The new harvesting device, which takes the form of two panels, has two functions. Like a conventional solar cell it absorbs energy from the Sun (energy harvesting) and turns this into power. The device also undertakes radiative cooling, when heat escapes. Radiative cooling is the process by which a body loses heat by thermal radiation. The process of simultaneously and synergistically harvesting energy from two thermodynamics resources – the Sun and space – has never been realized.
It is the cooling effect which is novel. Any object will lose heat in the form of infrared radiation. While most of this is reflected back, certain infrared wavelength can escape into space. The effect of this is that materials that emit infrared wavelength become cooler than the ambient air temperature. For a person, radiative cooling is commonly experienced on cloudless nights. Here frost or black ice can form on surfaces exposed to the clear night sky, even when the ambient temperature remains above freezing.
The new device succeeds in collecting energy from the Sun and cooling a structure at the same time. According to The Verge, the complexity with the development was with building object that is both hot and cold at the same time. This required the use of a vacuum chamber to surround the radiative cooler and to ensure that the heating and cooling parts do not interact.
With the two panels, the solar upper part of the device can be heated up to 24 degrees Celsius above the normal temperature, while the cooler part can reach 29 degrees Celsius below the ambient temperature, enabling the heating and cooling effect to occur. The device remains at the prototype stage, as built by the research team at Southeast University, Nanjing, China, although the initial results are promising.
The implications of the technology on energy use could be significant, especially where cooling is required. For example, air conditioning accounts for nearly fifteen per cent of the primary energy used by buildings in the U.S. This alone means that a new type of passive cooling system that cools without any electricity input would have a major impact on energy consumption.
The new research has been published in the journal Joule, with the paper titled “Simultaneously and Synergistically Harvest Energy from the Sun and Outer Space.”
