Re: [Discuss] Eclipses Re: Great talks last night, however...

[Bill Bogstad]

On Mon, Jul 24, 2017 at 12:10 AM, grg  wrote:
> On Sun, Jul 23, 2017 at 04:59:08PM -0400, Richard Pieri wrote:
>> On 7/23/2017 3:42 PM, grg wrote:

>> The ground can hold a lot of heat energy but it doesn't conduct it much.
>> That's why a GHP spreads its ground loop system out across a large area.
>> You're not getting that from burying big battery packs unless you also
>> install the same kind of extensive ground loop system which costs to
>> install and maintain.
>
> Look at it this way: if you put a battery in the ground underneath a solar
> panel, the warming of the ground from that battery is going to be strictly
> less than the warming of the ground from the sunlight hitting it directly
> before the solar panel was installed.  With an 85% charge/discharge
> efficiency, the ground is being warmed only 15% as much as under direct
> sunlight.  Since there wasn't runaway heat buildup under sunlight, only 15%
> of that amount of heating is also not going to exceed the earth's ability
> to sink the heat away.

Grg, I suspect that the above section is correct overall; but you do
seem to be assuming
that the absorption/radiation characteristics of a solar panel
installation across the entire
spectrum are the same as bare ground.  Of course, you have the
advantage that a nominal
85% of the energy you put into the batteries is going to be delivered
back out to some "remote"
location so that energy isn't going to be warming up the local battery
environment anyway.
That probably provides sufficient breathing room to make it even less
of an issue for small
scale installations.

For larger utility grade systems, we might be looking at flow
batteries in the long run anyway
and there is no reason that the storage system needs to be that close
to the generation
system.  Build them wherever cooling/heating/physical space/proximity
to load considerations
make the most sense.

This article from ars technica:

https://arstechnica.com/business/2017/07/german-energy-company-wants-to-build-flow-batteries-in-old-natural-gas-caverns/

talks about a commercial project to do just that in Germany as well as
other projects elsewhere.  Without any pricing info,
it is difficult to say if this is viable, but it seems like a number
of groups think that it might be.

Bill Bogstad
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Re: [Discuss] Eclipses Re: Great talks last night, however...

[grg]

On Sun, Jul 23, 2017 at 04:59:08PM -0400, Richard Pieri wrote:
> On 7/23/2017 3:42 PM, grg wrote:
> > In the paper they show that a conventional li-ion battery holds 90% of the
> > original charge after 3000 cycles (~9 years of daily cycling); and after
> 
> BS.
> 
> http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

Hmm... did you look at the peer-reviewed journal article published in
"Advanced Energy Materials" in 2014 which is the one making the claim you're
calling BS (on the basis of "batteryuniversity.com")?  Here are those links
again for your perusing convenience:
  
http://onlinelibrary.wiley.com/doi/10.1002/aenm.201401408/abstract;jsessionid=CBDD74C72BBF0C1C53B7FBB1AC2DB1B5.f04t03
  
https://www.osti.gov/pages/biblio/1185480-solid-electrolyte-key-high-voltage-lithium-batteries

As for the "batteryuniversity.com" page which appears to have been written
in 2010, can you point at which part of it you think contradicts the
peer-reviewed article?  For one, I fear that "batteryuniversity.com" page
isn't reporting on the same battery technology; e.g. they say "Figure 1
illustrates the capacity drop of 11 Li-polymer batteries" but the numbers I
quoted from the journal article aren't measuring Li-po batteries at all,
they're measuring li-ion batteries with a liquid electrolyte (not polymer).
Indeed, the whole point of that journal article is that the choice of
electrolyte is critical for battery longevity.

Second, the "batteryuniversity.com" article is showing numbers for 1-hour
charge and discharge cycles, while the journal article is showing numbers
for 10-hour charge and discharge cycles, much more relevant for solar power
storage.  Cycles as short as 1 hour significantly reduce the lifetime of
these batteries; even that batteryuniversity.com page warns not to go
any faster than 1 hour.

My takeaway here is that when engineering solar power storage I'd pick the
2014 liquid electrolyte batteries the journal paper used as a baseline
instead of the 2010 Li-polymer batteries that batteryuniversity.com
reported on, and use ~12 hour charge and discharge cycles.


> > Nor do those characteristics describe millions of homes and buildings.  How
> > many buildings do you think are destroyed in Kansas by tornados each year?
> > Hundreds, for a survival rate of 99.99%.  So no, it's not because cows are
> > running away from approaching tornados or because they're sharing Farmer
> > John's storm cellar, it's actually because 99.99% of the spots in Kansas
> > don't have a tornado land on them.
> 
> The size of a home or even a large barn in rural Kansas is a tiny
> faction of the size of a 150km^2 (say) power station. Rural homes in
> Kansas are spread out dozens to hundreds of kilometers apart. So when a
> tornado touches down the chances of hitting a given home is small and
> the chances of it hitting several is practically nil.
> 
> Unless it hits Topeka.
> 
> That 150km^2 power station? That's the size of Topeka which got
> clobbered by a sequence of tornadoes in 1966.

Yes, that was an awful awful natural disaster in the middle of the last
century - claimed to be the 7th most damaging tornado event in all of
recorded history.  Of the 50,000 homes in Topeka at the time, almost 850 of
them were destroyed and 3,000 were damaged in some way.  So ~2% of homes in
Topeka were destroyed, and ~6% had some damage.  Of the 900,000 homes in
Kansas at the time, that's ~0.1% destroyed, so only 99.9% survival rate of
homes in Kansas for that year instead of the long-term average of 99.99%.
Terrible for those who fell into that small percentage (and even worse for
the 17 people killed, giving a human survival rate of only 99.99% in Topeka
and 99.999% in Kansas); but with this outcome for one of the worst tornado
disasters of all time, I still feel the cows and corn and solar panels have
the odds in their favor.


> > I guess you'll be surprised to learn that the ground is actually an
> > effective heat sink; see the ground loops in heat pumps, which provide air
> > conditioning by sinking the removed heat into the ground.  Here's a source
> > for you:  https://energy.gov/energysaver/geothermal-heat-pumps
> 
> The ground can hold a lot of heat energy but it doesn't conduct it much.
> That's why a GHP spreads its ground loop system out across a large area.
> You're not getting that from burying big battery packs unless you also
> install the same kind of extensive ground loop system which costs to
> install and maintain.

Look at it this way: if you put a battery in the ground underneath a solar
panel, the warming of the ground from that battery is going to be strictly
less than the warming of the ground from the sunlight hitting it directly
before the solar panel was installed.  With an 85% charge/discharge
efficiency, the ground is being warmed only 15% as much as under direct
sunlight.  Since there wasn't runaway heat buildup under sunlight, only 15%
of that amount of heating is also not 

Re: [Discuss] Eclipses Re: Great talks last night, however...

[Richard Pieri]

On 7/23/2017 6:48 PM, Bill Ricker wrote:
> Experience on Mars with Rover was exactly the opposite,  a gustanado
> cleared accumulated dust OFF panels and restored system efficiency.

The Mars rovers' panels are constructed with electrostatic layers. Run a
charge through the ES layers and they repel dust. This works well in
arid environments like Mars and the deserts of Arizona, Nevada,
California and the UAE, but it does increase the cost and it saps some
of the power being generated so you need more capacity to offset.

ES repellers don't work well, or at all, in humid environments where
dust + moisture sticks like mud. For example, the high humidity that
generates terrestrial tornadoes.

-- 
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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Bill Ricker]

Even a small tornado won't simply "take out one part of a solar power
station". It's going throw dust and debris all over the place.


Experience on Mars with Rover was exactly the opposite,  a gustanado
cleared accumulated dust OFF panels and restored system efficiency.

(N=1 is anecdote not data, but it is the only tornado vs solar datum I
have.)
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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Richard Pieri]

On 7/23/2017 5:01 PM, Robert Krawitz wrote:
> If a tornado takes out one part of a solar power station, the rest is
> still usable.

Even a small tornado won't simply "take out one part of a solar power
station". It's going throw dust and debris all over the place. Here's
hoping your contract with NOMADD is paid up.

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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Robert Krawitz]

On Sun, 23 Jul 2017 16:59:08 -0400, Richard Pieri wrote:
> On 7/23/2017 3:42 PM, grg wrote:
>> Nor do those characteristics describe millions of homes and buildings.  How
>> many buildings do you think are destroyed in Kansas by tornados each year?
>> Hundreds, for a survival rate of 99.99%.  So no, it's not because cows are
>> running away from approaching tornados or because they're sharing Farmer
>> John's storm cellar, it's actually because 99.99% of the spots in Kansas
>> don't have a tornado land on them.
>
> The size of a home or even a large barn in rural Kansas is a tiny
> faction of the size of a 150km^2 (say) power station. Rural homes in
> Kansas are spread out dozens to hundreds of kilometers apart. So when a
> tornado touches down the chances of hitting a given home is small and
> the chances of it hitting several is practically nil.
>
> Unless it hits Topeka.
>
> That 150km^2 power station? That's the size of Topeka which got
> clobbered by a sequence of tornadoes in 1966.

If a tornado takes out one part of a solar power station, the rest is
still usable.
-- 
Robert Krawitz 

***  MIT Engineers   A Proud Tradition   http://mitathletics.com  ***
Member of the League for Programming Freedom  --  http://ProgFree.org
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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Richard Pieri]

On 7/23/2017 3:42 PM, grg wrote:
> In the paper they show that a conventional li-ion battery holds 90% of the
> original charge after 3000 cycles (~9 years of daily cycling); and after

BS.

http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries


> Nor do those characteristics describe millions of homes and buildings.  How
> many buildings do you think are destroyed in Kansas by tornados each year?
> Hundreds, for a survival rate of 99.99%.  So no, it's not because cows are
> running away from approaching tornados or because they're sharing Farmer
> John's storm cellar, it's actually because 99.99% of the spots in Kansas
> don't have a tornado land on them.

The size of a home or even a large barn in rural Kansas is a tiny
faction of the size of a 150km^2 (say) power station. Rural homes in
Kansas are spread out dozens to hundreds of kilometers apart. So when a
tornado touches down the chances of hitting a given home is small and
the chances of it hitting several is practically nil.

Unless it hits Topeka.

That 150km^2 power station? That's the size of Topeka which got
clobbered by a sequence of tornadoes in 1966.


> I guess you'll be surprised to learn that the ground is actually an
> effective heat sink; see the ground loops in heat pumps, which provide air
> conditioning by sinking the removed heat into the ground.  Here's a source
> for you:  https://energy.gov/energysaver/geothermal-heat-pumps

The ground can hold a lot of heat energy but it doesn't conduct it much.
That's why a GHP spreads its ground loop system out across a large area.
You're not getting that from burying big battery packs unless you also
install the same kind of extensive ground loop system which costs to
install and maintain. Oh, and you've added an extra vulnerability to
earthquakes. Yay.

Can ground-based work? Maybe. I don't think so. But even if it can be
done? It's still just a stop-gap being marketed as a solution by a man
who has a vested interest in selling batteries.

-- 
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Re: [Discuss] Eclipses Re: Great talks last night, however...

[grg]

On Sun, Jul 23, 2017 at 01:20:05PM -0400, Richard Pieri wrote:
> On 7/23/2017 12:29 PM, grg wrote:
> > OK, so you're saying that instead of single-digit percentages, there are
> > real-world battery installations which get 75%-80% charge/discharge
> > efficiency; meaning that if using them we'd only need to make 20%-25% more
> > solar power, not 1000% more, to compensate for the loss in batteries.
> 
> When new under good conditions. Those numbers drop as conditions change
> (extremes of heat and cold) and batteries wear out.
> 
> > http://www.sandia.gov/ess/docs/pr_conferences/2014/Friday/Session10/04_Vishwanathan_V_Powin_Dispatchable_Battery.pdf
> 
> And what are their numbers after 3, 4 or 5 years?

Actually, the coulombic efficiency (CE, the battery's component of the
overall charge/discharge efficiency) of lithium-ion batteries stays well
above 99% for the full life of the battery, and even improves a bit as the
battery ages.  What drops as batteries age is instead the total capacity of
the battery.

Here's a source - behind a paywall, but the abstract is free and gives the
relevant highlights: "A solid-state high-voltage (5 V) lithium battery is
demonstrated to deliver a cycle life of 10,000 with 90% capacity
retention. The solid electrolyte enables the use of high-voltage cathodes
and Li anodes with minimum side reactions, leading to a high Coulombic
efficiency of 99.98+%."

http://onlinelibrary.wiley.com/doi/10.1002/aenm.201401408/abstract;jsessionid=CBDD74C72BBF0C1C53B7FBB1AC2DB1B5.f04t03

In the paper they show that a conventional li-ion battery holds 90% of the
original charge after 3000 cycles (~9 years of daily cycling); and after
those 9 years it actually has the highest coulombic efficiency (CE) of its
life so far, well over 99%. (That's their baseline; the paper's goal is to
present a battery improvement which has that performance to 10,000 cycles =
30 years instead of just 3,000 cycles = 9 years.)  So actually, in contrast
to your claim, the efficiency goes up a bit as they age and "wear out".

Oh, I found a non-paywalled version of that paper (formatting's not nearly
as nice as the paywalled version, but hey, it's free):
https://www.osti.gov/pages/biblio/1185480-solid-electrolyte-key-high-voltage-lithium-batteries


> > But somehow, 99.99% of people and corn and cows (not counting that
> > unfortunate animal in the movie Twister) have managed to survive there.
> > I'm betting solar panels will have a similar tornado survival rate, unless
> > we decide to install them only at trailer parks.
> 
> That's because people and livestock can seek shelter in foul weather,
> and plants grow and heal or at the least can be plowed under and the
> land replanted. None of these describe thousands of square kilometers of
> solar panels.

Nor do those characteristics describe millions of homes and buildings.  How
many buildings do you think are destroyed in Kansas by tornados each year?
Hundreds, for a survival rate of 99.99%.  So no, it's not because cows are
running away from approaching tornados or because they're sharing Farmer
John's storm cellar, it's actually because 99.99% of the spots in Kansas
don't have a tornado land on them.


> > One standard solution to weather exposure would be to house them below the
> > frost line, which is only 2'-3' deep in Kansas:
> > https://www.ngs.noaa.gov/PUBS_LIB/GeodeticBMs/#figure13
> > You'll get a moderate temperature all year round.
> 
> Then you're insulating them which means they'll be that much hotter when
> charging during warm months. See previous about heat being bad for
> batteries.

I guess you'll be surprised to learn that the ground is actually an
effective heat sink; see the ground loops in heat pumps, which provide air
conditioning by sinking the removed heat into the ground.  Here's a source
for you:  https://energy.gov/energysaver/geothermal-heat-pumps

Excerpting: "Geothermal heat pumps (GHPs)...have been in use since the late
1940s.  They use the constant temperature of the earth as the exchange
medium instead of the outside air temperature.  Although many parts of the
country experience seasonal temperature extremes -- from scorching heat in
the summer to sub-zero cold in the winter -- a few feet below the earth's
surface the ground remains at a relatively constant temperature...The GHP
takes advantage of this by exchanging heat with the earth through a ground
heat exchanger."


> > Again, if you do the math, it's exactly pi.  The equator is a circle; the
> > sunlight incident on it is its shadow at this point in space, which is a
> > line that is the diameter of Earth - on that line every point is always at
> > "noon", and it would collect all the light the equator sees.  Will ascii
> > art help?
> 
> You're ignoring the atmosphere.

Actually, I already addressed that in previous emails when discussing the
"insolation" issue (instead of the "noon" issue here): 1370 W/m^2 in space,
of which ~1000 W/m^2 makes it to the surface on 

Re: [Discuss] Eclipses Re: Great talks last night, however...

[Richard Pieri]

On 7/23/2017 12:29 PM, grg wrote:
> OK, so you're saying that instead of single-digit percentages, there are
> real-world battery installations which get 75%-80% charge/discharge
> efficiency; meaning that if using them we'd only need to make 20%-25% more
> solar power, not 1000% more, to compensate for the loss in batteries.

When new under good conditions. Those numbers drop as conditions change
(extremes of heat and cold) and batteries wear out.

> http://www.sandia.gov/ess/docs/pr_conferences/2014/Friday/Session10/04_Vishwanathan_V_Powin_Dispatchable_Battery.pdf

And what are their numbers after 3, 4 or 5 years?


> But somehow, 99.99% of people and corn and cows (not counting that
> unfortunate animal in the movie Twister) have managed to survive there.
> I'm betting solar panels will have a similar tornado survival rate, unless
> we decide to install them only at trailer parks.

That's because people and livestock can seek shelter in foul weather,
and plants grow and heal or at the least can be plowed under and the
land replanted. None of these describe thousands of square kilometers of
solar panels.

> One standard solution to weather exposure would be to house them below the
> frost line, which is only 2'-3' deep in Kansas:
> https://www.ngs.noaa.gov/PUBS_LIB/GeodeticBMs/#figure13
> You'll get a moderate temperature all year round.

Then you're insulating them which means they'll be that much hotter when
charging during warm months. See previous about heat being bad for
batteries.

> Luckily, the 10,000 km^2 solar+battery farm will still meet the entire US's
> energy needs even if you replace the batteries more frequently.

Oh, yes. Replace unsustainable batteries more frequently. That's exactly
what Musk wants because guess what? He sells batteries. Can you smell
the marketing yet?


> Again, if you do the math, it's exactly pi.  The equator is a circle; the
> sunlight incident on it is its shadow at this point in space, which is a
> line that is the diameter of Earth - on that line every point is always at
> "noon", and it would collect all the light the equator sees.  Will ascii
> art help?

You're ignoring the atmosphere.

-- 
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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Richard Pieri]

On 7/23/2017 9:58 AM, Robert Krawitz wrote:
> "As low as" 50% is a whole lot more than 10%.

As low as 50% when new. Efficiency drops off as batteries age. If you've
ever replaced a phone or notebook battery because the battery was worn
out then you've experienced this first hand.


> Supercaps have their own problems...not very dense compared to
> batteries, for example.  And a lot more expensive for the same
> storage.

You don't need the same storage. That is, you don't need 14+ hours of
storage with geostationary solar stations like you do with ground
stations. You only need ~70 minutes of storage which obviates the
self-discharge problem that makes supercapacitors less than ideal for
long term storage.

This assumes one station. With 2 or more stations you will never be
without exposure, further reducing the need for eclipse storage.


> The pinnacle at present, maybe.  While it's true we can't count on
> particular breakthroughs, it's pretty clear we can count on
> breakthroughs of some kind happening.  There may be improvements in
> Li-ion that improve lifetime, charge density, etc.  Hopefully we'll

You mean like Li-air and other metal-air concepts, which haven't had the
several necessary breakthroughs in the past almost 50 years since the
concept was introduced? Breakthroughs are rare, and when you need
several for something to be viable? I wouldn't bet on it.

> find something based on non-lithium chemistry, since lithium's
The only element better than lithium is hydrogen. Nothing else is
capable of higher charge densities. Since we can't have metallic
hydrogen at room temperature and pressure we use lithium.

As previously noted, Li-sulfur shows promise but it has serious problems
that need to be overcome before it can be commercially viable.

> scarce.  And not renewable?  Since when?  Extract the lithium and use
> it to fabricate new batteries.

Recycling Li-ion batteries costs more than mining the metals and
refining the plastics from fossil fuels. Until this changes they cannot
be considered sustainable. And, of course, the elimination of the
petrol-based plastics is necessary as well.


> Interesting that we can't count on breakthroughs in battery
> technology but we can in space...

We don't need breakthroughs in space for SBSP. All of the technologies
exist today.  What we don't have is launch capacity to put 10+ kilotons
(CAST's estimate for their proposed 1GW station) into orbit. Doing this
doesn't require any breakthroughs, just a lot of brute force and enough
nations or corporations willing to foot the bills.

That said, there are advances which could significantly reduce those
costs. CAST's proposal includes lunar manufacture. With no atmosphere
and 1/6th the gravity, launching from the Moon is quite a lot easier
than terrestrial launch. Then again, with no atmosphere and 1/6 the
gravity, lunar manufacture has it's own problems to overcome.

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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Robert Krawitz]

On Sun, 23 Jul 2017 00:46:22 -0400, Richard Pieri wrote:
>> OK, so here you're saying that instead of a <10% charge/discharge
>> efficiency, batteries actually have a 75%-80% charge/discharge efficiency?
>
> No. I'm saying that chemical batteries have *at best* a charge
> efficiency of around 75-80% in the real world.

There's a long way from 10% to 75-80%, and you're the one who cited 10%.

>> Agreed!  And Utah, and Arizona, and New Mexico, and large parts of
>> Colorado, Wyoming, Idaho, Oregon, and Washington by your map.  And don't
>> forget Great Plains states like Texas, Montana, North Dakota, South
>> Dakota... hey, I think we're over 0.15%!
>
> There are three problems that I would consider breakers for these regions:
>
> First, you just described the heart of Tornado Alley.

I'm more worried about big hail than tornadoes to be honest, but
really big hail (and tornadoes) are actually extremely rare at any
given point (I believe I've read that the return period for tornadoes
at any given point is 2000 years; I don't know what the return period
for, say, 3" hail is).

> Second, you can't charge Li-ion batteries when they are below freezing
> (0C) which makes much of these areas useless for Musk's storage systems
> for significant portions of the year.

Are you saying Tesla cars are useless (can't be recharged) when the
temperature's below freezing?  I see plenty of Teslas here in
Massachusetts all winter, so I guess they find a way.  Use some of
that charge to keep the battery warm, of course.

> And third, high temperatures (above about 25C) reduces efficiency, and
> it causes batteries to wear out faster than their published ratings
> which means you'll be replacing them that much more frequently if you
> set up your stations in the non-freezing areas.

That's harder to solve, of course, but again, there are Tesla owners
in hot climates who don't keep their cars in air conditioned garages.
So I guess it does actually work Well Enough.

>> FWIW, on that last non-technical bit, I and I wager many others on this
>> mailing list see very many places in all the named locales which have good
>> potential for solar.  And that's one of the great things about solar power:
>
> Maybe good on small scales like homes and offices. Not so good for large
> scale like replacing global dependence on fossil fuels.

Actually, it scales both up and down pretty nicely.
-- 
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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Robert Krawitz]

On Sun, 23 Jul 2017 00:23:26 -0400, Richard Pieri wrote:
> On 7/22/2017 8:56 PM, Robert Krawitz wrote:
>> But it's considerably more than 10% in practice, right?
>
> It depends. It's as much an ideal as Musk's asserted 90% efficiency for
> Tesla and Powerwall when in reality Tesla and other EV owners see as low
> as 50% with new cells. And as noted previously, that figure drops as
> batteries wear.

"As low as" 50% is a whole lot more than 10%.

>> You still need storage for those blackouts (albeit less), right?
>
> Yes, but with blackout windows of ~70 minutes you can effectively use
> supercapacitors which in principle should be superior to chemical
> batteries for short term storage.

Supercaps have their own problems...not very dense compared to
batteries, for example.  And a lot more expensive for the same
storage.

>> The author is quite clear that he simply doesn't see this as being
>> plausible any time soon.  And no doubt batteries will improve along
>> the way.
>
> I do doubt it. Li-ion appears to be it, the pinnacle of commercial
> battery technology. Li-air has potential but it needs a breakthrough to
> make it commercially viable and you can't count on breakthroughs.
> Likewise Li-sulfur which has wear and volatility (read: safety) issues.
> And, of course, batteries aren't renewable.

The pinnacle at present, maybe.  While it's true we can't count on
particular breakthroughs, it's pretty clear we can count on
breakthroughs of some kind happening.  There may be improvements in
Li-ion that improve lifetime, charge density, etc.  Hopefully we'll
find something based on non-lithium chemistry, since lithium's
scarce.  And not renewable?  Since when?  Extract the lithium and use
it to fabricate new batteries.

Interesting that we can't count on breakthroughs in battery
technology but we can in space...
-- 
Robert Krawitz 

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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Richard Pieri]

> OK, so here you're saying that instead of a <10% charge/discharge
> efficiency, batteries actually have a 75%-80% charge/discharge efficiency?

No. I'm saying that chemical batteries have *at best* a charge
efficiency of around 75-80% in the real world.


> Agreed!  And Utah, and Arizona, and New Mexico, and large parts of
> Colorado, Wyoming, Idaho, Oregon, and Washington by your map.  And don't
> forget Great Plains states like Texas, Montana, North Dakota, South
> Dakota... hey, I think we're over 0.15%!

There are three problems that I would consider breakers for these regions:

First, you just described the heart of Tornado Alley.

Second, you can't charge Li-ion batteries when they are below freezing
(0C) which makes much of these areas useless for Musk's storage systems
for significant portions of the year.

And third, high temperatures (above about 25C) reduces efficiency, and
it causes batteries to wear out faster than their published ratings
which means you'll be replacing them that much more frequently if you
set up your stations in the non-freezing areas.


> Right - as in my prior email, when you do the math it comes out to a factor
> of pi (and 24/pi is 7.64 hours, within the range you give).

No. It's significantly more than that because a geostationary station is
always at "noon" when it's exposed to the sun while a ground station's
noon is only a fraction of it's exposure period.


> FWIW, on that last non-technical bit, I and I wager many others on this
> mailing list see very many places in all the named locales which have good
> potential for solar.  And that's one of the great things about solar power:

Maybe good on small scales like homes and offices. Not so good for large
scale like replacing global dependence on fossil fuels.

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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Richard Pieri]

On 7/22/2017 8:56 PM, Robert Krawitz wrote:
> But it's considerably more than 10% in practice, right?

It depends. It's as much an ideal as Musk's asserted 90% efficiency for
Tesla and Powerwall when in reality Tesla and other EV owners see as low
as 50% with new cells. And as noted previously, that figure drops as
batteries wear.


> You still need storage for those blackouts (albeit less), right?

Yes, but with blackout windows of ~70 minutes you can effectively use
supercapacitors which in principle should be superior to chemical
batteries for short term storage.


> The author is quite clear that he simply doesn't see this as being
> plausible any time soon.  And no doubt batteries will improve along
> the way.

I do doubt it. Li-ion appears to be it, the pinnacle of commercial
battery technology. Li-air has potential but it needs a breakthrough to
make it commercially viable and you can't count on breakthroughs.
Likewise Li-sulfur which has wear and volatility (read: safety) issues.
And, of course, batteries aren't renewable.

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Re: [Discuss] Eclipses Re: Great talks last night, however...

[grg-webvisible+blu]

On Sat, Jul 22, 2017 at 12:31:08PM -0400, Richard Pieri wrote:
> On 7/22/2017 1:14 AM, Gregory Galperin wrote:
> > You seem to be claiming here that the lithium ion batteries Musk is selling
> > have less than a 10% charge/discharge efficiency.  But when I look for a
> > number on charge/discharge efficiency of lithium ion batteries I find
> > numbers in the range 80%-90% efficient depending on battery age (with
> > measured numbers like 86%).  This says you'd need ~15% more solar power to
> > compensate for the losses, not 1000% more.  Can you point me at something
> > which explains this discrepancy?
> 
> Certainly. Musk's figures are marketing. Actual Tesla, Leaf and Volt
> owners see much lower figures, as low as 50% for newish battery packs
> (75-80% is typical). As a Li-ion battery wears and its charge density
> decreases the thermal waste increases.

OK, so here you're saying that instead of a <10% charge/discharge
efficiency, batteries actually have a 75%-80% charge/discharge efficiency?
If so, we now pretty much agree on this point.

And FWIW I wasn't citing Musk's numbers at all; every university research
source I see says 80%-90%, starting at 90% for newer batteries and dropping
to 80% as they age, with a life-averaged value of about 86%.  Our ranges
overlap at 80%, so let's just call it 80%.  So you need to generate 20% more
solar power to compensate, rather than 1000% more.


> > OK, so the 10,000 km^2 would have to be 11,500 km^2 if you put all of it up
> > at the Canadian border above NY & VT.  Not sure why anyone would do that
> > instead of using some area in TX, but even if someone did, this doesn't
> > seem like a big deal -- 11,500 km^2 is 0.15% of the land area of the
> > continental US, rather than 0.13% of it for 10,000 km^2.  Hard to see how
> > that 0.02% would be a dealbreaker even if Texas did secede.
> 
> This assumes that the land up north is flat like Texas. Hilly terrain
> creates shade which reduces the time per day that PV panels are

See my previous email that there's more flat Great Plains in the North than
in Texas.  Given that, seems like the "north has flat land" assumption is
safe ;)


> effective. While there is flat land up north, much of it is either farm
> or forest. Good luck stripping that for large solar farms.

Remember, we're only looking for 0.15% of land area in all.  Farms have a
good amount of area already stripped (and incidentally already have barns
or silos with large roofs good for mounting large solar panels).  If people
live in forests, that land is already similarly stripped; if people don't
live there, I'm not sure why we'd be trying to put solar panels there
instead of in other places (like deserts and plains).  So overall, I don't
foresee a problem finding 0.15% of land in the North which suits.


> > ranges (California to Canada)...  Do you know of an analysis showing that
> > northern states have "much less flat land"?
> 
> Look at a map. Like this one:
> http:%2F%2Fwww.earthscienceeducation.org%2FDi-BiosphereNotPost%2FEPA-EcoregionsLev01x600.jpg=9f6cecc9d6e3992197bd8e271bb214fc

OK, I'm looking at that map 
(http://www.earthscienceeducation.org/Di-BiosphereNotPost/EPA-EcoregionsLev01x600.jpg)
and I see "Ecological Regions" drawn which have little variation as you
go north-south.  That seems to show that northern states have the same
composition as the southern states, in contrast to the claim.


> The eastern half of the country is off the table because it's forests
> and I see clear-cutting to make room for solar farms to be a hard sell.

Well, it marks nearly everything east of the Mississippi as "forest", and
I'm pretty sure there are some fairly flat, treeless large cities in there
somewhere.  I'm beginning to think this particular map might not be
depicting the information salient to this discussion.  And remember, we're
only looking for 0.15% of land area - we don't need the eastern half of the
country to be 100% flat and clear, we only need it to be 0.15% flat and
clear (or already covered with e.g. roofs).  Categorically dismissing half
the country misses a lot of opportunities.

(Also note that "forest" on the map doesn't mean "not flat", in reference
to the question this was presented as an answer to.)


> The Great Plains are partially off the table as well because that's
> where the bulk of our livestock production comes from and that's our
> number two in agriculture after corn (maize).
...
> The Pacific Northwest is out due to forests and mountainous terrain much
> like the Atlantic Northeast.

Again, looking for 0.15% of land.  I wouldn't write off the entirety of the
Great Plains and say there's no room for any solar there just because some
of that land is used for cows and corn.


> The Nevada and southern California deserts might be good choices.

Agreed!  And Utah, and Arizona, and New Mexico, and large parts of
Colorado, Wyoming, Idaho, Oregon, and Washington by your map.  And don't
forget Great Plains states like Texas, 

Re: [Discuss] Eclipses Re: Great talks last night, however...

[Richard Pieri]

On 7/22/2017 12:22 PM, Robert Krawitz wrote:
> 10x?  Battery charging isn't that inefficient -- 85% for lead-acid
> batteries, for example
> (http://www.solar-facts.com/batteries/battery-charging.php).

"Overall, an efficiency level of 85% is often *assumed*."

Emphasis mine. The rest of that paragraph goes on to explain some of the
reasons why you can and will get less than this. Also, these are lead
acid batteries which have longer lifespans than the Li-ion batteries
Musk is selling, and they will hold to their higher efficiencies for longer.


> That's the least of the problems.  You have to keep it in orbit, the
> beam has to keep station (that kind of concentrated beam had better
> not leak), and a geosync orbit is still eclipsed part of the time.

At geostationary altitude a station is eclipsed from the sun for only 70
minutes per day, and this is only when the sun is near the equatorial
plane. In practice, a geostationary PV station would have ~99.3%
exposure over the course of a year vs. a ground station which has at
best ~33% exposure, and that ~99.3% exposure is always "noon" vs. the
ground station's noon being a fraction of its exposure time.

> Care to discuss what you see as the problems and how to go about
> addressing them?

https://dothemath.ucsd.edu/2012/03/space-based-solar-power/
covers them pretty well, and I do agree with the conclusion that SBSP
isn't worth it in the short term. Putting that much mass into orbit is
too expensive right now.

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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Richard Pieri]

On 7/22/2017 1:14 AM, Gregory Galperin wrote:
> You seem to be claiming here that the lithium ion batteries Musk is selling
> have less than a 10% charge/discharge efficiency.  But when I look for a
> number on charge/discharge efficiency of lithium ion batteries I find
> numbers in the range 80%-90% efficient depending on battery age (with
> measured numbers like 86%).  This says you'd need ~15% more solar power to
> compensate for the losses, not 1000% more.  Can you point me at something
> which explains this discrepancy?

Certainly. Musk's figures are marketing. Actual Tesla, Leaf and Volt
owners see much lower figures, as low as 50% for newish battery packs
(75-80% is typical). As a Li-ion battery wears and its charge density
decreases the thermal waste increases.


> OK, so the 10,000 km^2 would have to be 11,500 km^2 if you put all of it up
> at the Canadian border above NY & VT.  Not sure why anyone would do that
> instead of using some area in TX, but even if someone did, this doesn't
> seem like a big deal -- 11,500 km^2 is 0.15% of the land area of the
> continental US, rather than 0.13% of it for 10,000 km^2.  Hard to see how
> that 0.02% would be a dealbreaker even if Texas did secede.

This assumes that the land up north is flat like Texas. Hilly terrain
creates shade which reduces the time per day that PV panels are
effective. While there is flat land up north, much of it is either farm
or forest. Good luck stripping that for large solar farms.


> Actually, the Great Plains (which is known for being flat) tends to widen
> as you go North.  It's at its narrowest in Texas (including the NW Texas
> site described) and is noticeably wider in Kansas, the Dakotas, Montana...:

Point: you. I did mean northeast and northwest. I should have been more
specific.


> ranges (California to Canada)...  Do you know of an analysis showing that
> northern states have "much less flat land"?

Look at a map. Like this one:
http:%2F%2Fwww.earthscienceeducation.org%2FDi-BiosphereNotPost%2FEPA-EcoregionsLev01x600.jpg=9f6cecc9d6e3992197bd8e271bb214fc

The eastern half of the country is off the table because it's forests
and I see clear-cutting to make room for solar farms to be a hard sell.

The Great Plains are partially off the table as well because that's
where the bulk of our livestock production comes from and that's our
number two in agriculture after corn (maize).

The Nevada and southern California deserts might be good choices.

The Pacific Northwest is out due to forests and mountainous terrain much
like the Atlantic Northeast.


> Oh, maybe you mean that a panel on the equator is in the dark half the day,
> and you're arranging to put your solar panels in a sun-synchronous orbit so
> they're never behind the Earth?  OK, that would make for a factor of pi
> difference, but that's only halfway to the "at least an order of magnitude".
> What accounts for the rest?

Partially. An equatorial GBSP station is actually only good for about
7-8 hours a day, not 12. Efficiency drops off as the angle increase and
more atmosphere needs to be penetrated (problem shared by northern
ground stations).  Combine this with PV efficiencies that are much
greater than equatorial PV (the figures I've seen say at least 140%
greater). You can do the math but I think that's close enough to a order
of magnitude for a first order approximation.

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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Richard Pieri]

On 7/21/2017 4:57 PM, Robert Krawitz wrote:
> I question your claim that there isn't enough surface area with
> sufficient solar exposure to power the world.  Your calculations,
> please?

http://blogs.ucl.ac.uk/energy/2015/05/21/fact-checking-elon-musks-blue-square-how-much-solar-to-power-the-us/

"Fact checking Elon Musk’s Blue Square: How much solar to power the US?"

Problem is -- and the article points this out -- Musk isn't selling
solar power. He's selling batteries. His numbers ignore the
inefficiencies of charging that storage. To actually supply the entire
US, solar power + battery would need to be at least 10 times the area
that Musk presents. In reality it would be much more than that because
solar efficiency drops off as you move north and northern states
generally have much less flat land for solar farms than Texas. As you
move north into Canada the efficiency of solar PV drops even further.

It might work if the world's nations could build enough equatorial solar
farms to supply the entire world. I don't foresee that happening any
time soon.


> So you still have the problem of getting it through the atmosphere,
> and you still have conversion loss.  How do you propose to get it
> through the atmosphere without the same kinds of losses (if not more)
> than ground-based solar power?  Since land area is a concern you

I don't care about that because space-based solar generation capacity is
at least an order of magnitude greater than equatorial ground-based
solar. Transmission and storage losses become acceptable when you have
that much of a potential surplus.

Yes, SBSP has problems. I wrote as much. And they've been well-documented.

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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Robert Krawitz]

On Fri, 21 Jul 2017 11:50:27 -0400, Richard Pieri wrote:
> On 7/21/2017 9:25 AM, Bill Bogstad wrote:
>> From an economic perspective, it is beginning to look like
>> residential solar + batteries might be preferable in the near future
>> to current fossil fuel based grid power.  Or at least that is the
>> argument that many people are starting to make.   Are they wrong?  If
>> they aren't wrong, is there some reason other than economics why
>> switching from fossil fuels to solar + batteries would be a bad
>> idea.
>
> I do maintain that they are wrong. Ground-based solar power can't
> provide nearly enough power to run the world. There isn't enough surface
> area with sufficient solar exposure. Adding a dependence on chemical
> batteries would require on the order of 10 times that power generation
> to offset charging waste. GBSP + battery makes sense on the small scale,
> like homes and office buildings and the like, to reduce dependence on
> fossil fuel power generation but it doesn't, and can't, scale up as a
> global replacement for fossil fuels.

I question your claim that there isn't enough surface area with
sufficient solar exposure to power the world.  Your calculations,
please?

>> I suspect you have some other energy solution in mind then the ones 
>> that have been mentioned so far on this thread.  Care to share?
>
> Space-based solar power. SBSP has its own share of problems but power
> generation capacity isn't one of them.

So you still have the problem of getting it through the atmosphere,
and you still have conversion loss.  How do you propose to get it
through the atmosphere without the same kinds of losses (if not more)
than ground-based solar power?  Since land area is a concern you
express, any beam will have to be of much greater power per unit area
than sunlight.  It had *better* fail safe -- *very* safe -- if you're
not going to inadvertently scorch surrounding land.  And you still
have the problem of needing a lot of surface area to catch the
sunlight.  Where are you going to put that receiver, and in what kind
of orbit?

If you're talking geostationary orbit with superconducting cables or
some such, let's just say that there are a whole bunch more problems.
-- 
Robert Krawitz 

***  MIT Engineers   A Proud Tradition   http://mitathletics.com  ***
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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Richard Pieri]

On 7/21/2017 9:25 AM, Bill Bogstad wrote:
> So lets say that I accept everything you say about both the 
> inefficiency and unclean characteristics of solar PV + battery
> storage.   Are the current incumbent solutions (Oil, Coal, Natural 
> Gas) any better on either characteristic?  When doing your
> efficiency calculations, please don't cheat.

I doubt it. But I'm not asserting that fossil fuels are better. My
assertion is that batteries are the worst thing we've ever invented for
storing electricity, except for all of the others. Regardless of how you
generate power, chemical batteries for long term storage (more than a
few minutes, maybe an hour or two at most) is part of the problem, not
part of the solution.

> From an economic perspective, it is beginning to look like
> residential solar + batteries might be preferable in the near future
> to current fossil fuel based grid power.  Or at least that is the
> argument that many people are starting to make.   Are they wrong?  If
> they aren't wrong, is there some reason other than economics why
> switching from fossil fuels to solar + batteries would be a bad
> idea.

I do maintain that they are wrong. Ground-based solar power can't
provide nearly enough power to run the world. There isn't enough surface
area with sufficient solar exposure. Adding a dependence on chemical
batteries would require on the order of 10 times that power generation
to offset charging waste. GBSP + battery makes sense on the small scale,
like homes and office buildings and the like, to reduce dependence on
fossil fuel power generation but it doesn't, and can't, scale up as a
global replacement for fossil fuels.


> I suspect you have some other energy solution in mind then the ones 
> that have been mentioned so far on this thread.  Care to share?

Space-based solar power. SBSP has its own share of problems but power
generation capacity isn't one of them.

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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Mike Small]

Bill Bogstad  writes:
> So lets say that I accept everything you say about both the
> inefficiency and unclean
> characteristics of solar PV + battery storage.   Are the current
> incumbent solutions (Oil, Coal, Natural
> Gas) any better on either characteristic?  When doing your efficiency
> calculations,
> please don't cheat.   i.e. Do total life cycle back to when the
> material was first buried
> underground.  I suspect that even turning corn into ethanol is more energy
> efficient then the process that created fossil fuels.

This book is helpful on this topic:
http://withouthotair.com/

It's a little old, but the way he calculates makes me think his numbers
should hold up pretty well over time. He avoid economics, so I'm
thinking the recent advancements in solar (mostly concerning price per
unit energy?) don't change things. He does concentrate on the picture
from a U.K. perspective, though. It's kind of like a Doctor Who episode,
where the aliens somehow always come to England, but with renewables
instead. Still, people on this list probably can take his calculations
and apply them to Massachusetts easily enough.

I'm wondering maybe for MA if the answer shouldn't be buying lots of
Quebec and Labrador hydro (my old country is not paying me to say this,
honest) to fill in the power troughs left by solar and wind. I mean,
what, you can turn on gas power quickly too, I think, but that's a
greenhouse gas, and, jesus, if we ever leave this era of low natural gas
prices anyone with a few panels up will quickly find a way to appreciate
every last kwh they generate even if it's not coming quite at the right
time. What's NE ISO's mix at now, like 60% natural gas? And the next
proposed major step (with the first being largely taking advantage of
gas prices dropping to be less than coal as I understand it? or perhaps
that's unfair) for MA's climate change policy is to switch to electric
cars. Yikes.

Nuclear still sounds like a needed thing, but I have a hard time
imagining a new plant around here anytime soon, and the ones we have are
winding down. More reason to fear a gas hike, not to mention the
difficulty of building sufficient renewables quickly enough, their
disappointingly low power generation per unit land area numbers, or
their intermittency.

And then there's stuff like this:
http://www.bostonglobe.com/news/nation/2017/07/20/dakota-access-developer-new-pipeline-rankling-regulators/LpMzzvtTpFT3KJH6wb7WJO/story.html

-- 
Mike Small
sma...@sdf.org
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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Robert Krawitz]

On Thu, 20 Jul 2017 20:14:15 -0400, Richard Pieri wrote:
> On 7/20/2017 7:36 PM, A. Richard Miller wrote:
>> How else might we store solar energy? As an environmentalist, I rather 
>> like the Northfield Mountain pumped-storage project 
>> . It's been rather benign 
>> environmentally for 45 years now. The mountain habitat is well-managed 
>
> Except for the initial habitat destruction incurred by the creation of
> the reservoir in the first place.
>
> Mechanical storage isn't any better than chemical storage. It's
> different with different problems like friction and mechanical wear.
>
> The problem isn't how we store electricity. It's that we store
> electricity. Regardless of how we end up generating electricity,
> converting it for storage and then converting it back for use will
> always be less efficient than using electricity directly.

If you're using the same generation method ("all other things being
equal"), yes.

Thermodynamic efficiency isn't always the overriding concern, though.
Solar energy is plentiful, and clean after the initial fixed cost
(solar panels basically don't wear out).  So as long as the storage
method isn't dirty, that we're wasting more of the energy by storing
it is less of a problem than the cost of burning fossil fuel.

Which itself, when you get right down to it, is simply
chemically-stored solar energy.
-- 
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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Bill Bogstad]

On Thu, Jul 20, 2017 at 6:22 PM, Richard Pieri  wrote:
> On 7/20/2017 4:03 PM, Bill Ricker wrote:
>> I wouldn't worry about solar power lost to the coming eclipses. Over the
>> next 10 or 100 years, you'll lose far more to thunderstorms blotting  out
>> the sky; they cast bigger shadows more frequently.
>
> Yeah. And I'm even more concerned with the 10-14 hour (or more in some
> parts of the world) solar outages we experience every day. Or night if
> you prefer. For reals. Because despite Elon Musk's assertions, chemical
> batteries are terrible ways to store electricity. They're inefficient
> (~90% waste as heat). They're dirty (strip mining for rare metals,
> hazardous chemicals needed to manufacture). They're non-renewable (while
> some of the plastics and rare metals can be reclaimed, most of a
> worn-out battery is landfill). Without an affordable, efficient, clean,
> renewable and scalable way to store electricity, ground-based solar
> can't be a solution.

[sometimes stating the obvious below]

So lets say that I accept everything you say about both the
inefficiency and unclean
characteristics of solar PV + battery storage.   Are the current
incumbent solutions (Oil, Coal, Natural
Gas) any better on either characteristic?  When doing your efficiency
calculations,
please don't cheat.   i.e. Do total life cycle back to when the
material was first buried
underground.  I suspect that even turning corn into ethanol is more energy
efficient then the process that created fossil fuels.

>From an economic perspective, it is beginning to look like residential
solar + batteries
might be preferable in the near future to current fossil fuel based
grid power.  Or at least
that is the argument that many people are starting to make.   Are they
wrong?  If they aren't
wrong, is there some reason other than economics why switching from
fossil fuels to
solar + batteries would be a bad idea.

I suspect you have some other energy solution in mind then the ones
that have been mentioned
so far on this thread.  Care to share?

Bill Bogstad
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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Richard Pieri]

On 7/20/2017 7:36 PM, A. Richard Miller wrote:
> environmental pollution issues, 90% thermal loss, on that scale, and 
> except for where it can provide NEEDED heating, becomes DIRECT Climate 
> Warming all on its own. IS it that extreme with electrical storage 

No. You can't get more waste heat from charging batteries with solar
power than what you get from solar energy warming the planet directly.
You can't get more energy out of a system than you put into it.

> How else might we store solar energy? As an environmentalist, I rather 
> like the Northfield Mountain pumped-storage project 
> . It's been rather benign 
> environmentally for 45 years now. The mountain habitat is well-managed 

Except for the initial habitat destruction incurred by the creation of
the reservoir in the first place.

Mechanical storage isn't any better than chemical storage. It's
different with different problems like friction and mechanical wear.

The problem isn't how we store electricity. It's that we store
electricity. Regardless of how we end up generating electricity,
converting it for storage and then converting it back for use will
always be less efficient than using electricity directly.

-- 
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Re: [Discuss] Eclipses Re: Great talks last night, however...

[Richard Pieri]

On 7/20/2017 4:03 PM, Bill Ricker wrote:
> ​I wouldn't worry about solar power lost to the coming eclipses. Over the
> next 10 or 100 years, you'll lose far more to thunderstorms blotting  out
> the sky; they cast bigger shadows more frequently.

Yeah. And I'm even more concerned with the 10-14 hour (or more in some
parts of the world) solar outages we experience every day. Or night if
you prefer. For reals. Because despite Elon Musk's assertions, chemical
batteries are terrible ways to store electricity. They're inefficient
(~90% waste as heat). They're dirty (strip mining for rare metals,
hazardous chemicals needed to manufacture). They're non-renewable (while
some of the plastics and rare metals can be reclaimed, most of a
worn-out battery is landfill). Without an affordable, efficient, clean,
renewable and scalable way to store electricity, ground-based solar
can't be a solution.

-- 
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