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I recently came across the idea of gravity storage for the
electrical grid. Pumped storage <link> has been used for
some time and works well, put simply you run a
hydroelectric dam forwards or backward depending upon
the supply-demand situation. To make a pumped
storage system, you need lots
of water, mountains-
and people who don't mind you flooding their valley. This
great for Canada, Wales, and Norway but badly suited to
One clever chap, with a suspiciously Halfbakery-like back
catalog, decided to use all the standard pumps and
generators with water as the working fluid. The mass,
however, would come in the form of rock. The idea
<link> is to cut out a 200m diameter cylindrical
piston from granite bedrock, seal it with conveyor-belt
piston rings then move it up and down with water
in response to supply-demand. It's likely to work in the
rather inevitable way that hydraulics do. In fact, Detroit
should immediately commission a V8.
An advantage of the system derrives from the density of
rock, about 3 fold that of water which translates directly
to energy storage capacity. Another thing that has a lot
mass, is a nuclear power station. Such stations need
lots of supply-demand balancing and during construction,
lots of expensive groundwork. So why not just pop the
power station right into that piston.
The station should be built into a network of hollows and
galleries within the piston, ensuring a ~10m thick
peripheral wall. Granite makes excellent radiation
shielding is twice as strong and has a track record longer
than reinforced concrete. Even better is the way the
incentives are aligned, want a thicker concrete wall?
will cost more and take longer. Thicker granite? less
drilling, faster and cheaper. That drilling is much
than 10 years ago because of the 10 fold fall in
manufactured diamond, the by-product is valuable
In operation, the system can perform as a series or
hybrid. In series, the turbines can be used to
pump water that pushes the piston up while the
generation is performed only by pressurized water. In
parallel, the nuclear station would generate constant
electricity in a conventional manner, while separate
pumps/generators responded to supply-demand
Should one of many potential disasters strike, the system
provides excellent safety opportunities. Flood? Raise the
piston 10m above ground level to keep flood waters out.
Earthquake? Build an air chamber into the water network
and operate the piston as a tuned mass damper, 10
tonnes should work well. Meltdown? pffft. At Chernobyl
corium melted its way through a few meters of concrete.
Here, it can do that, and it's still in a big granite cup.
Meanwhile the piston is allowed to sink to the bottom of
the stroke so that the reactor is now deep at the base of
bedrock shaft. Clean up could be as simple as back filling
with rubble and concrete and walking away. "Radiation
you say? that's granite for you, radon you know, want to
buy a ventilation fan for your cellar?
[bs0u0155, Dec 11 2018]
[bs0u0155, Dec 11 2018]
|Pah. Enough with these footling small-scale dabblings in
energy storage. Once the UK has been sufficiently fracked,
and all the useful stuff has been extracted, we just need to
pump high-pressure water down all the fracking holes,
lifting the country by fractions of a millimetre per GWh.
Energy can then be recovered by reversing the process when
|As a bonus, if the UK economy does really well, we can
bulk-buy energy from the French and store it by lifting the
UK several tens of metres. We will then be able to look
down on the French, rather than simply glaring at them
across the English (note) channel.
|I haven't done the exact calculations on this one, because
the village shop has run out of 0's due to pre-Brexit panic
buying. However, I've made an approximation using 9's, and
the whole scheme looks highly favourable.
|// This is great for ... Wales //
|And no, it's not, because the primitive, superstitious natives panic when they see water in a lake going up and down and immediately assume the End Times have arrived. Then they try to practise human sacrifice to placate their deities, and so they come swarming across the English border to kidnap humans.
|// we can bulk-buy energy from the French //
|The notion of paying them for anything, rather than just sending a few battalions of men-at-arms over to simply take it, is uncomfortably radical, and a surprise coming from you given your family's notably poor track record in settling debts of any sort.
|// the village shop has run out of 0's due to pre-Brexit panic buying. //
|<Stuffs several handfuls of 0's into a padded envelope/>
|// However, I've made an approximation using 9's, and the whole scheme looks highly favourable. //
|We agree. You'd get even higher energy density if you made the mass piston out of DU.
|//store it by lifting the UK several tens of metres//
|The crust-mantle seems to react a bit like a slow
waterbed, pile up a few miles of ice and northern Britain
starts to sink, while France rose. Logically, we could raise
Britain* by pushing France down? Brief research suggests
that France's high point is a frankly vulgar 4800m. A
reasonable average of this and sea level suggests that
France sits at 2400m elevation, which must be
challenging. By depressing France by 2300m it would sit
at a very agreeable 100m above mean sea level on
average**. That should have near-universal benefits for
| *and the Dutch, who frankly need it more.
**there may be SOME flooding, it's back of the envelope
|//higher energy density if you made the mass piston out of
|Bits of it are. 100% DU gets prohibitively expensive,
something like a hundred billion dollars.
|// we could raise Britain* by pushing France down? //
|In that phrase, you've concisely summarized English foreign policy from 1135 AD to the present day.
|// France's high point is a frankly vulgar 4800m. //
|If you think that's vulgar, you should see some of the low points.
|// there may be SOME flooding, it's back of the envelope stuff. //
|Not good, if you get water on your envelope it will go all soggy and the ink may run.
|//By depressing France// I think their own government has
that in hand.
|I've had an idea for Heindl Energy on my list of ideas to post for about 3
years, so I guess I should post that soon.
|// Thicker granite? less drilling, faster and cheaper. //
|I don't see how. Thicker walls will mean a larger piston, having a greater
circumference that needs to be cut, right?
|// a tuned mass damper, 10 million tonnes should work well //
|Doesn't sound very tuned to me. More of an untuned mass damper, I'd say.
That's just fine if it has to deal with impulses only, which is pretty much
what earthquakes are. Skyscrapers use the tuned kind because they have
known resonant frequencies excited by the wind.
|//// Thicker granite? less drilling, faster and cheaper. //
| I don't see how. Thicker walls will mean a larger
|The whole setup starts out as 100% solid bedrock. You
then cut out a sold granite cylinder. I was quite impressed
with the method, you drill 2 boreholes, and put pullyes at
the bottom of them. Then, you run diamond studded
cutting cable to the bottom of the hole, around the
pulley and back up to the top... over the rock and do the
same with the next hole . Then you can saw 20m sections
down from the top. Anyhow, the point is, you create a 10
million tonne granite cylinder. To build a power station in
to crown of that, you have to REMOVE rock, the less you
remove the cheaper it is. Like milling, a reductive
technique. Concrete power stations are ADDITIVE, the
more walls/shielding you want the more you have to
|Oh, you mean you'd get thicker walls by cutting a smaller
pocket for the power plant in a granite cylinder of the same
size? I would think you can't just arbitrarily scale down a
power plant and maintain the same power output.
|That hydraulic lifting is an interesting idea, [MB]. Could
address global warming the same way as well.
|Re: thicker walls, etc...
To increase the wall thickness, you only increase the
circumference; a linear increase. But that gives you an
increased volume of granite in your walls (for the particle
absorbing); a cubic increase. So (due to economies of scale
or something) going bigger wins!
|But thickness, not volume, is what determines absorption.
And circumference and radius are linearly related. However,
we're not dealing with pure radius here, because some of
that radius (at the center) is taken up by the power plant.
Therefore, wall thickness is radius minus some constant.
Therefore, you do indeed get thicker walls for less cutting
the bigger you make it, but it's still a linear function, just
one that's offset from zero.
|How big do you have to go until the globularity of the Earth becomes an issue?
|You'll hit limits caused by fractures in the rock long before that becomes a problem. "Solid" rock is, in reality, full of cracks. Take a look at any quarry workface.
|The answer is probably to dig a huge cylindrical pit into thick limestone beds, then convert the extracted material to cement. Line the cylinder with concrete, and make a rubble-filled concrete piston that's a near-interference fit. The power plant can be integrated into the piston at build time. All you then need is a sutable quantity of lard to lubricate the conformal seal at the piston-cylinder interface, a bit like a giant gasometer.
|Although making all that concrete is going to need rather a lot of energy ...
|A side benefit is that the structure of the piston would be a great place for a nuclear waste repository.