Geothermal engine

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Geothermal engine

Postby ting_says » Mon Sep 29, 2003 4:12 pm

There is a reasonable amount of talk about turbines run off of
geothermal energy. Would using a Stirling type engine be more
efficient? I know it is really of vague. Can someone expand more and
explain to me how geothermal turbines work, or is it just the
expanding hot air from vents in the crust powering a fan. I ask this
because of the thermal vents on the deep ocean floor, because the
heat difference between the ocean water at that depth and the
gas/water from the vent would be pretty large wouldn't it? The
question of getting the energy obtained from the engine would be
really difficult, but considering the amount of work put into an
offshore oil rig this wouldn't be too much of an undertaking.
Stripping the rig and modifying it house engines run off the
geothermal energy would be cool. Maybe some oil company with
futuristic goals would be able to do this and....but probably not,
sorry I'm new at this stuff.
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Response to Geothermal engine

Postby yonseiaspiration » Tue Sep 28, 2004 9:26 pm

Hi Jon Ting,

It makes sense to me too. The idea of a closed cycle engine with no emissions, no fuel inputs and no need to even be on the surface seems like an idea worth pursuing.

Ian Gordon
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Response to Geothermal engine

Postby bptdude___2569 » Sat Jan 13, 2007 3:49 am

In the time of Thomas Edison, somebody once looked at Niagra Falls and smacked thier head going "holy lightbuld, batman, do you know how much juice that thing could make?".

I'm dumbstruck why nobody can watch the river of steady flow hot lava from the big island in Hawaii flow into the cold ocean, and not think the same thing.

The state could be exporting hydrogen fuel like the arabs export oil.

Either Stirling engines are not what people claim they are or the world can't tell the empereor has not clothes.

Am I missing something?
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Response to Geothermal engine

Postby parkerpokorski » Thu Sep 27, 2007 7:18 pm

Here's an interesting variation from the, 'hot magma flow' version of geothermal energy.
Why couldn't we develop a Stirling Engine to generate electricity from the 'heat & cold sinks' (sorry if my technical ignorance shows here) found on a closed-loop geothermal system for home/business heating & cooling?
Of course, this type of geothermal energy is at roughly 50 degrees Farenheit year-round, but the key is found with the compression/ evaporation unit that makes that 50 degree temperature either hotter (for heating) in the Winter or colder (for cooling) in the Summer. Obviously, depending on the type of delivery-system (e.g. forced-air, floor-radiation, etc.) in the home, the amount of compression/ evaporation would need to be adjusted to create adequate heat or cold delivery. In the same way, I believe a Stirling Generator could be used to reduce, eliminate, or surplus (sell back) such a geothermal system's (and other household watt) use of electricity from the local power grid.
I'm no dreamer!!! This is a PLAN! But, if I'm wrong and it can't be done, SHOW ME WHY!
Thanks, David J. Parker, parkerpokorski@hotmail.com
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Response to Geothermal engine

Postby senn36 » Sat Dec 06, 2008 3:42 pm

I have just been to the big island presently they are building a solar concentration system andanother using the top and deep wather temperature differential to produce electricity.
It is amasing they are not using geothermal, after some discussion they dont seem to be concient of the Stirling possibility and all that sugar cane scrap that is simply burned, a lot can be done
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Response to Geothermal engine

Postby bptdude___2569 » Sat Dec 06, 2008 10:45 pm


On the big island, they actually do have steam based heat recovery generating electricity, but it is only a moderate scale pilot program.

Someday, somebody who is prone to be rich anyways, will be a new billionare but selling to the public something like "science experts have discovered ways to extract energy from heat". It sounds stupid to us, but this is the kind of thing it will take.
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Response to Geothermal engine

Postby ting_says » Sun Dec 07, 2008 1:01 am

Well I'm back with about 5 years of additional education under my belt and I can now say with confidence that this should potentially work. I've got bigger plans now, but this is a nice reminder of where I started on the entire alt energy thing.

The real trick is to get really rugged Stirling engines such that maintenance isn't too much of a problem. Running the power lines shouldn't be too expensive in the grand scheme of things. One could even run a multi-piston cycle where the expansion of one drives the compression of the other.

The biggest problem I foresee is the amount of torque a Stirling engine (in my experience anyway) is pretty low, though the RPM can be extremely high. Unless the piston is huge, like old Stirling steamboat big. I mean calculating the correct size of the engine for the job (and building a long lasting transmission if needed) would probably need quite a bit of data. Everything else should already exist, the generator and transformers and whatnot.

If I make my millions with the other thing I'm planning I'll get back to this, right now it seems a bit more risky (though surprisingly less dependent on people). There will always be a place in my heart for these little heat engines.

-Jon Ting
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Response to Geothermal engine

Postby bptdude___2569 » Sun Dec 07, 2008 1:14 am


Jon, you problem really is people. You do not need a Stirling design to start. There are several ways to extract heat into electricity. You would more easily get funding for a very modern large scale steam plant, than an iffy Stirling design.

You wondered about transmission lines.. Please take this advice. Turn the electricity from hot lava/cold ocean, and turn it into hydrogen. Ignore every idiot who tries to talk you out of it because they say it is not the most efficient { which it is not, true }.

Contact Shell Hydrogen for turnkey geothermal plant plans, as developed in Iceland.

Get the Hawaiians hooked on using hydrogen like propane, like a drug dealer giving free samples at first. In the words or Ronald Reagan, if you get the hogs to smell the slop, your problems of people in the way will just go away in a hurry.

The modern Stirling will be born a child of the public cry to turn heat into bottled hydrogen. You will be amazed how quickly bright minds will suddenly focus on cool new concepts to push this along.

- Joe
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Response to Geothermal engine

Postby benrk5 » Tue Jan 20, 2009 8:56 pm

Hi!

Just reading myself into the whole Stirling-Engine thing, I like the household geothermal idea, has anybody ever made the calculations, with around +20C inside the house & -10 to -40C outside in the wintertime, could one build an engine simply by placing one cylinder inside & the other outside, that works economically to provide the electrical power for a geothermal heat pump or would such a system waste more heat than it creates electricity to replenish the lost heat?

Greetz, Ben
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Response to Geothermal engine

Postby ting_says » Tue Jan 20, 2009 11:36 pm

Unfortunately I don't think that would work. Because all mechanical engines are inherently inefficient it would probably suck more heat out of the house than it would generate electricity; H lost > E gained. You could however run one in reverse and use it as a heater, though I don't think that's terribly practical either.

This is all because of the nature of the isothermic and adiabatic lines that represent compression and expansion are curved when it comes to the graph representing pressure to volume. As a matter of course you want those lines to be as perpendicular and straight as possible, however there's always going to be a loss (unless you have the cold plate at absolute zero, I'm pretty sure that would yield an engine approaching the limit of absolute efficiency even if the hot plate was only at 1 kelvin). So it's kind of a lost cause.

It would still be a fun experiment, though your heating bills might go up a bit.
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