
New rail-based gravitational energy storage project begins in California - Osiris30
http://www.utilitydive.com/news/first-of-its-kind-rail-energy-storage-project-targets-role-in-caiso-ancilla/417817/
======
strommen
Gravitational storage is hard.

For perspective: if the U.S. loaded up all 1.5 million of its rail freight
cars to 30-ton capacity and sent them 4km up to the top of Mt. Rainier, that
would store 494 GWh of energy.

That's just over an hour's worth of our average electricity usage.

Gravitational storage is _hard_.

~~~
dragontamer
We don't need to store everything.

We just need to store enough to make load-shifting environmentally (and
commercially) available. The 30 Gigawatt Hour Bath County Station gets there
([https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Sta...](https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Station)),
but even the "smaller" Tesla 50MWhr projects do too.

Compressed Air is hitting 300MW-hr designs
([https://www.greentechmedia.com/articles/read/texas-calls-
for...](https://www.greentechmedia.com/articles/read/texas-calls-for-317mw-of-
compressed-air-energy-storage2)). That's enough for a metropolitan solar
community to loadshift the 12:00 noon sun to the 5:00 dusk peak-energy period.
(Average home: 30kwhr per day. 300MW-hr design would serve over 10,000 homes
easily, and doesn't need to actually hold the electric usage for the whole
day. It'd realistically only need to hold 1/10th the energy or so, to load-
shift a few hours here and there).

ARES seems to be in the 12MW-hr to 100MW-hr design size. This is smaller than
Pumped Hydro but still useful. Smaller, cheaper projects that partially solve
the problem is still a good thing.

It seems like a perfectly good solution to the problem. Buying up cheap energy
from night (or noon-power solar arrays), and selling it during the 3pm to 7pm
peak-energy time. As long as there's at least a 20% differential in peak
pricing somewhere in the day, "small" 1MW-hr to 300MW-hr plants will be
profitable.

\----------

In any case: Wind continues to work at night. Nuclear works throughout the
day. Hydro works throughout the day. We don't need to store EVERYTHING, we
just need to store the excess from Solar from noon, and then load-shift it to
5pm to 8pm, while the sun is setting and solar arrays generate less
electricity.

~~~
rando18423
To finance this, a bank will want to see they've managed to hedge their
business and are in the business of capturing those spreads rather than
speculating on the widening of that spread (only to have it contract).
Interestingly, this may be exceedingly hard to do on the open market and may
require setting up an expensive structured product with the trading group of
some bank, where they pay you a fixed price each day and take on the
daily/monthly (and particularly in power markets, term) risk. That won't be
cheap, especially if these aren't located to one of the major grid nodes where
there are liquid markets available.

Basically, I'm just wondering how hedging costs affect your numbers.

~~~
dragontamer
> To finance this, a bank will want to see they've managed to hedge their
> business and are in the business of capturing those spreads rather than
> speculating on the widening of that spread (only to have it contract)

The spread is grossly positive. Pumped-Hydro provides a location for baseline
power plants (nuclear, coal, and even Wind / Solar) to continue to pump energy
into the grid without getting shut down. Coal, Wind, and Nuclear plants, in
particular, are typically very difficult to start back up again.

So it is profitable for these plants to continue to generate power, even when
the plants pay money for the privilege for someone to "waste" it somewhere.

Then of course, later in the day, the "batteries" (ARES, Pumped Hydro, CAES,
and what-not) sell the energy back to the grid when peak-energy occurs
(usually around 5:00, when businesses still have the factories running but
people have also begun to return home and turned on their air conditioning
again).

------
nraynaud
There was this Swedish train transporting minerals from a mine up in the
mountains down to the sea harbor, it was going downhill with a load and uphill
empty, and producing some energy for the neighboring town.

~~~
Hondor
That suggests a whole new type of power generation - moving rocks from
mountains down to sea level. It would also have the advantage of creating more
level land that could be more suitable for farming and construction. Not
sustainable at all though so don't tell environmentalists :P

~~~
labster
You just need to hide it behind buzzwords. "Gravilithic energy is a carbon-
neutral alternative to chemical weathering."

------
dragontamer
Sisyphus would be proud.

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

~~~
WiseWeasel
They missed a great marketing opportunity!

------
chiph
> ARES wants to lay a nearly 5.5 mile track up an 8 degree slope, gaining
> about 2,000 feet top to bottom.

An 8 degree gradient is super steep. Regular trains (not funiculars) start to
have traction problems around 2-2.5%

~~~
takno
Generally speaking in the UK this was addressed by adding banking engines (the
steepest sustained mainline gradient in the UK is 1:37 and this isn't enough
to cause problems for modern trains). This suggests the problem is an economic
one with a mix of banks and flat running. If you are only running a gradient
you can provide more traction power and have done

~~~
chiph
The problem is adhesion (lack of). Modern traction control systems (anti-slip)
help quite a bit, but eventually you'll exceed what the steel-on-steel mating
surface can provide in terms of grip. Traditionally, you overcome this by
using a heavier locomotive - which is one reason why the Union Pacific Big Boy
was 1.2 million pounds (544,000 kg). It sounds like they're addressing this by
making pretty much every car it's own locomotive.

[https://www.youtube.com/watch?v=0cd5Vcbi1gg](https://www.youtube.com/watch?v=0cd5Vcbi1gg)

------
mrfusion
I'd be curious to see gravitational energy storage built individually into
each wind turbine. If you think about it you already have a lot of height from
the tower.

Have the turbines directly lift a weight. And then lower the weight as needed
to generate electricity.

~~~
strommen
A typical wind turbine is 80m high and and generates 1.5MW [1]. Gravitational
storage in Joules is (mass in kg) * (height in m) * 9.8 (gravity). Divide by
3.6 million to convert to kWh.

Suppose we raise a 30-ton weight (i.e. a big shipping container filled to
capacity with rocks) all the way up that 80m turbine. We've stored 30,000 * 80
* 9.8 / 3600000 = 6.5 kWh of energy.

That's _16 seconds_ worth of energy from the turbine spinning at full speed.

[1]
[https://en.wikipedia.org/wiki/Wind_turbine#Design_and_constr...](https://en.wikipedia.org/wiki/Wind_turbine#Design_and_construction)

~~~
usrusr
Impressive way to put the power generation capability into perspective.

Also makes me wonder how a spring (instead of or in addition to those 30 tons)
would scale to turbine tower size. Just don't think of the destruction when
something breaks!

~~~
beamatronic
Catastrophic energy release doesn't care if you're a spring, a flywheel, a
lithium battery, or a chemical bomb - in fact all those things start to look
pretty similar at high enough energy levels.

~~~
seanp2k2
But you must admit that an 80m (~262ft or ~24 stories) wind turbine blasting
off like a giant pogo stick into the sky is by far the most comical.

Maybe gravitational doesn't make sense, but compressed air might. Big
compressor directly driven by the turbine (so as not to waste energy
converting to electricity to turn an electric compressor motor) being used to
compress normal air into large tanks inside the wind turbine tower which can
later be used to spin another turbine-based generator using the same air. Not
a physics major, but this seems feasible. Not sure of the potential energy
storage, but I feel like the direct conversion of rotational energy to spin
the pump has to be much more efficient than converting it to electricity
first, then using that [many miles away] to compress air or drive a train up a
mountain.

~~~
WiseWeasel
Bonus points if you can spin the wind turbine with the discharge of the
compressed air, on the lag edge of the propellers.

------
Osiris30
There are some demo videos here [http://www.vox.com/2016/4/28/11524958/energy-
storage-rail](http://www.vox.com/2016/4/28/11524958/energy-storage-rail)

------
jlg23
> Cost comparisons with pumped hydro are difficult, he said, because there are
> so few projects and not many data points.

There are 36 in Germany alone[1].

[https://de.wikipedia.org/wiki/Liste_von_Pumpspeicherkraftwer...](https://de.wikipedia.org/wiki/Liste_von_Pumpspeicherkraftwerken)
(the corresponding English article lists much less)

~~~
aaron695
Pretty sure they are everywhere

This list is missing the one I know about -

[https://en.wikipedia.org/wiki/List_of_pumped-
storage_hydroel...](https://en.wikipedia.org/wiki/List_of_pumped-
storage_hydroelectric_power_stations)

Given the first thought is how does this compare to pumped hydro, I worry this
is vaporware.

------
madaxe_again
Based on the very lightweight comparison with pumped hydro storage, I think
they realise it's going to be hard to compete with. _How_ are the costs lower
than a pipe a pump a pond and a turbine?

~~~
Osiris30
Yeah we don't know what the actual costs will be apart from their claim that
its 60% cheaper than pumped-hydro. However, having done some run-of-the-river
hydro projects - even a small 1MW mini-hydro (which is basically roughly a
pumped hydro in reverse) requires 2 years of civil engineering for the
penstock and weir (the water channel). I would imagine that 1-10MW pumped
hydro systems would cost and take a lot longer to engineer. Plus pumped hydro
is very geography/topography specific.

I don't have hard data - but wouldn't engineering a rail system not be as
hard, and need less civil engineering work?

~~~
madaxe_again
Given the mass of the cars they're talking about, they'd need substantial
engineering to get a good solid level grade that's not going to subside or
slip, which isn't always going to be straightforward.

As you say, however, it's very geo/topo specific - so in places like North
Wales, pumped hydro is still clearly the way to go, but in the Mojave, this
rail based system could work well.

It reminds me of the defunct system we had in a house I used to live in - 8"
or so diameter shaft in the basement floor with a weight, a cable, a winding,
and a dynamo - you'd have the servants crank it up during the day so you could
have electric light at night. Quite popular in the late nineteenth century
among early adopters of electricity.

~~~
seanp2k2
Fascinating; know what that system is called?

------
tlb
If they can buy power at $20 and sell it for $50 / MWh, then their 12.5 MWh
storage capacity generates $375 / cycle. They'd have to cycle it many times
per day to make significant amounts of money. Does the grid require more than
1 or 2 cycles per day? (Solar cycles once / day, domestic demand has 2 peaks).

~~~
dragontamer
> Kelly also said that the economics of the Nevada project will be aided by
> recent pricing trends at CAISO, which has been seeing negative pricing from
> over generation from wind power at night and from solar power in the
> morning. Under those circumstances, the ARES project could be paid to take
> power off the grid, Kelly said.

Its cheaper to keep running a Wind Turbine and PAY to put energy onto the
grid, than to actually power-off a Wind Turbine. If those Turbines stop
spinning, its very, very difficult to get them spinning again.

But someone needs to "take" the energy. This ARES project is going to be paid
in __both __directions. They profit as Wind / Solar farms pay for the
privilege for their excess energy to be stored somewhere, and then they profit
later in the day as they sell the energy back to the grid.

------
supahfly_remix
Each train stores 20 kWh in potential energy for each meter it reaches in
elevation (P = mgh).

------
carapace
Here's an idea, dunno if it's a good one:

Use water as the working mass. Lift it by converting it to steam and sending
it up the mountain through insulated pipes. Condense it at the top, recovering
the heat as possible, and let it run down to a turbine.

You have to counter losses, of course, and if you could get the heat energy
back down to the bottom to reuse it that would be great. Otherwise, just use
Solar and waste energy to heat the water to steam.

I think you might be able to get more energy out by "mining" gravity this way
than you had to put in to run the steam cycle. You're taking advantage of the
fact that water falls while steam rises.

Like I said, I have no idea if this would actually be feasible.

------
pflanze
Are those trains going to be driven by humans?

2000 feet are 609.6 m, thus according to supahfly_remix max. 12000 kWh can be
stored per train, 5.5 miles are going to take about 4 minutes to climb and
another 4 minutes to descend, let's assume (from thin air) the usage is 3
times below its max, then a train will buy and sell (0.05 also taken mostly
from thin air) 2.5/h * 12000 kWh * 0.05 USD/kWh = 1500 USD, which means that
salary for the driver is going to be perhaps 2-4% (depending on whether fully
driving, or just observing for safety).

~~~
Osiris30
I think it is fully automated. See the demo video's here

[https://vimeo.com/39364772](https://vimeo.com/39364772)

[https://vimeo.com/46460725](https://vimeo.com/46460725)

~~~
reitanqild
I found the second especially interesting as it shows the system as scale.

------
radikalus
Naively, is this reasonable because of the density relative to the hydro pump
solutions? Intuitively, moving liquids feels easier to me.

~~~
beat
Density helps. But environmental issues help more. There are only so many
viable locations for large-scale hydro storage, and it always means drowning
some valley. Just building a set of rails up a hill is much less
environmentally invasive.

One of the biggest wins of this model, really, is the low environmental
impact, relative to hydro or batteries. Fewer regulatory hurdles, more
potential locations. But in the end, cost effectiveness is what will win, and
to some degree, that will be location-dependent. Is there geography we can
exploit? Will it be in a populated area? What's the proximity to wind or solar
farms?

Solving the storage problem in a cost-effective way is the key to
transitioning from poison fuels to clean power. Once it's cheaper than
coal/LNG/nuclear, the world will switch over quickly.

~~~
marcosdumay
Rocks have about 4 times the density of water, thus you'll need 1/4 of the
volume of a reservoir to hold as much energy. Since pilling trains is much
more expensive than holding water, I can assure you this project will use much
more land area than an equivalent lake.

Also, this thing requires a straight line high inclination slope and plain
areas both up and down. I don't know how that compares with high walled
valleys, but it is not a very common formation in nature. All said, it may be
useful because it uses a different kind of landscape from water storage, so it
can increase the total capacity.

Anyway, I agree, costs alone will say how much of it is created.

------
castratikron
>When an induction motor that powers a train or car is reversed, it produces
electricity.

This is only true if the motor is connected to the grid (ie powerered). You
need a magnetic field to create the current. If the induction motor wasn't
powered when you spun it, it would not create any current as an induction
motor does not need permanent magnets to create the field.

------
Roritharr
is this so much cheaper to build than a traditional watertower solution?

~~~
Osiris30
...If this works - one of the apparent benefits is scale. Water-tower, and
other water-pressure based systems are hard to engineer above 1-10MW (I
think).... The benefit of this system is it seems to be able to scale to
100MW+ sizes. Which is what one needs to provide effective frequency
regulation, smoothing and backup to a utility-scale solar/wind park. Of
course, we don't know what the costs are yet...

------
soared
If Minecraft had a system for energy (it already has logic gates) this would
be incredibly interesting to test in a video game.

------
TylerE
Seems a little weird they're using something that resembles more or less
standard guage rail.

Imagine if they scaled it up where instead of a few rail cars you scaled up to
something along the lines of NASA's [https://en.wikipedia.org/wiki/Crawler-
transporter](https://en.wikipedia.org/wiki/Crawler-transporter) but on rails
instead of tracks.

~~~
secabeen
Probably because they can just buy commodity rails, cars, engines, etc. from
existing rail supply companies.

------
jefurii
TLDNR Excess renewable energy is fed to electric rail cars which move boxes of
rocks up a slope. When renewables are not producing power the rail cars roll
down the slope and regenerative braking produces power. A very creative
combination of existing technologies. Zero emissions, nearly zero waste, and
can probably switch back and forth between consumption to production on a
minute-by-minute basis. Also, looks like a crazy Factorio project.

~~~
Retric
Vastly more costly than pumped water, high upkeep costs.

Does have relatively high efficiency though.

PS: "Cost comparisons with pumped hydro are difficult, he said, because there
are so few projects and not many data points." Is pure BS, here is someones
coursework on the subject:
[http://large.stanford.edu/courses/2014/ph240/galvan-
lopez2/](http://large.stanford.edu/courses/2014/ph240/galvan-lopez2/)

~~~
joezydeco
If your state is running out of water, the switch to rocks might be something
you can't avoid.

~~~
Retric
Or stop farming Almonds which use 1/2 as much water as all non farm use
combined. Agriculture alone is 80% of all water use in the state. So, running
out is less of an issue than trying to farm land that's just shy of a desert.

~~~
jefurii
The real problem is all the alfalfa and the cows. Per pound of
protein/carbs/whatever, cows consume way more water than pretty much any
plant. And much of our alfalfa is just being shipped to China.

~~~
Retric
Cutting Alfalfa production is fairly cheap in the long term which fits well
with California's regular droughts. However, using prehistoric water to farm
Alfalfa is crazy IMO.

The problem with Almonds is they are trees, so letting them die is far more
costly.

~~~
vanattab
What is prehistoric water?

~~~
Retric
Underground water gained by lowering the water table. There seems to be
several terms in common usage.
[https://en.wikipedia.org/wiki/Aquifer](https://en.wikipedia.org/wiki/Aquifer)

Basically, if the water table is dropping then people are pumping out water
faster than its being replaced. If you look into when that water was put there
you quickly get into geologic timeframes. Aquifer's often do flow meaning that
specific drop may only be decades old, but replenishment rates in many places
are vastly smaller than extraction rates.

EX: Some places in China have seen 10+ feet drops in the water table _per
year_.

PS: “Fossil water” or paleowater is a related idea. Basically water that's
been undisturbed for long periods.
[https://en.wikipedia.org/wiki/Fossil_water](https://en.wikipedia.org/wiki/Fossil_water)

------
franciscop
This totally highlight the problem with Imperial Units:

"ARES wants to lay a nearly 5.5 mile track up an 8 degree slope, gaining about
2,000 feet top to bottom. ARES would then put up to seven 8,600-ton trains on
the track"

If the units were in SI[1], 1000 * 5.5[km] * 8/100 = 55 * 8 = 440m (no
calculator/conversion needed)

And for the energy stored, just do 440m * ~10m/s2 (g) * 8,600,000kg

[1]no conversion, just an example

~~~
madaxe_again
Wait, 8,600 TON trains?!

How big are these things?

8600 tons of lead would be 680 cubic meters - so ten or so standard sized
shipping containers.

Two locos, four cars... I still don't see how that fits.

Unless these are HUGE trains, or they're using exotic matter, I don't see how
that's possible.

~~~
zimpenfish
Going off
[https://en.wikipedia.org/wiki/Heaviest_trains](https://en.wikipedia.org/wiki/Heaviest_trains)
I'd reckon probably about 1000m length for 8600t trains.

(And also that 8600t isn't anything special.)

~~~
madaxe_again
So 200m long cars, given that there are four in a train of that mass from TFA?
I suppose it's not inconceivable, but it seems weird to be re-inventing the
railway carriage format.

Also, having a long train is surely undesirable for this application, unless
you have a plateau at the top and bottom at least as long as the train.

~~~
secabeen
If you look at the video, they have a neat system where the mass is stored
perpendicular to the rails in the storage yard, then cars come in, pick up the
masses, rotate them parallel to the rail for transport, then re-rotate them
back to perpendicular for storage at the other end.

~~~
dragontamer
That's probably how they'd scale. It looks like they're just going to be
moving the trains up/down the slope.

------
daveguy
Come on guys. Ruby can't do _everything_.

Edit: Also, they are claiming 93% mechanical and electrical efficiency. I'm
not sure if that is each or total, but either way it sounds impressive for
storage and retrieval in a wide demand range.

Edit2: Is this company publicly traded? Or is it owned by a publicly traded
parent company?

Edit3: It is a startup (and they are looking for funding).

