For over 150 years, Kirchhoff’s law of thermal radiation has stood as an undisputed principle in the field of physics. However, recent groundbreaking research conducted by Harry Atwater’s lab at the California Institute of Technology (Caltech) challenges this long-held belief. Through the development of an innovative device, the traditional relationship between an object’s absorbed and emitted efficiencies is shattered, holding significant implications for sustainable energy harvesting systems and the advancement of camouflage technologies.
Traditionally, Kirchhoff’s law of thermal radiation explains the equal connection between an object’s ability to absorb and emit energy in the form of electromagnetic radiation. This law dictates that the absorptive and emissive efficiencies are equal at every wavelength and angle of incidence. However, electrical engineering graduate student Komron Shayegan, the lead author of the new research, brings attention to a recent shift in the design of emitters and absorbers. The aim now is to move away from the conventional one-to-one equality between emissivity and absorptivity.
This decoupling of the two properties holds significant implications, especially in energy-harvesting systems. Take, for example, a photovoltaic (solar panel) that re-emits some of the absorbed energy back towards the energy source, the sun, as heat. This lost energy diminishes the efficiency of the system. However, by redirecting the emitted radiation towards another energy-harvesting object, it becomes possible to achieve higher energy conversion rates.
The device developed by Atwater’s lab serves as a breakthrough in the field. By placing the device in a moderate magnetic field, the equality between the absorptive and emissive efficiencies is disrupted. The device combines a material with a strong magnetic-field response and a patterned structure that enhances absorption and emission in the infrared wavelengths. Notably, the effect can be easily observed by heating the device above room temperature and comparing the emissive efficiency to the absorptive efficiency.
This pioneering research carries significant implications for various fields, particularly in sustainable energy harvesting. By breaking the tightly bound relationship between absorptive and emissive efficiencies, new possibilities arise for improving energy conversion rates. Through redirecting emitted radiation towards other energy-harvesting objects, higher efficiencies can be achieved in photovoltaic systems and other energy-harvesting technologies.
Beyond energy harvesting, this breakthrough also has profound implications for the development of advanced camouflage technologies. By manipulating an object’s emissive properties, it becomes possible to control its thermal signature, making it more challenging to detect using infrared imaging techniques. This development holds important applications in military and defense contexts, where effective camouflage can be vital for survival.
The revolutionary device created by Atwater’s lab challenges the long-established Kirchhoff’s law of thermal radiation. By decoupling absorptive and emissive efficiencies, new possibilities emerge in sustainable energy harvesting systems and the development of advanced camouflage technologies. This groundbreaking research paves the way for future innovations in the field of thermal radiation and its applications across various industries.
The groundbreaking invention developed by Harry Atwater’s lab at the California Institute of Technology (Caltech) disrupts the fundamental principle of Kirchhoff’s law of thermal radiation. This decoupling of the traditionally equal relationship between absorbed and emitted efficiencies opens up new possibilities in sustainable energy harvesting systems and the advancement of camouflage technologies. With this newfound knowledge, the potential for higher energy conversion rates and improved camouflage effectiveness in various industries becomes a tangible reality. The implications of this research are profound and pave the way for future innovations in the field of thermal radiation.
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