Viability of closed loop deep geothermal plants?

[PraAnan]

Hello everyone,
Just posting this because I was wondering if it's possible to build 5-10km deep closed loop geothermal power plants from microgrid sizes of 1-5MWe to commercial power plant sizes of 0.5-1GWe that can have construction costs in the $3,000,000 per MWe range (similar to solar and coal).

The most difficult and expensive part seems to be the drilling but with current technologies such as hydrothermal spallation, plasma drilling etc. can this not be made cheaper?

By drilling deep doesn't the location of potential plants become much less strict?

Might be a silly question but if you're extracting the heat from a specific area won't you cool the surrounding rock and in turn reduce the temperature of the liquid in the pipes. In other words, do deep geothermal plants produce less power over time? Or is it like trying to extract heat from a kettle which is constantly boiling where any heat you take out is replaced?

Thanks for reading.

 

[mfb]

Might be a silly question but if you're extracting the heat from a specific area won't you cool the surrounding rock and in turn reduce the temperature of the liquid in the pipes. In other words, do deep geothermal plants produce less power over time?

Yes, that's why you need a larger area to harvest the heat - a single pipe will lead to huge temperature drops directly around the pipe and the power you get will be small.

 

[PraAnan]

Thanks for your reply.

Even if you have a large number of pipes scattered around the place eventually they will cool down as well right?

Is there a way to calculate the amount of pipes you would need per MW that would keep the underground temperature at a good level so the plant could be used for 50 years?

Why isn't more research being done in deep geothermal?

What got me interested is what this company has written: http://www.consiliari.pl/geothermal-power.html

 

[mfb]

Is there a way to calculate the amount of pipes you would need per MW that would keep the underground temperature at a good level so the plant could be used for 50 years?

It is certainly possible to model that, but it is nothing you can do properly in a few minutes.

Why isn't more research being done in deep geothermal?

There is research done. And it does not look like the most promising option for widespread application.

That link gives me a 403 forbidden error.

 

[PraAnan]

The page (as well as the rest of the site) is down for me as well.

In your opinion, what would be the most promising option for widespread application?

 

[mfb]

All those things that are used around the world, except power plants that burn fossile fuels. And maybe fusion in a few decades.