V

Vacuum Evaporation - The deposition of thin films of semiconductor material by the evaporation of elemental sources in a vacuum.

Vacuum Zero — The energy of an electron at rest in empty space; used as a reference level in energy band diagrams.

Valence Band — The highest energy band in a semiconductor that can be filled with electrons.

Valence Level Energy/Valence State — Energy content of an electron in orbit about an atomic nucleus. Also called bound state.

Varistor — A voltage-dependent variable resistor. Normally used to protect sensitive equipment from power spikes or lightning strikes by shunting the energy to ground.

Vented Cell — A battery designed with a vent mechanism to expel gases generated during charging.

Vertical Multijunction (VMJ) Cell — A compound cell made of different semiconductor materials in layers, one above the other. Sunlight entering the top passes through successive cell barriers, each of which converts a separate portion of the spectrum into electricity, thus achieving greater total conversion efficiency of the incident light. Also called a multiple junction cell. See multijunction device and split-spectrum cell.

Volt (V) — A unit of electrical force equal to that amount of electromotive force that will cause a steady current of one ampere to flow through a resistance of one ohm.

Voltage — The amount of electromotive force, measured in volts, that exists between two points.

Voltage at Maximum Power (Vmp) — The voltage at which maximum power is available from a photovoltaic module.

Voltage Protection — Many inverters have sensing circuits that will disconnect the unit from the battery if input voltage limits are exceeded.

Voltage Regulation — This indicates the variability in the output voltage. Some loads will not tolerate voltage variations greater than a few percent.