
From liquid air to supercapacitors, energy storage is poised for a breakthrough - jsingleton
http://www.theguardian.com/environment/2016/feb/04/from-liquid-air-to-supercapacitators-energy-storage-is-finally-poised-for-a-breakthrough
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jonawesomegreen
I've spent the last couple years working on a very interesting project using
ultra-capacitors for energy storage. We are storing 33kWh of energy in ultra
capacitors, charging and discharging with a very short period (seconds) for
peak-demand shaving. It really is an exciting time for energy storage
technology. I think we are going to see a lot of cool innovation in the next
few years, even just finding new uses for existing technologies.

~~~
saosebastiao
What sort of volume/weight dimensions are required for 33kWh of ultra
capacitors?

~~~
jonawesomegreen
They are quite large, but in the particular application weight and volume are
not a huge concern. All sitting side by side they are about 20 meters long, 3
meters high, and a meter deep. Probably weighs on the order of 15 tonnes.

~~~
zachrose
Wow, how much capacitance is that?

~~~
aexaey
16.3 megafarads, assuming typical cell voltage of 2.7v, and total energy of
33kWh:

[http://www.wolframalpha.com/input/?i=33kWh%2F%282.7v%29**2](http://www.wolframalpha.com/input/?i=33kWh%2F%282.7v%29**2)

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dragontamer
A good overview, although missing Vanadium Redox Flow batteries (liquid
battery), which is one of my favorites.

Redox Flow batteries can be pumped into storage tanks and distributed
(theoretically anyway). In contrast, the entire set off Lithium Ion battery
needs to be connected to the grid to take advantage of its storage, you can
"pump" Redox Flow batteries into storage tanks to increase capacity without
increasing power.

For day/night cycle storage (or longer), I'd expect Redox Flow to be more cost
efficient than Lithium Ion, despite LiIon having numerous advantages (density
/ power / etc. etc.). Mainly because you can save on "Power Output" and
instead build larger and larger tanks to store the charged electrolyte.

LiIons get more and more expensive ($$$ per KW-hr storage) the "bigger" they
get. Redox Flow batteries achieve scalability (cheaper $$$ per KW-hr the
bigger they get). I do realize I'm imprecisely using the word "bigger", but I
hope yall will forgive me on that :-)

My personal favorites:

1\. Pumped Hydro -- Old technology, but a favorite of mine. Very simple
design, just take advantage of lakes that already exist in your vicinity and
use the water in the lake as a gravity storage device.

2\. Flywheels -- Store energy by spinning a heavy object. Spin-spin-spin...
spinning and gyroscopes are cool.

3\. Vanadium Redox Flow Battery -- Liquid batteries, how cool is that?

~~~
AnkhMorporkian
> (...) you can "pump" Redox Flow batteries into storage tanks to increase
> capacity without increasing power.

Why wouldn't you keep them at maximum capacity all the time?

~~~
dragontamer
Cost efficiency.

If your neighborhood only needs 50MW of power, but you want 1000 MWhr of
storage (~20 hours at full power), a Redox flow battery would be able to do
that. Or if you were building a Hospital (Lets say 5MW of power) and need to
spec out 3-days of power (ie: 360 MWhrs of storage on 5MW Power), you just
build a tank that can store a lot of the electrolyte.

I guess... the best way of putting it is that Lithium Ion batteries are like
AAA batteries, while a Redox Flow battery could be configured as a larger D
battery. D Batteries don't give any more power or voltage than AAA batteries,
but are more efficient for energy storage.

It is very easy to imagine how to build a 3000MW-hr 50MW Redox Flow battery
(just build a huge storage tank). It is almost impossible to imagine the same
with Lithium Ion (I guess you can build massive Li-Ion cells, but note that
the Tesla is powered by tiny 3.7V 18650 cells wired up together. So it really
hasn't been done before)

Day/Night cycle storage is a low power (Megawatts) high-storage (Megawatt-
hours) use case. Lithium Ion batteries are more useful for high-power /
medium-storage situations (like frequency balancing, or maybe a couple hours-
long storage).

Flywheels are exactly the opposite. They are high-power low-storage devices.
Flywheels would be very useful for smoothing out power when birds / clouds
come up in front of solar panels (for example). Its easy to build a 300MW
flywheel with almost no capacity (only a few __minutes __of storage).
Flywheels could be used when a power-source goes offline suddenly, while a few
minutes need to be spent spinning up a new power-source. (ex: Main grid goes
down, you need 30 seconds before your diesel generator fully turns on. The
flywheel will keep very high-power for the next 2 minutes while things switch
over). Although supercapacitors are also a promising technology for this
problem.

Different storage technologies for different purposes.

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jsingleton
I posted this yesterday but today there's a story about "Welsh home installs
UK's first Tesla Powerwall storage battery". Good news.

[http://www.theguardian.com/environment/2016/feb/05/welsh-
hom...](http://www.theguardian.com/environment/2016/feb/05/welsh-home-
installs-uks-first-tesla-powerwall-storage-battery)

This project to store energy in trains also looks interesting.

[http://www.aresnorthamerica.com](http://www.aresnorthamerica.com)

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beat
Energy storage is such a no-brainer. It makes solar/wind viable for both base
load and peak load generation. The numbers required are very measurable and
predictable. It doesn't require magical, exotic technology (as the elevated
reservoir and compressed air mechanisms show). There's always going to be some
thermal losses in transformation, but they're going to be pretty similar
across technologies.

Another nice thing about solar + storage is that it can scale very small, very
inexpensively. Imagine putting a set of solar panels or a wind turbine plus
some storage in a village in Africa. It may not be worth wiring it to an
expensive grid, but just getting electricity there can make so many other
differences.

Beyond that, the ability to small-scale and decouple reduces the power and
influence of large corporations and the government-industrial complexes that
wreak so much havoc. You don't need the drama and abuse of the petroleum or
nuclear industries anymore.

~~~
SilasX
Scalable? Compressed air and reservoirs are about the opposite of energy-dense
and require a lot of space per unit energy.

I'm optimistic about the role that energy storage can play in converting green
tech to base-load capability, but it seems like it requires some technological
advances unless you want to devote huge territories to becoming low-density
batteries.

~~~
beat
I'm not talking about physical size. I'm talking about cost and complexity. An
air tank with a compressor pump at one end and a turbine at the other is
simple, reliable, well-understood, off-the-shelf technology. How much energy
can you store in an air tank that would fit on the back of a truck? Hook it up
to another truck full of solar panels, and you have a local electric grid,
capable of powering at least a few buildings, at very reasonable cost and
minimal sophistication required for operation and maintenance.

~~~
SilasX
Scalability covers _spatial_ scalability, and so necessarily involves talking
about physical size relative to energy stored in this context.

~~~
beat
Is that actually important, though? Does it mean inexpensive small-scale
energy caching in off-grid areas is impossible? Would a truck-carried air tank
(or bank of them) hooked to solar-powered compressors not actually work, or be
cost-prohibitive?

Size doesn't actually matter here.

~~~
SilasX
But it does. The Wikipedia numbers [1] give a mass density for compressed air
storage of 40 kJ/kg and volume density of 8 kJ/L. That's 0.011 kWh/kJ or
0.0014 kWh/L. So a 10,000 L tank gets you only 14 kWh, or ~$1.50 worth of
energy.

[1]
[https://en.wikipedia.org/wiki/Compressed_air_energy_storage#...](https://en.wikipedia.org/wiki/Compressed_air_energy_storage#Specific_energy.2C_energy_density_and_efficiency)

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1024core
This stuff is always "poised for breakthrough". But we are still stuck on LiOn
batteries, which have been around for what, 20 years? Wake me up when we have
something that doubles the capacity of LiOn batteries in a similar form-factor
and safety rating, propelling Teslas to 600km+ ranges. That would be a real
"breakthrough".

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nordify
Could somebody enlighten me on the economics of energy storage?

The local retail energy prices are approximately 10c/kWh year round, rain or
shine. The price is fixed, unless you buy a contract based on the spot market.

All the energy storage products I've heard about cost more or about the same
per kWh just to store the energy. So even if the energy to charge the energy
storage was free, it still would not make economic sense to store energy if
you have grid power.

Am I missing something or is consumer energy storage only for off-grid
applications?

~~~
mikeash
Not all places are like this. Some places have variable time-of-use rates with
high premiums at peak times and large discounts at times of extreme low
demand. For example, rates with Southern California Edison can be as high as
45 cents/kWh and as low as 11 cents/kWh. If you can charge up a storage system
at times of low demand and then use it at times of high demand, you could save
a lot of money.

The bigger use is probably industrial applications, though. Commercial users
can get hit with huge surcharges if they draw a lot of power, for example, so
users which only draw huge amounts of power briefly could save a lot of money
by using storage to smooth that out. The utilities themselves can end up
paying extremely high rates for extra capacity at peak time, so if they can
use storage to eliminate that need it can save them a lot of money.

~~~
nordify
> Not all places are like this.

Is there a reason why all places couldn't be like this? Wouldn't a well run
and properly regulated power grid solve these problems?

~~~
mikeash
Demand inherently varies at different times of day and different times of the
year. Given variable demand, variable pricing is expected. Fixed prices are
basically a leftover from when technology didn't support sophisticated
metering for time-of-use pricing, and sticks around because people prefer
simplicity in pricing.

~~~
nordify
For the sake of the argument, let's accept the premise that variable demand
requires variable pricing.

Is there a technical reason price differentials have to be so large in
California? In an efficient market, even with variable prices, would the
differences be so extreme and would peak demand prices still exceed the cost
of storage?

~~~
mikeash
I'm pretty sure California is an example of a badly run system, and price
differentials wouldn't be so big if it were run better.

In an efficient market, peak prices wouldn't exceed the cost of storage pretty
much by definition, because the utility would use storage to even out demand
as long as it's cost effective.

But I assume you mean whether it would happen without storage. That depends a
lot on the underlying assumptions, I'd say. Does an efficient market mean one
where you can build coal plants anywhere you feel like and pay only the cost
of extraction, but not the cost of pollution? Or does it mean one where you
pay the full cost of fossil fuels, rather than the weak and inconsistent
controls we currently have?

I think you'll almost always benefit from _some_ storage. You'll get
diminishing returns as you increase generating capacity to match peak load, so
storage would become the cheaper option at some point (assuming you're not
shedding loads for extreme peaks).

Consider that no other industry operates on such a sharp just-in-time way,
where supply and demand have to be matched on a second-by-second basis.
Whether it's fruit or car parts or passenger airplanes, there's always some
storage to allow slack in the system. The electrical grid historically hasn't
been this way just because the technology wasn't there, but it's finally
catching up.

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stcredzero
Contextually relevant question: How much would it cost to do a major revamp of
the North American electrical grid? (For various values of "major revamp" of
course.) I found this article that mentions a $2 Trillion figure from Rocky
Mountain Institute, but I take that with a big grain of salt. [1]

Since the patents around Tesla's Supercharger are open, what about the idea of
giving the US highway commission a few hundreds of millions to double the
number of Supercharger stations? (This would create more demand while not
improving the infrastructure, but I would benefit personally.)

    
    
        [1] - http://www.renewableenergyworld.com/news/2015/04/us-power-grids-2-trillion-upgrade-needs-european-efficiency.html

~~~
mikeash
Superchargers only work with Teslas, and Tesla is doing fine when it comes to
doubling the number of installations on their own (there are currently 270,
and they installed 113 of those last year), so having the government come in
and install them doesn't seem like a good use of money.

Further, what's the relevance of Supercharger stations to electrical storage?
Maybe I'm missing something but that seems like an irrelevant tangent here.

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oconnore
These buzz articles always focus on the sexy energy storage methods: lithium
ion, liquid batteries, electrolysis, supercapacitors, etc. I've seen very
little evidence that these can compete on either $/kWh, or efficiency, with
pumped hydro (where available), thermal (Isentropic Energy Ltd [1]), or
kinetic.

[1]: [https://www.greentechmedia.com/articles/read/Isentropics-
Pum...](https://www.greentechmedia.com/articles/read/Isentropics-Pumped-Heat-
System-Stores-Energy-at-Grid-Scale)

~~~
ohitsdom
Correct me if I'm wrong, but none of the options you listed are portable.

~~~
oconnore
Right. In the context of grid storage of renewable energy, that doesn't
matter.

You need a li-ion or similar in your phone and your laptop (and maybe your
car), but that doesn't make it the best tech for flattening out a peaky
solar/wind grid.

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gravypod
"It doesn’t always rain when you need water, so we have reservoirs - but we
don’t have the same system for electricity,” says Jill Cainey, director of the
UK’s"

Actually... we do. It is called pumped hydroelectric storage [1], and it is
essentially just a reservoir, a pump, and a turbine.

[1] [http://energystorage.org/energy-
storage/technologies/pumped-...](http://energystorage.org/energy-
storage/technologies/pumped-hydroelectric-storage)

