SF Technotes

Unlimited Energy beneath Our Feet

By Michael Castelluccio
July 26, 2022
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Drill deep enough underground or submerge deep-sea turbines into the right ocean currents, and you might tap almost endless terawatts of clean energy.

 

That’s the shared goal of a geothermal project in upstate New York by Quaise Energy, which is based in Boston, Massachusetts, and by the IHI Corporation working in the Kuroshio current off the coast of eastern Japan. Quaise is attempting to drill the deepest hole yet through Earth’s crust to tap the heat energy below for a new geothermal source, and IHI is testing its underwater turbines in the current that flows off the coast, capturing the force of the thermohaline circulation of the Kuroshio current.

 

Image/Quaise Energy

 

CLEAN GEOTHERMAL

 

In 2018, a small company spun out from the Plasma Science and Fusion Center at Massachusetts Institute of Technology (MIT). Called Quaise Energy, the company embarked on an effort to create the deepest geothermal system by boring down to 20 kilometers (12.427 miles) where the temperatures are around 500 degrees Celsius (932 degrees Fahrenheit) and geothermal energy becomes far more efficient than anything existing today. A senior fusion research engineer at MIT, Paul Woskov said that extracting just 0.1% of that energy could supply the entire world’s energy needs. Loz Blain, reporting in newatlas.com, describes that type of geothermal as “a rare example of totally reliable, round-the-clock green power generation. The Sun stops shining, the wind stops blowing, but the rock’s always hot.”

 

Image courtesy Quaise Energy

 

The primary challenge for Quaise is to invent drilling equipment sturdy enough to sink the boreholes. To date, the deepest hole drilled by man is the Kola Well in Russia, and it took 20 years to reach 40,318 feet. At that point, the temperatures reached 180 degrees C (356 degrees F) instead of the expected 100 degrees C (212 degrees F), and drilling deeper was deemed unfeasible.

 

The Quaise Energy team is at an abandoned coal power plant in upstate New York where they hope to use new drilling techniques to ultimately retrofit a new power plant using geothermal energy. Their drilling rig has both conventional rotary bits for the softer materials and a gyrotron-powered energy beam that’s able to melt and vaporize harder materials. Nuclear fusion research has helped develop gyrotrons capable of continuous beams with more than a megawatt of power, and the penetration rate of these drills can be 70 meters/hour (230 feet/hour). The high-power linear-beam vacuum tubes generate millimeter-wave electromagnetic waves with vaporizing strengths. The team believes it will take only 100 days to reach their 20-kilometer goal.

 

Along with the benefits of clean cogeneration of heat and electricity, at this depth, the millimeter wave drilling will remove the entanglement of geopolitics that shrouds fossil fuels. Quaise describes the potential for universal access to this resource. “Deeper geothermal is more universal. At these depths, we can reach geothermal anywhere on Earth, making it a truly global energy source. It provides a path to energy independence for every nation.” And hotter geothermal has more power density. According to Quaise, “At these temperatures (500 degrees C/932 degrees F), geothermal is so powerful that it can repower most fossil-fired power plants around the world. It enables a much faster energy transition.”

 

Quaise projects the following goals for future progress:

 

 

OCEAN CURRENTS

 

The heavy-machinery manufacturer IHI Corporation of Japan has demonstrated the world’s largest ocean-current turbine called Kairyu, a 100 kW-class ocean-current power generator. The system is designed for use in the Kuroshio, one of the world’s most powerful ocean currents. IHI engineers estimate, “If the energy present in the Kuroshio could be harnessed, it would amount to approximately 205GW, which is comparable to Japan’s total electric power generation.” The Kuroshio, off the eastern coast of Japan can be up to 100 kilometers across, wide enough to accommodate a large-scale power-generation farm.

 

Positioning the turbines in the currents (Images courtesy of IHI)

 

Ocean currents are generated by salinity. The salt content of the waters at the poles increases as the sea water freezes because the ice can’t contain salt, and the denser waters sink toward the ocean floor. The process is called thermohaline circulation because these dense streams are pushed toward the equator as more water sinks at the poles. The winds at the equator cause upwelling, which creates a pulling force for the polar streams. The flow completes a return as the currents move northward and more cold water sinks at the poles and the warmer equatorial waters loop toward the vacated polar spaces. The immense Kuroshio current can travel up to 75 miles a day pulling a water volume of 6,000 large rivers. Like winds, this massive movement can be used to activate turbines and generators, but unlike wind or tidal currents, thermohaline currents flow with a consistent power that’s unaffected by weather. Another advantage of ocean current power is that, unlike solar and wind, it doesn’t need large grid-level batteries to keep the output consistent. The current flows indifferent to dark nights or surface storms.

 

In June 2022, Will Lockett reported in medium.com on the current progress of IHI’s Kuroshio project. He writes that the company has tested and validated the concept and is now “looking to move up to a full-scale near-production prototype.” This will involve rigs 40 meters across with two turbines on a floating platform. The next prototype will be capable of 2 megawatts, 2,000 times more capable than the Kairyu model. The final step plans for a farm with 100 units to produce 200 megawatts.

 

Our current renewable energy sources—wind, solar, and batteries—share the same vulnerability. They’re variable because night, weather, and climate can seriously influence their availability. Harnessing ocean currents also can be affected by climate change because warming the oceans will slow the currents, but deep geothermal seems to be the most immune to the damage we continue to inflict on our environment. The effort to convert the upstate power plant from coal fires to planetary fires ultimately might be the most important engineering experiment of our generation.

 



Michael Castelluccio has been the technology editor for Strategic Finance for 26 years. His SF TechNotes blog is in its 23rd year. You can contact Mike at mcastelluccio@imanet.org.


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