HVAC is an outdated business that has changed very little over the last 50 years, according to Jack Alvarenga, research scientist at the Wyss Institute.

He said the global demand for cooling continues to rise which is why it is time to address the environmental impact of cooling via new technology.

Alvarenga is working with a team at Harvard University’s Wyss lab on an innovative solution.

The vast majority of today's air conditioners still use mechanical vapor compression, which has not changed much since the 1920s, despite mounting environmental concerns.

It is a system that uses potent refrigerants and requires a lot of energy.

Indirect evaporative cooling (IEC) cools via the evaporation of water but IEC systems contain a heat exchange unit that isolates the evaporating water from the air removing heat without adding humidity.

The good news is that IEC systems require very little energy to run but they are difficult to manufacture due to the complexity of the heat exchange unit, which makes them expensive and their performance difficult to optimize.

The technology being trialled at Wyss is called cold-SNAP (Superhydrophobic Nano-Architectured Process), which uses up to 75% less energy than mechanical vapor compression air conditioners, and relies on water rather than refrigerants.

cold-SNAP achieves its high performance thanks to the integration of old and new: ceramic, one of the earliest, cheapest, and most widely available building materials; and a novel surface coating developed recently in the lab of Wyss Core Faculty member Joanna Aizenberg, Ph.D.

The coating's nanoscale roughness makes it super water-repellent and, when applied to a slab of highly water-absorbent ceramic, the result is a very efficient heating exchange unit that can effectively isolate evaporating water from cooled air.

Because ceramic is very malleable, an entire heating exchange unit can be produced via the extrusion or 3-D printing of a single piece, and its shape can be adjusted to maximize the surface area available for heat transfer and evaporation.

The hydrophobic coating is then selectively applied to the components that will manage the flow of dry air, coupled to a water pump, fan, and controls.

Preliminary studies have indicated that the cold-SNAP system can be up to four times more efficient than conventional air conditioners as measured by the Coefficient of Performance (COP).

The team is currently exploring different manufacturing techniques through a pilot study to see how the system performs in real-world hot and humid conditions.

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