Grid-connected photovoltaic power system Solar energy gathered by photovoltaic solar panels, intended for delivery to a power grid, must be conditioned, or processed for use, by a grid-connected inverter. Fundamentally, an inverter changes the DC input voltage from the PV to AC voltage for the grid. This inverter sits between the solar array and the grid, draws energy from each, and may be a large stand-alone unit or may be a collection of small inverters, each physically attached to individual solar panels. See AC Module. The inverter must monitor grid voltage, waveform, and frequency. One reason for monitoring is if the grid is dead
Mir Docking Module November, leaving STS-71 as the only Shuttle-"Mir" docking mission requiring "Kristall" to be relocated. In addition to simplifying space shuttle docking missions, "Mir"'s docking module was also used as a carrier for two new photovoltaic arrays, mounted to the module in boxes, which were later deployed on "Kvant"-1 during spacewalks. The first, the "Mir" Cooperative Solar Array, was jointly designed by NASA and Russia in order to test designs for the future International Space Station. The array was 42 m² in area, and provided 6.7 kW of power when installed on the station during expedition EO-21 in 1996. The array