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Category: energy

Microscale roughness breakthrough defies 80 years of fluid dynamics

Logically, you would think a sleek surface has optimal aerodynamics—but recent research at Tohoku University turns this fundamental principle on its head. Applying an irregular microscale surface texture reduced the aerodynamic drag of a test model. The innovation has potential applications in the design of fuel-efficient vehicles. The study is published in the Journal of Fluid Mechanics.

For more than 80 years, a fundamental principle of fluid dynamics has held that smoother surfaces produce less aerodynamic drag. However, a research group led by associate professor Aiko Yakeno at the Institute of Fluid Science, Tohoku University, has overturned this long-standing assumption. By applying Distributed Micro-Roughness (DMR)—irregular microscale surface textures—to a test model, the team achieved the world’s first experimental demonstration of up to 43.6% aerodynamic drag reduction.

By reducing drag in this innovative way, researchers may be able to reduce fuel consumption and CO₂ emissions across aviation, automotive, marine and rail transportation in the future.

Two-color lasers aim electron currents through semiconductor with no electric field

Researchers at the University of Michigan have created a device that enables them to control the flow of electrons through a semiconductor using only laser light—no electrical power source required. The device was built to explore fundamental physics and realize a previously unobserved behavior, but it could also open doors for new applications in areas that bridge optics and electronics, including sensing, imaging and telecommunications.

The paper is published in the journal Physical Review Letters.

The phenomenon could help improve how signals are sent through and between devices, as well as create new opportunities to store more information in those signals.

Scientists Broke a 160-Year-Old Law of Physics to Create Programmable Heat

There are certain laws of physics that heat must follow.

Take Kirchhoff’s law of thermal radiation, for example, which applies the idea of reciprocity to heat, and dictates that a surface’s ability to absorb heat at a specific angle and wavelength must also match its ability to emit heat at the same angle and wavelength.

It’s a rule that makes thermal energy difficult to control in ways we might like to, and although workarounds have been found before, they’re inefficient and volatile.

Transforming vibrations into clean fuels and chemicals through piezosynthesis

From ocean waves and flowing rivers to the systems used to transport and treat water, vibrations are everywhere. But can vibrations do more than just shake water? Can they split water or drive the production of useful chemicals from water? A research team led by Professor Sai Kishore Ravi from the School of Energy and Environment (SEE) at City University of Hong Kong (CityUHK) has successfully demonstrated how mechanical vibrations can be harnessed to drive the production of useful chemicals from water.

The team showcased these breakthroughs in two recent studies: one on vibration-driven hydrogen peroxide generation, published in Nature Communications under the title “Bulk polarization field and interfacial electron sink in MXene-modified iodine-doped Bi4Ti3O12 enhance piezocatalytic H2O2 generation”; and another on hydrogen production, published in Advanced Energy Materials under the title “Enhanced Lattice Polarization and Directed Charge Transport Toward Pt Surface Sites Accelerate the Volmer Step in Piezocatalytic H2 Evolution on Co-Doped BiFeO3.”

The studies contribute to the emerging field of piezosynthesis, where mechanical deformation in piezoelectric materials generates charges that can be directed to drive redox reactions in water. A key challenge is preventing the loss of these charges through recombination before they reach surface reaction sites.

Molecules stop carbon nanotubes clumping, unlocking record heat-to-electricity performance

QUT researchers have overcome a challenge that has limited next-generation energy-harvesting materials for more than two decades, opening the door to more powerful wearable electronics and new ways of turning wasted heat into electricity. The breakthrough centers on carbon nanotubes, which are flexible, conductive microscopic rods that have long shown promise for wearable technologies but have been difficult to control.

QUT researchers have developed a new molecular strategy that prevents the nanotubes from clumping together and losing performance, enabling a new benchmark for materials that convert heat directly into electricity.

Lead author and QUT PhD researcher Shanshan Zhou said the work established a new way of tackling one of the biggest challenges facing carbon nanotubes.

Quantum entanglement without transport: Leaky qubits offer route around noisy channels

The inevitable leakage of energy and information from a quantum system into its surrounding environment is the enemy of quantum technology. Now, researchers have demonstrated that it can be exploited to generate entanglement—the “resource” that quantum technologies use to perform tasks inaccessible to standard classical technologies.

A collaboration between physicists at the University of Illinois Urbana-Champaign and the University of Chicago has realized a theoretical prediction in which an externally driven quantum system achieves entanglement through dissipation. While the original prediction relies on highly idealized settings, the researchers developed a new technique called synthetic squeezing to realize the phenomenon in a laboratory setting with a pair of superconducting qubits.

Moreover, the generated entanglement is in a steady state, meaning that, in principle, it can be maintained indefinitely over arbitrarily large distances. The researchers believe that this technique holds promise as a more robust and reliable alternative to current methods of entanglement generation.

Why the actual fuel consumption of plug-in hybrids is often higher

Vehicles with plug-in hybrid drives are intended to facilitate the transition to electric mobility. They can cover shorter distances purely on electric power and offer a combustion engine as a backup for longer trips. According to Empa studies funded by the Swiss Federal Office for the Environment (FOEN), the actual proportion of purely electric driving depends heavily on usage—and, in particular, charging behavior. “If someone owns a plug-in hybrid and does not charge the vehicle regularly, that person is effectively driving a heavier vehicle with a combustion engine. Due to the additional weight of the battery and electric motor, consumption can even be higher than with a comparable conventional gasoline engine,” explains study author Miriam Elser.

Vehicle design is also crucial: Vehicle weight, drive design and battery size influence how efficiently a plug-in hybrid performs on the road.

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