Nuclear battery

[Rick C]

Here is the type of battery that really is needed.

"In the U.S., the Silicon Valley-based firm introduced its new battery technology called Megapack last month that Pacific Gas & Electric Co. plans to use in California. Mitsubishi Hitachi Power Systems is developing high-capacity batteries for a 1,000-megawatt venture in Utah that it touts as the world's largest renewable-energy storage project."

A GW of power in one installation. Not bad. It's not even a Tesla so no free Supercharging.

--

Rick C.

+++ Get 1,000 miles of free Supercharging
+++ Tesla referral code - https://ts.la/richard11209

 

[Bill Sloman]

On Monday, August 19, 2019 at 11:55:17 PM UTC+10, Rick C wrote:

Here is the type of battery that really is needed.

"In the U.S., the Silicon Valley-based firm introduced its new battery technology called Megapack last month that Pacific Gas & Electric Co. plans to use in California. Mitsubishi Hitachi Power Systems is developing high-capacity batteries for a 1,000-megawatt venture in Utah that it touts as the world's largest renewable-energy storage project."

A GW of power in one installation. Not bad. It's not even a Tesla so no free Supercharging.

https://en.wikipedia.org/wiki/Vanadium_redox_battery

The entry lists seven installations, none of them all that big. Apparently there's one being installed in China at the moment that's going to be 200MW and 800MW.hour when all the bits are in place.

One GigaWatt would be appreciably bigger, but high technology puff pieces do like to make that kind of claim.

Dinorwig in the UK is 1.728 GW and can store 9.1 GW.hours, but it has been there since 1984, and is pumped water. It predates "renewable power" so the puff writer seems to have felt free to ignore it.

In Australia the Snowy 2 scheme will be able to deliver 2GW and store 350 GW.hours, if it does get built.

--
Bill Sloman, Sydney

 

[Martin Brown]

On 18/08/2019 03:21, Bill Sloman wrote:

On Sunday, August 18, 2019 at 12:48:50 AM UTC+10, Rick C wrote:
On Saturday, August 17, 2019 at 4:44:01 AM UTC-4, Martin Brown
wrote:
On 16/08/2019 23:36, Rick C wrote:

They still have not released enough information to say what
was wrong. I saw in another group that the frequency drop (the
trigger for most of the load shedding) happened some minutes
before the gas plant went offline and that a couple minutes
before the wind farm went offline. So it is not at all clear
what was cause and what was effect.

That is utter bollocks. The raw frequency data for a few sites
have been published online with timestamps that match that event
see for example:

https://groups.google.com/forum/#!search/%22Manchester$20$232%22$20power$20cut/uk.d-i-y/n0CaxawZRR4/-d6gHUIECwAJ



The frequency (and voltage) dip and load shedding was all over inside a
five minute period and then bounced back. 16:52:44 - 16:57:00

Don't know about "utter bollocks"...

*COMPLETE AND UTTER BOLLOCKS*

You mention 16:52 and yet the shutdowns occurred after 16:55. I
think you are verifying my claim. If you look at the data you
linked to, it also shows maximum frequency deviation prior to
16:55. West Midlands shows frequencies below 49.5 as early as
16:52:44.

The LFDD shutdowns started in earnest once the frequency breached the
lower limit of 48.8Hz at 16:53:50 and continued until the frequency rose
to 50Hz (and then overshot slightly). Until that point it was mostly
local systems making self protection decisions based on f and/or df/dt.

Here is the data I saw on 15 second measurements rather than 1
minute. By 16:55 the frequency is back to 49.5 Hz.

The frequency deviations are the "event". The shutdowns are
consequences of the event. Feed the wrong kind of transient into a
system, and you get increasing deviations until something trips out.
The deviations can swing from positive to negative in the process.

They claim publicly that a lightning strike on a transmission line close
to Little Barford took out 1 of three generators there and that this was
followed "seconds" later by Hornsea suddenly dropping out (itself a bit
surprising since East Anglia was a lot closer to ground zero). Then
cascade failure at Little Barford took out the rest of that plant as
well as various smaller local players. The sum of these exceeded their
spare capacity by almost a factor of two and so to halt the cascade
failure they dropped 5% of load off the grid under LFDD rules.

The railways own protection systems just went haywire and were *NOT*
disconnected by Nation Grid the damage they had was all self inflicted!

The initial report is out but finding a copy online is rather hard. This
makes me suspicious. I have now found a copy marked Highly Confidential
- I don't know how long it will stay there:

https://www.ofgem.gov.uk/system/files/docs/2019/08/incident_report_lfdd_-_summary_-_final.pdf

It isn't highlighted in the summary but the timeline of events shows
that some sort of over sensitivity on the part of the bulk component
747MW of Hornsea wind farm was responsible for bringing the network
down. The report summary is very careful not to draw attention to the
detailed timeline which shows that Hornsea probably went down first!
Barford timestamps at present are only good to the nearest second.

Hornsea started deloading just 230ms after the transient blue phase
fault and the first generator at Barford within 1s. It is fair to say
that the lightning strike probably initiated both events.

Barford was *very* close to the lightning strike see map on page 8.

See page 11 "Timeline of Events" and p13 "Annotated frequency chart"

They imply that the protection systems at Hornsea have since been
adjusted to make them somewhat more tolerant of ms transient faults.
See page 14.

It may well be that they both dropped off together but the Little
Barford only lost the first 244MW steam turbine whereas Hornsea lost
737MW. A small part of Hornsea continued to supply a meagre 62MW.

Little Barford's other generators soldiered on but GT1A tripped about a
minute after the initial failure and GT1B was manually shut down 30s
after that. By then load shedding was well under way since frequency was
a long way out of spec and at 48.8 had triggered a full LFDD response.

National Grid appear to have performed extremely well to manage the
situation in real time even if the knock on effects were substantial. It
was all over bar the shouting in just under 5 minutes clock time.

--
Regards,
Martin Brown

 

[Martin Brown]

On 19/08/2019 15:41, Bill Sloman wrote:

Dinorwig in the UK is 1.728 GW and can store 9.1 GW.hours, but it has
been there since 1984, and is pumped water. It predates "renewable
power" so the puff writer seems to have felt free to ignore it.

Dinorwig was built to compliment the UK's intended nuclear capacity and
smooth out the peaks. In part it was pushed up the agenda a bit by the
OPEC induced acute oil crisis of the 1970's and the "Save It" campaign.

In Australia the Snowy 2 scheme will be able to deliver 2GW and store
350 GW.hours, if it does get built.

UK apparently has 472MW of battery backup capacity at present according
to the report on the grid failure. It doesn't say how many MWhr though.

--
Regards,
Martin Brown

 

[piglet]

On 19/08/2019 4:24 am, Rick C wrote:

On Sunday, August 18, 2019 at 6:16:03 AM UTC-4, piglet wrote:
On 18/08/2019 08:57, Rick C wrote:

Like I said, no one has mentioned any event that could have caused the initial problem. I've not heard anyone talk about lightning impacts at the time of the initial frequency deviation. Have you?


Yes, many reports have talked about a lightning strike shutting down one
of the generators - where they have differed is that some say the wind
farm was struck and others say the gas plant!

Clearly then the lightning report is highly reliable.

Well now we know the sequence:
1. Lightning strike
2. Wind farm disconnects
3. Gas plant struggles then disconnects

<https://www.nationalgrideso.com/document/151081/download>

piglet

 

[nuny@bid.nes]

On Thursday, August 15, 2019 at 3:49:18 PM UTC-7, John Larkin wrote:

(Damn- I screwed up the attribution. Anyway...)

I prefer the plastic filled with doped strontium aluminate - just needs
to be in the sun for a few hours to work all night. 3M had an emergency
torch that used it to great effect just before power LEDs became common.

I tried that, but there's not enough daylight in that bedroom to
charge the strontium aluminate. Strontium aluminate is amazing stuff.

Strontium-90 is dangerous because it replaces calcium in vivo.

Calcium aluminate is used in Portland cement replacements. Does it do the same thing? I haven't noticed many sidewalks glowing at dusk...


Mark L. Fergerson

 

[Martin Brown]

On 20/08/2019 22:23, nuny@bid.nes wrote:

On Thursday, August 15, 2019 at 3:49:18 PM UTC-7, John Larkin wrote:

(Damn- I screwed up the attribution. Anyway...)

I prefer the plastic filled with doped strontium aluminate - just
needs to be in the sun for a few hours to work all night. 3M had
an emergency torch that used it to great effect just before power
LEDs became common.

I tried that, but there's not enough daylight in that bedroom to
charge the strontium aluminate. Strontium aluminate is amazing
stuff.

Strontium-90 is dangerous because it replaces calcium in vivo.

This is a compound of ordinary natural non-radioactive strontium with
amazing ability to absorb photons and re-emit them later. It makes the
old glow in the dark toys look like - well toys. If I leave my find in
the dark torch in the sun it will allow you to see by it after dark once
dark adapted without having to switch it on!

Calcium aluminate is used in Portland cement replacements. Does it do
the same thing? I haven't noticed many sidewalks glowing at dusk...

It is very specific to a rare earth doped strontium aluminate.

--
Regards,
Martin Brown

 

[Dave Platt]

In article <qjgebu$1756$1@gioia.aioe.org>,
Martin Brown <'''newspam'''@nezumi.demon.co.uk> wrote:

The initial report is out but finding a copy online is rather hard. This
makes me suspicious. I have now found a copy marked Highly Confidential
- I don't know how long it will stay there:

https://www.ofgem.gov.uk/system/files/docs/2019/08/incident_report_lfdd_-_summary_-_final.pdf

It isn't highlighted in the summary but the timeline of events shows
that some sort of over sensitivity on the part of the bulk component
747MW of Hornsea wind farm was responsible for bringing the network
down. The report summary is very careful not to draw attention to the
detailed timeline which shows that Hornsea probably went down first!
Barford timestamps at present are only good to the nearest second.

It might (or might not) be significant that the reported loss of
generated power from Hornsea and Little Barford was 1.378 GW. That's
just above the threshold required to activate a flux capacitor and
initiate time travel.

 

[John Larkin]

On Tue, 20 Aug 2019 22:36:54 +0100, Martin Brown
<'''newspam'''@nezumi.demon.co.uk> wrote:

On 20/08/2019 22:23, nuny@bid.nes wrote:
On Thursday, August 15, 2019 at 3:49:18 PM UTC-7, John Larkin wrote:

(Damn- I screwed up the attribution. Anyway...)

I prefer the plastic filled with doped strontium aluminate - just
needs to be in the sun for a few hours to work all night. 3M had
an emergency torch that used it to great effect just before power
LEDs became common.

I tried that, but there's not enough daylight in that bedroom to
charge the strontium aluminate. Strontium aluminate is amazing
stuff.

Strontium-90 is dangerous because it replaces calcium in vivo.

This is a compound of ordinary natural non-radioactive strontium with
amazing ability to absorb photons and re-emit them later. It makes the
old glow in the dark toys look like - well toys. If I leave my find in
the dark torch in the sun it will allow you to see by it after dark once
dark adapted without having to switch it on!

A modest sheet of that stuff could be left outdoors in sunlight, in
some village without electricity. It would immuminate the indoors for
hours after dark, enough probably for a kid to read a schoolbook by.

It must be 200x better than the old zinc sulfide stuff.

This glows in the dark, for a minute or so.

https://www.dropbox.com/s/06ct6tqdr0dzxmu/4FP7.jpg?raw=1

P7 radar phosphor.

 

[Rick C]

On Tuesday, August 20, 2019 at 5:08:09 PM UTC-4, Dave Platt wrote:

In article <qjgebu$1756$1@gioia.aioe.org>,
Martin Brown <'''newspam'''@nezumi.demon.co.uk> wrote:
The initial report is out but finding a copy online is rather hard. This
makes me suspicious. I have now found a copy marked Highly Confidential
- I don't know how long it will stay there:

https://www.ofgem.gov.uk/system/files/docs/2019/08/incident_report_lfdd_-_summary_-_final.pdf

It isn't highlighted in the summary but the timeline of events shows
that some sort of over sensitivity on the part of the bulk component
747MW of Hornsea wind farm was responsible for bringing the network
down. The report summary is very careful not to draw attention to the
detailed timeline which shows that Hornsea probably went down first!
Barford timestamps at present are only good to the nearest second.

It might (or might not) be significant that the reported loss of
generated power from Hornsea and Little Barford was 1.378 GW. That's
just above the threshold required to activate a flux capacitor and
initiate time travel.

Maybe that's why initial reports of the cause of Little Barford dropping out and the timing were all inaccurate. The time line hadn't sorted things out and restabilized yet. Once the time travel event was properly integrated with the power levels, all was well.

--

Rick C.

---- Get 1,000 miles of free Supercharging
---- Tesla referral code - https://ts.la/richard11209

 

[Martin Brown]

On 20/08/2019 22:02, Dave Platt wrote:

In article <qjgebu$1756$1@gioia.aioe.org>,
Martin Brown <'''newspam'''@nezumi.demon.co.uk> wrote:
The initial report is out but finding a copy online is rather hard. This
makes me suspicious. I have now found a copy marked Highly Confidential
- I don't know how long it will stay there:

https://www.ofgem.gov.uk/system/files/docs/2019/08/incident_report_lfdd_-_summary_-_final.pdf

It isn't highlighted in the summary but the timeline of events shows
that some sort of over sensitivity on the part of the bulk component
747MW of Hornsea wind farm was responsible for bringing the network
down. The report summary is very careful not to draw attention to the
detailed timeline which shows that Hornsea probably went down first!
Barford timestamps at present are only good to the nearest second.

It might (or might not) be significant that the reported loss of
generated power from Hornsea and Little Barford was 1.378 GW. That's
just above the threshold required to activate a flux capacitor and
initiate time travel.

That or a T1000 arriving. What is clear though is that the report's
executive summary widely reported in the media is wilfully misleading.
Let us hope that the technical report is not so compromised.

--
Regards,
Martin Brown

 

[nuny@bid.nes]

On Tuesday, August 20, 2019 at 2:37:00 PM UTC-7, Martin Brown wrote:

On 20/08/2019 22:23, nuny@bid.nes wrote:
On Thursday, August 15, 2019 at 3:49:18 PM UTC-7, John Larkin wrote:

(Damn- I screwed up the attribution. Anyway...)

I prefer the plastic filled with doped strontium aluminate - just
needs to be in the sun for a few hours to work all night. 3M had
an emergency torch that used it to great effect just before power
LEDs became common.

I tried that, but there's not enough daylight in that bedroom to
charge the strontium aluminate. Strontium aluminate is amazing
stuff.

Strontium-90 is dangerous because it replaces calcium in vivo.

I only mentioned that because of the very similar chemistry of strontium and calcium. Calcium is however considerably cheaper than strontium.

This is a compound of ordinary natural non-radioactive strontium with
amazing ability to absorb photons and re-emit them later. It makes the
old glow in the dark toys look like - well toys. If I leave my find in
the dark torch in the sun it will allow you to see by it after dark once
dark adapted without having to switch it on!

Okay...

Calcium aluminate is used in Portland cement replacements. Does it do
the same thing? I haven't noticed many sidewalks glowing at dusk...

It is very specific to a rare earth doped strontium aluminate.

I was just wondering if they'd even tried similarly doped calcium aluminate. Hell, do you know what it's doped with, and how much? I haven't done any experimental garage chemistry in a while...


Mark L. Fergerson

 

[Martin Brown]

On 21/08/2019 11:09, nuny@bid.nes wrote:

On Tuesday, August 20, 2019 at 2:37:00 PM UTC-7, Martin Brown wrote:
On 20/08/2019 22:23, nuny@bid.nes wrote:
On Thursday, August 15, 2019 at 3:49:18 PM UTC-7, John Larkin
wrote:

(Damn- I screwed up the attribution. Anyway...)

I prefer the plastic filled with doped strontium aluminate -
just needs to be in the sun for a few hours to work all
night. 3M had an emergency torch that used it to great effect
just before power LEDs became common.

I tried that, but there's not enough daylight in that bedroom
to charge the strontium aluminate. Strontium aluminate is
amazing stuff.

Strontium-90 is dangerous because it replaces calcium in vivo.

I only mentioned that because of the very similar chemistry of
strontium and calcium. Calcium is however considerably cheaper than
strontium.

This is a compound of ordinary natural non-radioactive strontium
with amazing ability to absorb photons and re-emit them later. It
makes the old glow in the dark toys look like - well toys. If I
leave my find in the dark torch in the sun it will allow you to see
by it after dark once dark adapted without having to switch it on!

Okay...

Calcium aluminate is used in Portland cement replacements. Does
it do the same thing? I haven't noticed many sidewalks glowing at
dusk...

It is very specific to a rare earth doped strontium aluminate.

I was just wondering if they'd even tried similarly doped calcium
aluminate. Hell, do you know what it's doped with, and how much? I
haven't done any experimental garage chemistry in a while...

Calcium aluminate doesn't play or they would use it instead.

Dopant is usually Europium (and/or other REEs). See

https://en.wikipedia.org/wiki/Strontium_aluminate

You can buy the powder on eBay. 3M used to make a very good plastic
using the stuff and a dayglo yellow marker pen dye to down convert blue
photons into the peak band for human vision. It is more than an order of
magnitude brighter than old zinc sulphide phosphorescent materials and
much longer lasting (mine literally lasts all night in summer ~6 hours).

The snag with 3Ms product was that most people didn't understand the
advantage of having an emergency torch you could find in pitch darkness.
Modern mains supplies are so reliable people have forgotten the dark!

--
Regards,
Martin Brown

 

[Martin Brown]

On 21/08/2019 15:09, jlarkin@highlandsniptechnology.com wrote:

On Wed, 21 Aug 2019 11:52:12 +0100, Martin Brown
'''newspam'''@nezumi.demon.co.uk> wrote:

The snag with 3Ms product was that most people didn't understand the
advantage of having an emergency torch you could find in pitch darkness.
Modern mains supplies are so reliable people have forgotten the dark!

An good LED is visible in the dark at 1 uA or less. An amp-hour of
battery computes to...

Even at 10uA which is what I tend to run them at (previous generation)
they still last a very long time. But the 3M product was back when LEDs
were indicators and torches used 3v filament bulbs at 1A or so.

I have some emergency lanterns that blink an LED in the dark without
much affecting battery life.

A Tadiran lithium battery and an LED and a 1M or so resistor will be
visible for 40 years or so.

Lithium batteries make most "energy harvesting" idea look silly.

I still think that the 3M glo-plastic has a place in remote locations
where charging a battery or the price of one is prohibitive.

--
Regards,
Martin Brown

 

On Wed, 21 Aug 2019 11:52:12 +0100, Martin Brown
<'''newspam'''@nezumi.demon.co.uk> wrote:

On 21/08/2019 11:09, nuny@bid.nes wrote:
On Tuesday, August 20, 2019 at 2:37:00 PM UTC-7, Martin Brown wrote:
On 20/08/2019 22:23, nuny@bid.nes wrote:
On Thursday, August 15, 2019 at 3:49:18 PM UTC-7, John Larkin
wrote:

(Damn- I screwed up the attribution. Anyway...)

I prefer the plastic filled with doped strontium aluminate -
just needs to be in the sun for a few hours to work all
night. 3M had an emergency torch that used it to great effect
just before power LEDs became common.

I tried that, but there's not enough daylight in that bedroom
to charge the strontium aluminate. Strontium aluminate is
amazing stuff.

Strontium-90 is dangerous because it replaces calcium in vivo.

I only mentioned that because of the very similar chemistry of
strontium and calcium. Calcium is however considerably cheaper than
strontium.

This is a compound of ordinary natural non-radioactive strontium
with amazing ability to absorb photons and re-emit them later. It
makes the old glow in the dark toys look like - well toys. If I
leave my find in the dark torch in the sun it will allow you to see
by it after dark once dark adapted without having to switch it on!

Okay...

Calcium aluminate is used in Portland cement replacements. Does
it do the same thing? I haven't noticed many sidewalks glowing at
dusk...

It is very specific to a rare earth doped strontium aluminate.

I was just wondering if they'd even tried similarly doped calcium
aluminate. Hell, do you know what it's doped with, and how much? I
haven't done any experimental garage chemistry in a while...

Calcium aluminate doesn't play or they would use it instead.

Dopant is usually Europium (and/or other REEs). See

https://en.wikipedia.org/wiki/Strontium_aluminate

You can buy the powder on eBay. 3M used to make a very good plastic
using the stuff and a dayglo yellow marker pen dye to down convert blue
photons into the peak band for human vision. It is more than an order of
magnitude brighter than old zinc sulphide phosphorescent materials and
much longer lasting (mine literally lasts all night in summer ~6 hours).

The snag with 3Ms product was that most people didn't understand the
advantage of having an emergency torch you could find in pitch darkness.
Modern mains supplies are so reliable people have forgotten the dark!

An good LED is visible in the dark at 1 uA or less. An amp-hour of
battery computes to...

I have some emergency lanterns that blink an LED in the dark without
much affecting battery life.

A Tadiran lithium battery and an LED and a 1M or so resistor will be
visible for 40 years or so.

Lithium batteries make most "energy harvesting" idea look silly.

 

On Wed, 21 Aug 2019 15:17:18 +0100, Martin Brown
<'''newspam'''@nezumi.demon.co.uk> wrote:

On 21/08/2019 15:09, jlarkin@highlandsniptechnology.com wrote:
On Wed, 21 Aug 2019 11:52:12 +0100, Martin Brown
'''newspam'''@nezumi.demon.co.uk> wrote:

The snag with 3Ms product was that most people didn't understand the
advantage of having an emergency torch you could find in pitch darkness.
Modern mains supplies are so reliable people have forgotten the dark!

An good LED is visible in the dark at 1 uA or less. An amp-hour of
battery computes to...

Even at 10uA which is what I tend to run them at (previous generation)
they still last a very long time. But the 3M product was back when LEDs
were indicators and torches used 3v filament bulbs at 1A or so.

I took a good green LED up to the cabin where it's really dark at
night. I got up at 2AM and ran a little test. The threshold of
visibility was about 1 nA. I didn't expect that an LED would emit any
photons at 1 nA, much less that I could see them.

Maybe I'll try that again, with the super-good Osrams of various
colors. The blue is blinding at 5 mA, even though human vision peaks
in the green.

 

[Martin Brown]

On 21/08/2019 16:07, jlarkin@highlandsniptechnology.com wrote:

On Wed, 21 Aug 2019 15:17:18 +0100, Martin Brown
'''newspam'''@nezumi.demon.co.uk> wrote:

On 21/08/2019 15:09, jlarkin@highlandsniptechnology.com wrote:
On Wed, 21 Aug 2019 11:52:12 +0100, Martin Brown
'''newspam'''@nezumi.demon.co.uk> wrote:

The snag with 3Ms product was that most people didn't understand the
advantage of having an emergency torch you could find in pitch darkness.
Modern mains supplies are so reliable people have forgotten the dark!

An good LED is visible in the dark at 1 uA or less. An amp-hour of
battery computes to...

Even at 10uA which is what I tend to run them at (previous generation)
they still last a very long time. But the 3M product was back when LEDs
were indicators and torches used 3v filament bulbs at 1A or so.

I took a good green LED up to the cabin where it's really dark at
night. I got up at 2AM and ran a little test. The threshold of
visibility was about 1 nA. I didn't expect that an LED would emit any
photons at 1 nA, much less that I could see them.

It is surprising just how good the human eye is at detecting photons
once it is fully dark adapted. Big cats are better. At 10uA even with
the previous generation you can see to walk around once dark adapted.

Maybe I'll try that again, with the super-good Osrams of various
colors. The blue is blinding at 5 mA, even though human vision peaks
in the green.

I have a resistor with a 1970's era red LED and a modern high brightness
one in series for science lectures. Startling difference! I am gradually
running out of 1970's era ones - you can make their brightness improve
enormously by dipping in LN2 to stiffen the crystal lattice and enhance
the QE. They can only stand a few dozen or so cycles of this treatment.
Latest generation high power LEDs the surface brightness of the die
surface is approaching that of the suns photosphere!

--
Regards,
Martin Brown

 

On Wed, 21 Aug 2019 20:46:52 +0100, Martin Brown
<'''newspam'''@nezumi.demon.co.uk> wrote:

On 21/08/2019 16:07, jlarkin@highlandsniptechnology.com wrote:
On Wed, 21 Aug 2019 15:17:18 +0100, Martin Brown
'''newspam'''@nezumi.demon.co.uk> wrote:

On 21/08/2019 15:09, jlarkin@highlandsniptechnology.com wrote:
On Wed, 21 Aug 2019 11:52:12 +0100, Martin Brown
'''newspam'''@nezumi.demon.co.uk> wrote:

The snag with 3Ms product was that most people didn't understand the
advantage of having an emergency torch you could find in pitch darkness.
Modern mains supplies are so reliable people have forgotten the dark!

An good LED is visible in the dark at 1 uA or less. An amp-hour of
battery computes to...

Even at 10uA which is what I tend to run them at (previous generation)
they still last a very long time. But the 3M product was back when LEDs
were indicators and torches used 3v filament bulbs at 1A or so.

I took a good green LED up to the cabin where it's really dark at
night. I got up at 2AM and ran a little test. The threshold of
visibility was about 1 nA. I didn't expect that an LED would emit any
photons at 1 nA, much less that I could see them.

It is surprising just how good the human eye is at detecting photons
once it is fully dark adapted. Big cats are better. At 10uA even with
the previous generation you can see to walk around once dark adapted.

Maybe I'll try that again, with the super-good Osrams of various
colors. The blue is blinding at 5 mA, even though human vision peaks
in the green.

I have a resistor with a 1970's era red LED and a modern high brightness
one in series for science lectures. Startling difference! I am gradually
running out of 1970's era ones - you can make their brightness improve
enormously by dipping in LN2 to stiffen the crystal lattice and enhance
the QE. They can only stand a few dozen or so cycles of this treatment.
Latest generation high power LEDs the surface brightness of the die
surface is approaching that of the suns photosphere!

We used to run the old Cree blue LEDs at 50 mA, from a couple of
7438's in parallel. As they got better, customers started complaining.

Blue led's tend to be annoying for some reason.

 

[Jasen Betts]

On 2019-08-21, Martin Brown <'''newspam'''@nezumi.demon.co.uk> wrote:

On 21/08/2019 11:09, nuny@bid.nes wrote:
On Tuesday, August 20, 2019 at 2:37:00 PM UTC-7, Martin Brown wrote:
On 20/08/2019 22:23, nuny@bid.nes wrote:
On Thursday, August 15, 2019 at 3:49:18 PM UTC-7, John Larkin
wrote:

(Damn- I screwed up the attribution. Anyway...)

I prefer the plastic filled with doped strontium aluminate -
just needs to be in the sun for a few hours to work all
night. 3M had an emergency torch that used it to great effect
just before power LEDs became common.

I tried that, but there's not enough daylight in that bedroom
to charge the strontium aluminate. Strontium aluminate is
amazing stuff.

Strontium-90 is dangerous because it replaces calcium in vivo.

I only mentioned that because of the very similar chemistry of
strontium and calcium. Calcium is however considerably cheaper than
strontium.

This is a compound of ordinary natural non-radioactive strontium
with amazing ability to absorb photons and re-emit them later. It
makes the old glow in the dark toys look like - well toys. If I
leave my find in the dark torch in the sun it will allow you to see
by it after dark once dark adapted without having to switch it on!

Okay...

Calcium aluminate is used in Portland cement replacements. Does
it do the same thing? I haven't noticed many sidewalks glowing at
dusk...

It is very specific to a rare earth doped strontium aluminate.

I was just wondering if they'd even tried similarly doped calcium
aluminate. Hell, do you know what it's doped with, and how much? I
haven't done any experimental garage chemistry in a while...

Calcium aluminate doesn't play or they would use it instead.

Dopant is usually Europium (and/or other REEs). See

https://en.wikipedia.org/wiki/Strontium_aluminate

You can buy the powder on eBay. 3M used to make a very good plastic
using the stuff and a dayglo yellow marker pen dye to down convert blue
photons into the peak band for human vision. It is more than an order of
magnitude brighter than old zinc sulphide phosphorescent materials and
much longer lasting (mine literally lasts all night in summer ~6 hours).

The snag with 3Ms product was that most people didn't understand the
advantage of having an emergency torch you could find in pitch darkness.
Modern mains supplies are so reliable people have forgotten the dark!

Also people carry emergency light sources in their pockets. My cellphone
has an OLED display one one side and a high power LED on the other.

--
When I tried casting out nines I made a hash of it.

 

[Martin Brown]

On 22/08/2019 09:58, Jasen Betts wrote:

On 2019-08-21, Martin Brown <'''newspam'''@nezumi.demon.co.uk> wrote:

The snag with 3Ms product was that most people didn't understand the
advantage of having an emergency torch you could find in pitch darkness.
Modern mains supplies are so reliable people have forgotten the dark!

Also people carry emergency light sources in their pockets. My cellphone
has an OLED display one one side and a high power LED on the other.

Indeed. Although before the invention of smartphones that wasn't the
case. 3M were very unlucky that power white LEDs came along soon after
their rather nicely engineered emergency dayglo torch was launched.

It was interesting to see people using them in anger during the recent
UK powercut when emergency lighting in some London tube stations failed
to work (probably due to cuts to non-essential maintenance budgets).

I am surprised that modern LED torches don't bridge their switch with a
10M resistor. It doesn't affect battery life significantly and it makes
the thing so much easier to find in total darkness.


--
Regards,
Martin Brown