Creating devices can turn heat into electricity

Using metamaterials (metamaterials), scientists are developing a device capable of radiating infrared rays with controlled frequencies. They expect that in the future, this device will be able to recover excess heat from manufacturing operations to recycle into electricity.

Similar to visible light rays, infrared rays are also a form of electromagnetic radiation and they carry energy with them. It is possible that for example, blast furnaces, steel, metal . are high-power heat radiation sources and they often use electricity to burn furnaces. But because the efficiency of the incinerator is not high, most of this electricity is converted into thermal energy in the form of radiation and is wasted into the environment. Therefore, scientists have thought of how to reclaim this wasted heat to turn them into electricity and reuse them for other purposes. The technique of extracting heat radiation to convert into electricity is called thermophotovoltaics (TPV) , which is essentially similar to solar electricity.

The construction of a TPV device to turn heat into electricity.

But so far, TPV devices have basically been rarely used in practice because the heat range they can absorb is quite narrow, usually above 900 ° C. The cause of this situation is mainly in the absorption / radiation (absorb / emit) layer, which has a narrow working range. This detail leads to very low conversion efficiency from heat to electricity, insignificant for investment. Therefore, researchers at Duke University located in North Carolina (USA) desire to improve the situation, thereby helping TPV to be more applicable. In addition, it allows the creation of more efficient "infrared optical cloak" used to camouflage the thermal glass in military environments.

Willie J. Padilla, the lead researcher, described the nature of thermal radiation: "Because the amount of infrared radiation, which is intense, is controllable. So this new infrared radiation layer can be opened. "There is a new way to attract and reuse lost heat. There is a lot of interest in reusing excess heat, and our technology can improve this heat recovery process."

The core element of technology that Padilla and students expect is meta material . These are synthetic materials, which do not exist in nature but have some extremely special properties, which come from a different physical structure than the original structure of the original material. in nature. Specifically, Padilla's team has combined a meta-material designed for high-performance infrared radiation absorption and radiation, with mechanical microelectronic systems (MEMS). This combination has created a device with infrared properties that can be quickly changed based on a pixel scale.

Meta materials with "reverse" properties of ordinary materials in nature.

Named Optica, this infrared device consists of an 8 x 8 array of controllable pixels, each measuring 120 x 120 microns (0.12mm). Initial evaluation results show that Optica is capable of obtaining a fairly large infrared range with sampling frequencies up to 110 KHz. And the number could still increase further, allowing the team to create infrared robes to help distinguish the enemy / us in combat conditions.

But the most noticeable point compared to Optica's traditional TPV devices is that it can still change the emitted infrared radiation without any heating or cooling methods. Optica can still operate at normal temperatures where the supported radiation range is still not as narrow as old TPV devices. This allows Optica-based TPV devices to convert more infrared forms to electricity, from both the body heat to the car engine heat, which is quite low compared to the emitted temperature. from kilns or smelting metals.

The ability to radiate heat arbitrarily allows to create "invisible" camouflage layers of temperature.

In the future, the team is planning to increase the size of the MEMS layer to 128 x 128 pixels, allowing the device to be more applicable. From transforming infrared heat into electricity to hiding infrared radiation and the human body or vehicle, it helps soldiers to camouflage better before the enemy's thermal goggles.