
Gravitricity - tempestn
http://www.gravitricity.com/
======
andrewliebchen
Good thing HN wasn't around durning the development of most of humanity's
great inventions. "So your telling me I'm going to have to hold my food over
this fire for 15 minutes before I eat it? No thank you, I'd stick with my raw
meat."

~~~
msandford
The majority of humanity's great inventions didn't have basic physics saying
"this isn't brilliant" long before a prototype got built. Most of humanity's
great inventions were things that were difficult because human beings thought
they were difficult, or complicated or intricate or whatever.

On their webpage they say " The biggest single cost is the hole, but it is
expected that firstly this will have a very long life and secondly, as the
technology rolls out, the costs of drilling will reduce significantly. So the
economics will improve in time."

Drilling will not get cheaper without a serious reform of the law, and that's
unlikely to happen. There are two primary kinds of drillers; water and energy.
Folks involved in water have VERY protective rules in all states. The reasons
are 1. good lobbying and 2. if you screw up you destroy the water supply.

Energy drilling is no cheaper. Drilling rigs are huge machines that aren't
moved easily and cost at least $50k a day on land and $500k a day for
seagoing. That's before you pay another $20k per day in staff and god knows
how much for fuel for everything; a rig will produce at least 5MW of power.

Could they custom build a rig just for drilling for their idea and would that
work? Sure. But they'd probably spend several million and then you've got to
have it running 24/7 for it to pay off.

The regulatory hurdle is going to be non-trivial as well. They're going to
case it which helps. But the casing would probably need to be cemented in
place which is a non-trivial cost as well. And convincing lawmakers that this
doesn't quack like some other kind of well is going to be no easy feat.

~~~
waps
Sadly what you say is true. Despite the fact that humanity has been drilling
holes into various types of soil for over 8000 years, we don't really have a
good way to do it. The situation is not quite as bad as you're describing
though. It is not $50k per day, more like $5k. That is for machines that can
only do soil, not rock, and aren't as much drilling as they're making a hole.
But in places where you can do agriculture, you'd have at least 5m of soil
above rock, and more usually 50+ meters. I wonder how much power this system
would have with a 10 meter deep hole (like is regularly installed for heating
water in homes these days).

These guys may be on to something. Scaling down seems to me to be the key.
Full gridless operation with solar panels (at least in earthquake-free zones).

~~~
kwhitefoot
It is quite easy to calculate how much energy can be stored and how much power
can be generated for how long.

The potential energy of a mass in joule is simply

    
    
      m * g * h
    

where m is in kilogram, g is 9.8 m/s^2, h is the height in metre.

So, for example, 100 ton lifted 100 metre gives 98MJ.

That's 1MW for 98 seconds.

To make this very concrete my house uses, in the summer, about 40kW-hr per day
for water heating, cooking, and the rather large amount of computer equipment
we have.

That is 40000 * 3600 = 144MJ. So assuming that your solar power system can
supply that over a 12 hour period we need to store half of it, 72MJ, to keep
us going after dark. Your ten metre deep hole would need a 734 ton weight:
735000 kg * 9.8 m/s^2 * 10 m = 72MJ

~~~
tripzilch
Average energy use in the Netherlands is 3340 kW-hr per household per year,
which amounts to about 9.15kW-hr per day (and seeing that these are averages,
I gather that the type of household to pioneer this sort of tech will be
sufficiently energy-conscious to use quite a bit less than that).

Either way, I think you'd have to round your estimate to order-of-magnitude
anyway, because of the rather big assumption "that your solar power system can
supply that over a 12 hour period we need to store half of it, 72MJ, to keep
us going after dark", because getting max solar power for half the day and no
solar power for the rest is not exactly how it works, nor does one use the
same amount of energy during day and night (which is why I can opt in to an
energy plan that gives you discount on electricity at night, because there's a
surplus then).

~~~
kwhitefoot
3340 kW-hr is a remarkably low figure. Anyway the point was not to be accurate
but to show the kind of working that gives the answers.

Even if we accept your figure the peak daily use is probably at least double
your 9kW-hr/day (winter for example) and even if you use less at night you
still need probably about 12MJ storage to allow solar to work per household,
etc., etc. So, yes, in the Netherlands you need a smaller mass but it is still
in the order of 100 ton.

The point of my reply was to show the person I was replying to how easy it is
to find out how much mass and height is needed, you just have to plug in your
own energy consumption and generation figures.

------
jmadsen
I love how every Tom, Dick & Harry with a bit of math & engineering thinks he
can "dispel the myth" of HN Idea X with two minutes of off-the-top-of-his-head
equations.

Read about these two:
[http://www.gravitricity.com/#people](http://www.gravitricity.com/#people)

Do they seem like complete morons? Do you think they haven't studied this just
a _little bit more_ than you have? It doesn't mean their idea is good or will
work - just that you aren't going to rip it apart with two hastily written
paragraphs.

People who _ask questions_ about the costs, process, etc. are in the right
spirit. People who think they can show off how clever they are really make me
/facepalm

~~~
bduerst
You don't need to be a carpenter to tell if a house is built poorly.

~~~
jmadsen
You don't need to be a carpenter to tell if the doors are hung straight.

You DO need to be one to actually assess the overall build and structure.

~~~
bduerst
The picture they're drawing isn't very straight, as many have demonstrated.

Until these "experts" provide evidence otherwise, it's useless to berate
readers for pointing out the obvious.

~~~
logicallee
Bduerst, I have almost never downvoted anyone over anything. But I must say
you have no right to put "experts" in quotation marks. Given their bio, they
are experts. Which makes your comment a troll comment. (Unheard-of on HN.)

Really, what do you think the definition of an expert is? "Just because he
teaches the stuff at the University of Edinburgh, has sold a company to
Siemens that created the world's only installed MW-scaled marine turbines
(with the sale described by Bloomberg as a 'blow to the UK'[1]), and received
an MBE for his contributions, does not make him an energy expert."

Of course they're experts, even if they're ones you disagree with.

[1] [http://www.bloomberg.com/news/2012-02-17/siemens-to-take-
ove...](http://www.bloomberg.com/news/2012-02-17/siemens-to-take-over-u-k-
tidal-turbine-maker-in-next-few-weeks.html)

~~~
bduerst
I should have been more specific because I don't think what I was trying to
communicate came across. I did not mean to imply that these people are not
experts at anything, just that they should publish findings, test results, or
at least a white paper on proof of concept.

As it is, this website reads like they did the napkin math for the idea and
are using only their credentials to legitimize it. Its an appeal to authority.

~~~
jmadsen
Those are valid points, but I think too many here are assuming they don't have
anything more substantial & this website is their entire speil.

I don't think people like these two would risk their considerable reputations
publishing something that every one of their peers could take apart at a
cocktail party. More likely, there's more behind this website.

HN readers rarely give that obvious benefit of the doubt.

------
apsec112
Let's do out the math on this...

A subway tunnel might have a diameter of about 6 meters, so cross section = 3
* 3 * pi = 28 square meters. Digging subway tunnel through rock costs about
$100M per kilometer. On the one hand, these holes would be vertical, which is
harder than horizontal; on the other hand, they wouldn't need ventilation and
train tracks and stuff. Let's handwave and say it's $100M for a 1 km deep
hole.

Now, you can't fill the whole tunnel perfectly or the air can't escape, so our
total volume of mass will be about 25 m^2 * 1000 m = 25,000 cubic meters. If
the weights are made from lead, that's a total mass of ~280,000 tons or 2.8 *
10^8 kg, at a mean depth of 500 meters, so our total potential energy is 2.8 *
10^8 * 500 * 9.8 = 1.4 TJ, or 1.3 TJ net assuming you get the efficiency they
claim. 1 kWh is 3.6 MJ, so you can store ~400,000 kWh at $100M capital cost
(ignoring for the moment the cost of weights, generators, etc.), which is $250
per kWh installed capacity.

That's pretty good... but you also have to pay for weights and a bunch of
other stuff. Bulk lead costs about $2,000 per ton on the current market, so
that's $560M for the weights, which puts you back in the $2,000 per kWh range
which doesn't beat lithium batteries. So you have to use iron or some cheaper
material... but then you don't have as much storage capacity because the
density is lower, and even with iron you're paying $400 per metric ton or $80M
for all your weights. So this isn't obviously impossible like Solar Roadways,
but even in the best case it won't make storage dramatically cheaper.

~~~
cperciva
_Digging subway tunnel through rock costs about $100M per kilometer. On the
one hand, these holes would be vertical, which is harder than horizontal_

I would have thought that a better comparison would be oil wells, which cost
about $500 per ft of depth, or $1.5M per km.

 _our total volume of mass will be about 25 m^2_ 1000 m = 25,000 cubic meters.
If the weights are made from lead, that's a total mass of ~280,000 tons*

You seem to be assuming that the entire depth of the shaft is filled by
weights. My impression was that the weight was much smaller than the shaft it
fell down.

~~~
msandford
Oil wells are also only a foot in diameter. Makes the economics worse, really.

------
elektropionir
The energy density for gravity is just immensely small, that's why you need
dams holding back rivers to use them to generate electricity. For a 1km hole
(that's in the middle of their 500m - 1500m range) you have an energy density
of 10kJ/kg of the weight that stores the energy. The energy stored in a Tesla
roadster battery pack is around 50kWh which is 180MJ. This means that you need
a 18,000kg weight in a 1km deep (immovable) hole to have the equivalent of a
Roadster battery pack. I'd go with the battery pack.

~~~
jostmey
Okay, so what if you built a huge artificial dam way above sea level? To store
energy you would pump water uphill. Usable work could then be extracted when
the water is allowed to travel back downhill.

~~~
jccooper
Well known as "pumped storage". They're competing with it, but dry and upside
down. Is it more economical? Maybe. Is it safer? See
[http://en.wikipedia.org/wiki/Taum_Sauk_Hydroelectric_Power_S...](http://en.wikipedia.org/wiki/Taum_Sauk_Hydroelectric_Power_Station)

At least if this contraption breaks, there's nothing important below it.

------
awjr
Is a 500m-1500m shaft is pretty much going to fill with water? I could see a
well designed weight being able to work in water (although water turbulence
would erode the shaft walls. I don't see how air compression would solve this.

The principle however of storing energy by raising a weight could also be used
anywhere with a steep enough hill/cliff/montain and the weight could in theory
be on a rail not just suspended.

Efficiency would potentially not be on par, however linked into solar/wind
systems this is less about efficiency and more about creating a 1MW long term
battery with a lifetime of 50+ years.

Guessing cost of digging and maintaining a hole compared to installing a guide
rail is significantly higher.

~~~
pbhjpbhj
> _Is a 500m-1500m shaft is pretty much going to fill with water?_ //

So you're saying you get a free well as part of the deal?

------
Animats
OK, a typical mine hoist is about 10 metric tons. 10 metric tons descending at
1m/sec is very close to 100KW. So a 1000 meter deep hole can deliver 100KW for
1000 seconds, or 27 KWH. That's about $3 worth of electricity, and about 1/3
of the battery capacity of a Tesla Model S with the large batter option.

Numbers not looking reasonable for this concept.

~~~
slashnull
I don't know how heavy are the planned weights, but it sure as hell will be
heavier than 10 tons.

~~~
Retr0spectrum
Even if it was 1000 tons, it would still only be about $300 worth of power.

~~~
toomuchtodo
Depends on the spot price of power. Power on the open market (where utilities
have to buy it to provide to customers) changes every minute. Its usually
cheap at night until the early morning, starts to increase, and then spikes
around 3-4pm (+_30-60 minutes, depending on the country).

If you delivered power when it was most expensive (ie high demand) and
consumed it in the middle of the night, the arbitrage may work out.

------
ramses0
I think the coolest thing about this concept (for me) is viewing it as a
"whole-system" energy storage procedure.

It is effectively 100% renewable, 100% distributable, using 100% commodities
(ie: rocks in a hole).

As a thought experiment: if on average you can meet 110%+ daily power
expenditure captured from renewables (solar, wind, whatever), and store it by
lifting up these weights, then you've broken into the "free energy" loop.

More specifically, don't look at the power input or storage, look at the power
output / usage. If your input + storage capacity is greater than your output
rate then energy effectively becomes "free forever".

Simulate it on a small scale. Get a pinwheel to run a small motor that winds
something up. Attach a small LED to it that you only run occasionally.
Basically, just so long as you have a really small output draw compared to
your input rate and storage capacity, this "battery" will give you energy when
you want it with minimal maintenance costs and minimal consumables.

------
abdullahkhalids
The key figure of merit for comparing energy storage is not $/KWh, but rather
$/KWh*Number of cycles. Li-ion only has about a 1000 cycles. Assuming one
cycle per day (solar charge during day+discharge during night) in 50 years
there are 18000 cycles.

The figure of merit for Li-ion is 250x1000=2.5e5. My estimate (and those of
others) is that this costs up to about $2000/KWh. So the figure of merit for
this is 1000x18000=0.9e7. Two orders of magnitude better than Li-ion.

Edit: I am ignoring the cost of capital, interest rates etc. Somebody should
do this analysis.

~~~
jpau
I did some quick analysis comparing the proposed project against Li-ion,
adjusting for storage and lifespan, and the result is very hopeful. I used
values for $/KWh and lifespan from abdullahkhalids' comment. The analysis
shows that if you can get more than one cycle per day out, the proposal offers
fantastic value.

Model visible here - [http://imgur.com/KmQPb8P](http://imgur.com/KmQPb8P)

Finance uses something called 'equivalent annual cash flows' (EACFs) to
compare projects of different lifespans. Using EACFs makes this analysis very
simple.

Using abdullahkhalids' figures and assuming a single cycle per day, the
equivalent annual cash flows per KWh are equal when the cost of capital is
about 4.35%.

Something magical happens when you assume can get more than one cycle per day.
At two cycles per day, your funding costs could be 10% and the project still
feasible! At four cycles per day and with a 5% cost of capital, Li-ion costs
almost _four times as much_ as the proposed project.

Could someone shine some light on how many cycles per day is realistic for
both Li-ion & the proposal?

PS if you find this sort of analysis interesting and want to hit me up to talk
about such things, feel free to send me an email (available in my profile).

------
sz4kerto
This came up a long time ago. It doesn't work well, the amount energy it
stores is simply too low. I've seen a calculation somewhere, but it's too late
here so can't reproduce - does anyone remember?

Edit:

here it is.
[https://news.ycombinator.com/item?id=6739349](https://news.ycombinator.com/item?id=6739349)

------
michaelbuckbee
This is just rampant speculation - but what if they used depleted uranium as
the weight? They could get paid to take the material off others hands (instead
of buying lead) and it's almost 70% more dense.

~~~
bequanna
Wouldn't the initial cost savings be offset by the ongoing challenges of
dealing with a big moving chunk of hazmat?

~~~
tempestn
Probably... but it's still an intriguing idea! Especially since their
pressurized gas proposal already calls for a sealed cavity; maybe there
actually is potential there. (Of course, there would probably be a significant
PR cost too.)

That said, they can already get more weight by making the weight taller, so
density likely isn't a huge benefit. Whatever's the cheapest cost/kg (and
without the other issues of Uranium) would probably be best.

------
tasty_freeze
Although I think the idea isn't workable (energy density is too low, cost of
boring the hole is tremendous), most of the other commenters here seem to
think they'd just have one weight, whether it is 1000 KG or 50,000 KG.

Any sane plan would be to have more than one weight. When the first weight
hits the bottom, it would release from the cable and another weight up top
would grab the cable and start dropping. To store energy, the top weight would
get winched up, and when it hit the top it would lock into place somehow and
the next weight at the bottom of the shaft would engage the lifting cable,
etc. The cable would have to follow a circular track, rather than having 1KM
of cable for each weight.

~~~
Sorgam
What advantage does this provide over combining all your weights together into
one big one? If you want to limit the tension on the cable, just use more
cables.

You shouldn't be so confident that you know the only "sane" way to design such
a thing. It's not a field anyone has experience in. These are only guesses.

~~~
Pxtl
Well, it does mean your cables and dynamo can be smaller. But then you've got
a new problem of coupling the cables to the load at the bottom and somehow
storing loads at the top that the cables must reach past/through.

~~~
tasty_freeze
You have a shaft 1km or 1.5km deep. You can afford to stack a lot of weights
vertically. Imagine each has a hole running through the middle, where the
cable runs, and a mechanism whereby the weight can engage/disengage from the
cable. The cable forms a circular loop that passes through all the weights
from the top of the shaft to the bottom, then circles around past a large
pulley and back to the top, completing the loop.

At the top of the shaft there would be hefty prongs that retract when the
weight needs to start dropping, and when the weight returns during a recharge
cycle, the prongs reinsert themselves in to the shaft when the weight is
lifted back into position.

Most likely each weight would have a "C" cross section with a nearly closed
mouth -- just a slot from the edge of the weight to the larger central opening
so that the weight can be removed/replaced from the cable if needed.

------
madaxe_again
This is neat, but not novel. I used to live in a house (UK, middle of nowhere)
that had a deep borehole that was used for this purpose 130 years ago. The
weight and winding were long gone, but the dynamo was still sat there. Oh, and
it wasn't raised by water, rather, servants, back in the day.

------
callmeed
Funny, I just finished Peter Thiel's book. In the final chapters, he discusses
the cleantech flame-out companies of the 2000's and how many were run by old
suits. He contrasts them with true technology innovators (like Elon) who are
"t-shirt and jeans" people.

Interesting to scroll down and see suits at this site.

------
phacops
Seems like this would be more cost effective as a component of sky-scrapers.
Generator on top, series of weights on rails down the sides.

~~~
ars
Not even close. First a 1KM tall skyscraper? Second they are talking quite a
lot of weight - the skyscraper would have to be MUCH stronger.

~~~
jacquesm
[http://en.wikipedia.org/wiki/Kingdom_Tower](http://en.wikipedia.org/wiki/Kingdom_Tower)

------
gatehouse
Is 90% efficiency really feasible for electrical -> mechanical -> electrical?

~~~
KaiserPro
95% efficient each way, it does sound a bit much.

~~~
tormeh
Not really. Electrical engines and generators are incredibly efficient. It's
not the transition there that is the problem. In fact, if it was only for that
loss the efficiency would be more like 97%. The problem is the friction in the
mechanical parts; the wires, gears and so on.

~~~
tanzam75
Amtrak still uses motor-generators on some parts of the Northeast Corridor to
convert 60 Hz AC grid power to 25 Hz AC traction power.

It's exactly what it sounds like: a motor that is mechanically coupled to a
generator. The motor runs on 60 Hz AC and turns the generator at the correct
speed to produce 25 Hz AC.

~~~
tormeh
Haha, wow, a mechanical engineer was on duty that day.

------
grondilu
What determines the depth of the whole?

I mean, since E = mgh, you can get the same energy storage capacity with a
less deep hole if you use a heavier weight. And you can get a heavier weight
either by using more expensive material (why use a cheap one? it's not like
it's going to wear or anything), or a larger hole.

I'm not sure what determines the cost of digging a whole, but I suspect depth
matters more than area.

Also, does the shaft has to be vertical? You could dig it with a sharp slope,
and put your weight on rails. That would make the shaft longer for the same
depth, but it would probably be easier to build and maintain.

~~~
gus_massa
I still not sure about the details, and I don't like how they use the word
"cheap" there.

Nevertheless, the density of Lead is 11.35 g/cm3 (the density of water is 1
g/cm3). The densest element in this table is Osmium with 22.6. So replacing if
you replace a Lead weight with a more expensive weight you only gain x2.

[http://www.lenntech.com/periodic-chart-
elements/density.htm](http://www.lenntech.com/periodic-chart-
elements/density.htm)

~~~
Sorgam
Gold is about 20g/cm^3, and although it sounds expensive, there's a lot of
gold just sitting in storage. Why not store it underground here instead? This
is in contrast to tungsten which has direct commercial value and would be
wasted just being stored.

~~~
gus_massa
You have to add the cost of the armed guards, because a big block of gold will
be a nice target of a robbery.

~~~
pm90
Well, yes. To be fair, if there was like a farm of these devices, it might
makes sense to swallow that expense.

I wish gold wasn't so rare! Its such an amazing material, and our economy is
not based on precious materials anymore (except the commodity markets or
course), so it seems like a really sad thing that we can't have more abundant
gold just yet

------
transfire
I thought of this decades ago, and I am sure many others have too. And no the
math does not come out favorably. While technically feasible, the cost is
prohibitive. The reason is simple, you need LOTS OF WEIGHT to get any
appreciable storage capacity.

Try it yourself: [http://hyperphysics.phy-
astr.gsu.edu/hbase/gpot.html](http://hyperphysics.phy-
astr.gsu.edu/hbase/gpot.html)

Note that 1 joule = 2.77777778 × 10-7 kilowatt hours

------
Pxtl
There's interesting variations here - at first glance a single big weight is
the same as many small ones, but you have to think of the engineering
challenges of cabling and motors for a 1 kilotonne mass. So you could use many
smaller objects in a stack and move them one at a time, but then you've got
the problem of decoupling/recoupling the cable and reaching _through_ the ones
that are at the top while lowering/raising the ones at the bottom.

Now, the next obvious consideration is using mountains instead of a pit. The
rockies are full of 4000M peaks. But a mountain means suddenly we have so many
new considerations - mountains aren't exactly a constant slope from peak to
foot. But extreme loads on rails are a solved problem - the world's heaviest
single fully-loaded rail-car was about a kilotonne (a special schnabel car
carrying a reactor up to the Alberta tar-sands).

Of course, then you've got a new construction problem - building a train-track
that's a near-straight-line up a mountain and can support incredibly heavy
trucks.

It's probably not workable because of the energy-density concerns, but it sure
is _neat_.

------
joering2
I have this idea in my mind for a while now and it seems great subject to
share it with you.

Imagine an elevator going kilometers into the oceans dept. A huge tank is
mounted on the top of it. It gets filled in with pressurized air. Because its
heavy it sinks to the bottom. Then an air is released. Air travels into the
surface but on its way it is actually captured into a little traps. When
enough air is trapped, the entire structure built from hundreds of traps is
lifted into the surface, together with the tank. of course during this trip,
it triggers friction and the dynamo mounted on the surface translates this
movement into electricity.

Once on the surface, the tank is filled in with air, and the process starts
all over.

With long enough elevator in deep enough ocean, the electricity produced
thanks to the travelling elevator would be greater than electricity used to
put air into the tank.

If you ignore the rules of gravity and that trapped air travels to the surface
of a water, this could be a perpetuate mobile.

What's wrong with my idea?

~~~
jakobegger
The deeper you go, the higher the pressure. The higher the pressure, the
smaller the (trapped) air bubbles. The smaller the air bubbles, the lower the
upward force.

As a result, the deeper you go, the more air you will need to pump into your
tank.

Or in other words: with a given amount of air inside your tank, there's a
maximum depth you can go. If you go deeper, the air bubbles will no longer
lift the tank.

~~~
joering2
Of course, and that's what happened to Kursk.

But:

The released air would go up, regardless how pressured it is. While going up
it would decompress taking up more space and therefore having greater force to
push the tank up (as I mentioned, released air would be capture in a
construction similar to a tree with leaves. Imagine leaves upside-down
capturing the air.

I'm sure you can find different type of mix that would be less-compressible
and overal better for this experiment.

~~~
jakobegger
If the bubbles are captured higher up, say 500m above the tank, so that the
increase in deplaced water can lift the tank, you couldn't lift the tank all
the way up to the surface; it would be stuck at 500m below surface.

It's the basic law of conservation of energy. You need to provide the energy
required to lift the tank by compressing the air. The energy required to lift
the tank is m _g_ h (mass of tank, gravitational constant, height to lift the
tank). The energy stored inside the tank is proportional to p*V (pressure
times volume). You can't lift the tank further than the amount of energy you
have available, so you can never have a surplus of energy.

------
etamponi
If you drill a hole 1500m deep, and you use concrete as the material of the
object used for energy storage, and the volume of the object is V [cube
meters], when the object is at its maximum level you have stored an energy of:

E = 10 x V KWh

This means that with 10 cube meters of concrete you can store 100 KWh (more or
less the energy consumed by 10 households per day). If what they claim about
doubling the energy storage is true, with the same amount of concrete you can
store 200 KWh. 10 cube meters of concrete would weight just 24 tons, not so
much after all.

Assuming a hole 1600m deep, and a system of cables capable of handling 250
tons (100 cube meters of concrete), you can store up to 2000 KWh (so you can
serve 200 households for a day).

I don't know the price of drilling a hole 1600 meters deep, but with these
premises, if the price is in the range of 1-5 millions $, a medium
neighborhood can afford the operation.

------
throwawayaway
> Most expensive component – the hole in the ground – can have a life of well
> over 50 years

Well well well, I must buy a well.

~~~
ZoFreX
They missed a perfect opportunity to use "sunk cost".

------
pm90
I really hope these guys succeed, even if they don't replace conventional
batteries everywhere. One thing I've been thinking for a long while is that:
the future of humanity is in how advanced drilling equipment we can make.
Think about it: asteroid mining, colonizing planets or even just conventional
mining...all require drilling. If this technology catches on, there will be so
much research done in finding better drilling techniques. In fact there is so
much resources to be found in our Earth itself, if we drill deep enough.

Also, imagine if we have a base on the moon powered by solar cells: having the
technology to drill quickly and cheaply would be indispensable in storing
energy captured during lunar "days". Although I imagine you would need deeper
holes because of the smaller g.

------
pbhjpbhj
So basically clock-type counterweights. PSH seems like it would be far more
efficient - there's surely a lot of mechanical losses in the sort of system in
the OP?

If the hole could be used for some sort of heatpump too then maybe that would
weigh off [no pun intended!] some of the problems.

------
aetherspawn
If we had a dyson sphere around something heavy then the crank part could be
in space with the weight dangling into the atmosphere:
[https://en.wikipedia.org/wiki/Dyson_sphere](https://en.wikipedia.org/wiki/Dyson_sphere)

~~~
k__
How about the Moon? :D

~~~
aetherspawn
Yeah, I thought about that, but there wouldn't be enough gravity and it might
be a bit too far to beam the energy back.

------
AndrewDucker
Okay, so energy density is low - but what are the costs like?

If you can build one of these cheaply, and the running costs are trivial, then
it's worth doing.

How many of them would you need to smooth out the energy of a wind farm, for
instance?

------
Stately
I'm far from being even slightly knowledgeable in this topic, but would it be
possible to build this in very deep waters? Like a massive column containing a
tunnel? Seems cheaper than digging a 1km hole.

~~~
delinka
You'd be anchoring a buoyant tube to the ocean floor, trapping all that
energy. Instead, float a barge in deep enough water, drop a weight to generate
power, raise it to store.

------
ggchappell
FTA:

> The key requirement is a deep hole in the ground; it could be a disused
> mineshaft brought back into use, or it could be a purpose drilled or sunk
> shaft.

So, apparently, "sinking" a shaft involves making a hole using some technique
other than drilling. What technique is that?

Dictionaries are no help. Wikipedia[1] says:

> Shafts may be sunk by conventional drill and blast or mechanised means.

"Mechanized means" is pretty vague. Can anyone clarify?

[1]
[https://en.wikipedia.org/wiki/Shaft_mining](https://en.wikipedia.org/wiki/Shaft_mining)

~~~
jmadsen
This may be of interest:

[http://en.wikipedia.org/wiki/New_drilling_technologies](http://en.wikipedia.org/wiki/New_drilling_technologies)

------
dmritard96
Been attempted before. Its interesting that below ground is preferable to
above ground. Water tables in many places will be a problem.

------
jacquesm
[http://www.launchpnt.com/portfolio/energy/grid-scale-
electri...](http://www.launchpnt.com/portfolio/energy/grid-scale-electricity-
storage/)

[http://www.greentechmedia.com/articles/read/Gravity-
Power](http://www.greentechmedia.com/articles/read/Gravity-Power)

------
KaiserPro
So how many joules can it contain?

I mean, technically I can get a super cap the size of jam jar to kick out 1
kw, just not for very long.

A watt is a unit of how much energy is expended in a second, not how much
energy is stored. There is a reason why hydrostations in wales use lakes to
store energy, because you need a lot of mass at great height to be of any use.

~~~
bsilvereagle
Work = Force*distance, so theoretically the number of Joules would be mgh^2.

~~~
schoen
Your units got messed up there -- it's just mgh. There's no reason to square
the distance.

    
    
      $ units
      Currency exchange rates from 2013-07-11 
      2562 units, 85 prefixes, 66 nonlinear units
      
      You have: 1000 kg gravity 1 km
      You want: J
     	* 9806650
     	/ 1.0197162e-07

~~~
bsilvereagle
That's what I get for doing intermediate thermo & fluids all day and then
trying to make a comment on basic dynamics. Thanks for the catch.

~~~
schoen
Sure. This is also neglecting the compressed air part of this technology
(which thermodynamics might actually be quite appropriate for modelling!).

------
zaroth
I was really hoping it would keep scrolling down nearly forever, with
something neat waiting at the bottom :-)

------
arfar
He's managed to get a patent for it
[http://worldwide.espacenet.com/publicationDetails/biblio?CC=...](http://worldwide.espacenet.com/publicationDetails/biblio?CC=WO&NR=2013005056A1&KC=A1&FT=D)

------
cjbenedikt
At least you'll have to appreciate that these guys have started a viable
enough business before for Siemens to buy it. However, when they started out
it appeared equally unfeasible at the time..."impossible is an opinion not a
fact"

------
blubbi2
I'm probably missing something, but what's the advantage of drilling a hole as
opposed to "simply" building a kind of drain or sky scraper. I doubt it would
be more expensive.

Sure, the pressure-aspect would be away, but besides that...

------
goodmachine
If this catches on everywhere we'll run out of gravity in no time.

------
krschultz
Keep in mind, we currently remove entire mountains to extract coal. If there
is one thing we can do at scale it's dig holes, move concrete, and make steel
cable.

------
thisjepisje
What about springs for energy storage?

[https://www.youtube.com/watch?v=YCs002BywAE](https://www.youtube.com/watch?v=YCs002BywAE)

------
Zikes
I look forward to Elon Musk's proposal for unconventional energy storage,
because he wouldn't dare call it anything other than Eccentricity.

~~~
revelation
This is just a pun, but of course his proposal for energy storage already
exists, and (surprise surprise) its lithium ion batteries. Significant parts
of the projected gigafactory capacity are reserved producing cells for
SolarCity home energy storage appliances and other storage systems.

In fact, right now the Tesla factory has 4GWh of lithium ion batteries
installed for smoothing energy demands and they are actively building 400kWh
storage units:

[http://www.greentechmedia.com/content/images/articles/straub...](http://www.greentechmedia.com/content/images/articles/straubel1.jpg)

I'm sure that the end game idea in his mind is using the 85kWh+ batteries of
Teslas everywhere for distributed energy storage.

~~~
pm90
Yep, and as the maker of the most efficient of those batteries, he can make a
nice clean profit. Good on him though, he (and the whole Telsa team really)
did put in a lot of effort to get there.

------
pizzashark
This sounded so much more interesting before I knew what it was.

------
rebootthesystem
They are using the wrong approach. It's the difference between Karate and
Aikido.

Can one use potential energy to, well, store energy? Duh. This, however, is
the wrong way to do it.

------
robertmarley
Digging that hole seems expensive.

------
aaron695
Good to see these's still a sucker born every minute.

Intelligent people on HN are pointing out huge holes with this idea but some
people are still defending their Nigerian princes, because... they want it to
be true?

The warning signs here are huge. It's an incredibly simple idea, if it was
possible it'd be already done. Nothing here really seems to rely on scale
either.

------
scottcanoni
Where can I buy one? I'll start digging in my backyard ;)

------
phragg
Drilling into the ground should almost never happen.

~~~
ars
Why?

