Geothermal from mines?

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HavocXphere

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Rickster said:
Geothermal could run the whole country...just saying.
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Anyone know why this isn't a thing in SA?

A quick google suggests the issue is depth...4km - 6km is needed for SA. Yet TauTona mine is already 4km down. Surely that can be used as a starting point & then drill the remaining bit?
 
not hot enough down in the mine, we need to get closer to the magma [lava].
The zama lives down there with no problem.
 
Geothermal is a great idea, but super expensive. You can get more watts per Rand with amorphous Si PV panels and wind. If your energy farm is large enough, you can approximate base load.
 
Buy coal to increase fuel costs.


And eskom would milk more money from the customers if they use fossil fuels.
 
HavocXphere said:
At 50+ the only thing Zamas would be digging is their own grave.
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Even at 50+, you can't boil water to turn a turbine. You need to boil a fluid with a lower boiling point, which is inefficient.

Additional drilling, and ejection of water in the mines would be deeply dicouraged, since it would increase seismicity and put peoples' lives at risk.
 
The deep mines are positioned where they are because the area has a low geothermal gradient ( basically the relationship between temperature and depth). They are basically in the worst place possible for a geothermal power station.

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agentrfr said:
Geothermal is a great idea, but super expensive. You can get more watts per Rand with amorphous Si PV panels and wind. If your energy farm is large enough, you can approximate base load.
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Approximate base load? How large is large enough? I doubt it, peak hours is outside the time that the sun shines. Until energy storage is economically viable, solar will not be supplying base load. Solar/wind is great for renewable, crappy for transmission control and load management.

I did a couple of Geothermal plants and it is great for base load, technologies also does not have to be expensive if you know what you're doing.
 
$0.14 is R2, thats not that far off Medupi coal @ R1.8 odd /kw based off current costs (although excluding environmental ones).

Plus @ R2, you're not polluting the planet. We should be looking into this, in addition to the other cheaper renewable solutions.
 
4-6 km down? That's one helluva head of water. How much energy will it take to get the superheated water back to the surface to turn a turbine? I reckon it'll take more than you're gaining from geothermal.
 
TooFastTim said:
4-6 km down? That's one helluva head of water. How much energy will it take to get the superheated water back to the surface to turn a turbine? I reckon it'll take more than you're gaining from geothermal.
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I may have this wrong, but I think it goes something like this...
You have an 'in' hole feeds water in, and an 'out' hole which is where the steam/hot stuff comes out, as you feed in one side, it comes out the other. Think of it like a natural geyser, 'hot' expands, rises to top, increase pressure, boom, tourist attraction. Now, instead of waiting for enough water to filter in, heat up and increase pressure, we keep feeding the water in, increasing pressure, so the hot water and steam naturally comes out the other side feeding the turbine, basically, the 'out' powers itself
 
ellyally said:
so the hot water and steam naturally comes out the other side feeding the turbine, basically, the 'out' powers itself
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Yeah, but don't you want super heated water so that the water expands and turns into steam just before the turbine?

<not an expert here just trying to learn>
 
TooFastTim said:
Yeah, but don't you want super heated water so that the water expands and turns into steam just before the turbine?

<not an expert here just trying to learn>
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Also, haven't a clue:)
But my thinking is its a closed high pressure system, so all water is super heated and is 'released' into turbine system, that sudden pressure release turns it to steam. /shrug

Will read up later tonight on how they actually work
 
ellyally said:
Also, haven't a clue:)
But my thinking is its a closed high pressure system, so all water is super heated and is 'released' into turbine system, that sudden pressure release turns it to steam.
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Oh, that bit I'm pretty sure about. I'm not sure how much energy would be imparted to the superheated water vs how much would be needed to get that head of water back to the surface. I reckon it that it would take more to get it back to the surface.

The Kiwis use a lot of geothermal but that geothermal's quite close to the surface.
 
If the turbine is at the bottom of the hole, and the hole is set up properly perhaps gravity and condensation can be used to feed the water back into the system to be reheated to keep spinning a turbine.
4km's, pretty sure that vapour will be liquid long before it sees the surface.
 
AstroTurf said:
If the turbine is at the bottom of the hole, and the hole is set up properly perhaps gravity and condensation can be used to feed the water back into the system to be reheated to keep spinning a turbine.
4km's, pretty sure that vapour will be liquid long before it sees the surface.
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That's why it's better to pump hot water up to the surface and drop that pressure at the surface, a process which will turn it into steam, and use it to drive a turbine.
 
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