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
Generating set of a module ideal "m" and residue field "k" and "M" finitely generated module. Then Nakayama's lemma says that "M" has a minimal generating set whose cardinality is formula_3. If "M" is flat, then this minimal generating set is linearly independent (so "M" is free). See also: minimal resolution. A more refined information is obtained if one considers the relations between the generators; cf. free presentation of a module. Generating set of a module In algebra, a generating set "G" of a module "M" over a ring "R" is a subset of "M" such that the smallest submodule of "M" containing "G" is