[tooldtocare]

Attached is a conceptual drawing of a potential geothermal energy gathering machine. Do you think it could work-?[img][img]http://www.imageurlhost.com/images/e8u8ri3so2cdm5pdrch_SEAFLUM_thumb.jpg[/img][/img]

[RapaNui]

Molten lava?
Hee hee.

[JustaGirl]

Yes. We're saved. That was close!

[Tanada]

Attached is a conceptual drawing of a potential geothermal energy gathering machine. Do you think it could work-?

Sorry to dissipoint you but no, I don't think it would work. If you really wanted to try something of this sort it would be a lot more practical to drill a well into one of those thousands of 'hot black smokers' on the sea floor where superheated mineral rich water wells up naturally. You could then run the superheated water through a turbine at depth and just collect the electricity via cable to the shore.

Probably need a really robust design and teflon surfaces because the mineral deposits would gum up the works fairly quickly unless you prevent them from sticking.

[fiedag]

Attached is a conceptual drawing of a potential geothermal energy gathering machine. Do you think it could work-?[img][img]http://www.imageurlhost.com/images/e8u8ri3so2cdm5pdrch_SEAFLUM_thumb.jpg[/img][/img]

You should look at Geodynamics who are doing some really great work (disclosure: I am a shareholder) on geothermal energy. If you look at their reports closely there is quite a bit of technical detail on what they're doing.

As far as getting to molten lava, there are probably not that many places on the globe where the earth's crust is sufficiently thin.

Drilling to 5km poses some intricate technical challenges. There are a lot of granite-based heat resources around at 4-6km depth, whereas I believe lava sits much deeper in most cases.

[zeke]

I'm not crazy about "tapping into" a source of energy which results from the shifting of tectonic plates or the building/releasing of pressure by processes which are, for the most part, in equilibrium.

I like my terra firma to remain both firma AND terra; not flowy and lava-ish or with great big cracks opening up large enough to swallow chicago or san fran.

you know how humans are with resources: if 1 is good, then 10000 trillion must be heaven.

[tooldtocare]

what will replace oil-?
My only concern here is for my children’s future. If solar panels and wind-powered systems can take the load needed to run our industrial complex then I’m one happy camper. But being a pessimist I have my doubts. If we become complacent and rely on a technology that can not meet our future needs then we have gone down the wrong path. I think solar and wind have their place in the energy grid but my bet is they can never meet the energy demands we now take for granted. Having said that I must ask is there an alternative-?

I say there is and it is geothermal. When I research geothermal heat mining I find experts saying that this approach is unworkable because magma is just too hot to handle. This may have been true in the past but now I think we need to rethink this energy resource in a big way. In 2005, total worldwide energy consumption was 500 EJ (= 5 x 1020 J) (or 138,900 TWh) with 86.5% derived from the combustion of fossil fuels

http://en.wikipedia.org/wiki/World_ener ... onsumption


Fossil fuels are finite and when this runs out I seriously doubt that wind and solar will replace it.

[dorlomin]

Takes an increadible amount of energy to drill deep enough into the continental crust to get up to the kinds of temperatures where the water will become steam. For one thing the deeper you drill, the higher that temperature becomes (pressure you see). The energy content of the amount of steam you would be getting back to the surface would be a pittance compared to the energy content of something like an oil well.

You are going to have to decide if you would rather keep the water liquid all the way down and all the way back up, only release the energy it had gained from contact with a hot surface (the pipes, being heated by the rock) when it was released into a low pressure enviroment (i.e. a turbine) or drill deep enough that the water is a gas as it comes back to the surface, in which case you need to work out how you are going to keep it a liquid on the way down.

You will need to get a more accurate idea of the amount of water that you will be returning to the surface to get an estimate of the amount of thermal energy you will be generating for a given time (i.e. per hour). You will get the energy content from the depth you intend to drill, the thermal gradient of the rock you are drilling through and the amount of time the water will be in contact with rock.

The thermal gradiant of the rock on the big continental cratons will be reasonably low and the cost of drilling even modest bore diameter pipes will be very very high. Take the estimated energy you will harvest per hour then compare that to the cost of drilling a oil or gas pipe the same depth. This way you can come up with a very very basic idea of the economics of how much it will cost in initial capital expenditure to extract x amount of energy using your method.

You may also need to do some reading up on steam turbines as they generally really need superheated dry steam to work at maximum efficiency.

[tooldtocare]

dorlomin wrote: “The thermal gradiant of the rock on the big continental cratons will be reasonably low and the cost of drilling even modest bore diameter pipes will be very very high.”

You are assuming that the drilling would be on dry land hundreds if not thousands of feet above sea level. That is not the place that I have in mind. The bottom of the ocean is several miles below sea level reducing the distance to the magma by a long shot. And you also need to consider where the tectonic plats are separating. At these points molten rock is oozing up to the surface. At these points little if any drilling would be required.

Please take a look at the drawing that I have provided, see post #2. If you have a tube extending from the ocean surface to the bottom and you pump water out of the top gravity will force water in the bottom to replace the water pumped out. This will cause the water column to rise refilling the tube. When the super hot seawater rises to the surface it will start to boil. This is where you get the energy extraction. Look at it like a huge coffee pot percolator.

ps thanks for your comments

Thomas

[Ludi]

That is not the place that I have in mind. The bottom of the ocean is several miles below sea level reducing the distance to the magma by a long shot.

And it's so easy and inexpensive to operate at those depths.

[dorlomin]

Maga freezes to solid rock almost as soon as it reaches the surface. You are going to have to come up with something a tad more substantial than a picture of some kind of hoover or pipe over a bit of magma. If you are going to reach temperatures of 100C minimum, you are going to have to come up with a means of penetrating the crust, no matter how thin. Then you are going to have to explain how this drilling will survive the regular tectonic activity at these points. Additionaly you are going to have to flesh out the behaviour of steam at whatever temperture you intend to achive in a pipe in the order of 8km verticle. You will be loosing huge amounts of energy to friction and heat loss to the sea.

[JJ]

[quote="tooldtocare"]what will replace oil-?"

isn't that the problem? Trying to *replace* oil so we can continue to live the way we do now?

[vaseline2008]

Here is the Wikipedia site for Geothermal Power.

[tooldtocare]

Ludi wrote: “And it's so easy and inexpensive to operate at those depths.”

Actually it is.

First, buoyancy due to the water density makes it easy to move very heavy things around.

Second, robotics would do all the work operated by remote control on land. How easy can it be if you are on the 12th floor of a building in Houston, Texas operating a machine that is thousands of miles away.

A push of the button can go a long way.

[tooldtocare]

vaseline2008, thanks for the link which states:

The key characteristic of an EGS (also called a Hot Dry Rock system), is that it reaches at least 10 km down into hard rock. At a typical site two holes would be bored and the deep rock between them fractured. Water would be pumped down one and steam would come up the other. [b]The MIT report estimated that there was enough energy in hard rocks 10 km below the United States to supply all the world's current needs for 30,000 years.[/b]

[tooldtocare]

dorlomin


“Maga freezes to solid rock almost as soon as it reaches the surface. you are going to have to come up with a means of penetrating the crust, no matter how thin.”

Magma cools and solidifies when the heat leaves the magma faster than it can be replenished. This problem does not exist if you have more heat being entering the system than is being extracted. Hot rock is a poor conductor of heat but molten rock is a good heat conductor. If the underlining magma pool is large enough you can extract large amounts of heat without solidifying the magma. And then there is another possibility; you cou8nd drive ceramic piles down into the molten rock. The ceramic piles would be the heat conductors protruding into the upper water column.

Then you are going to have to explain how this drilling will survive the regular tectonic activity at these points.

The machine doing the heat mining will be literally floating above the ocean sea floor unaffected by the shifting seabed.

“Additionaly you are going to have to flesh out the behaviour of steam at whatever temperture you intend to achive in a pipe in the order of 8km verticle.

Agreed

“You will be loosing huge amounts of energy to friction and heat loss to the sea.”

I disagree, I do not think there will be a large lose of heat as the water column rises to the surface. The exterior sides of the tube will be the only think in contact with the super hot seawater. The interior will only cool slightly. And the time it will take the super hot water to reach the top will be around 9-11 minutes, not enough time for the water column to cool very much.

dorlomin , thank you for you ideas and suggestions. At least you did not make a one liner post stating that is just can not work because it just can not work. If there is a will there is a way. We, the human race needs to be able to continue to grow economically into to foreseeable future and than means we need to stop depending on finite sources of energy. We need to do the R & D necessary to tap that limitless source of energy and that energy source is Geothermal.

[Sixstrings]

I think the bottom line is that *nothing* will replace oil. There simply is no alternative energy that would allow us to continue to live as we do today, and expect continued exponential growth.

Heck, we don't even have a replacement for easy to extract oil (the tar sands, ocean drilling, lower crude grades all have poorer EROEI), much less oil altogether..

[tooldtocare]

pstarr said: “In short, what you have proposed is dweebie sci-fi nonsense.”

Some people are just 100% pessimists and nothing will convience them that the earth is not flat.

There is enough geothermal energy to supply the world’s population growth for thousands of years and then some.