Air Conditioning

Air conditioning is the process of removing heat from an enclosed space to make its interior more comfortable, often while also controlling humidity, and can be achieved by mechanical air conditioners or by passive and ventilative cooling methods. Most mechanical systems use vapor-compression refrigeration, circulating a refrigerant through a cycle of phase changes between liquid and gas to move heat, typically through an outdoor condenser, an indoor evaporator, a compressor and an expansion valve. Willis Carrier built the first modern electrical air conditioning unit in 1901, and the technology spread through the twentieth century to reshape both industry and daily life. Air conditioning is credited with averting roughly 190,000 heat-related deaths annually, but current systems also consume about seven percent of global electricity and produce about three percent of greenhouse gas emissions.