. The project was funded by about US $5
>> million from Department of Energy through the stimulus program and the
>> California Energy Commission." ...
>
> Sadly the IEEE seems to have a moron on "journalism" duty.  Batteries are
> not measured in "hours" and "kilowatts" they are properly measured in
> amp-hours.

In what sense "properly"? Taken at face value, the article is saying 
that the batteries can supply 250 kilowatts for four hours. That's a 
perfectly reasonable way of describing the batteries. Indeed it provides 
more information than "amp-hour", given that that figure is usually 
based on a particular discharge rate, and doesn't indicate the amount of 
energy delivered, which depends on the how the battery voltage varies as 
the battery discharges.

Sylvia.

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#3605

In article <bvo5nuFc0cvU1@mid.individual.net>, Sylvia Else
<sylvia@not.at.this.address> wrote:

> On 10/06/2014 5:42 AM, Oregonian Haruspex wrote:
> > Rich <rich@example.invalid> wrote:
> >>
> >> http://spectrum.ieee.org/energywise/energy/the-smarter-grid/new-flow-batter
> >> y-aims-to-replace-gas-plants
> >>
> >> "Startup EnerVault will unveil tomorrow what it says is the largest
> >> iron-chromium flow battery ever made. Installed in Turlock, Calif., the
> >> four-hour, 250-kilowatt battery will be charged by a solar array and
> >> power an irrigation system. The project was funded by about US $5
> >> million from Department of Energy through the stimulus program and the
> >> California Energy Commission." ...
> >
> > Sadly the IEEE seems to have a moron on "journalism" duty.  Batteries are
> > not measured in "hours" and "kilowatts" they are properly measured in
> > amp-hours.
> 
> In what sense "properly"? Taken at face value, the article is saying 
> that the batteries can supply 250 kilowatts for four hours. That's a 
> perfectly reasonable way of describing the batteries. Indeed it provides 
> more information than "amp-hour", given that that figure is usually 
> based on a particular discharge rate, and doesn't indicate the amount of 
> energy delivered, which depends on the how the battery voltage varies as 
> the battery discharges.

I've been trying to point this out to the fathead but he seems to be
unable to grasp this simple point.

-- 
"If you're not able to ask questions and deal with the answers without feeling 
that someone has called your intelligence or competence into question, don't 
ask questions on Usenet where the answers won't be carefully tailored to avoid
tripping your hair-trigger insecurities."                  - D M Procida, UCSM

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#3608

Sylvia Else <sylvia@not.at.this.address> wrote:
> On 10/06/2014 5:42 AM, Oregonian Haruspex wrote:
>> Rich <rich@example.invalid> wrote:
>>> http://spectrum.ieee.org/energywise/energy/the-smarter-grid/new-flow-battery-aims-to-replace-gas-plants
>>> 
>>> "Startup EnerVault will unveil tomorrow what it says is the largest
>>> iron-chromium flow battery ever made. Installed in Turlock, Calif., the
>>> four-hour, 250-kilowatt battery will be charged by a solar array and
>>> power an irrigation system. The project was funded by about US $5
>>> million from Department of Energy through the stimulus program and the
>>> California Energy Commission." ...
>> 
>> Sadly the IEEE seems to have a moron on "journalism" duty.  Batteries are
>> not measured in "hours" and "kilowatts" they are properly measured in
>> amp-hours.
> 
> In what sense "properly"? Taken at face value, the article is saying that
> the batteries can supply 250 kilowatts for four hours. That's a perfectly
> reasonable way of describing the batteries. Indeed it provides more
> information than "amp-hour", given that that figure is usually based on a
> particular discharge rate, and doesn't indicate the amount of energy
> delivered, which depends on the how the battery voltage varies as the battery discharges.
> 
> Sylvia.

A good data sheet will provide several discharge curves at different
fractions of C, and chart the output voltage over time as well.  The
article doesn't even tell us the working voltage of the battery!

When I say that batteries are "properly" measured in amp-hours, I mean it. 
You don't have to believe me - find an electrical engineer, or a radio ham
with one of the upgraded licenses, and ask them.

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#3610

Oregonian Haruspex <bob_davis_retired@yahoo.com>:

> When I say that batteries are "properly" measured in amp-hours, I mean
> it. You don't have to believe me - find an electrical engineer, or a
> radio ham with one of the upgraded licenses, and ask them.

You don't have to boost your argument by appealing to authority. <URL:
http://en.wikipedia.org/wiki/Appeal_to_authority#Arguments>


Marko

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#3614

Marko Rauhamaa <marko@pacujo.net> wrote:
> Oregonian Haruspex <bob_davis_retired@yahoo.com>:
> 
>> When I say that batteries are "properly" measured in amp-hours, I mean
>> it. You don't have to believe me - find an electrical engineer, or a
>> radio ham with one of the upgraded licenses, and ask them.
> 
> You don't have to boost your argument by appealing to authority. <URL:
> http://en.wikipedia.org/wiki/Appeal_to_authority#Arguments>
> 
> 
> Marko

No, but apparently I have to do something to get people to realize that
there are proper, standard ways to talk about the capacity of a battery. 
Anyway as I did not appeal to a certain authority, but rather encouraged
people to find their own suitable expert, I'm not sure that any fallacy was
committed.

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#3616

On 2014-06-10, Marko Rauhamaa wrote:
> Oregonian Haruspex <bob_davis_retired@yahoo.com>:
>
>> When I say that batteries are "properly" measured in amp-hours, I mean
>> it. You don't have to believe me - find an electrical engineer, or a
>> radio ham with one of the upgraded licenses, and ask them.
>
> You don't have to boost your argument by appealing to authority. <URL:
> http://en.wikipedia.org/wiki/Appeal_to_authority#Arguments>
>
> Marko

Except that he's right.  I've been trying to avoid getting involved
here because this is a silly argument, but here goes:

I'm an EE, I do a good bit with electronics, and I'm also a general
class ham.  Batteries are measured in amp-hours.

To estimate whether a battery will work for a project, I need three
things:  battery chemistry, number of cells, and capacity in amp
hours.  Knowing the chemistry and number of cells tells you the
nominal voltage, as well as other things like how to recharge it (if
possible), what kind of protection circuitry I'll need, etc.

However, that's just for quick estimation.  If I need something
properly calculated, I need the discharge curves in the datasheet.
I'll have to account for average draw in amps, spike usage, depth of
discharge, and a whole bunch of other stuff.

If you can't tell nominal voltage given a battery's chemistry and
cell count, then you're not an EE.  I hate it when someone tells me
a battery's wattage, as if that's helpful.  I feel like I'm being
given a math problem, rather than useful info.


However, we don't use amp-hours when talking about grid power,
because it doesn't (generally) come from a battery.  Kilowatt-hours
makes more sense here.  Power draw is always in watts (not battery
capacity!), so a watt-hour is a reasonable unit of measurement to
describe how much power a person is using.

I'd prefer to use megajoules to measure and bill power, but I don't
mind the watt-hour -- it uses two units which everyone is already
familiar with.


In regards to the article:  the author ought to have described the
battery in terms of nominal voltage and amp-hours (because you
*always* do that for batteries), then estimated how much it can do
in the grid as kilowatts or kilowatt-hours over peak usage (because
amp-hours don't help you with grid power).

Now, can we all stop arguing about stuff you learn in engineering
101?

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#3620

Randy Westlund <Vorzakir@invalid.invalid>:

> Batteries are measured in amp-hours.

Nobody denies that. And the English measure their weight in stones.
Astrophysicists stick to parsecs. Europeans post speed limits in
kilometers per hour.

And, BTW, I would think quoting price per Ah for AA batteries would be a
big step up for the consumer.

However, I personally prefer SI units over the traditional ones and
don't see how Ah's make for easier math than joules.


Marko

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#3621

On 2014-06-11, Marko Rauhamaa wrote:
> Randy Westlund <Vorzakir@invalid.invalid>:
>
>> Batteries are measured in amp-hours.
>
> Nobody denies that. And the English measure their weight in stones.
> Astrophysicists stick to parsecs. Europeans post speed limits in
> kilometers per hour.
>
> And, BTW, I would think quoting price per Ah for AA batteries would be a
> big step up for the consumer.

That would be amazing, yes.

>
> However, I personally prefer SI units over the traditional ones and
> don't see how Ah's make for easier math than joules.
>
>
> Marko

If you're interested in theory, then by all means use joules.  But
if you're working on practical electronics, then you don't care how
much energy your battery holds.  You care about how long it can
power your circuit under your particular circumstances.

If I have a device powered by a 2000 mAh battery, and that device
pulls about 50 mA (common numbers for AA electronics), then I can
easily estimate that the device should remain powered for about 40
hours.

It's all about using the units that make your mental calculations
easier.

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#3622

Randy Westlund <Vorzakir@invalid.invalid>:

> If I have a device powered by a 2000 mAh battery, and that device
> pulls about 50 mA (common numbers for AA electronics), then I can
> easily estimate that the device should remain powered for about 40
> hours.

As an AA battery consumer, I have the device power consumption listed in
the spec sheet more often than current.

FWIW, Google finds 341,000 hits for "samsung galaxy milliwatts" but only
59,400 hits for "samsung galaxy milliamps". Granted, a Samsung Galaxy
doesn't take AA batteries.


Marko

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#3623

On 2014-06-11, Marko Rauhamaa wrote:
> Randy Westlund <Vorzakir@invalid.invalid>:
>
>> If I have a device powered by a 2000 mAh battery, and that device
>> pulls about 50 mA (common numbers for AA electronics), then I can
>> easily estimate that the device should remain powered for about 40
>> hours.
>
> As an AA battery consumer, I have the device power consumption listed in
> the spec sheet more often than current.
>
> FWIW, Google finds 341,000 hits for "samsung galaxy milliwatts" but only
> 59,400 hits for "samsung galaxy milliamps". Granted, a Samsung Galaxy
> doesn't take AA batteries.
>
>
> Marko

I think this is a recent shift.  As an engineer, I use amps much
more frequently than watts.  But as a consumer of phones and other
'all-in-one' devices, I do see watts being used more and more
frequently.  Hmm...

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#3626

In article <lna3al$l08$1@dont-email.me>, Randy Westlund
<Vorzakir@invalid.invalid> wrote:

> On 2014-06-10, Marko Rauhamaa wrote:
> > Oregonian Haruspex <bob_davis_retired@yahoo.com>:
> >
> >> When I say that batteries are "properly" measured in amp-hours, I mean
> >> it. You don't have to believe me - find an electrical engineer, or a
> >> radio ham with one of the upgraded licenses, and ask them.
> >
> > You don't have to boost your argument by appealing to authority. <URL:
> > http://en.wikipedia.org/wiki/Appeal_to_authority#Arguments>
> >
> > Marko
> 
> Except that he's right.  I've been trying to avoid getting involved
> here because this is a silly argument, but here goes:
> 
> I'm an EE, I do a good bit with electronics, and I'm also a general
> class ham.  Batteries are measured in amp-hours.
> 
> To estimate whether a battery will work for a project, I need three
> things:  battery chemistry, number of cells, and capacity in amp
> hours.  Knowing the chemistry and number of cells tells you the
> nominal voltage, as well as other things like how to recharge it (if
> possible), what kind of protection circuitry I'll need, etc.
> 
> However, that's just for quick estimation.  If I need something
> properly calculated, I need the discharge curves in the datasheet.
> I'll have to account for average draw in amps, spike usage, depth of
> discharge, and a whole bunch of other stuff.

None of that is important for the purpose of getting an order of
magnitude idea of feasibility of such a battery in the context of power
generation, which is what we are discussing. Then I need to know how
much *energy* it can store.

The Strines are talking about using molten salt as an energy store for
their solar power generators. Since most of their land is desert with
some kangaroos, it'll be interesting to see how it works. The solar
power generator uses a molten salt circuit with a reservoir for during
the night. Now I don't know the nominal voltage of molten salt, or how
many amp-hours I can store in 100 tons of the stuff. But oddly enough,
that doesn't matter. What matter is how many kWh it can store

> If you can't tell nominal voltage given a battery's chemistry and
> cell count, then you're not an EE.  I hate it when someone tells me
> a battery's wattage, as if that's helpful.  I feel like I'm being
> given a math problem, rather than useful info.

A battery is one way of storing energy, a talk of molten salt is
another. Let's try to use the same units in both cases, OK?

-- 
"People don't buy Microsoft for quality, they buy it for compatibility
with what Bob in accounting bought last year. Trace it back - they buy
Microsoft because the IBM Selectric didn't suck much" - P Seebach, afc

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#3631

Randy Westlund <Vorzakir@invalid.invalid> wrote:
> On 2014-06-10, Marko Rauhamaa wrote:
> > Oregonian Haruspex <bob_davis_retired@yahoo.com>:
> >
> >> When I say that batteries are "properly" measured in amp-hours, I mean
> >> it. You don't have to believe me - find an electrical engineer, or a
> >> radio ham with one of the upgraded licenses, and ask them.
> >
> > You don't have to boost your argument by appealing to authority. <URL:
> > http://en.wikipedia.org/wiki/Appeal_to_authority#Arguments>
> >
> > Marko

> Except that he's right.  I've been trying to avoid getting involved
> here because this is a silly argument, but here goes:

> I'm an EE, I do a good bit with electronics, and I'm also a general
> class ham.  Batteries are measured in amp-hours.

> To estimate whether a battery will work for a project, I need three
> things:  battery chemistry, number of cells, and capacity in amp
> hours.  Knowing the chemistry and number of cells tells you the
> nominal voltage, as well as other things like how to recharge it (if
> possible), what kind of protection circuitry I'll need, etc.

> However, that's just for quick estimation.  If I need something
> properly calculated, I need the discharge curves in the datasheet.
> I'll have to account for average draw in amps, spike usage, depth of
> discharge, and a whole bunch of other stuff.

> If you can't tell nominal voltage given a battery's chemistry and
> cell count, then you're not an EE.  I hate it when someone tells me
> a battery's wattage, as if that's helpful.  I feel like I'm being
> given a math problem, rather than useful info.


> However, we don't use amp-hours when talking about grid power,
> because it doesn't (generally) come from a battery.  Kilowatt-hours
> makes more sense here.  Power draw is always in watts (not battery
> capacity!), so a watt-hour is a reasonable unit of measurement to
> describe how much power a person is using.

> I'd prefer to use megajoules to measure and bill power, but I don't
> mind the watt-hour -- it uses two units which everyone is already
> familiar with.


> In regards to the article:  the author ought to have described the
> battery in terms of nominal voltage and amp-hours (because you
> *always* do that for batteries), then estimated how much it can do
> in the grid as kilowatts or kilowatt-hours over peak usage (because
> amp-hours don't help you with grid power).

> Now, can we all stop arguing about stuff you learn in engineering
> 101?

Seconded by a second EE.  Mr. Westlund is absolutely correct.

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#3611

On 11/06/2014 4:47 AM, Oregonian Haruspex wrote:
> Sylvia Else <sylvia@not.at.this.address> wrote:
>> On 10/06/2014 5:42 AM, Oregonian Haruspex wrote:
>>> Rich <rich@example.invalid> wrote:
>>>> http://spectrum.ieee.org/energywise/energy/the-smarter-grid/new-flow-battery-aims-to-replace-gas-plants
>>>>
>>>> "Startup EnerVault will unveil tomorrow what it says is the largest
>>>> iron-chromium flow battery ever made. Installed in Turlock, Calif., the
>>>> four-hour, 250-kilowatt battery will be charged by a solar array and
>>>> power an irrigation system. The project was funded by about US $5
>>>> million from Department of Energy through the stimulus program and the
>>>> California Energy Commission." ...
>>>
>>> Sadly the IEEE seems to have a moron on "journalism" duty.  Batteries are
>>> not measured in "hours" and "kilowatts" they are properly measured in
>>> amp-hours.
>>
>> In what sense "properly"? Taken at face value, the article is saying that
>> the batteries can supply 250 kilowatts for four hours. That's a perfectly
>> reasonable way of describing the batteries. Indeed it provides more
>> information than "amp-hour", given that that figure is usually based on a
>> particular discharge rate, and doesn't indicate the amount of energy
>> delivered, which depends on the how the battery voltage varies as the battery discharges.
>>
>> Sylvia.
>
> A good data sheet will provide several discharge curves at different
> fractions of C, and chart the output voltage over time as well.  The
> article doesn't even tell us the working voltage of the battery!

Why do we need to know? The batteries will be connected to an inverter 
anyway. The article provides the useful information, which is the energy 
capacity, and the rate at which the energy can be delivered. The rest is 
just implementation detail.
>
> When I say that batteries are "properly" measured in amp-hours, I mean it.
> You don't have to believe me - find an electrical engineer, or a radio ham
> with one of the upgraded licenses, and ask them.
>

You seem to be substituting reading for understanding.

Sylvia.

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#3613

Sylvia Else <sylvia@not.at.this.address> wrote:

> Why do we need to know? The batteries will be connected to an inverter
> anyway. The article provides the useful information, which is the energy
> capacity, and the rate at which the energy can be delivered. The rest is
> just implementation detail.

We don't need to know.  I was just commenting on the poor quality of
journalism produced by an alleged professonal electrical engineering
society, something that should be a bit disappointing to both it's members
and the members of the public who have a basic understanding of
electronics.

> 
> You seem to be substituting reading for understanding.
> 
> Sylvia.

This is the best you can do?  I guess it's unreasonable to expect more from
a person who defends poor quality pop science journalism.

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#3617

On Tue, 10 Jun 2014 18:47:52 +0000 (UTC), Oregonian Haruspex
<bob_davis_retired@yahoo.com> wrote:

>Sylvia Else <sylvia@not.at.this.address> wrote:
>> On 10/06/2014 5:42 AM, Oregonian Haruspex wrote:
>>> Rich <rich@example.invalid> wrote:
>>>> http://spectrum.ieee.org/energywise/energy/the-smarter-grid/new-flow-battery-aims-to-replace-gas-plants
>>>> 
>>>> "Startup EnerVault will unveil tomorrow what it says is the largest
>>>> iron-chromium flow battery ever made. Installed in Turlock, Calif., the
>>>> four-hour, 250-kilowatt battery will be charged by a solar array and
>>>> power an irrigation system. The project was funded by about US $5
>>>> million from Department of Energy through the stimulus program and the
>>>> California Energy Commission." ...
>>> 
>>> Sadly the IEEE seems to have a moron on "journalism" duty.  Batteries are
>>> not measured in "hours" and "kilowatts" they are properly measured in
>>> amp-hours.
>> 
>> In what sense "properly"? Taken at face value, the article is saying that
>> the batteries can supply 250 kilowatts for four hours. That's a perfectly
>> reasonable way of describing the batteries. Indeed it provides more
>> information than "amp-hour", given that that figure is usually based on a
>> particular discharge rate, and doesn't indicate the amount of energy
>> delivered, which depends on the how the battery voltage varies as the battery discharges.
>> 
>> Sylvia.
>
>A good data sheet will provide several discharge curves at different
>fractions of C, and chart the output voltage over time as well.  The
>article doesn't even tell us the working voltage of the battery!
>
>When I say that batteries are "properly" measured in amp-hours, I mean it. 
>You don't have to believe me - find an electrical engineer, or a radio ham
>with one of the upgraded licenses, and ask them.

 AH is a simple measure of battery capacity in common use for starter
batteries,  SLA batteries used for things like UPSes and other
_self_contained_ rechargable cell technology. However, there's no
reason why the manufacturer can't also quote a WH figure for their
battery. Indeed, a lot of laptop batteries have WH figures quoted as
part of their specification (very little Peukert effect to complicate
the calculation at the reasonably predictable discharge rates
involved).

 Getting a meaningful WH figure is complicated by the varying voltage
on discharge due to both internal cell resistance and rates of
discharge chosen to calculate the WH figure(s) in the case of lead
acid cells.

 The AH figures are important here when you're making up and
maintaining a battery string where all the cells in series have to
have equal AH ratings. It's not as important when it comes to putting
cells in parallel (usually pre-assembled batteries in parallel don't
have to have matching AH ratings, just equal voltages).

 In this case (Iron-Chromium Flow Battery), we're discussing a fuel
cell which can maintain a constant voltage up to a maximum power draw
limit for as long as there is 'fuel' available. It's not quite the
same situation we see with self contained sealed rechargable cells.

 When we get to fuel cell technology, it's the effective WH capacity
figure of the overall system that matters. In this case, the fuel cell
assembly used has a maximum power delivery rating of 250KW with a fuel
supply sufficient to maintain that level of power delivery for four
hours.

 In essence, that configuration has an effective figure of 1MWH which
could be doubled by simply doubling the fuel tank capacities (doubling
the endurance whilst leaving the maximum power delivery unchanged -
you'd also have to double up the fuel cell stack size to double the
power delivery rate over the original 4 hour period).

  What you're proposing is equivilent to assigning a torque hour
capacity to an internal combustion engine without regard to the rpm
limits and fuel tank capacity.

 A fuel cell is a lot like an ICE (only without the combustion). The
maximum amperage is the torque and the voltage, determined by the
number of cells in the stack, being the analogue of the rpm speed. The
KWH rating for an ICE plant is directly dependent on the fuel tank
capacity and  fuel cell power plant is no different in this regard.
-- 
J B Good

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