Novel materials could make practical air conditioners and refrigerators that use little or no electricity.
It could soon be more practical to cool buildings using solar water heaters and waste heat from generators. That's because of new porous materials developed by researchers from the Pacific Northwest National Laboratory. These materials can improve a process called adsorption chilling, which can be used for refrigeration and air conditioning.
All refrigerators and air conditioners cool by evaporating a refrigerant, a process that absorbs heat. They differ in how that refrigerant is condensed so that it can be reused for cooling. Unlike the technology inside most air conditioners, which employs electrically driven compressors to mechanically compress the vaporized refrigerant, adsorption chillers use heat to condense the refrigerant. Adsorption chillers are typically far less efficient than chillers that use electrical compressors, and are bulky and expensive. But they have the advantage of being cheap to operate, since they require very little electricity. "If you have waste heat, you can run it for free," McGrail says.
So far these chillers have been limited to applications where there is a lot of waste heat—such as industrial facilities and power plants—or where electricity isn't always available. Cutting their size and cost could make them attractive in more applications, including in homes, where they could be run using hot water from solar heaters, McGrail says.
Since current adsorption chillers can be two or three times larger than chillers that use electric compressors, "cutting the size of adsorption chillers by 75 percent could make them competitive," says Yunho Hwang, a professor at the Center for Environmental Energy Engineering at the University of Maryland. The chillers could be particularly useful for cooling with hot water from solar water heaters, since adsorption chillers can use the relatively low-temperature such heaters produce, he says.
Source: TechnologyReview
