Sun path, sometimes also called day arc, refers to the daily and seasonal arc-like path that the Sun appears to follow across the sky as the Earth rotates and orbits the Sun. The relative position of the Sun is a major factor in the heat gain of buildings and in the performance of solar energy systems.

Sun-free photovoltaics is a photovoltaics technology which does not require sunlight to produce electricity.

A portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light.

A wide area network that is international or trans continental.

A high-capacity capacitor with a capacitance value much higher than other capacitors, but with lower voltage limits, that bridges the gap between electrolytic capacitors and rechargeable batteries

A supercharger is an air compressor that increases the pressure or density of air supplied to an internal combustion engine.

Superconducting electric machines are electromechanical systems that rely on the use of one or more superconducting elements.

Superconducting magnetic energy storage systems store energy in the magnetic field created by the flow of direct current in a superconducting coil which has been cryogenically cooled to a temperature below its superconducting critical temperature.

Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material.

Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid.

Supercritical steam – up to the 1,000–1,050 °F (538–566 °C); requires advanced materials.

A supercritical steam generator is a type of boiler that operates at supercritical pressure, frequently used in the production of electric power.

The supercritical water reactor is a concept Generation IV reactor, mostly designed as light water reactor that operates at supercritical pressure (i.e. greater than 22.1 MPa).

Superfluidity is the characteristic property of a fluid with zero viscosity which therefore flows without any loss of kinetic energy.

In physics, superheating is the phenomenon in which a liquid is heated to a temperature higher than its boiling point, without boiling.

Superheated steam is steam at a temperature higher than its vaporization point at the absolute pressure where the temperature is measured.

Superheated water is liquid water under pressure at temperatures between the usual boiling point, 100 °C (212 °F) and the critical temperature, 374 °C (705 °F).

The superposition principle, also known as superposition property, states that, for all linear systems, the net response caused by two or more stimuli is the sum of the responses that would have been caused by each stimulus individually.

Supersaturation occurs with a chemical solution when the concentration of a solute exceeds the concentration specified by the value equilibrium solubility.

A decked structure on the freeboard deck extending from side to side or with the side plating not inboard of the shell plating more than 4% of the breadth (B), (ICLL).