Photovoltaic mounting system Photovoltaic mounting system Photovoltaic mounting systems (also called solar module racking) are used to fix solar panels on surfaces like roofs, building facades, or the ground. These mounting systems generally enable retrofitting of solar panels on roofs or as part of the structure of the building (called BIPV). The solar array of a PV system can be mounted on rooftops, generally with a few inches gap and parallel to the surface of the roof. If the rooftop is horizontal, the array is mounted with each panel aligned at an angle. If the panels are planned to be mounted before the
Injective module proved a useful result, usually known as Baer's Criterion, for checking whether a module is injective: a left "R"-module "Q" is injective if and only if any homomorphism "g" : "I" → "Q" defined on a left ideal "I" of "R" can be extended to all of "R". Using this criterion, one can show that Q is an injective abelian group (i.e. an injective module over Z). More generally, an abelian group is injective if and only if it is divisible. More generally still: a module over a principal ideal domain is injective if and only if it is divisible