These moisture-sucking materials could transform air conditioning

A surprising set of materials could soon help make more efficient air conditioners that don’t overtax the electrical grid on hot days. As extreme heat continues to shatter records around the globe, electricity demand for air conditioning is expected to triple in the next few decades—an increase of about 4,000 terawatt-hours between 2016 and 2050,…
These moisture-sucking materials could transform air conditioning

Rather than small silica beads, Blue Frontier’s cooling technology relies on a salt solution that’s so concentrated, it can pull moisture from the air.  

Here’s how Blue Frontier’s cooling system works: first, a stream of air passes through a channel and over a thin layer of desiccant, which pulls moisture out of the air. Next, the now-dry air goes through an evaporative cooling step, which lowers the temperature of the air (basically the same way sweat cools your skin). 

In the evaporative cooling step, the air is split into two streams. One runs past a thin layer of water, which absorbs energy and drops the air’s temperature. That cooler, humid air is used to cool a metal surface, which in turn sucks heat out of the other stream of still-dry air. The humid air gets funneled outside, and the cool, dry air is blown into the building.

Evaporation is an efficient cooling method, one that’s employed in low-cost devices called air coolers (also referred to as swamp coolers or evaporative coolers), which can use 80% less electricity than standard air conditioners. These devices usually add moisture to the air to cool it, which only works when starting with dry air, so their use is typically limited to dry environments, like the southwestern US. 

By pairing evaporative cooling with desiccants, Blue Frontier’s system can work in virtually any climate, Tilghman says. Its operations can be tweaked to handle changes in the weather or in the thermostat set point, altering the balance between cooling and dehumidifying, which could help unlock further efficiency gains. The company’s approach should be able to cut annual electricity use by a total of between 50% and 80% compared with a conventional air conditioning system, depending on the environment, Tilghman says.  

On thin ice

Liquid desiccants are sometimes used today to dehumidify warehouses or factories that need to keep strict controls on moisture in the air, such as in pharmaceutical or electronics manufacturing. But they haven’t been widely used in cooling partly because they’re expensive. One industry standard, lithium chloride, has been subject to price hikes and supply limitations because of demand for it in lithium-ion batteries. The materials can also be corrosive. (Blue Frontier is using a new desiccant that should address those concerns, Tilghman says.)