Friday is here, and the "A Taste of Science for the Weekend" column is back — number 103.
This time: what is a supercritical fluid, and does humanity's future lie hidden deep underground?
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The Earth is a giant battery.
Beneath our feet, a scorching mass churns slowly at temperatures of thousands of degrees, the product of gravity compressing it and radioactive decay. A small fraction of that energy reaches Earth's crust, providing an inexhaustible energy reservoir that can be converted into electricity.
Geothermal power plants work by drawing this heat from deep underground using a carrier fluid. The fluid heats up and is pumped back to the surface while scalding hot, where it becomes steam that spins a turbine to generate electricity.
This approach is practical mainly in specific locations on Earth — regions where a layer of rock is riddled with fractures that water can penetrate, allowing it to sink deep and heat up dramatically. As it heats, it rises toward a natural water reservoir, and cooler water flows in to take its place.
Reaching the necessary depth requires drilling through layers of hard rock. The extreme heat at depth softens and warps the drill bits, dissolved minerals crystallize on their way back up and clog the pipes, and steam pressure causes severe wear on the system and can tear it apart.
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The insatiable appetite for energy that defines the artificial intelligence revolution has sparked a renewed boom in the field, with technology companies such as Google and Meta already signing long-term agreements to purchase this type of energy.
To boost output, new methods have been developed in recent years for extracting energy even from areas that lack the required natural conditions. In one approach, water is injected at high pressure into a hard rock layer deep underground until fractures form, allowing the water to penetrate and heat up.
In another approach, a closed-loop metal pipe system is inserted deep into the ground, and the water inside absorbs heat through the pipe walls. This method is more stable and reliable, but also more complex to implement.
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Another intriguing method is based on supercritical fluid.
A supercritical fluid exists at temperatures and pressures so extreme that the distinction between liquid and gas ceases to apply. It is as dense and energy-rich as a liquid, yet its viscosity resembles that of a gas, allowing it to penetrate even the tiniest cracks.
What makes supercritical fluid particularly fascinating is that, unlike ordinary water, it does not form and break internal hydrogen bonds — which means it can carry between 5 and 10 times more energy.
In certain locations on Earth, underground reservoirs of water in this state already exist, but no drill bit yet exists that is hard enough to reach them and survive the scorching temperatures encountered along the way.
To solve the drilling problem, unconventional methods are currently being explored — including drilling with high-power electrical pulses, jets of superheated gas, and even electromagnetic waves.
Electromagnetic wave drilling relies on high-energy millimeter-wavelength radiation. The energy of these waves melts and vaporizes the rock, and recent experiments have demonstrated that this method can drill up to 50 times faster than conventional drilling.
If an economically viable way to extract energy in this manner is found, it will be possible to build a power plant that supplies completely green energy anywhere on Earth — and the world as we know it will be transformed beyond recognition.
In the video: a geothermal power plant in Iceland.
Shabbat Shalom 😊
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👋 Hi, I'm Shlomo Strauss, and my posts are not written by artificial intelligence.
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