Absorption refrigeration in HVAC systems is a type of cooling system that uses a heat source, such as natural gas, to drive the cooling process. This type of system does not require electricity to operate, making it an attractive option for many HVAC applications. In contrast, vapor compression systems use electricity to drive the cooling process. Vapor compression systems are more efficient than absorption refrigeration systems, but require more energy to operate. Additionally, vapor compression systems require more maintenance than absorption refrigeration systems, as they are more complex and require more frequent servicing.