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
Length of a module formal algebraic geometry. Let "M" be a (left or right) module over some ring "R". Given a chain of submodules of "M" of the form we say that "n" is the "length" of the chain. The length of "M" is defined to be the largest length of any of its chains. If no such largest length exists, we say that "M" has infinite length. A ring "R" is said to have finite length as a ring if it has finite length as left "R" module. The zero module is the only one with length 0. Modules with length 1 are