
Why energy storage sucks - atilev
https://medium.com/@atilev/why-energy-storage-sucks-in-practice-3d80d80320de
======
mangecoeur
Very limited view of energy storage tech frankly. Quick list of things I am
aware of (some deployed and some in labs)

\- Pumped hydro, by far the most widespread

\- Flywheel storage, used at grid scales for frequency regulation

\- Thermal storage used in conjunction with solar power using various
materials - molten salt, HTF, hot dry rock

\- Many different battery chemistries:

    
    
        - High temperature batteries (e.g. ZEBRA batteries specifically developed for cost effective grid scale storages https://en.wikipedia.org/wiki/Sodium%E2%80%93sulfur_battery)
    
        - Sodium-ion batteries
    
        - Metal hydride batteries
    
        - Redox flow batteries such as zinc-air systems
    

\- Compressed air storage

\- Phase change storage, including hybrid compressed/liquefied air storage

\- Seasonal thermal storage
[https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storag...](https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storage)

\- Water electrolysis + hydrogen fuel cell cycle

Probably missed a bunch too. All to say there are a lot more solutions then
lead-acids and lithium batteries- although in fairness those are the most
accessible options in small scale systems

~~~
dangravell
Some interesting products utilising PCMs in the domestic hot water markets...
Replacing traditional hot water cylinders which suffer from very high heat
loss even when insulated.

~~~
semi-extrinsic
The economics aren't great for replacing a hot water cylinder with something
more efficient.

According to this [1] a typical hot water cylinder wastes less than 2000 kWh
per year. That's a yearly expense of less than $400. This means a replacement
system aiming to break even over five years must cost less than $2000.

Replacing a hot water cylinder with a bog standard new one costs at least
$1000. Thus the PCM heater must be essentially as cheap as existing solutions,
and so it faces the challenge of not being able to get enough initial volume
to get the cost below break-even. Government subsidies are probably the only
way to make it work.

[1] [http://www.solarblogger.net/2012/11/heat-losses-from-hot-
wat...](http://www.solarblogger.net/2012/11/heat-losses-from-hot-water-
cylinders.html?m=1)

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jsingleton
There are broadly two types of energy storage. Grid scale and domestic. This
article is about the latter as it focuses on certain batteries. It's actually
pretty interesting but the scope is narrow.

Domestic is important as it can leapfrog other tech in places without a
reliable grid. Much like mobile phones leapfrogged fixed lines in Africa.
There are lots of options for the grid but only batteries really work at a
small scale.

For more on this watch this recent video from Al Gore:
[https://www.ted.com/talks/al_gore_the_case_for_optimism_on_c...](https://www.ted.com/talks/al_gore_the_case_for_optimism_on_climate_change)

At grid scale you can have exotic types of batteries, pumped storage and other
things. For example, there are plans to double Cruachan:
[http://www.bbc.co.uk/news/business-35666993](http://www.bbc.co.uk/news/business-35666993)

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paulsutter
Pumped hydro is much cheaper than batteries per KW (max storage rate) and KWh
(storage capacity) is limited only by reservoir size. The roundtrip efficiency
is about 80% and it's able to store for months at a time.

Heindl Energy in Germany is developing hydraulic storage, which can work even
on flat ground (basically, raising a rock formation with pumped water).
They've designed capacities up to 120GWh:

[http://www.heindl-energy.com/hydraulic-rock-storage/idea-
fun...](http://www.heindl-energy.com/hydraulic-rock-storage/idea-
function.html)

~~~
aolagers
Pumped hydro is interesting but the reservoir requirements are huuuge. This
post makes a very convincing case that scaling it up is not that simple:

[http://physics.ucsd.edu/do-the-math/2011/11/pump-up-the-
stor...](http://physics.ucsd.edu/do-the-math/2011/11/pump-up-the-storage/)

There is some discussion about the German rock variation in the comments. The
density doesn't seem to help THAT much compared to water only.

~~~
infogulch
Density isn't the only benefit of this system. At these scales, the water
requirements alone are significant. This replaces many cubic meters of that
water with rock.

~~~
masklinn
The other big advantage is that you don't need a tall hill to put a reservoir
on top of.

Sadly it seems the project has been at the "plan to get funding for a pilot"
stage for at least 5 years now, and I still don't see how it'd seal.

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brownbat
Surprised there's no mention of Vanadium Redox as an alternative that solves
several of these problems even better than Lithium Ion.

They can be fully cycled over 100,000 times (compare to Li-ion's 400-1200,
lead's 500-800) and are expected to last 20 to 30 years. They can stay in a
single state for long periods of time without degradation and can be rapidly
and efficiently charged or discharged. There's also no fire risk.

The biggest downside is size and weight. A refrigerator sized VRB in the attic
of a house would work, but that is a dealbreaker for some/most people. These
certainly won't go in cars, but as stationary appliances for those with the
space, they would work extremely well for solar storage.

DOE factsheet:
[http://energy.gov/sites/prod/files/VRB.pdf](http://energy.gov/sites/prod/files/VRB.pdf)

Wikipedia:
[https://en.wikipedia.org/wiki/Vanadium_redox_battery](https://en.wikipedia.org/wiki/Vanadium_redox_battery)

~~~
masklinn
> A refrigerator sized VRB in the attic of a house would work, but that is a
> dealbreaker for some/most people.

Even a refrigerator-sized VRB doesn't store that much energy, that's ~650
liters so about 40MJ, under 1.5L worth of fuel. And more importantly it
weights _half a tonne_ and (assuming it has the same shape as a standard
fridge) has an area density of ~1.5t/m^2.

~~~
mikeash
40MJ is a bit over 11kWh, which should be enough to run a typical house
overnight. My house uses something like 500W average, not counting the car, so
it could run almost a full day on this.

For a stationary application, half a ton doesn't seem like a big deal. Surely
a normal house can hold up that much weight? That's equivalent to only six or
seven people. If the weight is a problem, put it on the ground level or in the
basement.

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davedx
I really want to read this article, but there are too many spelling and
grammar mistakes or lack of punctuation. Please consider spellchecking it?

~~~
stcredzero
Spellchecking? What about innumeracy?

 _As you can see if you only drain your battery to 75% (meaning you only use
20% of your capacity) you get tremendously more cycle’s (more than double!)
then say using 50%. So when systems are designed for energy storage you
generally want your batteries to last a long time (since they’re expensive) so
you want the maximum amount of cycles for them, which means that you should
only discharge them 80%. As you can see this is getting quite frustrating, as
now simply to power you’re off-grid system at night you need to purchase 80%
more battery capacity than you actually need._

75 + 20 = 95. Okay, close enough to 100. But discharging to only 20% means you
need to buy 500% the capacity, not 180%!

~~~
aswanson
Yeah, I was hesitant to click on the article based on the title. Thanks for
confirming my suspicions.

~~~
Fjolsvith
I did learn a few things from the article, though. The big one has to do with
why the car batteries I use on a hydraulic and winch system have been failing
fast. It has to do with the way I run them all the way down before charging
them back up.

In my shed delivery business, I have a custom designed trailer with a
hydraulic lift for the tilt bed and a winch for loading and unloading the
buildings. They are 12 volt and I just run them with a car battery.

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spenrose
For medium.com would it make sense to include the username in the title, like
this:

    
    
        Why energy storage sucks (medium.com/@atilev)

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Faaak
Energy storage not only consists of batteries… Pumped hydro, for example,
works well and does not decays over time.

~~~
masklinn
Pumped hydro is absolutely great, but it's an option for tremendous (grid-
level) scales, and requires convenient locations (e.g. a hilltop you can "blow
up" with a large stream nearby, or a standard dam with a lake or lake-able
location close to its foot). It's way, way beyond the scales the article is
talking about (note the picture from a health clinic in Rwanda).

~~~
bloat
How big of a tank on your roof do you need to replace a box of lead acid
batteries?

~~~
mhandley
A 12V deep-discharge lead-acid battery is typically 120amp-hours. That's
1.4kWh. Suppose you only 50% discharge it for longevity, that's 700Wh. I'll
assume your box of batteries has ten of them, so a usable capacity of 7kWh.
1kWh = 3.6MJ, so 7kWh = 25MJ

How high is your roof? Lets say 10 metres. Potential energy U = mgh. (m=mass
in kg). h=10, g~=10, so U=100*m.

So, to equal those batteries, assuming 100% efficiency, the mass of water
needs to be 250000 kg, or 250 tonnes. Probably going to need to reinforce the
loft.

~~~
Dylan16807
So 'roof' is clearly out of the question. Now let's look at basement. I
install a 4x4x2 meter tank, then drill down 100 meters to create another such
tank. 32 tonnes lifted 100 meters gives me 32MJ, perfect.

Now how expensive is it to build a water storage area underground? Is this a
50 thousand dollar project or a 50 million dollar project?

If the ground water is at the right depth, you would only need to drill a
well. So this should be practical somewhere, at least.

~~~
debacle
Your 100 meter channel is going to get flooded.

~~~
Dylan16807
That's your biggest objection to the idea? A 100 meter waterproof pipe is the
easiest problem to solve here.

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zackmorris
The comment I was writing turned into a blog post, so I'll just post the
links. IMHO these are trending towards solving many of the problems faced by
alternative energy generation and storage:

[http://www.npr.org/sections/thetwo-
way/2016/02/04/465568055/...](http://www.npr.org/sections/thetwo-
way/2016/02/04/465568055/morocco-unveils-a-massive-solar-power-plant-in-the-
sahara)

[http://www.wsj.com/articles/energy-storage-startup-
lightsail...](http://www.wsj.com/articles/energy-storage-startup-lightsail-
plots-long-term-game-plan-1456110323)

[https://en.wikipedia.org/wiki/Nickel–iron_battery](https://en.wikipedia.org/wiki/Nickel–iron_battery)

[https://en.wikipedia.org/wiki/Sodium–sulfur_battery](https://en.wikipedia.org/wiki/Sodium–sulfur_battery)

[https://www.littleboxchallenge.com](https://www.littleboxchallenge.com)

[https://www.littleboxchallenge.com/pdf/finalists/56568-Tech....](https://www.littleboxchallenge.com/pdf/finalists/56568-Tech.pdf)
<\- PDF

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DiabloD3
So what happened to the idea of using some modern version of flywheels to
store power?

~~~
pjc50
They were deployed in Formula 1:
[https://en.wikipedia.org/wiki/Kinetic_energy_recovery_system](https://en.wikipedia.org/wiki/Kinetic_energy_recovery_system)

I'm not aware of any building or utility-scale systems.

~~~
mhandley
There are a few utility-scale flywheel systems deployed:
[http://beaconpower.com/stephentown-new-
york/](http://beaconpower.com/stephentown-new-york/)

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pocketstar
No mention of Ni-Fe batteries, they are significantly more robust than LA or
Li and have 30+ year lives.

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3327
Great article from a practical standpoint of what is actually deployed and
small scale.

