Glossary letter P

Parabolic Trough Power Plant (PTPP)

A solar power plant featuring an electro-solar system comprised of a number of parallel rows of trough collectors rotating on a horizontal axis, which enables them to follow the sun's course. The troughs focus the sun's heat on an axial tube containing a heat transfer fluid (HTF). Once the fluid reaches a high temperature (up to 500°C for some fluids), it flows to a water system, where it releases its heat to produce steam. The steam then drives a turbine and generates power.

Paralic Coal Basin

Sedimentary basin that originated near the sea, often taking the form of large, elongated lagoons parallel to the coast.

Parts Per Million (ppm)

Dimensionless quantity representing 10-6 (1 to 1 million). This proportion can be used for both weight (mass) and volume. For example, 400 ppm (or more precisely, ppmv – parts per million by volume) of CO2 in the atmosphere means an average concentration of 0.4 milliliters of carbon dioxide per 1 liter of air.

Passive Solar Architecture

Design intended to efficiently harness solar energy in buildings or homes. It focuses on shape, orientation, insulation, component quality and ventilation.

Peak Watt

Unit used to rate the performance of photovoltaic systems. It corresponds to output of 1 W of electrical power under standardized conditions (1,000 W/m² of solar insolation and temperature of 25°C).


Refers to the ability of a rock to transmit fluids. It is a critical factor in production, because it determines the flow rate of oil and gas wells. Permeability is typically measured in darcys (D) or millidarcys (mD).


Petrochemistry is the branch of chemistry that studies the conversion of crude and natural gas into useful products or raw materials oil derivatives. It is applied in the manufacture of many everyday products.

Petroleum Cut (Fraction)

A product obtained through the fractional distillation of oil. Crude oil is heated to 370°C before transfer to a column where it separates naturally as the vapor gradually condenses as it rises. The heaviest components (bitumen and wax) collect first at the bottom, followed by heavy fuel oil, fuel oil, diesel, kerosene, naphtha and finally gas (LPG), each one higher up the column.


Particle associated with electromagnetic radiation and the quantum of light. It is electrically neutral and has zero mass and very low energy (of around 2 eV).


Process used by plants to fuel their growth. Light energy from the Sun is utilized to convert carbon dioxide and water into carbohydrates (sugars) and oxygen.

Photovoltaic Cell (Solar Cell)

Electronic component that converts energy from sunlight into electricity.

Photovoltaic Collector

A photovoltaic solar collector converts sunlight (photons) into electricity via a specific photoelectric effect. The collector is made up of many thin layers of silicon, a semiconductor that, when impinged by photons, transfers the resulting energy to its electrons, generating electrical voltage.

Photovoltaic Effect

Creation of electric current when a semiconductor material is struck by light photons.

Photovoltaic Solar Energy

Energy produced by the photovoltaic effect.

Pipeline (Oil or Gas)

Pipeline used to transport crude oil, petroleum products or gas.


An instability phenomenon that occurs when seepage through a dam is not properly filtered and soil particles continue to progress, forming sink holes in the dam. This can result in a sudden, spectacular dam failure.

Polyethylene (PE)

Polyethylenes (PE) are the simplest synthetic polymers and the cheapest to produce. They are polymers of ethylene (see definition). Low-density polyethylenes (LDPE) are used to make plastic bags, garbage bags, food-grade plastic wrap and flexible containers. High-density polyethylenes (HDPE) are used in more rigid plastics of the kind found in bottles and other containers. Cross-linked polyethylenes (XLPE) are used to make cable insulation.

Polyethylene Terephthalate (PET)

Polyethylene terephthalate, PET for short, is a plastic used to make bottles, many food-grade plastic wrap and packaging solutions and transparent films for LCD screens and other optical devices. It also has medical applications, such as the manufacture of plastics for synthetic ligaments and prosthetic cardiac devices. PET is recyclable and is used to make textile fibers such as polar fleece. Chemically, PET is a polymer of terephthalic acid ester and ethylene glycol.


Process in which a large number of relatively small molecules known as monomers combine to form a single macromolecule called a polymer. The synthesis reaction requires specific temperature and pressure conditions and a catalyst. Synthetic monomers are often alkenes, a type of unsaturated hydrocarbon. There are also natural polymers such as cellulose (polysaccharides), collagen (alpha-polypeptides found in leather) and keratin (polypeptides found in dander and silk).

Polypropylene (PP)

Polypropylene is a semi-rigid, hard plastic material that is highly scratch-resistant. It is used to make automotive parts such as bumpers, dashboards and gas tanks. It is also used to make grease-proof food packaging, heavy-duty textiles used by building trade workers, disposable work wear, cord and rope, synthetic rugs and carpeting, and upholstery fabric. It is even used for banknotes in Israel, Mexico and Australia. Chemically, polypropylene is a semi-crystalline thermoplastic whose monomer is the CH2=CH-CH3 propylene (propene).


Polystyrene is a plastic with a wide range of uses, the most common being expanded polystyrene, a compact white foam used to pack and cushion fragile objects from knocks and vibrations and for thermal insulation in buildings. However, it is also found in office equipment, CD cases, models, fresh food trays and disposable dishware. Chemically, polystyrene is a polymer of the styrene CH2=CH-[phenyl].


Percentage of pore volume or void space within rock. In subsurface rock, this void space can contain fluids, usually water and sometimes oil or gas. Porosity varies significantly depending on rock type and depth, from zero for evaporates, found in salt crystals, and up to 50% for clays.

Potential Deposit

The potential hydrocarbon reserves that could be extracted from a deposit.

Potential Energy

Energy contained in an object or physical system that has the potential to be converted into kinetic energy. All objects on Earth possess gravitational potential energy, which causes them to move towards the center of the Earth until a fixed obstacle blocks this movement.


In physics, power is the amount of energy supplied by a system per unit time. In simpler terms, power can be viewed as energy output. Power is always work done using force or pressure, multiplied by speed or output. The watt (see definition) is the derived unit of power in the International System of Units (SI).

Preservation (Hydrocarbons)

The final phase in petroleum system formation, after a deposit has accumulated. Threats to preservation include bacteria capable of damaging crude oil in deposits near the surface, where temperatures are below 50°C.

Pressurized Water Reactor (PWR)

Type of nuclear reactor that uses pressurized water (which remains in a liquid state in the primary system) as both coolant and moderator. Water in the secondary system is vaporized in steam generators. The steam drives a turbine to generate power. Known as second-generation reactors, PWRs are the most widely used in the world.

Primary Energy

All energy sources that have not undergone any conversion process and remain in their natural state. Examples include crude oil, natural gas and sunlight.

Primary System

A reactor in a nuclear power plant has three major systems: the primary, secondary and cooling water systems. The primary system, also called the reactor coolant system, transfers heat produced by the fission of uranium and plutonium atoms to the steam generator.

Production (Hydrocarbons)

The commercial operation of an oil or gas deposit.

Production Sharing Contract (or Agreement)

Oil contract under which the oil that is produced is shared between the state and the oil company. The company is entitled to a predetermined percentage of any oil produced to recoup its exploration and production costs; this is known as cost oil. The remaining production, known as profit oil, is shared between the state and the oil company (roughly 82% and 18% respectively). The state sets the production rate. This type of contract is the subject of hard bargaining, particularly when costs are being negotiated.


Propylene or propene is an alkene (olefin, see definition) with three carbon atoms and a formula of CH2=CH-CH3. It is the monomer of polypropylene plastics (see definition). Propylene is produced by three main processes: thermal cracking in oil refineries, propane dehydrogenation and as a byproduct of producing ethylene.

Prospect (Hydrocarbons)

A potential hydrocarbon deposit. Explorationists seek to locate prospects, determine their configuration and size, estimate the volumes of oil and gas that they could contain, and calculate the likelihood of encountering these volumes.


A positively charged particle. Protons and neutrons form the nucleus of an atom.


Thermochemical decomposition of organic material at elevated temperatures, carried out in an oxygen-free or low-oxygen environment to avoid oxidization or combustion. The temperature varies between 200 and 1,000°C, depending on the compound being processed (wood, coal, etc.). Generally it produces a liquid (oil), gas (syngas) and a carbon-rich solid residue. Also called thermolysis.

Pyrolysis Unit

Pyrolysis is thermochemical decomposition of organic material in the absence of oxygen. Pyrolysis units produce gases and a solid residue known as pyrolysis coke. The gases — CO, H2, CH4 and others — are burned and generate heat, some of which is used for pyrolysis and the rest by manufacturers and municipalities. Coke can also be used as a fuel. However, its calorific value is lower than that of coal and it accumulates contaminants, mainly heavy metals. It represents an alternative to incineration or methanation for treating municipal solid waste and organic waste in general.