Principally retrofitting describes the measures taken in the manufacturing industry to allow new or updated parts to be fitted to old or outdated assemblies (like blades to wind turbines).
The production of retrofit parts is necessary in manufacture when the design of a large assembly is changed or revised. If, after the changes have been implemented, a customer (with an old version of the product) wishes to purchase a replacement part then retrofit parts and assembling techniques will have to be used so that the revised parts will fit suitably onto the older assembly.
Retrofitting is an important process used for valves and actuators to ensure optimal operation of an industrial plant. One example is retrofitting a 3-way valve into a 2-way valve, which results in closing one of the three openings to continue using the valve for certain industrial systems.
Retrofitting can improve a machine or system’s overall functionality by using advanced and updated equipment and technology—such as integrating Human Machine Interfaces into older factories.
Another example of this is car customizing, where older vehicles are fitted with new technologies: power windows, cruise control, remote keyless systems, electric fuel pumps, driverless systems, etc.
Trucks and agricultural machines can also be given retrofits to make them driverless.
The term is also used in the field of environmental engineering, particularly to describe construction or renovation projects on previously built sites, to improve water quality in nearby streams, rivers or lakes. The concept has also been applied to changing the output mix of energy from power plants to cogeneration in urban areas with a potential for district heating.
Sites with extensive impervious surfaces (such as parking lots and rooftops) can generate high levels of stormwater runoff during rainstorms, and this can damage nearby water bodies. These problems can often be addressed by installing new stormwater management features on the site, a process that practitioners refer to as stormwater retrofitting. Stormwater management practices used in retrofit projects include rain gardens, permeable paving and green roofs. (See also stream restoration.)