uninfinite,
you seemed to find two matters of concern in the tenor of my post. Let me deal with these first, before getting back on topic:
1. This is a science forum. You have displayed, in many other threads, a clear head, considerable knowledge, logical thinking and other attributes I associate with a trained scientist or engineer. Therefore I do not feel a need to "treat you gently". Therefore I dealt robustly with your suggestions since it never occurred to me you would not welcome that approach.
I did not call your idea silly. I said, very simply and very clearly, I could see no advantage in it. Frankly, I expected you to come back with some specifics challenging my dismissal of the notion, as a prelude to an interesting discussion.
So, I see nothing to apologise for in relation to my response. (At the risk of inflaming a minor disagreement I shall note if one does not wish to have uneducated guesses criticised then avoid making uneducated guesses.)
2. You chose to make an implicit insult when you said "If this is the expertise we were waiting upon, colour me disappointed." uninfinite, I suggest that you cannot have it both ways. Faced with "uneducated guesses" and a request for information I naturally pitched it at a very basic level. Your own post did not suggest you were someone who had "a definition of the term 'geothermal energy' to hand". I responded accordingly.
For the record, I am not an expert in geothermal exploration. I am an expert in aspects of the drilling process.
Back on Topic: uninfinite » Sun May 22, 2016 6:52 am wrote:[quote="[url=http://www.sciencechatforum.com/viewtopic.php?p=299233#p299233]
"As you are familiar with volcanoes, may I canvass your view on vulcanism as a source of (in theory) virtually limitless amounts of energy.
Why is it not more widely used?''
Two reasons:
1. Economic
2. Technical.
EconomicOil, gas and coal have been much more suitable, less expensive, alternatives in most parts of the world. Concern with AGW and air pollution have partially overcome this.
Geothermal exploitation is inherently more expensive since its technology is less developed and therefore more costly than conventional energy sources.
TechnicalAll proposals I am aware of for geothermal work involved drilling boreholes. While it may seem apparent that the greatest benefits could be derived by getting close to the highest temperatures this raises huge difficulties.
1. Drilling fluids are adversely affected and become very much more expensive when designed to handle high temperatures. This does not only add to the direct cost of materials and expertise, but substantial rig time may be required to periodically circulate and condition the drilling fluid before resuming drilling. This would be to an extent beyond what would be required in conventional wells.
2. To maximise effective retrieval of thermal energy directional wells will often be favoured:
a) Directional sensor electronics cannot tolerate high temperatures.
b) Directional equipment requires seals. Traditional elastomer seals cannot tolerate high temperatures.
c) Although fixed cutter bits can replace roller cone bits, whose bearing systems are temperature sensitive, the geothermal industry has been uncomfortable with their cost. And in very high temperatures even thermally stable PDC will be compromised.
3. Completion equipment, for isolating zones; fracking equipment, for exposing more of the target zone; logging equipment, to characterise and correlate; all of these will either not function, function poorly, or be vastly more expensive than in conventional wells.
4. I also have reservations about the long term effects of cyclic temperatures upon drill pipe.
I can expand on any of these points if required and address any specific or general questions you may have.