A system for electromagnetically transferring heat from one region to another region. To cool one region in a chamber, antennas in the chamber to be cooled preferably have a broad beam to collect thermal radiation as much as possible within the chamber. Antennas to be used for heat pumping are preferably of high directivity where the antenna beam is pointed to a cold region such as the zenith of the sky. The system for electromagnetic heating is similar to that for electromagnetic cooling except heat flow is reversed. Here, the antennas outside a chamber have a highly focused beam to a hot area, such as the sun. The collected heat is channeled into an area to be heated by low-directivity antennas within an enclosed volume to be heated.

A system and method for operating a selective emitter is provided. One embodiment comprises a heat sink that absorbs heat from an ambient environment, a heat pipe comprising a cooling portion thermally coupled to the heat sink, a wick portion and a heat dissipation portion, and a selective emitter that is thermally coupled to the cooling portion of the heat pipe. The selective emitter converts absorbed heat into radiative energy that is emitted out through the Earth's atmosphere.

Various aspects as described herein are directed to a radiative cooling apparatuses and methods for cooling an object. As consistent with one or more embodiments, a radiative cooling apparatus includes an arrangement of a plurality of different material located at different depths along a depth dimension relative to the object. The plurality of different material includes a solar spectrum reflecting portion configured and arranged to suppress light modes, thereby inhibiting coupling of the incoming electromagnetic radiation, of at least some wavelengths in the solar spectrum, to the object at a range of angles of incidence relative to the depth dimension. Further, the plurality of material includes a thermally-emissive arrangement configured and arranged to facilitate, simultaneously with the inhibiting coupling of the incoming electromagnetic radiation, the thermally-generated electromagnetic emissions from the object at the range of angles of incidence and in mid-IR wavelengths.

Embodiments described herein relate a tunable heat transfer system. The tunable heat transfer system includes a controller, a first body, and a second body. The first body is communicatively coupled to the controller. The second body is communicatively coupled to the controller and spaced apart from the first body. The second body has a plurality of semimetal layers and a dielectric portion positioned between each of the plurality of semimetal layers. Each of the dielectric portions has a thickness to define a gap between each the plurality of semimetal layers in an expanded state and permitting each of the plurality of semimetal layers to abut each other in a contracted state. The controller is configured to change a near-field radiative heat transfer between the first body and the second body by changing the thickness of each of the dielectric portions between the expanded state and the contracted state.

Embodiments described herein relate to a bi-functional thermal cooling system. The bi-functional thermal cooling system includes a first body, a second body, and a third body. The second body has a first plurality of Weyl semimetal nanostructures. The second body is spaced apart from the first body. The third body has a second plurality of Weyl semimetal nanostructures. The third body is spaced apart from the second body. The second body and the third body are each configured to independently rotate with respect to the first body to change an optical property of the first plurality of Weyl semimetal nanostructures of the second body and an optical property of the second plurality of Weyl semimetal nanostructures of the third body.

Embodiments described herein generally relate a multi-mode heat transfer system. The heat transfer system includes an emitter device. The emitter device includes an inner core, a composite material pattern, and a surface coating pattern. The inner core is surrounded by an outer core having a thickness and an outer surface. The composite material pattern extends through at least a portion of the outer surface and at least a portion of the thickness of the outer core and is thermally coupled to the inner core. The surface coating pattern is on the outer surface and is changeable between a low emissivity state and a high emissivity state based on a surface temperature of the emitter device. In the low emissivity state, the emitter device transmits an omni-directional radiation and, in the high emissivity state, the emitter device transmits a focused radiation via the composite material pattern.

A material may be included in a cooling film or cooling panel to achieve cooling even under direct solar irradiation. The material includes one or more constituent materials and an outer surface configured to interact thermally with the atmosphere and with solar radiation. The material exhibits an emissivity of at least 0.8 in spectral range of 5 μm to 15 μm, an ultraviolet reflectivity of at least 0.5 in the spectral range of 275 nm to 375 nm, an ultraviolet absorptivity of at least 0.75 in the spectral range of 275 nm to 375 nm, or a combination thereof. A cooling film, or cooling panel, may be affixed to an exterior surface of a vehicle, structure, or system to provide cooling even under direct solar irradiance.

Systems and methods for radiative cooling and heating are provided. For example, systems for radiative cooling can include a top layer including one or more polymers, where the top layer has high emissivity in at least a portion of the thermal spectrum and an electromagnetic extinction coefficient of approximately zero, absorptivity of approximately zero, and high transmittance in at least a portion of the solar spectrum, and further include a reflective layer including one or more metals, where the reflective layer has high reflectivity in at least a portion of the solar spectrum.

A composite cooling film (100) comprises an ultraviolet-reflective multilayer optical film (120) and a reflective microporous layer (110) secured thereto. The ultraviolet-reflective multilayer optical film (120) hat is at least 50 percent reflective of ultraviolet radiation over a majority of the wavelength range of at least 340 but less than 400 nanometers. The reflective microporous layer (110) has a continuous phase comprising a nonfluorinated organic polymer and is diffusely reflective of solar radiation over a majority the wavelength range of 400 to 2500 nanometers, inclusive. The composite cooling film (100) has an average absorbance over the wavelength range 8-13 microns of at least 0.85. An article (1200) comprising the composite cooling film (100) adhered to a substrate (1210) is also disclosed.

Embodiments described herein relate to a system with an electroactive substrate, a plurality of nanoparticles, and a control unit. The plurality of nanoparticles deposited in communication with the electroactive substrate. The control unit is configured to manipulate a shape of the electroactive substrate between an unactuated mode and an actuated mode to change an absorption band or an emission band of the plurality of nanoparticles. When the electroactive substrate shape is manipulated, the absorption band or the emission band of the plurality of nanoparticles is changed to tune the system for a radiative cooling based on a current dominating wavelength.