R

Rated Battery Capacity — The term used by battery manufacturers to indicate the maximum amount of energy that can be withdrawn from a battery under specified discharge rate and temperature. See battery capacity.

Rated Module Current (A) — The current output of a photovoltaic module measured at standard test conditions of 1,000 w/m2 and 25 C cell temperature.

Rated Power — Rated power of the inverter. However, some units can not produce rated power continuously. See duty rating.

Reactive Power — The sine of the phase angle between the current and voltage waveforms in an alternating current system. See power factor.

Recombination — The action of a free electron falling back into a hole. Recombination processes are either radiative, where the energy of recombination results in the emission of a photon, or nonradiative, where the energy of recombination is given to a second electron which then relaxes back to its original energy by emitting phonons. Recombination can take place in the bulk of the semiconductor, at the surfaces, in the junction region, at defects, or between interfaces.

Rectifier — A device that converts alternating current to direct current. See inverter.

Regulator — Prevents overcharging of batteries by controlling charge cycle-usually adjustable to conform to specific battery needs.

Remote Systems — See stand-alone systems.

Reserve Capacity — The amount of generating capacity a central power system must maintain to meet peak loads.

Resistance (R) — The property of a conductor, which opposes the flow of an electric current resulting in the generation of heat in the conducting material. The measure of the resistance of a given conductor is the electromotive force needed for a unit current flow. The unit of resistance is ohms.

Resistive Voltage Drop — The voltage developed across a cell by the current flow through the resistance of the cell.

Reverse Current Protection — Any method of preventing unwanted current flow from the battery to the photovoltaic array (usually at night). See blocking diode.

Ribbon (Photovoltaic) Cells — A type of photovoltaic device made in a continuous process of pulling material from a molten bath of photovoltaic material, such as silicon, to form a thin sheet of material.

RMS — See root mean square.

Root Mean Square (RMS) — The square root of the average square of the instantaneous values of an ac output. For a sine wave the RMS value is 0.707 times the peak value. The equivalent value of alternating current, I, that will produce the same heating in a conductor with resistance, R, as a dc current of value I.