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Gravitricity

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171–180 of 222 posts

Re: Gravitricity

#171

Post by waps »

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…

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).

Re: Gravitricity

#172

Post by tanzam75 »

tormeh wrote: post #47
KaiserPro wrote: post #7

Earlier quoted context omitted.

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

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.

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.

Re: Gravitricity

#174

Post by bduerst »

jmadsen wrote: post #142
bduerst wrote: post #139

Earlier quoted context omitted.

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

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.

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.

Re: Gravitricity

#175

Post by brute »

elektropionir wrote: post #10

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…

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 country for a day.

I am somewhat sceptical, but this guy is totally serious about it.

Re: Gravitricity

#176

Post by joering2 »

jakobegger wrote: post #150
joering2 wrote: post #140

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…

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.

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.

Re: Gravitricity

#178

Post by 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...

Re: Gravitricity

#179

Post by logicallee »

bduerst wrote: post #174
jmadsen wrote: post #142

Earlier quoted context omitted.

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.

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.

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...

Re: Gravitricity

#180

Post by p1mrx »

mtdewcmu wrote: post #164
p1mrx wrote: post #27

Earlier quoted context omitted.

Other materials, like lead and antimony? http://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%... Lithium: 33 Lead: 37 Antimony: 62

That table uses a mass-based unit, so wouldn't that tend to create the misleading impression that lighter elements are more scarce? Energy storage capacity depends on the number of atoms, not mass (as you can intuit by comparing lithium batteries to lead or nickel-cadmium batteries -- heavier doesn't mean more powerful).

Well, if Pb and Sb are more scarce than Li by mass, then they're even more scarce when you're counting atoms.

If Ambri's technology does pan out, it will be due to a cheaper manufacturing process, not because they're avoiding lithium.

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