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February 22, 2010

Hoch Geothermal Plant

This past weekend I went camping with Great Outdoors down along the Salton Sea at Mecca Beach. We took various outings from there, and here's the first: a tour of the Hoch geothermal power plant owned by Calenergy in Calipatria, California. Google maps aerial view of the Hoch plant, which has a 42 MW capacity. Calenergy has 10 geothermal plants in the Imperial Valley.

The tour started off with a powerpoint presentation of history and facts of the geothermal industry. My secret pleasure during this was watching the eternally long boot-up of the corporate laptop (Windows XP Pro), followed by a nearly equally long series of mysterious errors identified only by number and cryptic message, each of which the laptop owner handled as routinely as morning coffee. After that I learned new things.

The precision-engineered turbine is the most expensive part of the geothermal plant. The Calenergy plants in the Imperial Valley bring up hot (about 800°F), highly pressurized brine from miles below the surface (compared to a depth of 1,250 feet for a recently constructed fresh water well for the Mission Springs Water District). When the pressure on the brine is released at the surface, it flashes instantly to steam, but you can't just shoot this hot, filthy briny steam directly into that precision turbine, so you'd like to get all those dissolved minerals to drop out of the solution, but not all at once. Not all at once, because you run into Problem Number One for geothermal plants: quick, thick, destructive mineral build-up inside the pipes. Carbon-steel pipes, BTW, won't last beyond two years at a geothermal plant, so they use titanium or more exotic materials for pipes.

At the Calenergy plants the hot brine passes through a series of steps where some pressure and steam are released at each step, extracting as many calories of heat from the brine as possible. The now cooler water is pumped a distance away from the source and injected back into the earth to reheat and recycle. There has been no evidence of subsidence in the Imperial Valley since the geothermal plants began operating about 1980. The waste minerals that are separated out (mostly silica) go to a landfill. They have tried extracting lithium and zinc from the waste minerals, but haven't been able to make a reliable profit doing that yet.

A new method in geothermal power extracts steam and heat only once and then re-injects the still very hot brine into the earth. While this method gets less electricity out of a gallon of hot brine, it lengthens the life of the pipes, which are the next biggest expense after the turbine.

Geothermal Plant (1)

Calenergy Hoch Geothermal Plant Control Room (8894)
The control room.

Calenergy Hoch Geothermal Plant (8929)

Calenergy Hoch Geothermal Plant (8882)
Big insulated pipes bringing in the hot brine; smaller uninsulated pipes returning cooler, used water to the earth.

Calenergy Hoch Geothermal Plant (8918)

Calenergy Tour Guide (5371)
Our tour guide.

Calenergy's Justin (5375)
Justin at the controls.

Seen at the geothermal plant (5368)
A sign that was displayed above the water faucets in all the restrooms mystified me.
If my Googling is correct, water in Calipatria is supplied by American States Water Company, a private company that gets its water from the Imperial Irrigation District. Here's their most recent water quality report, and everything seems to be within legal parameters so their water should be as safe as any other public water supply. What does Calenergy know about the public water supply that others don't?

More photos from our tour of the geothermal plant here.

Filed under California,Photography,Technology | permalink | February 22, 2010 at 01:39 PM


I called them "waste minerals" because the geothermal plant sends them to a landfill.

Posted by: Ron at Dec 1, 2017 7:01:57 PM

Waste minerals? What about the Cobalt 60, Cesium, Strontium, and the pounds of Arsenic that are in one gallon of the "brine"? Radioactive isotopes and an element that is a poison?

Posted by: kotcher at Dec 1, 2017 5:12:04 PM

Thanks foe your time and thought,Bruce

Posted by: Bruce at Jan 30, 2012 11:39:57 AM

So your answer to my question is that the photo you initially linked to shows a 1.5 foot drop.

And we know that's subsidence due to geothermal energy production because Flickr user rokskid suggests it is with some of his or her photos.

Personally, I think the photographic evidence of cloud cloaking UFOs is stronger.

Posted by: Ron's Log at Jan 30, 2012 7:32:23 AM

That is their story and they are sticking to it. They are basically self policing(The fox watching the hen house). About the link on doing the surveys from space, the Dept of Energy is funding a study on finding a method of Insar that will work in a agricultural area, but for now they have the annual ground surveys done and send a copy to the Imperial County Dept of Public Works where it is filed. While I am sure Cal Energy analyzes the data, that remains proprietary and is not forwarded to Imperial County or the State Dept of Conservation. This was all forecast in the original EIR, done in the 1970s. But now Imperial County, the State of California, and Cal Energy all have too much to lose. and eventually it will be to obvious for anybody to ignore. There currently is approximately 350 mw of geothermal production in Imperial Valley, 327 of which is at the Salton Sea. The Hudson1 comes online early this year, Hudson2 is going to construction this year, Black Rock Unit 6 is currently going to be built, Brawley East River has been permitted, Orita is in development, and many more. They plan on developing 2,500mw in the Imperial Valley. My charts show that the subsidence has increased as production has increased and with the further overproduction, it will get worse. The removal of fluid or material causes surface subsidence in most cases, it does not matter if it is water, oil, geothermal brine, or the mining of something like coal. The very process that creates oil, coal, or the rocks in a geothermal reservoir(gravity) is the same process that causes subsidence. The fact that it is done in a tectonically active area would seem to guarantee that the subsidence happens sooner and not later. There have been studies done at numerous sites some even in the same region, that have determined that that the removal of fluid has resulted in subsidence. Here are a few: Coso CA., East Mesa Imperial Valley CA., Brady's Hot Springs NV., Steamboat NV., Cierro Prieto Mexico, Wairakei and Tauhara New Zealand, Euganean field Italy, The Geysers CA., Borrego Valley CA., Allegretti Ranch CA., and Coachella Valley CA., just to name a few. Like I said some of these are in the same tectonic area and the conclusion is that it is caused by mans activities. Of the two types of geothermal reservoirs, steam and liquid dominated, liquid dominated is the most susceptible to subsidence. Salton Sea is this type. The production of power from geothermal fluid involves much more fluid than an oil well or water well. The difference in the amount of material produced and the amount of material re-injected is enough to cover 452 sq miles 1 foot deep. Although the reservoir is said to be robust, the permeability and communication between different areas is low, so I would imagine the actual area influenced by the removal of material is probably much smaller and would subside much more. Here is an image of the area with the totals of data taken from the annual subsidence surveys: http://www.flickr.com/photos/sinkingranches/6780701489/in/photostream The red circle are benchmarks that have over 20 inches of subsidence.
The next image is of the benchmark locations with red circles of locations that I have charted. http://www.flickr.com/photos/sinkingranches/6780297339/in/photostream
The next four images are charts of benchmarks showing the increasing trend of subsidence as more power plants have come online. The next two are spreadsheets with the benchmark elevations and total subsidence. One is for 1982-1986 and the other is for 1982 -1989 showing that in the early years, when production was small there was very little subsidence, and if the subsidence rate remained the same as the 82-86 rate at benchmark U-5 and U-12 the total subsidence would be less than 3 inches. The actual subsidence is 14.26 inches at U-5 and 17.02 inches at U-12. The results are similar for 82-89, but the rate has already started to increase at U-5. The next two are totals for the subsidence detection network from two time periods, 1989-2011 and 1991-2011. I included the 1991-2011 data because it includes data for an extended network, or more benchmarks farther from the production area. It also shows that as you get farther away the numbers turn positive indicating uplift, but is actually subsidence at a lower rate than their reference benchmark S-1246 on Obsidian Butte, which is close to the production area. That is all for now, and I know I am not an expert in this field, but I think it only requires a little common sense. You would not believe the road blocks and number of people initially willing to talk and research this, and then go silent. And the original photo I linked may not look to be a 1.5 foot drop, but it looks substantial, and what would you think if it was in your front yard?
Thanks, Bruce

Posted by: Bruce at Jan 29, 2012 10:14:06 PM

For the lay audience, would you please explain in detail what I'm supposed to be seeing in that photo that proves subsidence due to geothermal energy production?

I've seen lots of bumps and waves in the ground in California, and I don't think they are all due to geothermal energy production.

OTOH, here's a report that says "To date, little if any geothermal subsidence has occurred in the Imperial Valley." Unfortunately, it's an undated article, so the phrase "to date" is meaningless.

Here's an article about how subsidence is measured and it does not include eyeballing one spot with a pocket camera.

None of which is to say that the guys at Hoch weren't just spinning a line. But those photos tell me nothing.

Posted by: Ron's Log at Jan 27, 2012 7:39:50 PM

There has been no evidence of subsidence in the Imperial Valley since the geothermal plants began operating about 1980. This statement is false! There have been multiple cases of differential subsidence in excess of 21 inches since 1989. Pictures here:

Posted by: Bruce at Jan 27, 2012 7:15:01 PM

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