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
Injective module number of results are known, . Let "S" and "R" be rings, and "P" be a left-"R", right-"S" bimodule that is flat as a left-"R" module. For any injective right "S"-module "M", the set of module homomorphisms Hom( "P", "M" ) is an injective right "R"-module. For instance, if "R" is a subring of "S" such that "S" is a flat "R"-module, then every injective "S"-module is an injective "R"-module. In particular, if "R" is an integral domain and "S" its field of fractions, then every vector space over "S" is an injective "R"-module. Similarly, every injective "R"["x"]-module is an