The tremendous technological advances in geothermal energy
Solar energy and wind energy are the leading renewable energies, although there are still drawbacks such as the continuous availability of energy, storage, and transportation. In addition, the solutions proposed to improve their use are still sometimes expensive, such as the price of some batteries for example.
However, the Earth has an almost unlimited energy resource, continuously available in the depths of the earth’s underground. The start-up Quaise Energy, born at MIT in 2018 and which has just received $40 million in funding, proposes to use a new drilling technology that is powerful enough to reach a sufficient depth to recover the heat that the center of the Earth stores.
The principle developed to drill toward the planet’s heart is to vaporize the rock instead of breaking it. This technique requires replacing the tips of traditional drills with millimeter wave light beams, without contact with the stone. These drills can penetrate up to 20 kilometers into the Earth’s crust, at a depth where the rock reaches a temperature of 350˚C.
The recovered water would then be sucked out and turned into steam and energy. To make this project a reality, Carlos Araque, the co-founder, and CEO of the start-up recognizes that it remains to prove that the technology works and, for that to happen, to manage to drill to such a depth.
Until recently, geothermal energy was not the object of particular attention because its exploitation depends on specific conditions. In Iceland, for example, whose electricity grid is primarily geothermal, lava from volcanoes and water from the ocean meet almost at the surface, and there is no need to drill to recover the water vapour and transform it into energy.
Conventional geothermal power plants are installed according to natural conditions to recover steam from crevices in the rock at depth to power turbines to generate electricity.
In contrast, new advanced geothermal systems, EGS, seek to create the conditions to recover steam from underground. EGS will fracture the rock with a high-pressure fluid, using the same principle as hydraulic fracturing used in the oil industry. However, unlike the oil industry, EGS uses fluids with a lower risk of groundwater pollution and creates smaller fractures with less pressure, thus limiting the risk of seismic activity.
The principle developed by Quaise Energie is different because it requires hitting the rock at a depth where the temperature is even higher. At this level of temperature and pressure, the water goes to the supercritical state in which it acquires new capacities and contains 4 to 10 times more energy per unit of mass, allowing it to double its conversion into electricity.
Recovering water at these depths means recovering more energy and producing more electricity no matter where on the planet you are. With traditional techniques, the temperature of the rock rises with the drilling time, which eventually causes the electronics to overheat and the drills to pull out and have to be replaced regularly.
But at these depths, the time needed for these operations would be much too significant, especially to bring the drills up and down. To solve this difficulty, Quaise Energy based itself on the work of Paul Woskov of MIT on non-contact drilling. The principle is to drill the rock without touching it thanks to millimeter waves, a high frequency electromagnetic frequency, of the microwave type, generated by a gyrotron on the surface.
The microwave beam is injected into the drill hole with a gas such as nitrogen, air or argon, and will vaporize the rock layers. The gas will then bind to the vaporized rock and bring it to the surface as an ash cloud. Quaise Energy hopes to start drilling in 2024, gradually increasing the depth. If this technology works, it would be possible to use conventional power plants by adapting them for geothermal energy.
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