Engineering is heading towards perpetual motion machines 2

[kacarrol]

It was zelgar and btrueblood who brought up the contamination issue, they just reminded me that I had read an article on contamination at a mine site near Marmora a long time ago.

I really do hope that the project gets the go ahead, Marmora and area could use the jobs. My pet peeve lies with journalists who are incapable of getting the facts straight. I also get a little annoyed with everyone labeling their projects as green, but that's a minor beef.

 

[ivymike]

soo... maybe I haven't read carefully enough, or thought enough about the comments above to understand what's meant by a negative efficiency...

 

[btrueblood]

"Agenda much?"

Sorry, Greg, but yes. Poorly planned use of crappy sites is what does in a lot of projects, usually way too late to do much about it. Too often, the current owner is just looking for any available dodge to get out from under EPA/Bureau of Mines or whatever your country's equivalent laws regarding mine reclamation are.

No huhu from me about pumped hydro storage, frankly it's the best megawatt storage idea I've seen with any merit and will, implemented properly, be an enabling technology for solar, wind and other renewable source energy production schemes.

 

[MintJulep]

Negative efficiency. It's a pretty simple concept really. I'm surprised it needs any explanation.

You see on the one hand you've got your energy in. And on the other hand you've got your energy out.

Then you see.....uhm....well the ratio or energy out to energy in.....errr.....

And of course there are losses inherent in the process that ..... ahhhh.....

And anyway, lot's of numbers less than 1 are negative. Yeah, that's it.

 

[GregLocock]

Btb, yes that's a reasonable comment, mine was aimed at the OP who seems to be looking for any stick with which to bash the project. When people pointed out that pumped water electricity storage is actually a good idea he then went off on another tack.

Cheers

Greg Locock


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[moltenmetal]

Dunno, I personally wouldn't be pumping vast quantities of water anywhere near a project with arsenic contamination. The water will go places it shouldn't- rain and snow will ensure that.

Properly designed and implemented, I have no problem with pumped water storage. The trouble with using an old mine site is that the temptation to do this wrong to save money and get a quicker payback will be great.

 

[zelgar]

I don't think the OP was trying to "bash the project", just correct the falicy in the article that this project would be generating more energy than it was consuming. I was the first to indicate that there may be potential issues of using a mine for water storage (e.g., potential contamination issues). I didn't have any "Agenda" other than to bring up a potential issue that should be considered in this design.

I think a lot of current environmental problems could have been prevented if someone had taken a little time to consider the environmental impacts during the design phase.

---

A thought just occurred to me. Could there be potential structural problems associated with filling the mine with water? Depending upon the characteristics of the geology and the structural support of the mine itself, could flooding of the mine result in problems?

 

[btrueblood]

molten,

Don't disagree with that, but if the pit is currently open, and the tailings uncapped, then a good thing can be accomplished. First adding sealing to the pit, and building a berm from tailing pile and capping it, could remediate the site and provide a pumped hydro storage project in a single go, which accomplishes two good things from what was a bad one.

 

[moltenmetal]

btrueblood: true enough- provided the project is designed AND implemented properly. The trouble is, the more money you spend on doing those good things, the longer the payback on the project will be. The temptation to cut corners will be very high indeed.

 

[cranky108]

Maybe I missed something, but are you proposing to seal the mine?
I believe an old mine will emit gas, which must be allowed to escape.

Filling an old mine with water will allow the gas to escape, but the water usually won't stay in the mine. It will seep to other places, unless there is a containment in the mine, which at the volumes of water you are talking about can be quite expencive.

 

[Yagonyonok]

Not to detract from the mine issues being discussed, but here is another seemingly perpetual motion idea.

http://www.engineeringmotion.com/videos/610/gravity-powered-aircraft-concept

I got a laugh out of the comment that because it has no fuel it will be less of a terrorist target.

Use of product voids warranty.

 

[kacarrol]

Ha ha! Thanks Yagonyonok I needed a laugh, that was fantastic.

 

[KENAT]

Ah yes, fuel less flight. They actually have some interesting points on buoyancy when you look into it, I just think they don't seem to properly take into account the energy used to alter the buoyancy.

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[rb1957]

of course there are gravity powered airplanes ... the space shuttle, gliders, B767s and A330s (on occassion), ... the energy tends to be pretty easy to spend, but expensive to buy, and problems sometimes arise when you run out of it ... you're either at your arrival gate or at the bottom of a smoking hole.

 

[btrueblood]

Cranky,

Yes, seal the mine, via a clay seal layer, concrete, geo-membrane, something impermeable to water so you don't get mine-contaminated water leaching to places you wouldn't want it. Also keeps the water where you do want, i.e. inside the reservoir. Your question makes it seem that you think this is a shaft mine, but it's an open pit according to the op. Quite a bit simpler to seal.

Old mines (and construction sites too) "generate gas" mostly due to oxidation of exposed rocks. Stop the oxygen, you stop (most) of the noxious gas formation. Some mines (esp. coal) also seep natural gas, but this happens most quickly when the mine is first dug, and decays over time. Some coal mine reclamation includes a gas vent system, but more commonly the gas is left to find its own way out. Once the coal is mined out, there really isn't much natural gas left anyway.

 

[cranky108]

Thanks for updating me. I have heard of salt mines that were sealed, exploding, then imploding (exploding as in seapage turning to gas exit). Open pit would be easer to seal, and a water feature would be much than building houses on it (like I have seen also). It would also keep rain water from collecting the minerals and washing them into the water table.

I actually thought mines produce gas because of gas movement in the rocks. But it makes since that the decay of coal, however I don't know where the hydrogen comes from.

 

[kacarrol]

Cranky108,

Just a guess, but it could be that hydrogen comes from iron and water becoming rust:

Fe2+ + 2 H2O ? Fe(OH)2 + 2 H+
Fe3+ + 3 H2O ? Fe(OH)3 + 3 H+

It comes to mind because I read a lessons learned on how a confined space may become oxygen depleted from the rapid formation of rust (slightly different reaction but a reminder of chemical processes).

 

[cranky108]

My question wasen't the chemical processes so much, but I was thinking coal mines as being dry, and therefore a lack of water to react. (under ground mines). This true of salt mines, as the salt would become moble if hydrated.