Volcanic power?

[ScienceNostalgia101]

 

Please pardon the crude illustration, this is merely meant to make it clearer where I'm going with this.

 

I'm picturing a power source; I'm not sure whether it's already covered under the "geothermal" umbrella or not; that uses the heat of volcanoes to turn turbines through steam.

 

The idea is that water would be pumped into an active volcano, and a tube would be placed at or near the top to contain the resulting volcanic gases (or at least most of them) and use the force applied by their escaping; or at least from the steam escaping; to turn turbines.

 

This leaves me with a few questions.

 

1. Would this be a "renewable" resource, wherein heat from the mantle will continuously re-melt the magma frozen by the water, or would too thick a layer of frozen rock eventually block the heat permanently?

 

2. Either way, would the amount of power required to pump water to the summit of a volcano be greater than or less than the amount of power generated by the escaping gases?

 

3. If seawater and/or sewer water were used, would the effects thereof on the chemical composition of said magma be carried by the mantle toward other volcanoes?

[mistermack]

I've often wondered why more use isn't made of volcanoes, but it's probably the unpredictability that puts off investment. The course of flows can change without warning, making it dangerous and financially risky.

I don't think you'd have to pump water to the top, you could drill into the side till you struck a significant heat source. 

Iceland might be a good place to research, they have more geothermal per person than anywhere else, by a big margin.

[ScienceNostalgia101]

Wouldn't drilling into the side cause the pressure from all the lava at and above that point to force it out of the hole? I get that it's more viscous than water, but still, that's an enormous pressure gradient at the hole.

 

I'm not sure what you'd need to predict... that the volcano won't erupt before installation is complete? If so, why not install the setup remotely?

Edited November 6, 2018 by ScienceNostalgia101

[mistermack]

Presumably you would monitor the temperature of the rock you are drilling, and stop when it got hot enough for your purposes, so you wouldn't be reaching liquid lava. Once you start injecting water, you would be tending to solidify the nearest lava, so it wouldn't be inherently dangerous. ( I think  )

[CaptainPanic]

To create power with steam, you do not need temperatures associated with molten rock. A much lower temperature (i.e. a few hundred degrees Celsius) is also still acceptable.

Volcanic power is used at quite a large scale. Iceland has a LOT of these power stations. However, it is much better to drill a hole a few kilometer away from the volcano than to use the slope of the active volcano itself. The temperature is still sufficient, but the rocks are more stable.

 

[pavelcherepan]

On 10/25/2018 at 8:13 AM, ScienceNostalgia101 said:

1. Would this be a "renewable" resource, wherein heat from the mantle will continuously re-melt the magma frozen by the water, or would too thick a layer of frozen rock eventually block the heat permanently?

 

2. Either way, would the amount of power required to pump water to the summit of a volcano be greater than or less than the amount of power generated by the escaping gases?

 

3. If seawater and/or sewer water were used, would the effects thereof on the chemical composition of said magma be carried by the mantle toward other volcanoes?

Well, you wouldn't normally need to pump water all the way to the summit of the volcano. For vast majority of the time most volcanoes are not erupting and at those times magma is located deep underground in deep magma chambers. This would lead to temperature steadily increasing as you approach the chamber, and it doesn't specifically need to happen near volcano itself.

But then you have ground waters, that will get heated but, due to them being under a lot of pressure, will assume a superheated state, where the water itself might be well above boiling temperature, but pressure prevents it from actually boiling.

Now, if you drill two holes - one to penetrate the aquifer in a close vicinity to the heat source and the other - further away, you will have yourself a more or less renewable hydrothermal power plant. Steam will come out of the first hole, you will use this steam to rotate the steam turbine. Then later you pump all residual water into the second hole, which intersects the same aquifer, but at much lower temperatures.

So, your method, while possible, is not very sensible or economical.

And also the water will never be in direct interaction with magma, so it doesn't matter what composition of it you have, but if you use ground waters, it will obviously be quite salty.

[Nod2003]

If you dump water directly on the magma, you will get steam, but there is a good amount of sulphuric dioxide in a volcanic eruption, so I assume it is generally outgassing SO2 from exposed magma.  Anyways.  Mix that with water and you will get some sulphuric acid steam.  Highly corrosive to your turbine.

[John Cuthber]

Reaction of sulphur dioxide with water does not make sulphuric acid, it makes sulphurous acid which is less corrosive.

But there would certainly be corrosion  problems from that and other gases- such as HCl.

On the other hand, with care you could collect these materials for use- sulphuric acid can be made by oxidation of sulphurous acid and it is a sellable product.

It would also reduce the local effects of air pollution by the volcano.

However, I'm not sure it's practical.

I'd not really want to invest my money in a building on the side of a volcano.

[Nod2003]

Sorry you are right, I misremembered which acid that made.