Glossary of Terms - P

• P/N - A semiconductor (photovoltaic) device structure in which the junction is formed between a p-type layer and an n-type layer.
• Packing Factor - The ratio of array area to actual land area or building envelope area, for a system; or, the ratio of total PV cell area to the total module area, for a module.
• PAD (or PADD) - Petroleum Administration for Defense District. The United States is divided into five distinct marketing regions in which prices might differ due to variations in the supply or demand.
• Panel (Solar) - A term generally applied to individual solar collectors, and typically to solar photovoltaic collectors or modules.
• Panel Radiator - A mainly flat surface for transmitting radiant energy.
• Panemone - A drag-type wind machine that can react to wind from any direction.
• Paper Barrels - A term used to denote trade in non-physical oil (futures, forwards, swaps, etc.) markets which give a buyer or seller the right to a certain quantity and quality of crude oil or refined products at a future date, but not to any specific physical lot.
• Par or Basis Grade - The grade or grades specified in a given futures contract for delivery. A contract may permit substitutions for and deviations from the par grade subject to specified premiums or discounts.
• Parabolic Aluminized Reflector Lamp - A type of lamp having a lens of heavy durable glass that focuses the light. They have longer lifetimes with less lumen depreciation than standard incandescent lamps.
• Parabolic Dish - A solar energy conversion device that has a bowl shaped dish covered with a highly reflective surface that tracks the sun and concentrates sunlight on a fixed absorber, thereby achieving high temperatures, for process heating or to operate a heat (Stirling) engine to produce power or electricity.
• Parabolic Trough - A solar energy conversion device that uses a trough covered with a highly reflective surface to focus sunlight onto a linear absorber containing a working fluid that can be used for medium temperature space or process heat or to operate a steam turbine for power or electricity generation.
• Parallel - A configuration of an electrical circuit in which the voltage is the same across the terminals. The positive reference direction for each resistor current is down through the resistor with the same voltage across each resistor.
• Parallel Connection - A way of joining photovoltaic cells or modules by connecting positive leads together and negative leads together; such a configuration increases the current, but not the voltage.
• Parallel Path Flow - This refers to the flow of electric power on an electric system's transmission facilities resulting from scheduled electric power transfers between two other electric systems. (Electric power flows on all interconnected parallel paths in amounts inversely proportional to each path's resistance.)
• Partial Load - An electrical demand that uses only part of the electrical power available.
• Particulates - The fine liquid or solid particles contained in combustion gases. The quantity and size of particulates emitted by cars, power and industrial plants, wood stoves, etc are regulated by the U.S. Environmental Protection Agency.
• Parties - The Transmission Provider and the Transmission Customer receiving service.
• Passivation - A chemical reaction that eliminates the detrimental effect of electrically reactive atoms on a photovoltaic cell's surface.
• Passive Solar (Building) Design - A building design that uses structural elements of a building to heat and cool a building, without the use of mechanical equipment, which requires careful consideration of the local climate and solar energy resource, building orientation, and landscape features, to name a few. The principal elements include proper building orientation, proper window sizing and placement and design of window overhangs to reduce summer heat gain and ensure winter heat gain, and proper sizing of thermal energy storage mass (for example a Trombe wall or masonry tiles). The heat is distributed primarily by natural convection and radiation, though fans can also be used to circulate room air or ensure proper ventilation.
• Passive Solar Heater - A solar water or space-heating system in which solar energy is collected, and/or moved by natural convection without using pumps or fans. Passive systems are typically integral collector/storage (ICS; or batch collectors) or thermosyphon systems. The major advantage of these systems is that they do not use controls, pumps, sensors, or other mechanical parts, so little or no maintenance is required over the lifetime of the system.
• Passive Solar Home - A house built using passive solar design techniques.
• Payback - The length of time it takes for the savings received to cover the cost of implementing the technology.
• Peak - Periods of relatively high system demands.
• Peak Clipping - Peak clipping reduces a utility's system peak, reducing the need to operate peaking units with relatively high fuel costs. Peak clipping is typically pursued only for the days the system peak is likely to occur, and the resources are not expected to meet the impending load requirements.
• Peak Demand - Maximum power used in a given period of time.
• Peak Load Plant - A plant usually housing old, low-efficiency steam units, gas turbines, diesels, or pumped storage hydroelectric equipment normally used during the peak-load periods.
• Peak Power - Power generated by a utility unit that operates at a very low capacity factor; generally used to meet short-lived and variable high demand periods.
• Peak Shifting - The process of moving existing loads to off-peak periods.
• Peak Watt - A unit used to rate the performance of a solar photovoltaic (PV) cells, modules, or arrays; the maximum nominal output of a PV device, in Watts (Wp) under standardized test conditions, usually 1000 Watts per square meter of sunlight with other conditions, such as temperature specified.
• Peak Wind Speed - The maximum instantaneous wind speed (or velocity) that occurs within a specific period of time or interval.
• Peaking Capacity - Capacity of generating equipment normally reserved for operation during the hours of highest daily, weekly, or seasonal loads. Some generating equipment may be operated at certain times as peaking capacity and at other times to serve loads on an around-the-clock basis.
• Peaking Hydropower - A hydropower plant that is operated at maximum allowable capacity for part of the day and is either shut down for the remainder of the time or operated at minimal capacity level.
• Peaking Unit - A power generator used by a utility to produce extra electricity during peak load times.
• Pellet Stove - A space heating device that burns pellets; are more efficient, clean burning, and easier to operate relative to conventional cord wood burning appliances.
• Pellets - Solid fuels made from primarily wood sawdust that is compacted under high pressure to form small (about the size of rabbit feed) pellets for use in a pellet stove.
• Pelton Turbine - A type of impulse hydropower turbine where water passes through nozzles and strikes cups arranged on the periphery of a runner, or wheel, which causes the runner to rotate, producing mechanical energy. The runner is fixed on a shaft, and the rotational motion of the turbine is transmitted by the shaft to a generator. Generally used for high head, low flow applications.
• Penstock - A component of a hydropower plant; a pipe that delivers water to the turbine.
• Percent Difference - The relative change in a quantity over a specified time period. It is calculated as follows: the current value has the previous value subtracted from it; this new number is divided by the absolute value of the previous value; then this new number is multiplied by 100.
• Perfluorocarbon Tracer Gas Technique (PFT) - An air infiltration measurement technique developed by the Brookhaven National Laboratory to measure changes over time (one week to five months) when determining a building's air infiltration rate. This test cannot locate exact points of infiltration, but it does reveal long-term infiltration problems.
• Performance Attributes - Performance attributes measure the quality of service and operating efficiency. Loss of load probability, expected energy curtailment, and reserve margin are all performance attributes.
• Performance Ratings - Solar collector thermal performance ratings based on collector efficiencies, usually expressed in Btu per hour for solar collectors under standard test or operating conditions for solar radiation intensity, inlet working fluid temperatures, and ambient temperatures.
• Perimeter Heating - A term applied to warm-air heating systems that deliver heated air to rooms by means of registers or baseboards located along exterior walls.
• Period of Analysis - The number of years considered in the study.
• Permeance - A unit of measurement for the ability of a material to retard the diffusion of water vapor at 73.4 F (23 C). A perm, short for permeance, is the number of grains of water vapor that pass through a square foot of material per hour at a differential vapor pressure equal to one inch of mercury.
• Petrochemical - An intermediate chemical derived from petroleum, hydrocarbon liquids, or natural gas, such as ethylene, propylene, benzene, toluene, and xylene.
• Petroleum - A mixture of hydrocarbons existing in the liquid state found in natural underground reservoirs often associated with gas. Petroleum includes fuel oil No. 2, No. 4, No. 5, No. 6; topped crude; kerosene; and jet fuel.
• Phase - One of the characteristics of the electric service supplied or the equipment used. Practically all residential customers have single-phase service. Large commercial and industrial customers have either two-phase or three-phase service.
• Phase Change - The process of changing from one physical state (solid, liquid, or gas) to another, with a necessary or coincidental input or release of energy.
• Phase-Change Material - A material that can be used to store thermal energy as latent heat. Various types of materials have been and are being investigated such as inorganic salts, eutectic compounds, and paraffins, for a variety of applications, including solar energy storage (solar energy heats and melts the material during the day and at night it releases the stored heat and reverts to a solid state).
• Phosphorous (P) - A chemical element, atomic number 15, used as a dopant in making n-semiconductor layers.
• Photobiological Hydrogen Production - A hydrogen production process that process uses algae. Under certain conditions, the pigments in certain types of algae absorb solar energy. An enzyme in the cell acts as a catalyst to split water molecules. Some of the bacteria produces hydrogen after they grow on a substrate.
• Photocurrent - An electric current induced by radiant energy.
• Photoelectric Cell - A device for measuring light intensity that works by converting light falling on, or reach it, to electricity, and then measuring the current; used in photometers.
• Photoelectrochemical Cell - A special kind of photovoltaic cell in which the electricity produced is used immediately within the cell to produce a useful chemical product, such as hydrogen. The product material is continuously withdrawn from the cell for direct use as a fuel or as an ingredient in making other chemicals, or it may be stored and used subsequently.
• Photoelectrolysis Hydrogen Production - The production of hydrogen using a photoelectrochemical cell.
• Photogalvanic Processes - The production of electrical current from light.
• Photon - A particle of light that acts as an individual unit of energy.
• Photovoltaic (Conversion) Efficiency - The ratio of the electric power produced by a photovoltaic device to the power of the sunlight incident on the device.
• Photovoltaic (PV) - Pertaining to the direct conversion of light into electricity.
• Photovoltaic (PV) Peak Watt - Maximum "rated" output of a cell, module, or system. Typical rating conditions are 0.645 watts per square inch (1000 watts per square meter) of sunlight, 68 degrees F (20 degrees C) ambient air temperature and 6.2 x 10-3 mi/s (1 m/s) wind speed.
• Photovoltaic (PV) System - A complete set of components for converting sunlight into electricity by the photovoltaic process, including the array and balance of system components.
• Photovoltaic (Solar) Module or Panel - A solar photovoltaic product that generally consists of groups of PV cells electrically connected together to produce a specified power output under standard test conditions, mounted on a substrate, sealed with an encapsulant, and covered with a protective glazing. Maybe further mounted on an aluminum frame. A junction box, on the back or underside of the module is used to allow for connecting the module circuit conductors to external conductors.
• Photovoltaic Device - A solid-state electrical device that converts light directly into direct current electricity of voltage-current characteristics that are a function of the characteristics of the light source and the materials in and design of the device. Solar photovoltaic devices are made of various semi-conductor materials including silicon, cadmium sulfide, cadmium telluride, and gallium arsenide, and in single crystalline, multi-crystalline, or amorphous forms.
• Photovoltaics - A technology that directly converts light into electricity. The process uses modules, which are usually made up of many cells (thin layers of semiconductors).
• Photovoltaic-Thermal (PV/T) Systems - A solar energy system that produces electricity with a PV module, and collects thermal energy from the module for heating. There are no commercially available systems available (as of 11/97).
• Physical Vapor Deposition - A method of depositing thin semiconductor photovoltaic) films. With this method, physical processes, such as thermal evaporation or bombardment of ions, are used to deposit elemental semiconductor material on a substrate.
• Pilot - A utility program offering a limited group of customers their choice of certified or licensed energy suppliers on a one year minimum trial basis.
• P-I-N - A semiconductor (photovoltaic) device structure that layers an intrinsic semiconductor between a p-type semiconductor and an n-type semiconductor; this structure is most often used with amorphous silicon PV devices.
• Pin Risk - The risk to a trader who has sold an option that, at expiration, has a strike price identical to, or pinned to, the underlying futures price. In this case, the trader will not know whether he will be required to assume his options obligations.
• Pipeline - A pipe through which oil or natural gas is pumped between two points, either offshore or onshore.
• Pit or Ring - The place on the floor of an exchange where a commodity futures or options contract is traded by open outcry. Platinum Group Metals (PGM) Platinum and related metals, including palladium, rhodium, ruthenium, and iridium.
• Pitch Control - A method of controlling a wind turbine's speed by varying the orientation, or pitch, of the blades, and thereby altering its aerodynamics and efficiency.
• Planned Generator - A proposal by a company to install electric generating equipment at an existing or planned facility or site. The proposal is based on the owner having obtained (1) all environmental and regulatory approvals, (2) a signed contract for the electric energy, or (3) financial closure for the facility.
• Plant - A facility at which are located prime movers, electric generators, and auxiliary equipment for converting mechanical, chemical, and/or nuclear energy into electric energy. A plant may contain more than one type of prime mover. Electric utility plants exclude facilities that satisfy the definition of a qualifying facility under the Public Utility Regulatory Policies Act of 1978.
• Plant Use - The electric energy used in the operation of a plant. Included in this definition is the energy required for pumping at pumped storage plants.
• Plant-Use Electricity - The electric energy used in the operation of a plant. This energy total is subtracted from the gross energy production of the plant; for reporting purposes the plant energy production is then reported as a net figure. The energy required for pumping at pumped storage plants is, by definition, subtracted, and the energy production for these plants is then reported as a net figure.
• Plenum - The space between a hanging ceiling and the floor above or roof; usually contains HVAC ducts, electrical wiring, fire suppression system piping, etc.
• Plug Flow Digester - A type of anaerobic digester that has a horizontal tank in which a constant volume of material is added and forces material in the tank to move through the tank and be digested.
• Point or Tick - The smallest monetary unit of change in a futures price or an options premium.
• Point(s) of Delivery - Point(s) of interconnection on the Transmission ProviderÌs Transmission System where capacity and/or energy transmitted by the Transmission Provider will be made available to the Receiving Party. The Point(s) of Delivery shall be specified in the Service Agreement.
• Point(s) of Receipt -Point(s) of interconnection on the Transmission ProviderÌs Transmission System where capacity and/or energy will be made available to the Transmission Provider by the Delivering Party. The Point(s) of Delivery shall be specified in the Service Agreement.
• Point-Contact Cell - A high efficiency silicon photovoltaic concentrator cell that employs light trapping techniques and point-diffused contacts on the rear surface for current collection.
• Point-to-Point Transmission Service - The reservation and/or transmission of energy on either a firm basis and/or a non-firm basis from Point(s) of Receipt to Point(s) of Delivery, including any Ancillary Services that are provided by the Transmission Provider in conjunction with such service.
• Point-to-Point Transmission Service Tariff - The Transmission ProviderÌs Point-to-Point Transmission Service Tariff as such tariff may be amended and/or superseded from time to time.
• Polycrystalline - A semiconductor (photovoltaic) material composed of variously oriented, small, individual crystals.
• Polyethylene - A registered trademark for plastic sheeting material that can be used as a vapor retarder. This plastic is used to make grocery bags. It is a long chain of carbon atoms with 2 hydrogen atoms attached to each carbon atom.
• PoolCo - This will serve as a model for the restructured electric industry that combines the functions of an ISO and a Power Exchange. In its least flexible form, a PoolCo also prohibits direct transactions between buyers and sellers (I.e. all producers selling to the Pool and all consumers buy from the Pool.)
• Portfolio - The collection of investments, assets and goods owned by one individual or organization.
• Portfolio Standard - The requirement that an electric power utility generate or purchase a specified percentage of the power it supplies/sells from renewable energy resources, and thereby guarantee a market for electricity generated from renewable energy resources.
• Position - The net total of a trader's open contracts, either long or short, in a particular underlying commodity.
• Position Limit - For a single trader or firm, the maximum number of allowable open contracts in the same underlying commodity.
• Posted Price - The price some refiners will pay for crude of a certain API gravity from a particular field or area.
• Potential Energy - Energy available due to position.
• Potential Peak Load Reduction - The amount of annual peak load reduction capability (measured in kilowatts) that can be deployed from Direct Load Control, Interruptible Load, Other Load Management, and Other DSM Program activities. It represents the load that can be reduced either by the direct control of the utility system operator or by the consumer in response to a utility request to curtail load. It reflects the installed load reduction capability, as opposed to the Actual Peak Reduction achieved by participants, during the time of annual system peak load.
• Pound of Steam - One pound of water in vapor phase; is NOT steam pressure, which is expressed as pounds per square inch (psi).
• Pound Per Square Inch Absolute (psia) - A unit of pressure [hydraulic (liquid) or pneumatic (gas)] that does not include atmospheric pressure.
• Pour Point - A temperature 5 degrees Fahrenheit higher than the temperature at which crude oil or a refined product stops flowing.
• Power - Energy that is capable or available for doing work; the time rate at which work is performed, measured in horsepower, Watts, or Btu per hour. Electric power is the product of electric current and electromotive force. The rate at which energy is transferred. Electrical energy is usually measured in watts. Also used for a measurement of capacity.
• Power (Output) Curve - A plot of a wind energy conversion device's power output versus wind speed.
• Power (Solar) Tower - A term used to describe solar thermal, central receiver, power systems, where an array of reflectors focus sunlight onto a central receiver and absorber mounted on a tower.
• Power Coefficient - The ratio of power produced by a wind energy conversion device to the power in a reference area of the free windstream.
• Power Conditioning Equipment - Electrical equipment, or power electronics, used to convert power from a photovoltaic array into a form suitable for subsequent use. A collective term for inverter, converter, battery charge regulator, and blocking diode.
• Power Density - The amount of power per unit area of a free windstream. The ratio of the power available from a battery to its mass (W/kg) or volume (W/l).
• Power Factor (PF) - The ratio of actual power being used in a circuit, expressed in watts or kilowatts, to the power that is apparently being drawn from a power source, expressed in volt-amperes or kilovolt-amperes.
• Power Grid - A network of power lines and associated equipment used to transmit and distribute electricity over a geographic area.
• Power Marketer - A wholesale power entity that has registered with the Federal Energy Regulatory Commission to buy and sell wholesale power from and to each other and other public entities at market-derived prices. Power marketing companies include investor-owned, utility-affiliated companies; natural gas marketing companies; financial intermediaries; independent power producers; and entrepreneurs. Typically, power marketers do not own generating facilities.
• Power Plant - A generating station where electricity is produced.
• Power Pool - An association of two or more interconnected electric systems having an agreement to coordinate operations and planning for improved reliability and efficiencies.
• Power Purchase Agreement - This refers to a contract entered into by an independent power producer and an electric utility. The power purchase agreement specifies the terms and conditions under which electric power will be generated and purchased. Power purchase agreements require the independent power producer to supply power at a specified price for the life of the agreement. While power purchase agreements vary, their common elements include: specification of the size and operating parameters of the generation facility; milestones in-service dates, and contract terms; price mechanisms; service and performance obligations; dispatchability options; and conditions of termination or default.
• Power Transmission Line - An electrical conductor/cable that carries electricity from a generator to other locations for distribution.
• Preheater (Solar) - A solar heating system that preheats water or air that is then heated more by another heating appliance.
• Premium - 1) The price or cost of an option determined competitively by buyers and sellers in open outcry trading on the exchange trading floor. 2) An upward adjustment in price allowed for delivery of a commodity of higher grade against a futures contract.
• Present Value - The amount of money required to secure a specified cash flow on a future date at a given rate of return.
• Present Worth Factor - The adjustment factor that discounts a sum of future dollars back to the current year.
• Pressure Drop - The loss in static pressure of a fluid (liquid or gas) in a system due to friction from obstructions in pipes, from valves, fittings, regulators, burners, etc, or by a breech or rupture of the system.
• Price - The amount of money or consideration-in-kind for which a service is bought, sold, or offered for sale.
• Price Cap - Situation where a price has been determined and fixed.
• Price Discovery - The manner of making prices visible and readily available to the public.
• Price Gaps - A chart pattern of the price movement of a commodity when the low price of one bar on a chart is higher than the high of the preceding bar (or inversely, the high is lower than the low of the preceding bar); depicting a price or price range where no trades take place. The price patterns are used by technical analysts to try to recognize changes in a price trend.
• Primary Air - The air that is supplied to the combustion chamber of a furnace.
• Primary Circuit - This is the distribution circuit (less than 69,000 volts) on the high voltage side of the transformer.
• Primary Stocks - Stocks of crude oil or refined products held in storage at leases, refineries, natural gas processing plants, pipelines, tankfarms, and bulk terminals that can store at least 50,000 barrels of refined products.
• Prime Mover - The engine, turbine, water wheel, or similar machine that drives an electric generator; or, for reporting purposes, a device that converts energy to electricity directly (e.g., photovoltaic solar and fuel cells).
• Process Heating - Energy Efficiency program promotion of increased electric energy efficiency applications in industrial process heating.
• Processing Plant - Plant which separates natural gas into methane and the various other gases (e.g., propane, butane, ethane).
• Producer Gas - Low or medium Btu content gas, composed mainly of carbon monoxide, nitrogen(2), and hydrogen(2) made by the gasification of wood or coal.
• Production - The act or process of generating electric energy.
• Production Costing - A method used to determine the most economical way to operate a given system of power resources under given load conditions.
• Products of Combustion - The elements and compounds that result from the combustion of a fuel.
• Profit - The income remaining after all business expenses are paid.
• Program Life - The length of time that the utility will be actively involved in promoting a demand-side management program (I.e. financing the marketing activities and the incentives of the program.)
• Program Maturity - The time it takes for the full benefits of a demand-side management measure or program to be realized.
• Project Financing - This is the most commonly used method to finance the construction of independent power facilities. Typically, the developer pledges the value of the plant and part or all of its expected revenues as collateral to secure financing from private lenders.
• Projected Area - The net south-facing glazing area projected on a vertical plane. Also, the solid area covered at any instant by a wind turbine's blades from the perspective of the direction of the windstream (as opposed to the swept area).
• Prompt Barrel - Product which will move or become available within three to four days.
• Propane - A natural hydrocarbon occurring in a gaseous state under normal atmospheric pressure and temperature, however, propane is usually liquefied through pressurization for transportation and storage. Propane is primarily used for rural heating and cooking and as a fuel gas in areas not serviced by natural gas mains and as a petrochemical feed stock.
• Propeller (Hydro) Turbine - A turbine that has a runner with attached blades similar to a propeller used to drive a ship. As water passes over the curved propeller blades, it causes rotation of the shaft.
• Prorated Bills - The computation of a bill based upon proportionate distribution of the applicable billing schedule. A prorated bill is less than 25 days ore more than 38 days.
• Provider of Last Resort - A legal obligation (traditionally given to utilities) to provide service to a customer where competitors have decided they do not want that customer's business.
• Proximate Analysis - A commonly used analysis for reporting fuel properties; may be on a dry (moisture free) basis, as "fired", or on an ash and moisture free basis. Fractions usually reported include: volatile matter, fixed carbon, moisture, ash, and heating value (higher heating value).
• Psi - Pounds of pressure per square inch.
• Psia - Pounds/force per square inch absolute.
• Psig - Pounds/force per square inch gauge.
• Psychrometer - An instrument for measuring relative humidity by means of wet and dry-bulb temperatures.
• Psychrometrics - The analysis of atmospheric conditions, particularly moisture in the air.
• P-Type Semiconductor - A semiconductor in which holes carry the current; produced by doping an intrinsic semiconductor with an electron acceptor impurity (e.g., boron in silicon).
• Public Authority Service to Public Authorities - Public authority service includes electricity supplied and services rendered to municipalities or divisions or agencies of State or Federal governments, under special contracts or agreements or service classifications applicable only to public authorities.
• Public Power - Public power utilities are governed locally and operated by local governments to provide communities with reliable, responsive, not-for-profit electric service.
• Public Street and Highway Lighting - Public street and highway lighting includes electricity supplied and services rendered for the purposes of lighting streets, highways, parks, and other public places; or for traffic or other signal system service, for municipalities, or other divisions or agencies of State or Federal governments.
• Public utilities Regulatory Policy Act (PURPA) of 1978 - A law that requires electric utilities to purchase electricity produced from qualifying power producers that use renewable energy resources or are cogenerators. utilities are required to purchase power at a rate equal to the avoided cost of generating the power themselves. (See Avoided Costs and Qualifying Facility)
• Public Utility - A utility operated by a non-profit governmental or quasi-governmental entity. Public utilities include municipal utilities, cooperatives, and power marketing authorities.
• Public Utility Commissions - State regulatory agencies that provide oversight, policy guidelines and direction to electric public utilities.
• Public Utility Holding Company Act (PUHCA) of 1935 - A law to protect consumers and investors. It placed geographic restrictions on mergers and limitations on diversification into non-utility lines of business and takeovers of electric and gas utilities, and also established regulated monopoly markets or service territories for utilities. PUHCA was enacted by the U.S. Congress to regulate the large interstate holding companies that monopolized the electric utility industry during the early 20th century.
• Public Utility or Services Commissions (PUC or PSC) - These are state government agencies responsible for the regulation of public utilities within a state or region. A state legislature oversees the PUC by reviewing changes to utility laws, rules and regulations and approving the PUC's budget. The commission usually has five Commissioners appointed by the Governor or legislature. PUCs typically regulate: electric, natural gas, water, sewer, telephone services, trucks, buses, and taxicabs within the commission's operating region. The PUC tries to balance the interests of consumers, environmentalists, utilities, and stockholders. The PUC makes sure a region's citizens are supplied with adequate, safe utility service at reasonable rates.
• Publicly Owned utilities - Municipal utilities (utilities owned by branches of local government) and/or co-ops (utilities owned cooperatively by customers).
• Pulse-Width-Modulated (pwm) Wave Inverter (PWM) - PWM inverters are the most expensive, but produce a high quality of output signal at minimum current harmonics. The output voltage is very close to sinusoidal.
• Pumped Storage - A facility designed to generate electric power during peak load periods with a hydroelectric plant using water pumped into a storage reservoir during off-peak periods.
• Pumped Storage Facility - A type of power generating facility that pumps water to a storage reservoir during off-peak periods, and uses the stored water (by allowing it to fall through a hydro turbine) to generate power during peak periods. The pumping energy is typically supplied by lower cost base power capacity, and the peaking power capacity is of greater value, even though there is a net loss of power in the process.
• Pumped Storage Hydroelectric Plant - A plant that usually generates electric energy during peak-load periods by using water previously pumped into an elevated storage reservoir during off-peak periods when excess generating capacity is available to do so. When additional generating capacity is needed, the water can be released from the reservoir through a conduit to turbine generators located in a power plant at a lower level.
• Pump-Over - An intra, or inter-facility transfer. For example, when one pipeline pumps crude oil or refined products from its tanks or mainline into the mainline or storage tank of the receiving pipeline.
• Purchased Power Adjustment - A clause in a rate schedule that provides for adjustments to the bill when energy from another electric system is acquired and it varies from a specified unit base amount.
• Pure Pumped Storage Hydroelectric Plant - A plant that produces power only from water that has previously been pumped to an upper reservoir.
• Put Option - An option which gives the buyer, or holder, the right, but not the obligation, to sell a futures contract at a specific price within a specific period of time in exchange for a one-time premium payment. It obligates the seller, or writer, of the option to buy the underlying futures contract at the designated price, should an option be exercised at that price. See call option.
• Pyranometer - A device used to measure total incident solar radiation (direct beam, diffuse, and reflected radiation) per unit time per unit area.
• Pyrheliometer - A device that measures the intensity of direct beam solar radiation.
• Pyrolysis - The transformation on a compound or material into one or more substances by heat alone (without oxidation). Often called destructive distillation. Pyrolysis of biomass is the thermal degradation of the material in the absence of reacting gases, and occurs prior to or simultaneously with gasification reactions in a gasifier. Pyrolysis products consist of gases, liquids, and char generally. The liquid fraction of pyrolisized biomass consists of an insoluble viscous tar, and pyroligneous acids (acetic acid, methanol, acetone, esters, aldehydes, and furfural). The distribution of pyrolysis products varies depending on the feedstock composition, heating rate, temperature, and pressure.