**W**
**Wafer**

Thin silicon slice (250 ÷ 350 thousandths of mm of thickness) made by sawing the ingots produced by melting scrap silicon of the electronic industry. It is a component of the PV cell.

**Watt [W]**

Unit of electric power. One Watt is the power developed or absorbed in a circuit fed by a current of 1 Ampere across a potential difference of 1 Volt. It is equal to 1/746 of Horsepower (HP).

**Watt-hour [Wh]**

Unit of energy. It is equal to a continuous output of 1 Watt per hour.

**Waveform**

The shape of the curve graphically representing the change in the AC signal voltage and current amplitude, with respect to time.

**Wind Energy**

The kinetic energy of wind converted into mechanical energy by wind turbines (i.e., blades rotating from a hub) that drive generators to produce electricity.