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Author Topic: Gravity Energy Storage - The New Stone Age  (Read 451 times)

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Re: Gravity Energy Storage - The New Stone Age
« on: May 23, 2018, 11:18:06 pm »
I'll take that as an attempt at peace-making and reciprocate.

When I bounce your own words (selected sentences) back at you, and in response you call me "full of s h i t" and other insults, I don't respond happily either and I don't think any other Diner would.  People that only know me through my writings (often in local newspapers) and then meet me face to face often comment that I am much nicer in person.  I take that as a compliment of my writing style, which is supposed to be in hard-edged newspaper style.

I have also been told I have a professorial style, giving little lectures to people on scientific subjects.  This is because I find the audience generally has a very poor grasp of scientific subjects and/or a very sloppy way of putting things when they need to be accurate.

For example, RE's energy storage system, as gravitational potential energy, is neatly expressed as:
E = m.g.h
where m is mass, h is height and g is the gravitational constant.
The units have to be converted to a consistent system, here the Metre-Kilogram-Second system giving an answer in Joules.

So lifting a tonne up a metre against earth's gravity, takes
Energy = (1,000 × 0.981 × 1) = 981 joules  = 981 watts for 1 second
  = 0.272 watts for 1 hour

which is not much, and explains why you need to do it on an unfeasibly BIG scale to store a useful amount of energy.


Three approaches come to mind at small scale.
1) Pumped micro hydro storage
2) Drag/roll trailer up/down a hill
3)Raised mass using a structure.

Most important point to understand is gravitational energy density is extremely low, 1 ton raised 100 ft only stores .076 kwhr.  A little over 25 ton raised 100 ft stores 1kwhr.  Building towers option 3 is expensive, building short towers less so.  Still at 10 ft of elevation difference you'd need to be moving 250 tons to get 1kwhr of storage.  Perhaps cement piers raising stone?  I think though it seems infeasible.  Moving up the list to #2 we could drag trailers up a hill and roll them down.  You'd need heavy hoist motor and cable at those mass amounts.  Thinking the winch is $1000 the cable $500 the trailer $1000 the controller and tie in $??  Maybe it could be done for <$3000   Option 1 is probably the most reasonable.  Each 225 gallons of water would store a kwhr over 100' of elevation.  The pumps and generator could be had for <$1000 the piping <$1000 and maybe a total system of <$3000.

However as cools as something like this is, its probably worth comparing to battery tech at this point.  That same 1 kwr storage can be had for like $400/kwhr and a tiny fraction of the space.

Well, for the Test Protoype it really doesn't matter how much energy it will store and you can get back, it will scale up.

The next question is how much storage does the individual Prepper need here?  How many KwHours is really necessary in a typical situation using all low energy consuming electrical devices?

Based on your early numbers, I would go with a 25' Hole in the Ground (you and LD can have a months long Digging Competitiion) and a 25' Tower above that.  What would the weight be?  I would try a 20 long ConEx filled with Concrete as a starter.  This will weigh well over 40 Tons.  How many KwHrs do you get out of 40 Tons raised 50'?

You will of course need more than steel pipe for this tower.  It might be built from reeinforced concrete, or you could use steel I-Beams.  You'll need a heck of a winch to yank this load up, no matter how you gear it.  You'll also probably want to get your gearing off a wrecked big rig, that will keep those costs down.  Cable will be a significant cost as well, that will need to be some prety thick and heavy stuff too.

In terms of cost efficiency, right now the chemical storage system is cheaper, but you depend on many things to keep that system running in the post collapse world.  This system has more resilience.  So it's a trade off.  I'd estimate WAG $20K to have a system good enough to run a house at typcal energy usage in a farm community.


Okay Roamer, I'll check the link out. Thanks for the positive reply, RE.

As to Palloy and his claim that gravity systems for energy storage need to be "unfeasbly" huge, he, as usual, is stating a half truth.

For example, it is it is possible to operate ALL the lights in a house throughout the night with a gravity generator system. The problem with our modern thinking is that we want some system to DO IT ALL. That is totally unnecessary, but it helps the Palloys of this world claim that this or that "will never work".

Roamer, I'm glad you are here. since you are a mechanical engineer, I wish you would find the time to put Palloy in his proper place. The guy is an expert in sophistry and is fond of poo pooing absolutely anything that departs from the unsustainable energy status quo. He may believe he is "professorial", but he is actually routinely offensively pedantic. I got sick of arguing with him and just don't bother any more.

At any rate Roamer, thanks for your input. I hope all is well with you.
Light is sown for the righteous, and gladness for the upright in heart. Ps. 97:11


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