Geothermal 101

 

Good morning and welcome back! It's been a while since my last post.  Things have been pretty crazy these past couple of months... In regards to work, we've been in the process of setting up our first operations in Central America.  I've come to label my trips down there "worcations" because of the breathtaking tropical-like settings. Needless to say, I always get the comments coming home, "did you even do any work down there?"



Hotel in San Salvador, El Salvador

My first trip to El Salvador.  It all started with a coconut and
a lawn chair.  Sometimes that's all you need...

Initially, our work there started off as our typical oil & gas work. But now, it has shifted into the realm of geothermal energy.  It's pretty fascinating stuff!  I feel like most people have a general idea as to what geothermal energy is all about, but couldn't tell you how it functions.  That will be the topic for this post... "Geothermal 101," class is in session.  Hopefully this post will broaden your horizons a little bit. As with previous posts, this is extremely surface level. 

Basically, the gist of geothermal is that you are trying to create, or pull, steam from hot rock which in turn powers a turbine, and those turbines generate power. The photo below gives a pretty basic example of this (photo courtesy of Green Mountain Energy).

The most prevalent geothermal areas within the USA are concentrated along the west coast (California, Oregon, Washington, and Nevada).  Some of the most prevalent areas across the globe are Mexico, Central American countries, Chile, Nigeria, Philippines, New Zealand, Germany, and who can forget Iceland.  You can kind of see that most of these countries fall along the Ring of Fire. 

What some people don't realize is that with modern advancements in geothermal technology, it is actually possible to use geothermal energy as a source of power almost anywhere. We will get more into that later. There are, essentially, three main ways of harnessing the heat of the Earth for mass power production:

• Dry Steam
• Flash Steam
• Binary Steam

DRY STEAM

The dry steam method is known as being the most economical.  The costs for constructing this sort of power plant are relatively low compared to the other two methods.  Power companies drill into rock that is already producing dry hot steam.  When they drill, they drill injector wells and production wells.  They use the production wells to pull the steam to the surface.  The injector wells are used to inject the condensed steam, which is now liquid, back into the rock.  That liquid then travels through the rock, where it is re-heated and extracted once again.  The whole process is a renewable cycle!

The reason that this method is the most economical is because when the resource is extracted from the rock, it does not require any further processing.  It can be pumped straight into a turbine and generate power.  The other two methods require some further processes at the surface to turn the resource into a usable power source.  The dry steam method is actually pretty rare due to the rarity of finding a natural hydrothermal resource.  However, this method is prevalent in an area known as The Geysers in Northern California. 

 

Flash Steam

 The second, and most common, type of geothermal resource is flash steam.  Hot water, upwards of 360 degrees in temperature, is extracted from the ground and sent into a flash tank.  In the flash tank, the pressure is dropped causing the hot water to turn to steam.  Anyone remember the Gas Laws? It's okay, I really don't either... The steam is then flowed through a turbine that generates power.  Excess water from the flash, along with condensed steam, are pumped back into the formation creating a renewable cycle. 

Within the US, this method is used in parts of Southern California in an area known as the Salton Sea.  It also carries over into Baja Mexico.  You can also find this method being used in parts of western Nevada around the Reno/Tahoe area. (pictured below)

 Binary Steam

The third and final method is the Binary Steam System.  This method can actually utilize temperatures well below what the other two methods require.  Temperatures as low as 150 degrees Fahrenheit can actually be used to produce geothermal energy.  For anyone following all of the new developments in the Eagle Ford shale plays, temperatures in this formation can range anywhere from 200 to 300 degrees Fahrenheit. 

The best part about this is that Texas could feasibly produce geothermal energy! As with anything, the more advanced the technology, the more expensive it usually is... Let's get down to how it works. 

Essentially, hot water is pulled from the ground and sent through a series of pipes where it then heats a fluid (typically butane) that has a lower boiling point than that of water.  That fluid then vaporizes and is sent through turbines, which in turn generate electricity. Once the fluid passes through the turbines, it is condensed and reused. 

There has actually been some work done to reuse non-producing oil wells and turn them into geothermal projects.  This is still VERY preliminary, but people are doing it.  The great thing about this is that there are no up front costs for drilling the wells!

That pretty much covers it for the three main methods.  There are variations of each, but that gives you a pretty high level knowledge...  Check out this video if you have time.  It gives a good overview of the whole process.  The video was produced by Calenergy which operates in the Salton Sea area of California.  Their power plants function off of the Flash Steam method as mentioned earlier. 



There you have it! Geothermal 101! Pretty cool stuff, huh? I'll leave you guys with a couple of photos from my trips to Central America.  Have a great day!

Iglesia la Merced in Granada, Nicaragua

Iglesia la Merced Granada, Nicaragua

Iglesia la Merced Granada, Nicaragua