U

UNINTERRUPTIBLE POWER SUPPLY (UPS) A power supply providing continuous, uninterruptible service—commonly used in telecommunications and computer networks.

UPWIND In relation to a wind turbine, toward the wind. An upwind turbine has its blades on the upwind side of the tower.

UTILITY GRID Commercial electrical energy distribution system. Synonyms: Mains, Grid.

UTILITY-INTERTIE (UI) SYSTEM See GRID-TIE SYSTEM.