
How Sustainable Is Stored Sunlight? - stonlyb
http://www.lowtechmagazine.com/2015/05/sustainability-off-grid-solar-power.html
======
Hermel
Great to see someone actually doing some calculations instead of just
presenting a cosy vision. For example, they argue that - contrary to what Elon
Musk implies with his illustrations - the solar cells on the roof of the
gigafactory will only be able to generate a small fraction of the energy
required to run it.

> The average solar insolation in Arizona is 1,964 kWh/m2/yr (in Phoenix). If
> we assume a solar PV efficiency of 15%, one m2 of solar panels would
> generate at most 295 kWh per year. Consequently, almost 68 square kilometers
> of solar panels (6,800 ha) would be required to power the factory -- a
> calculation that also relies on the assumption that solar energy is equally
> distributed throughout the days and the seasons (or stored in batteries),
> and that there's no open space between the panels. Remarkably, Tesla shows
> an illustration of the factory with solar panels on the roof. Knowing that
> the factory will occupy a surface of 1 ha, while 6,800 ha of solar panels is
> required to run it on renewable energy, Tesla's claim is an obvious example
> of greenwashing -- and everyone seems to buy it.

~~~
frossie
These are the kind of calculations that make me weep - somebody getting happy
with numbers without engaging their brain as to the answer. Obviously the
Tesla factory is not going to require 20,000,000 Megawatthours to operate -
that is as much as the whole electricity production of the State of New
Hampshire.

Assuming their input data is actually correct, I will speculate they are
calculating the energy cost of the entire lithium battery production from raw
materials, such as extracting lithium from mineral deposits, the majority of
which would happen before the materials arrived at the Tesla factory.

I also expect Elon Musk knows what his electricity bill is. Given his
investment in green technologies and his general success in delivering
projects, I would be rather surprised if he advertised a solar factory if
there was a chance he would be out by 4 orders of magnitude on how much power
he would need.

~~~
rybosome
According to this study[0], it takes about 116 kWh of input energy to create a
100 kWh battery, given the materials. The majority of the total energy usage
is in material production, not battery production. Assuming Tesla is not
making their own materials, this deflates the required input energy
substantially.

[0]:
[http://www.electrochem.org/dl/ma/202/pdfs/0068.PDF](http://www.electrochem.org/dl/ma/202/pdfs/0068.PDF)

~~~
ars
> Assuming Tesla is not making their own materials, this deflates the required
> input energy substantially.

And also inflates that amount of greenwashing involved...... Why crow over
renewable energy when your use of energy is irrelevant relative to your
suppliers?

~~~
e98cuenc
But their statement seems accurate and clear: they will operate the
GigaFactory using renewable energy. They don't claim or imply that they will
extract the materials using renewable's or that all their suppliers will use
renewable's.

~~~
Gravityloss
They should source their lithium from solar-powered contractors. Maybe even
sell them some panels for a good price. (I realize the brine is already
evaporated in the sun, but there's electrical separation after that.)

------
ars
Money quote: Using the worst assumption in each case, solar cells with storage
emit 631 gCO2e/kWh vs 337 gCO2/kWh for normal hydrocarbon fuel in spain.

Important takeaway: A solar cell embodies a huge amount of energy, yet can be
shipped. Make solar cells in places with lots of clean energy and ship them
elsewhere.

~~~
chongli
_Make solar cells in places with lots of clean energy and ship them
elsewhere._

What about the energy use and carbon emissions from shipping?

~~~
lotsofmangos
I thought that and then checked the numbers.

Shipping is negligible and when compared by energy per tonne per km, can be up
to almost 100x better than road, so going 200km by road can compare to going
nearly 20000km by sea in some cases.

Putting everything in one place could get savings from many factors, but
transport doesn't appear to be that major compared to the others.

------
dpierce9
The conclusion of this article is that a life cycle analysis of solar with
storage is better than the marginal contribution of greenhouse gases from
operating a traditional plant but not by a lot. Has anyone seen a life cycle
analysis of decommissioning a coal or nuclear plant or managing tailing ponds?
I commend the effort to make apples to apples comparisons but that would need
to be added in to make this genuinely apples to apples.

------
lotsofmangos
_" the manufacture of 1 kWh of lithium-ion battery storage requires 400 kWh of
energy, the factory would require 20,000 GWh of electricity per year to
manufacture all these batteries."_

The 20,000 GWh figure is clearly bollocks, one factory a hectare in size is
not going to be using the same amount of electrical power as the whole of
Nigeria.

edit - also, one thing I do not understand with their argument, is if Tesla's
illustration is really supposed to show that the factory can run entirely on
rooftop solar, why would it feature around 100 large wind turbines dotted all
across the hillside?

~~~
ZeroGravitas
Possibly they are counting the mining/transporting of materials to make the
batteries too?

~~~
lotsofmangos
So currently for batteries used by Tesla, that is getting the lithium from
Chile and Argentina, then transporting it to battery factories in China, then
shipping them to their car factory in California, as opposed to getting
lithium from Nevada, to a factory in Nevada, to the other side of the same
Nevada factory, as you also make the cars there.

The total embodied energy is going to get absolutely slashed.

edit - btw, I accidentally fat fingered the down button on your comment that
had the link to -
[http://www.withouthotair.com/](http://www.withouthotair.com/) \- sorry. I
hope that isn't what prompted you to remove the comment.

~~~
ZeroGravitas
No that wasn't the reason, though its nice of you to mention it.

I'd re-read the withouthotair site the other evening after seeing Elon's
presentation, as he made a similar case regarding the area of the USA needed
to be powered by solar. I was a bit bummed out by the conclusion for the UK
and wondered what the global equivalent was, as the UK is low on solar. I then
noticed I'd skipped a chapter that does the rough calculations for other
regions
([http://www.withouthotair.com/c30/page_231.shtml](http://www.withouthotair.com/c30/page_231.shtml))
the basic answer being that Solar may just save us, but it'll be an incredible
amount of work, both political and engineering.

(Which is basically the same answer as for the UK, though in the UK solar is
mostly replaced with wind/wave/hydro as we're relatively blessed with those).

~~~
phaemon
The Without Hot Air site seems to have got its sums wrong. It continually
makes the point that we'd need to cover the whole UK in renewable energy
generation, and that still wouldn't be enough.

However, we already generate 7.5% of our energy from renewables and clearly
7.5% of the country isn't covered in windfarms/solar/biofuels. Therefore he
must have made a mistake somewhere: if reality disagrees with theory, the
theory must be wrong.

~~~
pjc50
7.5% of our energy or 7.5% of our _electricity_? It's the latter. We're still
consuming the output of the North Sea plus a little bit more in petrol and
diesel.

~~~
phaemon
Actually, it's the former: 7.5% of energy. It's 15% of electricity.

------
Jedd
They lost me at their second sentence:

    
    
      > In order to fill these gaps [ night, cloud ] , a storage solution
      > or a backup infrastructure of fossil fuel power plants is required
      > -- a factor that is often ignored when scientists investigate the
      > sustainability of PV systems.
    

If you're approaching the problem with solar power with the assumption you
need storage or fossil fuel, you're basically arguing with yourself.

Note they did say 'solar power', not 'solar cells / PVC / etc'. Solar thermal
plants ride through periods of cloud, and well into the night, reasonably
well. But the big problem is that assumption that you must either store solar,
or you burn coal / oil ... followed by a complaint that scientists ignore
important factors.

~~~
ZeroGravitas
I'm not sure I follow your point? Even without solar power, storage is an
important part of many grids e.g. meeting peaks with pumped storage hydro.

Are you saying that solar thermal is enough storage for a predominantly solar
grid? I'd suggest it isn't. I'd also suggest that solar thermal _is_ a type of
storage solution and it's time-shifting properties are one of the things that
make it useful.

~~~
NickNameNick
You don't need pumped hydro. The wonderful thing about hydro is it throttles
easily, and leaving water in the lake is equivalent to putting more water into
the lake.

~~~
lotsofmangos
When the reservoir is full, Cruachan Power Station in Scotland can operate for
22 hours before it is emptied. Also, it is required to leave 12 hours water in
the lake at all times to provide emergency cold start backup on the grid. If
it wasn't pumped hydro and was only working from runoff, then it wouldn't
work.

------
throwaway90446
I'm _still_ trying to figure out why everyone, including Deutsche Bank, seems
to think the Tesla Battery is such a great deal at $3500 for 7kwh.

I can buy 18 35Ah 12v AGM batteries, plus 0 AGW conductors, for about $1350.
That's 7.5kwh for $1350.

What _exactly_ defines the "good deal" argument I keep seeing?

~~~
manicdee
Are you going to fully discharge that 7560kWh lead-acid system every day?

No, you are not. You are actually going to buy five times as many batteries
and work in the 20% of the storage range which is suitable for continual
cycling. So that's 90 batteries off the bat, or about $6750, almost double the
cost of the Powerwall, not including the ancillary equipment you haven't
budgeted for to bring your batteries into the same league as the Powerwall.

You still need the battery room to install them in, and the fire protection
system to put out electrical or chemical fires when things go wrong.

The Powerwall includes thermal and fire containment (the batteries are
swimming in gel), the Powerwall also takes care of the "battery room" issue by
storing the battery in a container on the wall.

For those with greater power requirements, there are rack mounted power cells,
again with thermal and combustion mitigation already in place.

The integration and packaging is why everyone is excited about these batteries
at this price.

------
ChikkaChiChi
I keep imagining a world where Solar is our primary source of electricity and
I keep seeing that world lose its mind when a volcanic ejection leaves us
powerless.

I get that it should be part of a much larger plan, but Solar in its current
iteration doesn't seem like that safe of a bet.

~~~
yincrash
Nuclear is the safe bet. However, in your block out the sun scenario, we will
have lots and lots of problems beside just power generation. Such as crops.

------
nnain
This new push towards off-grid, battery-powered solar power just doesn't sound
right. Batteries might have improved, but they are high maintenance and
polluting. Moreover this requires the addition of a lot of new electrical
circuitry at the point of installation - a waste of space, time and money.

It's the responsibility of the world's governments to work out ways to keep
the grid-connected solar solutions working. Maybe change the 'Net metering'
rules to buy the solar power from customers at a lower price, and let the
supply-demand work itself out.

It'll be very stupid if we let go a well-functioning grid based solar power
solution just because some power distribution companies don't find it
profitable.

~~~
graphene
_Maybe change the 'Net metering' rules to buy the solar power from customers
at a lower price, and let the supply-demand work itself out._

It won't be that simple, since even this (allowing customers to contribute
power back to the grid at scale) requires expensive infrastructure upgrades.

~~~
nnain
Nothing is ever that simple. Nevertheless I would rather opt for upgrading the
infrastructure than upgrading the installation at every home/office.

IMHO, smarter grids are much better than batteries all over the place.

~~~
brrt
I'd argue that one implication of a smarter grid would be that there'd have to
batteries all over the place, exactly because batteries can adapt quickly and
'smartly' (with a .05$ microchip) to energy supply and demand.

Whereas there is a limit to the maximum intelligence of refrigerators,
airconditioning devices, heat pumps, and washing machines.

------
kstenerud
It's a bit silly to argue over where materials are made when considering
sustainability, as that requires an assumption that the "dirty" productive
capacity would otherwise not be used for anything else.

~~~
lotsofmangos
I may be being overly cynical, but given the blog is dedicated to showing how
high technology solutions cannot work and has articles about PV generation
leading with the claim that solar can be often worse than coal, before you
drill down and realise that they are not talking about generation, but have
segued into running the figures on what happens when they are glued to the
casings of laptops and mobile phones (
[http://www.lowtechmagazine.com/2008/03/the-ugly-
side-o.html](http://www.lowtechmagazine.com/2008/03/the-ugly-side-o.html) ), I
think they are trying to find numbers to back an established view, rather than
adjusting the viewpoint to the numbers.

\---

edit - Actually, to be honest, I do not think in this case I am being overly
cynical. The article I linked to, titled _" The ugly side of solar panels"_
starts with:

 _" New research shows, albeit unintentional, that generating electricity with
solar panels can also be a very bad idea. In some cases, producing electricity
by solar panels releases more greenhouse gases than producing electricity by
gas or even coal."_

This claim is then not really addressed till right at the end of the article,
where we find the following:

 _" For rooftop and ground-base installations, the eco-friendliness can be
good or doubtful, depending on the solar insolation and the life expectancy.
But if we consider solar panels mounted on gadgets like laptops or mobile
phones, solar energy becomes a plainly bad idea._

 _If we take a life expectancy of 3 years (already quite optimistic for most
gadgets) and a solar insolation of 900 kWh /m² (quite optimistic too, since
these things are not lying on a roof), the result is 1,038 gram CO2 per kWh in
the worst case scenario (high-efficient mono-crystalline cells produced in the
US). That means that it is better for the environment to power a gadget with
electricity generated by coal, rather than by a solar panel."_

So, if you buy a laptop or mobile with a solar panel on it and then throw it
away after three years, then it is worse than coal.

Which is obviously a completely rational point to make on the subject, given
all those masses of mobile phones and laptops sold everywhere with solar
panels on them.

Then it gets even better:

" _All this does not mean that PV solar energy should not be promoted. For one
thing, it’s much better using silicon wafers to make energy generating
equipment instead of energy guzzling equipment (like computers, mobile phones
and car electronics)._ "

And by this point I am not sure if this is satire, or if the author thinks
their website is hosted on a steam powered abacus.

~~~
manicdee
Yes, we are clearly better off using the traditional coal-fired laptops, even
though the extra bulk of the thermal shielding and fire extinguisher can
sometimes be an inconvenience.

Actually, now that I think of it, I can't remember ever seeing a laptop with
its own coal fired power plant. I wonder why this isn't done?

------
spenrose
He's completely ignoring the effects on the grid, which will be huge.
Batteries are also a complement to wind, for example. Here's one piece
discussing that dynamic; there are many others at e.g. Greentechmedia.com.

[http://rameznaam.com/2015/04/14/energy-storage-about-to-
get-...](http://rameznaam.com/2015/04/14/energy-storage-about-to-get-big-and-
cheap/)

------
ansible
The article mentions getting 7000 charge/discharge cycles from lithium ion
batteries. That doesn't sound right to me. Most consumer electronics are lucky
to get 300 or so at 100% discharge.

~~~
fulafel
Phone batteries make their own tradeoffs, they want to minimize weight and
then make you buy a new phone.

Marine li-ion batteries advertise 2000 full cycles (80% depth of discharge).
Electric cars have 10 year battery warranties. Etc.

~~~
ansible
IIRC, the current EVs run run their batteries at about 85% depth of discharge
to meet their lifetime targets.

Unless the linked article is talking about lithium iron phosphate technology.
That is more durable than standard LiIon technology.

But that isn't in wide use, despite its initial promise.

~~~
manicdee
The Tesla Powerwall is indeed based on LiFePO4, at least according to all the
material Tesla have produced.

------
csirac2
I had to abandon my reading before I reached the end, I was too angry at the
disgustingly sloppy referencing. In particular his second paragraph put me in
a bad mood straight away:

> In order to fill these gaps, a storage solution or a backup infrastructure
> of fossil fuel power plants is required -- a factor that is often ignored
> when scientists investigate the sustainability of PV systems.

Um. Pardon? Either he's having an argument with himself, or he's reading some
pretty lame journals. Or is he just confused? Let's see:

> Obviously, this strategy requires a backup of fossil fuel or nuclear power
> plants that step in when the supply of solar energy is low or nonexistent.
> To make a fair comparison with conventional grid electricity, including
> electricity generated by biomass, this "hidden" part of the solar PV system
> should also be taken into account. However, every single life cycle analyse
> of a solar PV ignores it. [3, 2].

Yeah, okay. That's a perfectly debatable paragraph. So let's see the science
behind the claim: [2] has nothing to do with anything! It _addresses_ energy
storage, but is not _about_ energy storage; and it does NOT claim to be a
literature review, nor does it claim to reference "every single life cycle
analysis". Am I missing something? Is this citation of "[3, 2]" supposed to
represent the entire sum of human scientific knowledge on this matter? Am I an
idiot? Surely I'm the idiot, I didn't waste my time reading this article -
that point must be shooting straight over my head!

Okay, let's read the paper. It's on energy payback/cannibalism - a logical
presentation from what I skimmed - but is absolutely focused on the energy
life cycle analysis of a _whole technology_ experiencing _rapid growth_ \- Eg.
nuclear back in the day - whereby the energy invested to rapidly establish new
technologies may be greater than or at least massively offset any efficiencies
(or indeed, "zero emissions") they may have over existing (think "sunk cost")
incumbent energy production.

Which has nothing to do with central thrust of this article which seems to be
that we should point and laugh at all those idiot scientists who forgot that
the sun disappears each night!

But this writing forgets one thing - who is saying that PV (or wind for that
matter) can replace established baseload power generators in a 1:1 swap?

Nobody sane, that's for sure. So I'll give you a hint: it's electricity
buyers. They don't give a damn that they're destroying the planet by using PV
solar, the fundamental fact is that in countries like Australia, even though
you seemingly can't swing a cat without tripping over high-grade thermal coal
ideal for cheap power, we pay among the highest electricity rates in the
world. It's that kind of corrupted and/or government-regulated inefficiency
that is the only thing to blame for the fact that PV solar can compete at all,
even when subsidies are withdrawn.

I can't keep reading.

