Geothermal? Better in some states?

[Skogsgurra]

This made me wonder:

http://www.energycentral.com/centers/news/daily/article.cfm?aid=8222873

Geothermal energy has been tried in many places and seems to work well only in volcanic areas like Iceland and such.

Is there a difference between states in the US with regard to thermal energy? How do you judge the chances to make this work?

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

Oh yeah Gunnar, huge differences between states. The ones on the Ring of Fire are the only ones with magma anywhere near the surface. California has had a Power plant running for 45 years on Geothermal.

http://www.energy.ca.gov/geothermal/overview.html

http://www.energy.ca.gov/geothermal/

http://www.energy.ca.gov/maps/geothermal_areas.html

On a recent road trip to go shooting. Our family saw a bunch of steam rising from a part of the Nevada desert next to the highway. We pulled over to investigate. There were ditches filled with 200F water with signs warning of fatal temperatures. It was next to a plant of some sort. Don't know what the plant was using doing. But the geothermal waste was impressive.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jraef]

One major problem they will likely discover in Nevada with regards to extracting energy from geothermal sources of heat: water for the steam. At the geothermal fields in Northern California, that problem has already caused a major decline in their output. It had dropped to around 30% of what it was when they began. I was involved in a project 3 years ago where they began collecting treated wastewater from the various communities surrounding the fields and pumping it 40+ miles over the local mountains to be injected down into the earth to supply water for the steam. It took 4 pump stations of 7800HP each to get the water over the mountains. It began as a way to find a use for the treated water because the local river was becoming polluted, but by the time they completed the project, the water need to stem the decline in power output was more than they could supply.

In the areas around where they have found the geothermal heat source in Nevada, water is even more scarce and there are no large communities from which they can take advantage of treated wastewater without having to pump it hundreds of miles. At some point the laws of diminishing returns will kick in.

 

[Skogsgurra]

Interesting. I now remember that that company was (is?) also in some kind of funny motor thing.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[jraef]

Yes, their website smacks of that "revolutionary motor technology that will change the world" marketing garbage.

 

[itsmoked]

Why don't they just condense the water out in a coiling tower type affair, so they don't need to make up so much?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[niallnz]

Itsmoked

What jraef is saying is that as you draw off steam from under ground to run through your turbine, there is very little water comming into the steam field to replace what you take away. Hence, grandiose water reinjection schemes that suppliment the natural water inflows. The problem is not in the condensing end of the turbine it is in the "boiler" feed water supply.

Interesting that have used wast water for reinjection, here in NZ we have enough rain and river water for reinjection at our geothermal sites.

cheers niallnz

 

[ehanes75]

Hi Folks,

I saw ths post and figure I should throw in my 2 cents. I work for PG&E (the local electric and gas utility) and I am the electric transmission planning engineer for this part of N California. I have had the opportunity to see some of these units operating.

Currently, the Geysers Geothermal complex produces about 900 MW. The total installed generation capacity is around 1800 MW, based on "nameplate" generator output. From what I understand, there is enough heat in the ground theoretically extract about 4000 MW. In fact the 230 kV and 115 kV transmission system that connects the site to the rest of the grid was built out to handle this massive amount of power.

To put this in perspective, the peak electric power demand in California is around 45,000 MW during a hot day in summer.

Lack of water is the primary limit on steam (and power) production. The injection of treated wastewater supplements the natural process and has stabilised the steam fields. If steam is withdrawn at a faster rate than can be replaced by natural percolation of rainwater or reinjection, the the power production will decline. When the plants started operating in the 80's peak output was around

The current plants are operated in a open cycle. After the energy of the steam is extracted in a turbine the steam is vented. There are closed cycle systems that condense most of the steam and reinject. but these systems add cost and compexity and were not around for this application when these plants were built 20 yrs ago. In addition there is a whole bunch of nasty toxic stuff that comes out with the steam: sulpher, mercury, H2S gas, and chlorine. Really depends on the geology of the area. Some of the geysers units had to be shut down because of the chlorite deposits in the wells were creating HCL acid and eating up all the equipment. The underground rock matrix that contain the steam can be also be damaged if the steam is removed too quickly. this can plug up the bore hole and requires very expensive specialized drilling equipment to fix.

Here is a good article that talks about repowering of one of the generating units (I worked on the interconnection for this project):

http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2007/01/14/BUGV2NHQP61.DTL

Thanks,

Gene

 

[itsmoked]

niallnz; Thanks. I understand the process but if one is discarding the "waste" steam instead reclaiming it, or some percentage of it, then they are going to require a much, MUCH, larger supply of makeup water. (of course) Perhaps they are condensing and reusing the waste steam now - I don't know.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[ehanes75]

itsmoked,

Currently some of the steam is recycled and reinjected, I think about 20%. Nature provides most of the recharge, however this takes time. Currently, output is pretty stable a 900 MW. I think I see addition wastewater reinjection projects in the future and expansion of production.

Maybe someone could calculate how many liters of water, converted to 700 deg F dry steam, is required to produce 900 MW when run through 23 steam turbines, with 20% of the water reinjected?

Sounds like a question on a thermo exam!

 

[jraef]

Keith,
I asked the same question when I was working there. I think the part you may have missed in ehanes75's post is just how nasty the steam coming out of there is. As an example, when I was driving through the area I was not allowed to exit my vehicle or roll down the windows, nor could I even stop the vehicle for more than 5 minutes without special permission and supervision. I had to drive straight through and they even timed my passage. I got lost once and had to explain why I took too long to reach my destination.

As it was explained to me, reclaiming the steam would be problematic just from the H2S standpoint, let alone the other toxic substances. To allow the turbines to vent to the atmosphere is "natural", i.e. it was already happening there before the plants were built. For instance, around the wells, there is no vegetation and new vents spring up all the time, killing whatever vegetation there was in the vicinity. To capture and treat the steam just to reclaim the water would mean to take ownership of what comes with it, which means the cost of dealing with it.

 

[Skogsgurra]

Thanks for all very interesting answers! I had no idea that this seemingly simple technique had so many complications.

It makes wonder - again - does Raser have better technology or more experience in this field than others have? Seems a risky undertaking if you haven't been in this kind of operations before.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

Yes jraef I did miss that...in fact I missed the whole blithering post as ehanes75 put it up while I was writing my original response to niallnz. I was rather surprised to see it there this morning. HA! Sounds like a Texaco field I worked in once. (San Ardo)


Thanks ehanes75 you pretty much answered my question. Still seems to me that if they are running at less than possible due to lack of water condensing more of it and pumping it an all the poisons right back down the bore would still put them ahead. There's probably an equation floating about that sez NO!

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com