Photovoltaic system in northern climes to 5.61 kWh/m²/day in the sunniest regions. For large systems, the energy gained by using tracking systems can outweigh the added complexity (trackers can increase efficiency by 30% or more). For very large systems, the added maintenance of tracking is a substantial detriment. Tracking is not required for flat panel and low-concentration photovoltaic systems. For high-concentration photovoltaic systems, dual axis tracking is a necessity. Pricing trends affect the balance between adding more stationary solar panels versus having fewer panels that track. When solar panel prices drop, trackers become a less attractive option. Systems designed to deliver alternating
Module (mathematics) to zero by "f". The isomorphism theorems familiar from groups and vector spaces are also valid for "R"-modules. The left "R"-modules, together with their module homomorphisms, form a category, written as "R"-Mod (see category of modules for more.) This is an abelian category. Finitely generated. An "R"-module "M" is finitely generated if there exist finitely many elements "x", ..., "x" in "M" such that every element of "M" is a linear combination of those elements with coefficients from the ring "R". Cyclic. A module is called a cyclic module if it is generated by one element. Free. A free "R"-module