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Nuclear Generation Gravity Storage Hybrid

Match supply and demand with a big nuclear piston.
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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- valleys, and people who don't mind you flooding their valley. This is great for Canada, Wales, and Norway but badly suited to most places.

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 pressure 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 of mass, is a nuclear power station. Such stations need lots of supply-demand balancing and during construction, require lots of expensive groundwork. So why not just pop the nuclear 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? That will cost more and take longer. Thicker granite? less drilling, faster and cheaper. That drilling is much cheaper than 10 years ago because of the 10 fold fall in manufactured diamond, the by-product is valuable granite slabs.

In operation, the system can perform as a series or parallel hybrid. In series, the turbines can be used to mechanically pump water that pushes the piston up while the electrical 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 fluctuation.

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 million tonnes should work well. Meltdown? pffft. At Chernobyl the 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 a bedrock shaft. Clean up could be as simple as back filling it with rubble and concrete and walking away. "Radiation spikes you say? that's granite for you, radon you know, want to buy a ventilation fan for your cellar?

bs0u0155, Dec 11 2018

Pumped Storage https://www.hydro.o...ogy/pumped-storage/
[bs0u0155, Dec 11 2018]

Gravity Storage https://heindl-energy.com/
[bs0u0155, Dec 11 2018]

[link]






       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 needed.   

       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.
MaxwellBuchanan, Dec 11 2018
  

       // This is great for ... Wales //   

       Sp. "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 //   

       Sp. "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.
8th of 7, Dec 11 2018
  

       //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 surrounding countries.   

       *and the Dutch, who frankly need it more. **there may be SOME flooding, it's back of the envelope stuff.
bs0u0155, Dec 11 2018
  

       //higher energy density if you made the mass piston out of DU//   

       Bits of it are. 100% DU gets prohibitively expensive, something like a hundred billion dollars.
bs0u0155, Dec 11 2018
  

       99.9% is fine.   

       // 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.
8th of 7, Dec 11 2018
  

       //By depressing France// I think their own government has that in hand.
MaxwellBuchanan, Dec 11 2018
  

       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.
notexactly, Dec 12 2018
  

       //// Thicker granite? less drilling, faster and cheaper. //   

       I don't see how. Thicker walls will mean a larger piston,//   

       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 build.   

       I wish we had italic...
bs0u0155, Dec 12 2018
  

       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.
notexactly, Dec 12 2018
  

       That hydraulic lifting is an interesting idea, [MB]. Could address global warming the same way as well.
theircompetitor, Dec 12 2018
  

       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!
neutrinos_shadow, Dec 13 2018
  

       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.
notexactly, Dec 13 2018
  

       How big do you have to go until the globularity of the Earth becomes an issue?
pocmloc, Dec 13 2018
  

       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.
8th of 7, Dec 13 2018
  
      
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