The Closed-Loop Zone

Introduction to AGS

Hello fellow LinkedIn users! Today, let's talk about Advanced Geothermal Energy Systems (AGS), the latest buzz in the world of renewable energy. It's time to break it down for all those non-geothermal experts out there. First things first, let's clear the air - AGS is a fancy term for closed-loop geothermal energy systems. Yup, you heard it right. It's the same thing, but an easier acronym to remember.

How Does it Work?

So, how does an Advanced Geothermal System (AGS) work? AGS generate energy used for heating or electric power through a closed-loop circuit, which involves a complex system of wells and pipes. Here's a simplified breakdown of the process:

1. The system starts with a vertical injection well, which is drilled down to a depth of several thousand feet (That’s equivalent to approximately 0.61 kilometers for my coworker Boris who cannot wrap his head around American Standard Measurements and a small vein pops out on his forehead when I dare say things like Fahrenheit). The injection well is split into many more deviated or horizontal sidetracks where the majority of the energy is extracted from the rock formation.

2. A working fluid (usually a mixture of water and a small amount of antifreeze) is pumped down the injection well and into the set of sidetracks.

3. The working fluid absorbs heat from the rocks through heat transfer. This heat is then transferred back up to the surface via a separate production well.

4. As the working fluid returns to the surface, it passes through a heat exchanger. This transfers the heat from the fluid to a secondary fluid (usually a refrigerant), which boils and generates steam.

5. The steam is then used for heating applications or to power a turbine, which in turn generates electricity.

6. The cooled working fluid is then pumped back down into the well, where the process begins again.?

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Closed-Loop

As I mentioned before AGS operate on a closed-loop system, which means that the working fluid is constantly recycled and reused. This makes them a highly sustainable and low-emission source of energy. Simple right? It's rumored that this process was originally written down on a cocktail napkin at a dive bar in Oklahoma while country western music was blasting on the juke box.

Drawbacks

Okay, let’s get serious for a minute… While AGS has great potential, there have been some unsuccessful projects on the path to actual AGS related with EGS. Some unexpected drilling issues and insufficient hydraulic connections between injector and production wells turned out pretty nasty. Who would have thought these things would be an issue? Apparently not the experts, the positive outcome is that we learned from these mistakes.

Solutions

To tackle these issues, there have been attempts to replace hydraulic fracturing with a "drilled downhole heat exchanger" (DHE). This eliminates the problem of disposal of geothermal fluid, since only heat is removed from the well. The exchangers consist of a system of pipes or tubes suspended in the well through which "clean" secondary water is pumped or allowed to circulate by natural convection. AGS generate electric power through a closed-loop circuit, after a working fluid extracts thermal energy from rocks at great depths via heat transfer** from the geologic formation to the working fluid through an impermeable wellbore wall. Sounds fancy, doesn't it?

Advancements

One company leading the charge in AGS is Eavor, with projects in Canada, Germany and NM. But they're not alone in the race. Competitors like Eaposys from Switzerland and Green-Fire Energy with their Green Loop (a combination of closed-loop and monobore) are hot on their heels. Pun intended.

Conclusion

In conclusion, AGS is closed-loop geothermal energy systems with a fancy name. AGS remain uneconomical with current, standard drilling technologies. Therefore, significant advancements in drilling technologies are required to enable cost-competitive AGS implementations. Let's hope that with advancements in drilling technologies, AGS will become a more viable and cost-effective option for renewable energy.?

Footnotes

*Source article for motion graphic and great read https://www.ever-greenenergy.com/posts/technology-spotlight-geoexchange-energy-systems/

**Another great article explaining how heat exchange works in geothermal heating and cooling cycles https://www.geothermalindustries.com.au/how-it-works/

Links

Eavor, Canada (Pronounced EVER BTW) https://www.eavor.com/

Eaposys, Switzerland https://www.eaposys.com/

GreenFire Energy, USA https://www.greenfireenergy.com/