The Smart Roof made in USA saves energy all year round
Berkeley Lab researchers have developed a new smart device that, when fitted to the roofs of residential buildings, regulates the internal temperature according to the season
Innovation in the field of air conditioning: one of Berkeley Lab's latest research projects has shown that indoor temperature in homes can be regulated year-round, saving energy without using gas or electricity.
Developed by a team of scientists led by Professor Junqiao Wu, the new material called TARC (Temperature-Adaptive Radiative Coating) outperforms existing cool-roof systems for energy saving, by automatically regulating radiative cooling.
What’s the secret? Vanadium dioxide. The electrons in this metal make it a good conductor of electricity, although it does not conduct much heat. Like many other metals, when vanadium dioxide is below 67 degrees Celsius, it does not absorb thermal infrared light, but when it goes above that temperature, it starts to absorb thermal infrared light. This ability to switch from one phase to another – in this case from an insulator to a metal – is the main property of phase-change materials.
In order to test vanadium dioxide on a roofing system, Berkeley Lab scientists have designed a thin-film TARC device measuring 2cm x 2cm that in practice is very similar to adhesive tape, which can be laid on a hard surface such as a roof.
The testing of these smart roofs, involving several simulations across different climate zones in the United States, showed that TARC achieves very high performance in terms of energy savings in most of them.
"With the installation of TARC, an average US household could save up to 10 per cent of electricity," said co-research author Kechao Tang. "According to researchers' measurements, TARC reflects about 75 per cent of sunlight all year round, but its thermal output is high (about 90 per cent) when ambient temperature is warm (above 25 degrees Celsius or 77 degrees Fahrenheit), promoting heat loss to the sky. In colder climates, TARC's thermal emittance automatically drops to a minimum, helping to retain heat from solar absorption and indoor heating."
A big leap forward for the air conditioning industry, but Berkeley Lab researchers will not stop there: their intention is to develop more TARC prototypes on a larger scale, to carry out new experiments and further test their energy performance in rooftop systems.
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