Salt-driven air conditioner looks to slash energy

Hardware for the future of ACs? 7AC Technologies is designing a dessicant-driven air conditioner 

which uses half the energy of conventional ACs.

BOSTON--Startup 7AC Technologies hopes saltwater and high-tech plastic will lead to a more efficient air conditioner.

The Woburn, Mass.-based company is in the process of raising a $1.3 million round, expected to close in two months, to build a commercial prototype of its air conditioner design, said CEO Peter Vandermeulen earlier this week at the Conference on Clean Energy here.

By using a liquid dessicant to remove humidity from air, 7AC Technologies claims it can cut cooling costs by 50 percent to 75 percent and heating costs by about 50 percent. The company has a prototype in its lab and plans to beta test its efficient air conditioner with customers next spring, he said. Eventually, it intends to make a residential system, too, Vandermeulen said.

Traditional air conditioners run using a condenser, much like a refrigerator or heat pump, to remove moisture from the air to cool it. But there are a handful of companies, including Advantix Systems and ClimateWell, building air conditioners using dessicant materials in an effort to lower energy use.

7AC Technologies' air conditioner is designed around a series of flat, multi-layered plastic plates covered with a proprietary membrane licensed from the National Renewable Energy Laboratory. With water flowing inside each plate, a solution of salt water is sprayed over the surface of the plate. As the salt solution rolls down the surface of the plates, it attracts water vapor from humid air.

The salt water is then collected and passed through another set of plates which heat the solution and exhaust hot, moist air. Then, the salt solution, minus some water, is recirculated back toward the dehumidification plates, explained Vandermeulen.

The membrane, which is made out of polypropylene, is very porous so water can move in and out relatively easily, he said. "It's made using the same process they use to make garbage bags," he said. "Except if you saw it under a microscope, the plastic sheet would look like netting."

One of the advantages of the system is that it can operate using relatively low heat starting at only 100 degrees Fahrenheit. That means that heat could come from a variety of sources, including natural gas, solar panels, or even waste heat from a commercial building, Vandermeulen said.

With its funding, the company plans to build an air conditioner that could replace the existing systems on flat commercial rooftops. The system is a net user of water, but Vandermeulen notes that the on-site efficiency improvements mean that less water is used in central power generation.

The company had originally intended to market a system driven by heat from solar panels, which would cut the energy use even further. But the company decided to focus instead on the efficient air conditioning as its core technology. "When you talk about solar, investors start to pull their Blackberries out and lose interest," he said.