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Lava Power

Lava to thermal energy in situ
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Having an active volcano can be hazardous, but it can also be lucritive, if you handle the lava just right. For this idea, only cinder-cone volcanoes need apply. This idea relies on the viscous "pahoehoe" lava to work. My idea calls for a converted barge/freighter to be used in energy production. A duct that extends from the front would allow lava to flow directly into the ship (it would otherwise flow into the ocean). Once in the ship, the lava is directed into vats, about 1 feet deep. The vats are then sealed and doused with water, allowing for a flash of steam to be created which runs a set of turbines, generating electricity. Because this is a mobile power facility, it could use the electricity to create hydrogen/oxygen, which is later burned or converted through fuel cells into electricity. Once each vat is cool enough, it is a solid block of cooled lava rock. The vats are shaped to conveniently eject each cooled block either into the ocean, or onto another barge to be used for things such as water breaks, coral restoration, construction, etc. Land based power facilities have the drawback of zoning regulations. Usually, volcanoes are converted into nature preserves, or are otherwise federally protected, providing enough hassle in any process to try and allow for geothermal drilling. Geothermal drilling is also tied to earthquakes (I don't know how). With this barge, the power production capability can go to wherever the heat is, and have an automatic supply of water to boil for the turbines. As well as for power production, this could be use to provide tourists a close-up yet safe view of a lava flow. The lava is going to flow into the ocean anyway, creating large plumes of steam and adding to the island's land, why not take advantage of this wasted heat? Nothing survives around the area, so there are little evironmental issues.
twitch, Sep 20 2010

Geothermal Energy http://www.renewabl...tion-for-the-future
[Jinbish, Sep 21 2010]

[link]






       What is the amount of thermal energy available from, say, 1000 tons of lava? Basic numbers?
MaxwellBuchanan, Sep 21 2010
  

       Pahoehoe runs in the range of 1100-1200 C and room temperature Basalt has a specific heat of .2 kcal/kg C (can't find any numbers for the molten state). Assuming the stuff cools to 800 C before it reaches processing, that still give you 700 C of steam production (assuming you use the cooled stuff to pre-heat your water close to boiling). So 1 tonne of Lava is 140000 kcal or 585 MJ.   

       Please note some massive simplifying assumptions, limited available data, and your steam turbine is going to be significantly inefficient, but the numbers appear to be in the useful energy production range. Especially if the end result is cooled basalt blocks in useful sizes.
MechE, Sep 21 2010
  

       This would require a remarkably robust boat.   

       Why not simply drill a few wells near the lava flow and pump water continuously through the well network to produce a constant flow of steam without having to handle and tranship 1000 tons of basalt between steam cycles?
infidel, Sep 21 2010
  

       They need to be thin slabs, almost sheets, otherwise as they cool and crust over they will self-insulate.
8th of 7, Sep 21 2010
  

       I was picturing brick sized blocks, or you could preform something like cinder blocks with multiple thins sections.
MechE, Sep 21 2010
  

       Bricks would be good but don't use them for fireplaces. Basalt explodes when heated in a fire. The air bubbles in it make things very interesting when they expand rapidly.
infidel, Sep 21 2010
  

       //So 1 tonne of Lava is 140000 kcal or 585 MJ// //the numbers appear to be in the useful energy production range. //   

       In other words, 1 tonne of lava would provide the energy output of a smallish power station (500MW) for about 1 second.   

       Or, to put it another way, processing 1 tonne of lava would give you as much energy as burning 10 litres of petrol.   

       In what way, then, is this " in the useful energy production range"??
MaxwellBuchanan, Sep 21 2010
  

       As [Jinbish] linked and I suggested; Geothermal power is far more sensible. It doesn't however, produce a steady supply of stone bricks.   

       However, nor does it require massive amounts of energy to cart those bricks off to other places. You'd soon be sitting on a gigantic pile of bricks and blocks if you implemented this idea.
infidel, Sep 21 2010
  

       Because you're only processing 60 times as much lava as you would for the same energy from coal, which isn't excessive for a clean power plant. Especially if you locate it where there is a steady supply of lava.
MechE, Sep 21 2010
  

       Infidel I belive there are only a few plants in the US turning out cinderblocks already. The shipping is already happening, this just does it from a point that produces energy, instead of using it.
MechE, Sep 21 2010
  

       //Because you're only processing 60 times as much lava as you would for the same energy from coal, which isn't excessive for a clean power plant.//   

       It isn't? Then clean energy is surely doomed. I would have thought that this was a completely hopeless rate of return.   

       Also, would you be prepared to process 60 tons of coal to get the energy equivalent of one ton of coal, if that coal happened to be at 1000°C and located underwater at randomly changing locations?   

       If you're prepared to accept such low energy returns, then just start mining some of the less economical coal reserves, and then devote maybe half the energy produced toward active sequestration of CO2. Better all round.
MaxwellBuchanan, Sep 21 2010
  

       I'm picturing somewhere like Hawaii where there is a fairly steady supply of the stuff. And a 60 to 1 ratio isn't bad if you realize the fuel is free. You pay somewhat more in processing for a zero cost fuel.   

       Also the percentage of energy recovered would probably be higher, there's less energy input on the production side, and there's less energy and mess on the output side (especially if the output is usable directly as building materials). Thus resulting in a much higher actual energy return than the same volume of coal
MechE, Sep 21 2010
  

       //Thus resulting in a much higher actual energy return than the same volume of coal//   

       Qualitatively, I can't argue with you and you may be right. However, the statement above needs a bit of thought or, failing that, calculation.
MaxwellBuchanan, Sep 21 2010
  

       Sorry, I mis-stated, should have been a much higher energy return than the equivalent (meaning 60 to 1) volume of coal, not the same volume. I don't know how it balances out, you'll probably have to handle a bit more lava than coal, just not in the 60:1 range.
MechE, Sep 21 2010
  

       Fair enough.   

       I dunno. I may be having a bleak day, but most renewables just depress me. Fundamentally, we want and crave high power at high density, and have excellent ways of generating it cheaply.   

       For a lot of alternative energies, I just think they fuck up the landscape and eat raw materials, and that it would be more effective (financially and environmentally) to just remediate the adverse effects of conventional power generation.   

       But whichever.
MaxwellBuchanan, Sep 21 2010
  

       Or, to restate and summarize the world energy situation:   

       There are alternative energy sources. Unfortunately, they all, so far, fuck up the landscape and/or use large quantities of raw materials. It is currently more effective (economically and environmentally) to use conventional power and remediate their adverse effects.   

       Bleak, but concise and accurate.
Boomershine, Sep 21 2010
  

       Hang on.   

       Bleak I can admit to.   

       But no bugger calls me "concise" or "accurate" and walks away.
MaxwellBuchanan, Sep 21 2010
  

       First choice is to figure out more efficient ways to do something. Eventual universal conversion to LEDs will probably save more in the same time period than all the alternative energy sources combined.   

       Next, implement alternative/renewable where economically and environmentally feasible. Desert solar, urban wind (doesn't clutter up the scenery, minimal transport losses), etc. This may be one of the above.   

       Then maintain traditional fuel sources where necessary including much more nuclear (of the low, short half-life waste variety) and clean up after it. Of course once you figuring clean-up cost and the increasing cost of extraction, the EROEI starts to favor renewable sources more and more over and time.
MechE, Sep 21 2010
  

       //But no bugger calls me "concise" or "accurate" and walks away.//   

       Sorry.   

       Bleak and a bit touchy.
Boomershine, Sep 22 2010
  

       This is on a barge because the lava fields are always growing and moving. Plus, cooling the lava on its way to the ocean would cause a clog in the lava tube, altering its flow. This geothermal energy! It's just that we don't go down to get the energy, it comes up to us!
twitch, Sep 22 2010
  

       This is a brilliant idea. You could keep the rock nice and hot and runny by aiming a huge mirror at it and reflecting sun and moon light at it. That way the rock can be used again and again.
saedi, Sep 22 2010
  

       Don't be silly! Everyone knows that moonlight is cold. That's why it's warm during the day and cold at night.
infidel, Sep 22 2010
  

       saedi, that kind of goes against the whole geothermal concept here. You're proposing some kind of huge thermal battery, I think.
twitch, Sep 22 2010
  

       I was revisiting this because I just read an article that referred to lava hitting ocean. The temperature it mentioned is about right, but it doesn't lose as much heat in transit as I allowed.   

       I realized, however, I forgot to allow for heat of fusion. Again, hard to find exact numbers, but it appears to be another ~130 kcal/kg. If that's the case, then you can roughly double the energy output, or halve the ratio to coal.
MechE, Jun 15 2013
  
      
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