The United States brings together many scientific and technological talents from all over the world, and many major scientific research achievements and scientific and technological inventions were born in the United States. According to foreign media reports, a start-up technology company called Quaise Energy in the United States has received $40 million in financing, which will be used to develop a technology called "wave drilling" proposed by the company.
Wave drilling, a new type of drilling technology, the company intends to use this technology to drill 20,000 meters underground to extract geothermal energy deep in the earth's crust.
The earth's interior is rich in geothermal energy reserves, and in the short term, geothermal energy is equivalent to unlimited energy for human beings. To obtain geothermal energy more efficiently, it is necessary to advance deep underground. Until controlled nuclear fusion technology can be delayed, if this technology can really achieve breakthrough results, it will bring about huge changes.
What is the "wave drill" that can drill 20,000 meters underground?
When it comes to drilling depth, the most well-known is the Soviet-era Kola ultra-deep drill, which reached a depth of 12,262 meters. Decades later, the deepest drilling depth still does not exceed 13,000 meters, and the Kola ultra-deep borehole is still one of the deepest drilling depths in the world.
The depth of 13,000 meters is difficult to break, and it is clear that the drilling technology has not been broken. For a long time, we have used mechanical drill bits to drill deep underground. When drilling, the drill bit rotates at high speed, and friction with the rock produces high temperatures; and the closer you are to the deeper underground, the closer you are to the magma and the higher the temperature. Therefore, no matter how hard the material of the drill bit is, it will eventually be quickly worn out and need to be constantly replaced, which is very costly.
To circumvent this problem, the technology proposed by Quaise Energy does not have a physical drill bit, but uses millimeter waves to drill. Millimeter wave is an electromagnetic wave with a wavelength of 1 to 10 mm, which is located in the region where microwaves and far infrared waves overlap, and has the characteristics of two kinds of spectrum. According to reports, the use of this high-power millimeter wave, the rock in front of the drill bit can be evaporated to achieve contactless drilling.
As planned, the company plans to drill a mix of mechanical drill bits in 2024 and also use the drill to get 100 megawatts of electricity by 2026.
Is this way of obtaining geothermal energy through drilling reliable?
The average thickness of the Earth's crust is about 17,000 meters, of which the land crust is thicker, with an average thickness of about 40,000 meters. Beneath the earth's crust is the mantle. The mantle is divided into the upper mantle and the lower mantle, and at the top of the upper mantle there is a circle layer called the asthenosphere, which is composed of molten rocks and is located below 70,000 to 100,000 meters above the surface. It is speculated that the temperature here has reached 1300 degrees Celsius, and the pressure is 30,000 times the atmospheric pressure on the surface. In a way, the Earth's crust floats on this soft asthenosphere.
For this circle of asthort material, or the part of the rock that is closer to the asthenosphere, even if wave drilling technology is used, it is impossible to drill, because just drill a little better, this space will immediately be filled by the surrounding high-pressure high-temperature material.
However, in order to efficiently obtain geothermal energy, it is not necessary to drill so deeply. The deeper you go, the hotter it gets, and as a rule of thumb, the temperature rises by about 2°C for every 100 meters. At 20,000 meters underground, where the temperature has reached 400 ° C, it is still no problem to boil the water.
Nuclear power generation requires boiling water, and the power of water vapor is used to drive the generator set to rotate to generate electricity. Geothermal power generation also requires such a conversion process. Quaise Energy's idea should be to inject water into this deep, deep hole, absorb a lot of geothermal heat, quickly evaporate to produce water vapor, and then use it to generate electricity.
First of all, it is important to be clear that geothermal energy is not unlimited. The heat in the Earth's interior comes mainly from the waste heat at the beginning of the Earth's birth, as well as the heat released by the long-term decay of radioactive material in the Earth's interior. The Earth is 4.5 billion years old, and the heat in the Earth's interior has been dissipating, and according to scientists' estimates, in about 2 billion years, the Earth's interior will cool down and become like Mars.
The reason why it is considered to be infinite is because the total reserves of geothermal energy in the earth's interior are so amazing that at the current level of human energy consumption, it will not be a problem to use it for hundreds of millions of years.
However, even if geothermal energy is almost unlimited energy, it is not possible for humans to use it indefinitely, because the earth's interior relies on heat transfer and heat convection. Continuously drawing geothermal heat from a drilled well, when the earth's internal heat transfer cannot keep up with the loss of geothermal heat, the geothermal well loses its role in a short period of time and needs to be replaced.
In fact, the most important thing to consider is the cost problem, or the input-output problem. Drilling such a deep hole, this drilling technology is the use of millimeter wave evaporation of rock, obviously requires a continuous and large energy input to maintain, if the final income is not enough, then the use of this way to generate electricity has become an unrealistic fantasy.