- Radiation heaters
- Industrial process heating, e.g., curing
- Food processing
Lawrence Berkeley National Laboratory led by Ravi Prasher have developed a near infrared heater that is more efficient and increases human comfort in building heating applications, compared to current devices. The technology promises to increase manufacturing productivity and energy efficiency in manufacturing applications.
Specifically, the Berkeley Lab heater technology is a photonic device that predominately radiates in the near infrared (NIR) range of electromagnetic wavelengths (0.7˜3 um). More specifically, the invention relates to the multilayered stack, which can either be used as standalone photonic device or can be coated onto different host structures or substrates to turn them into the photonic devices.
Radiative heaters such as infrared (IR) heaters are readily available in the market, however they suffer from two fundamental problems: (1) The visible appearance of IR heaters greatly impacts the aesthetics of building interiors. As a result, these heaters have only been popular in outdoor and warehouse applications, where convective heating is impractical, and (2) IR heater coils for space heating are typically made of Nichrome, which operate at ˜800 degree C. The emission peak of these IR heaters is at ˜3 um, which coincides with strong liquid water absorption. Due to water absorption overhead, infrared heaters tend to overheat the exposed areas of the human body (face and head) and underheat the clothed areas (feet and legs), creating discomfort and skin dehydration.
In manufacturing applications, the generally used UV curing technology suffers from a high system cost and is subject to the photochemical reaction, and the IR radiation curing technology is not very effective due to its very small penetration depth into the material. In addition, recent research has also shown that if the radiative energy is absorbed in the top few microns of the coating. film formation may occur before full removal of solvents, which affects the film quality. This makes long wavelength IR radiation (>3 um) undesirable in coating curing processes.
Previous work has demonstrated structures with spectral selectivity over a wide range of wavelengths. There are other works which designed an optical structure that is transmissive in the visible range of light (0.4-0.7 μm) and highly reflective in the near infrared and infrared range. These inventions demonstrated photonic crystal designs that transmit desired visible light, which increase the efficiency of a visible light source.
Other works have designed devices for selective infrared transmissivity over a range of wavelengths, while reflecting visible light. However, no other work has aimed specifically at spectral selectivity in the near infrared range between 0.7 and 3 μm for the applications mentioned above. In addition, the prior work regarding spectrally selective infrared filters and emitters employed materials that lack thermal, chemical and mechanical stability at high operating temperatures. The Berkeley Lab technology is the first spectrally selective near infrared transmitters/emitters that operate at high temperatures associated with the noted industrial applications.
STATUS: Published U. S. Patent Application 15/878,885 (Publication No. US2018-0220491). Available for licensing or collaborative research.