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.
Length of a module precisely the simple modules. For every finite-dimensional vector space (viewed as a module over the base field), the length and the dimension coincide. The length of the cyclic group Z/"n"Z (viewed as a module over the integers Z) is equal to the number of prime factors of "n", with multiple prime factors counted multiple times. A module "M" has finite length if and only if it is both Artinian and Noetherian. (cf. Hopkins' theorem) If "M" has finite length and "N" is a submodule of "M", then "N" has finite length as well, and we have length("N") ≤ length("M"). Furthermore,