Question about using the sea or earth as a electricity producer

[radioactive8]

Hi!
I have been told that despite the different temperature between the surface and the Earth is different we can't use it to produce electricity by using the laws of thermodynamics .. shy isn't possible ?

 

[Pythagorean]

It is possible, it's called geothermal power. It's not considered sustainable, though.

 

[AlephZero]

It's not considered sustainable, though.

Really? I guess nobody told the 24 countries that are already using it. (Or about 70 countries, if you include geothermal heating as well as electricity generation)

There are some geothermal heating systems in the UK that have been running for more than 1000 years already. Doesn't that count as "sustainable"?

 

[Pythagorean]

I guess the technical nomenclature is not "renewable".

 

[Pythagorean]

But still, depending on how you define sustainability, and to what threshold you hold environmental impact, you might argue that the exhaustion of local heat budgets is not sustainable. It may be case-by-case too. Exhausting a particular local thermal supply might have impact on permafrost in the area which affects habitat, while other thermal supplies are relatively infinite compared to human energy consumption.

 

[davenn]

I guess the technical nomenclature is not "renewable".

its totally renewable ... its being constantly renewed by the natural processes in the earth

But still, depending on how you define sustainability, and to what threshold you hold environmental impact, you might argue that the exhaustion of local heat budgets is not sustainable. It may be case-by-case too. Exhausting a particular local thermal supply might have impact on permafrost in the area which affects habitat, while other thermal supplies are relatively infinite compared to human energy consumption.

for where a number of the geothermal power stations are, none of the above is really applicable

take the geothermal power generation in Wairakei in the upper North Island of New Zealand. The geothermal heat/steam is going to be naturally released into the local surrounds regardless of if it is captured for power generation or not. Its been "pumping" superheated water/steam out of the ground long before man was around to worry about it and will be still doing so long after we are all gone

Gosh ... its been a long time since I last visited there

cheers
Dave

 

[davenn]

radioactive8

looking back at your original question ... it was pretty unclear what you were really trying to define
Tho your thread title was a little more to the point

You do know the sea is used in at least a couple of places to generate electric power ?
They ( the countries involved) use the flow of the tides to turn turbines that then turn generators

Is there some other specific form of generation other than tides or geothermal that you were wanting to know about ?

Dave

 

[Bobbywhy]

Hi!
I have been told that despite the different temperature between the surface and the Earth is different we can't use it to produce electricity by using the laws of thermodynamics .. shy isn't possible ?

This is a patent for a system that does not use temperature differences to generate power, but does use tidal power of the sea, certainly a renewable energy source.

“Piezoelectric generation of electrical power from surface waves on bodies of water using suspended weighted members”
US 5578889 A
https://www.google.com/patents/US5578889

 

[Borek]

There were pilot installations made that used the temperature gradient between surface and deep sea waters to run the power plant. Main problem was the small temperature difference between the heat source and the heat sink (something like 20 K).

 

[Pythagorean]

its totally renewable ... its being constantly renewed by the natural processes in the earth

"Totally" is too strong, especially given your justification "constantly renewed".

Globally, it's definitely not the case... (the Earth's core is cooling over time). However, heat extraction takes very little heat compared to the total that for practical (political and commercial) reasons, many people use the word renewable (though still not technically renewable in academic terms) and that's fine with me.

Locally, on the other hand, it can go either way depending on the local heat budget. "The Geysers" (the largest geothermal plant in the world) is perhaps the most well-known example of local depletion (thought to be caused by human extraction):

http://onlinelibrary.wiley.com/doi/10.1029/2001JB000638/abstract