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Gravitricity

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Re: Gravitricity

#211

Post by brute »

joshvm wrote: post #196
brute wrote: post #175

Earlier quoted context omitted.

You just need more mass. Have a look at this concept: http://eduard-heindl.de/energy-storage/index-e.html (unfortunately the english version is very sparse, the german version has some more images and videos: http://eduard-heindl.de/energy-storage/ ) The idea is to cut a 1km diameter cylinder into the ground (solid rock), and then lift it up up to 500m by pumping water underneath it. The power stored can power a coun…

But presumably you'd need more than a day's worth of power to lift the damn thing? That's probably doable, but still, I suspect that'd be the main problem.

The efficency is said the be 80%, just like any other pumped storage system. It just uses considerably less space than a water reservoir (actually close to none, as the top of the cylinder remains untouched) and is scalable by adjusting the radius.

I guess the main problem is to keep the water confined (200bar of pressure) while keeping the mass movable. Maybe someday they build a small testing facility, so we know for sure.

Re: Gravitricity

#212

Post by jmadsen »

bduerst wrote: post #207
logicallee wrote: post #179

Earlier quoted context omitted.

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 install…

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 aut…

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.

Re: Gravitricity

#213

Post by CamperBob2 »

HarryHirsch wrote: post #151
cdoxsey wrote: post #144

Earlier quoted context omitted.

Except all those dire predictions turned out be wrong. We didn't run out of food or resources, and birth rates have now declined in almost every country in the world. Population growth is basically now a complete non-issue. In retrospect, ignoring the Paul Ehrlichs of the world turned out to be the right move - a far cry from mankind's greatest shortcoming. If we run out of lithium we'll figure something else out, ju…

Except that then we have run out of available lithium, which means that solutions that require lithium will be inaccessible. Running out of chemical elements is a problem. The helium shortage is a serious problem. High-energy physics is made from helium.

We will never "run out" of anything, including oil or lithium. We'll stop wasting these resources the minute their prices rise to a level where something else becomes more economical. Regardless of when that happens, there will be plenty of lithium left for any potential fusion sources that might be developed later.

Re: Gravitricity

#214

Post by 001sky »

benbojangles wrote: post #192
001sky wrote: post #123

Earlier quoted context omitted.

The responses in that Dropbox thread were pretty solid though. To all the naysayers, I mean. It's sort of a ritual format to test any new idea with the back and forth. That in and of itself isn't a problem. Real problems: Dismissive people who don't/can't/wont listen to good responses. Good founders/ideas but just really bad at communicating. Those are basically the type i and type ii errors of this format.[1] _____…

Why does it look like a Fracking drill? It looks like a Trojan horse.

YC still uses that Dropbox application as a case study. Not sure if they also reccomend their show HN, tho.

Re: Gravitricity

#215

Post by kwhitefoot »

waps wrote: post #171
msandford wrote: post #65

Earlier quoted context omitted.

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 li…

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 agricu…

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

Re: Gravitricity

#217

Post by deerpig »

msandford wrote: post #65
andrewliebchen wrote: post #58

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."

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 li…

There are a many places in the world where this approach would work and where regulation is not so onerous. Not everyone lives in the United States. And, as your comment seems to indicate, that is a good thing :)

Re: Gravitricity

#218

Post by tripzilch »

kwhitefoot wrote: post #215
waps wrote: post #171

Earlier quoted context omitted.

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 agricu…

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, cooki…

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).

Re: Gravitricity

#219

Post by tripzilch »

CamperBob2 wrote: post #108
Coincoin wrote: post #59

Earlier quoted context omitted.

"The greatest shortcoming of the human race is our inability to understand the exponential function."

"Everybody who has ever claimed that something is doomed because of an exponential function was wrong."

"... or dead."

Re: Gravitricity

#220

Post by kwhitefoot »

tripzilch wrote: post #218
kwhitefoot wrote: post #215

Earlier quoted context omitted.

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, cooki…

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…

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.

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