Mechanical equipment used to generate cold water to cool the buildings. Conventional chillers use electricity as energy source, and the gas chillers use clean natural gas. While conventional chillers have a compressor and use refrigerators, gas chillers have an absorbent, a generator, a pump and an alternator heat, and don’t use CFC’s, hazardous substancies to the ozone. The absorption cycle uses water (refrigerant) and lithium bromide (absorbent). Some absorption chillers use ammoniac as refrigerant and water as absorbent.