Within the EDGE framework, “waste heat recovery” from generators refers to capturing usable thermal energy from engine jacket water and exhaust gases that would otherwise be rejected to the environment. This recovered heat is a thermal resource, so it can directly serve end uses that require heat, such as space heating and domestic hot water heating. The curriculum also recognizes that recovered heat can indirectly support space cooling when it drives thermally activated cooling technologies, such as absorption chillers, where heat is used as the driving input to produce chilled water.

Mechanical ventilation, however, is fundamentally different. It is primarily an electrical end use because it relies on fans and motors to move air through ducts and provide required air changes. Thermal energy from recovered waste heat cannot power fan motors in the way electricity does. While waste heat might temper ventilation air through heat exchangers, that is not the same as being an energy source for the ventilation system itself. EDGE distinguishes between thermal end uses and electrical fan energy, so generator waste heat cannot be counted as a source of energy for mechanical ventilation.

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