A pyranometer is a type of actinometer used for measuring solar irradiance on a planar surface and it is designed to measure the solar radiation flux density (W/m2) from the hemisphere above within a wavelength range 0.3 μm to 3 μm.

PUREX (plutonium uranium reduction extraction) is a chemical method used to purify fuel for nuclear reactors or nuclear weapons.

A pumpjack is the overground drive for a reciprocating piston pump in an oil well.

A hydroelectric power plant that stores water above the level of the plant. During, usually, peak demand and therfore expensive electricity cost the water is released into another storage lower down. During off peak times the water is pumped back up to the upper water storage.

A pulverizer or grinder is a mechanical device for the grinding of many different types of materials.

A pulverized coal-fired boiler is an industrial or utility boiler that generates thermal energy by burning pulverized coal (also known as powdered coal or coal dust since it is as fine as face powder in cosmetic makeup) that is blown into the firebox.

Public works are a broad category of infrastructure projects, financed and constructed by the government, for recreational, employment, and health and safety uses in the greater community.

Psychrometrics, psychrometry, and hygrometry are names for the field of engineering concerned with the physical and thermodynamic properties of gas-vapor mixtures.

The first commercial concentrating solar power tower located in Spain producing 11 megawatts of electricity with 624 heliostats.

Proved reserves are the highest valued category.

In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected.

The prospective short-circuit current (PSCC), available fault current, or short-circuit making current is the highest electric current which can exist in a particular electrical system under short-circuit conditions.

IEC 61140 defines a PELV system as "an electrical system in which the voltage cannot exceed ELV under normal conditions, and under single-fault conditions, except earth faults in other circuits".

Propane is a three-carbon alkane with the molecular formula C3H8.

Neutrons born within 10−14 seconds of the fission are termed "prompt neutrons".

In nuclear engineering, prompt criticality describes a nuclear fission event in which criticality is achieved with prompt neutrons alone and does not rely on delayed neutrons.

A company, team or individual that manages a complete project on behalf of a client.

Project cycle management is the process of planning, organizing, coordinating, and controlling a project effectively and efficiently throughout its phases, from planning through execution then completion and review to achieve pre-defined objectives or satisfying the project stakeholder by producing the right deliverable at the right time, cost and quality

A project is a temporary endeavor designed to produce a unique product, service, or result with a defined beginning and end undertaken to meet unique goals and objectives, typically to bring about beneficial change or added value.

A programmable logic controller (PLC) is an industrial digital computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, robotic devices, or any activity that requires high reliability, ease of programming, and process fault diagnosis.