Our air conditioners still draw on principles that are around 100-years-old, sucking up power in the process. Researchers from the National University of Singapore (NUS) are working on an alternative: water-based air conditioners. Their system doesn’t need energy-intensive compressors or harmful chemical refrigerants – and can cool air all the way down to 18 degrees Celsius, or 64.4 degrees Fahrenheit. Over 40 percent of the energy consumption of a building in the tropics goes to air conditioning, according to NUS associate professor Ernest Chua.