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Technology that could multiply geothermal output fivefold

Far below the earth’s surface lies an energy source with huge and eternal potential: geothermal heat. But the forces in the scorching and inhospitable depths must be tamed. Researchers now know what this will take.

If the researchers succeed in their next attempt, it will increase the effect of geothermal heat by five to ten times.
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Presented by: SINTEF
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“Deep underground we find temperatures of more than 1,000 degrees Celsius, which can be converted into energy that is renewable and almost CO2-free. This geothermal heat is also independent, available, and stable 24 hours a day,” says Hieu Nguyen Hoang.

He is a research scientist at SINTEF, and one of those aiming to tame the inhospitable conditions deep within the earth. We're talking about corrosive liquids, extreme pressures, and temperatures that would destroy nearly everything. 

Geothermal energy could become a crucial energy source that the world desperately needs more of, but which today produces a lot of greenhouse gas emissions.

Hieu Nguyen Hoang is one of the technologists who has set out to tame the inhospitable conditions deep within the Earth.

The potential of geothermal energy is still relatively untapped. Today, less than three per cent of global energy comes from geothermal heat. High costs and high energy use associated with drilling are the main reasons for this. We need to reach temperatures high enough for profitable electricity production.

The closer we get to the Earth’s core, the hotter it gets.

Increases efficiency fivefold – at least

New technological advances are bringing us ever closer to the goal:

Iceland is already well on its way to taking advantage of the country’s unique geological conditions. Today, 99 per cent of Icelanders’ electricity comes from renewable sources. Geothermal energy is an important part of the energy mix.

The Iceland Deep Drilling Project (IDDP) is a research and development project. Over several years, researchers have investigated how to create wells that can withstand both the high temperatures and porous geological formations of Iceland.

The goal is to reach what they call supercritical water. This is a state of water that occurs when the temperature exceeds 374 degrees Celsius and the pressure rises to 218 times the air pressure at the surface. 

These extreme conditions produce five to ten times more electricity than traditional geothermal energy.

“Supercritical water, with its higher energy density, offers a unique opportunity for producing electricity. Unleashing this resource could revolutionise geothermal power and make it one of the most efficient renewable energy sources,” says Hoang.

Through two previous projects, the researchers have worked on finding solutions to this. So far, they have not been successful.

“The first well achieved superheat conditions, and the second one attained supercritical conditions at a depth of 4,650 metres. However, both wells experienced failures due to inadequate casing systems in the outer wall of the well,” he explains. 

Geothermal energy

Iceland’s leadership:

  • Iceland produces 5.8 per cent of the world’s geothermal electricity.
  • More than 99 per cent of the country’s electricity comes from geothermal and hydropower.
  • Geothermal energy covers 45 per cent of the country’s heating needs.

Global potential:

  • Globally, geothermal energy can produce over 200,000 terawatt-hours of electricity each year.
  • Geothermal resources are found in over 90 countries, especially in areas with volcanic activity or where tectonic plates meet.
  • Improved geothermal systems make it possible to use geothermal energy in areas that do not have naturally high temperatures near the surface.
  • By 2050, geothermal energy could supply 8.5 per cent of global electricity, reducing CO₂ emissions by 2.1 gigatonnes per year.

In addition to producing electricity, geothermal energy can be used for heating, in industry, and in greenhouses.

New super well

Researchers are now working on a new project called COMPASS. The goal is to construct a new well that can withstand both high temperatures and the porous geological formations. 

At the same time, costs must be kept as low as possible so that the project is profitable and more sustainable.

Researchers at work at a geothermal field in Iceland.

“Corrosive fluids, extreme pressures, and geothermal stresses are tough challenges for well design. Innovative solutions are essential to ensure the integrity and longevity of geothermal wells,” says Hoang.

Has to withstand ‘everything’

Extracting geothermal energy involves water from the reservoir flowing into the well and up to the surface. The porous formations with their natural cracks enable the water to move within the formations. 

The challenge is to ensure that the well does not get damaged over time under the extreme temperature and pressure conditions that exist in these geothermal environments.

In the project, the researchers will develop technology to create a stronger and more flexible well. It must be able to handle the extreme conditions. This includes the development of stronger and more flexible outer walls, called casings, to reduce thermal stress. 

The project will also focus on innovative, corrosion-resistant well designs.

“Using a laser, we’ll apply a protective layer to the pipe that resists corrosion and can withstand the high pressure and corrosive liquids,” says Tèrence Coudert. He is also a researcher at SINTEF.

A technological crystal ball

Researchers at SINTEF have developed an advanced simulation tool. According to them, it could completely change geothermal well design:

By simulating and extracting data from wells, the tool makes it possible to identify the physical phenomena that occur in the depths of the earth. 

The simulation also provides information about chemical reactions and which materials are needed to create a flexible structure.

“The tool provides us with quick calculations of the forces in the well and what the structure can withstand, so that we can keep developing the technology and reduce costs,” says Coudert.

In the previous project, the casing system quickly suffered damage in the super-hot conditions. As a result, the researchers were not able to measure the conditions in the well nor carry out the planned tests.

Hoang explains that the experiences from the first wells show how important the casing system is. The outer wall must be able to hold up.

Possible reuse of old wells

According to the researchers, geothermal energy could play an important role in the global energy transition. It can become a reliable and versatile alternative to traditional renewable energy.

However, geothermal energy is more than just a renewable energy source: It can also play a key role in a circular energy economy. 

By reusing wells for carbon capture, thermal energy storage, or hydrogen production, geothermal projects can extend their life cycle and minimise environmental impact.

“Our goal is to create wells with a lifespan of 30-plus years that can be adapted to future applications and conditions,” Lilja Tryggvadóttir at Reykjavik Energy says.

She adds that they are also exploring the possibilities of reusing and refurbishing old wells. Furthermore, they aim to extract energy from deeper resources.

These are the innovations in the project:

  • Thermal stress reduction: Advanced foam cement and flexible coupling systems allow the casings to expand and contract more flexibly, reducing structural failures caused by extreme temperature variations and ensuring long-term reliability.
  • Corrosion-resistant cladding: Using EHLA (Extreme High-Speed Laser Application) technology, COMPASS applies thin, high-performance corrosion-resistant layers to casing components. This innovation extends durability while minimising environmental impact compared to traditional methods.
  • Pressure relief systems: Pressure build-up in the well’s annular space, caused by expanding fluids during heating, is a primary cause of casing collapse. COMPASS introduces an innovative pressure relief system integrated into the casing, which temporarily releases excess pressure and automatically reseals, maintaining the structural integrity of the well.
  • Advanced simulation tools: Multiphysics simulations provide deeper insight into the interactions between thermal, mechanical, and chemical loads in wells. These tools enable precise, efficient designs optimised for super-hot geothermal fields.

About the project

The EU-funded COMPASS project is picking up where its predecessor HotCaSe left off.

SINTEF is responsible for developing the simulation tool for the well. Reykjavik Energy is responsible for drilling what will be the IDDP project’s third well. With its subsidiary On Power, they have prepared for the task through several research projects. The goal is to set new standards for well design with the help of an international team of experts.

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Read the Norwegian version of this article on forskning.no

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