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.
Galois module Z), as can be deduced from the theory of Gaussian periods (the Hilbert–Speiser theorem). On the other hand the Gaussian field does not. This is an example of a "necessary" condition found by Emmy Noether ("perhaps known earlier?"). What matters here is "tame" ramification. In terms of the discriminant "D" of "L", and taking still "K" = Q, no prime "p" must divide "D" to the power "p". Then Noether's theorem states that tame ramification is necessary and sufficient for "O" to be a projective module over Z["G"]. It is certainly therefore necessary for it to be a "free" module.