“It's not the heat, it's the humidity,” as a father somewhere said.
Your kids might frown, especially if they've ever spent a summer in the desert Southwest, but Dad is at least partly right: High humidity not only makes people less comfortable, it also puts a strain on air conditioners; half of the power used by a typical air conditioner is used to remove moisture from the air.
Air conditioning is a major concern for companies like Amazon, Walmart, UPS and FedEx, who operate huge warehouses where temperatures can become uncomfortably, or even dangerously, high.
One startup is trying to solve the humidity problem: Transera is developing a unique air conditioner for homes and apartments that uses special materials to remove moisture before cooling the air. More than 2 billion people still lack access to air conditioning in hot, humid regions, so the company hopes the air conditioner will help meet demand and reduce the amount of energy needed.
But it's starting by fine-tuning its product for consumers while it rolls out larger units for warehouses and other commercial buildings. On Tuesday, the company told TechCrunch exclusively that it had installed its first unit on a customer's roof. The dedicated outdoor air system (DOAS) dehumidifies fresh air entering a building, reducing the strain on air conditioners.
Transaera's DOAS unit is loaded onto a flatbed, with the team demonstrating the scale. Image courtesy of Transaera
“DOAS is a small part of the market, but it's a growing space,” co-founder and CEO Sorin Grama told TechCrunch. “It's just easier to get into.”
The Somerville, Massachusetts-based startup was founded in 2017 and has raised $7.5 million to date, including a $4.5 million seed round, according to Grama, and is currently raising $6 million to support field testing of its device.
Transera's core technology is a proprietary material that coats the heat pump's heat exchanger, which is similar to a car radiator. In a Transera DOAS, air enters the unit and passes over a special material that removes moisture from the air. The dry air then hits an evaporator coil, which cools the air to match the temperature inside the building.
Air conditioners and dehumidifiers generate heat in the process of removing moisture from the air. Normally that heat would be wasted, but Transera reuses it to remove moisture from a desiccant attached to a porous wheel. As the wheel passes over the incoming air, it absorbs the moisture. The packed desiccant then moves away from the incoming air and passes over the waste heat leaving the evaporator coil. The warm air carries the unwanted moisture outside. In the winter, the system runs in reverse, helping to maintain humidity inside as the heat pump warms the incoming air.
Many other DOAS systems currently installed on commercial rooftops also use heat pumps to dehumidify the incoming air, but because they use low temperatures to condense water on the coils, the air that comes out can be overly cooled compared to the air inside the building (especially in the spring and fall, when temperatures aren't warm enough to require air conditioning). The unit then has to reheat the air, often using natural gas. “It's a very inefficient and stupid way to run a dedicated outdoor air system,” Grama says.
Transaera's approach could save up to 40% more energy than today's top-of-the-line DOAS, Grama says. For now, the company's technology has been installed on commercial rooftops, but Grama says there are plans to install more. There's urgency: Removing moisture requires so much energy that it accounts for 1% of total greenhouse gas emissions, according to a recent study. That's about half the amount emitted by the aviation industry, which is subject to much more scrutiny. Reducing energy use for dehumidification by 40% would go a long way toward reducing this. And your dad would agree.