1) Scheme 2) System 
Any one of several components in a photovoltaic system (i.e., array, controller, batteries, inverter, load).
An element of a system that, in itself may constitute a system.
[n] - a system that is part of some larger system
noun a system that is part of some larger system
In computing, hardware and/or software that performs a specific function within a larger system. Silicon Graphics, for example, uses subsystems to perform the many calculations needed for computer animation
a secondary or subordinate system.