The Overnight capital cost is a term used in the power generation industry to provide a simplisitic comparison of the costs of building power plants.

Overtopping devices are long structures that use wave velocity to fill a reservoir to a greater water level than the surrounding ocean.

Physical safety markers placed on overhead transmission cables to aid in the sighting of the cables. Often used near airports, across rivers or other areas close to flight paths.

A method to transmit electricity through uninsulated cables that are suspended above ground from a tower.

A structure used in electrical power transmission consisting of uninsulated electrical cables being suspended by a tower.

Osmotic power, salinity gradient power or blue energy is the energy available from the difference in the salt concentration between seawater and river water.

These devices typically have one end fixed to a structure or the seabed while the other end is free to move.

Oscillating Water Column devices can be located onshore or in deeper waters offshore.

This type of winding structure creates an optimal fill factor (90.7%) for round wires.

An original equipment manufacturer (OEM) is generally perceived as a company that designs and manufactures engines and spare parts for those engines.

An organism is an entity capable of carrying on life functions.

An organic solar cell or plastic solar cell is a type of photovoltaic that uses organic electronics, a branch of electronics that deals with conductive organic polymers or small organic molecules, for light absorption and charge transport to produce electricity from sunlight by the photovoltaic effect.

An organic nuclear reactor, or organic cooled reactor (OCR), is a type of nuclear reactor that uses some form of organic fluid, typically a hydrocarbon substance like polychlorinated biphenyl (PCB), for cooling and sometimes as a neutron moderator as well.

Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments.

In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen bonds.

To make effective and efficient use of a resource

A schedule that producers use to anticipate future electricity demand, usualy 24 hours in advance of demand.

A commitment from large consumers to purchase electricity, usually a commitment made 24 hours in advance.

An optical coating is one or more thin layers of material deposited on an optical component such as a lens or mirror, which alters the way in which the optic reflects and transmits light.

A penalty imposed when the operational requirements are not met. This is usually a monetry value or credit from the supplier.