; and (B) uses mechanical, electrochemical, biochemical, or thermal processes— (i) to store energy generated at an earlier time for use at a later time; or (ii) to store energy generated from a mechanical process that would otherwise be wasted for delivery at a later time. (13) Federal clean energy credit The term Federal clean energy credit means a credit issued pursuant to subsection (e). (14) Generator The term generator means a unit or system of units that— (A) generates not fewer than 20 megawatt-hours of electric energy per calendar year; (B) delivers electric energy to the grid; and (C) is located in the United States. (15) Lifecycle greenhouse gas emissions The term lifecycle greenhouse gas emissions means the aggregate quantity of carbon dioxide equivalent emissions relating to the full lifecycle of electric energy production, including— (A) extraction, production, and distribution of fuels and materials for physical capital; (B) power generation and transmission; and (C) handling and disposal of waste, byproducts, and end-of-life materials. (16) Qualified combined heat and power system The term qualified combined heat and power system means a system that— (A) uses the same energy source for the simultaneous or sequential generation of electrical energy and thermal energy; (B) produces at least— (i) 20 percent of the useful energy of the system in the form of electricity; and (ii) 20 percent of the useful energy in the form of useful thermal energy; (C) to the extent that the system uses biomass, uses only qualified renewable biomass