Rooftop photovoltaic power station Rooftop photovoltaic power station A rooftop photovoltaic power station, or rooftop PV system, is a photovoltaic system that has its electricity-generating solar panels mounted on the rooftop of a residential or commercial building or structure. The various components of such a system include photovoltaic modules, mounting systems, cables, solar inverters and other electrical accessories. Rooftop mounted systems are small compared to ground-mounted photovoltaic power stations with capacities in the megawatt range. Rooftop PV systems on residential buildings typically feature a capacity of about 5 to 20 kilowatts (kW), while those mounted on commercial buildings often reach 100 kilowatts or more.
Injective module Injective module In mathematics, especially in the area of abstract algebra known as module theory, an injective module is a module "Q" that shares certain desirable properties with the Z-module Q of all rational numbers. Specifically, if "Q" is a submodule of some other module, then it is already a direct summand of that module; also, given a submodule of a module "Y", then any module homomorphism from this submodule to "Q" can be extended to a homomorphism from all of "Y" to "Q". This concept is dual to that of projective modules. Injective modules were introduced in and are