Glossary of Terms - S

• Sales - The amount of kilowatt-hours sold in a given period of time; usually grouped by classes of service, such as residential, commercial, industrial, and other. Other sales include public street and highway lighting, other sales to public authorities and railways, and interdepartmental sales.
• Sales for Resale - Energy supplied to other electric utilities, cooperatives, municipalities, and Federal and State electric agencies for resale to ultimate consumers.
• Salt Gradient Solar Ponds - Consist of three main layers. The top layer is near ambient and has low salt content. The bottom layer is hot, typically 160 F to 212 F (71 C to 100 C), and is very salty. The important gradient zone separates these zones. The gradient zone acts as a transparent insulator, permitting the sunlight to be trapped in the hot bottom layer (from which useful heat is withdrawn). This is because the salt gradient, which increases the brine density with depth, counteracts the buoyancy effect of the warmer water below (which would otherwise rise to the surface and lose its heat to the air). An organic Rankine cycle engine is used to convert the thermal energy to electricity.
• Satellite Power System (SPS) - Concept for providing large amounts of electricity for use on the Earth from one or more satellites in geosynchronous Earth orbit. A very large array of solar cells on each satellite would provide electricity, which would be converted to microwave energy and beamed to a receiving antenna on the ground. There, it would be reconverted into electricity and distributed the same as any other centrally generated power, through a grid.
• Savings Fraction - The percentage of consumption from using the old technology that can be saved by replacing it with the new, more efficient demand-side management technology. For example, if a 60-watt incandescent lamp were replaced with a 15-watt compact fluorescent lamp, the savings fraction would be 75 percent because the compact fluorescent lamp uses only 25 percent of the energy used by the incandescent lamp.
• Scalper - A speculator on the trading floor of an exchange who buys and sells rapidly, with small profits or losses, holding his positions for only a short time during a trading session. Typically a scalper will stand ready to buy at a fraction below the last transaction price and to sell at a fraction above, thus creating market liquidity.
• Scheduled Outage - An outage that results when a component is deliberately taken out of service at a selected time, usually for the purposes of construction, maintenance, or testing.
• Scheduling - Delivery of the commodity is arranged administratively - after a physical energy deal is struck.
• Scribing - The cutting of a grid pattern of grooves in a semiconductor material, generally for the purpose of making interconnections.
• Sealed Combustion Heating System - A heating system that uses only outside air for combustion and vents combustion gases directly to the outdoors. These systems are less likely to backdraft and to negatively affect indoor air quality.
• Seasonal Energy Efficiency Ratio (SEER) - A measure of seasonal or annual efficiency of a central air conditioner or air conditioning heat pump. It takes into account the variations in temperature that can occur within a season and is the average number of Btu of cooling delivered for every watt-hour of electricity used by the heat pump over a cooling season.
• Seasonal Performance Factor (SPF) - Ratio of useful energy output of a device to the energy input, averaged over an entire heating season.
• Second Law Efficiency - The ratio of the minimum amount of work or energy required to perform a task to the amount actually used.
• Second Law of Thermodynamics - This law states that no device can completely and continuously transform all of the energy supplied to it into useful energy.
• Securitization - The act of pledging assets to a creditor through a note, lien or bond. This is a mechanism to allow a utility to recover stranded costs up front in a single lump sum payment. Under a securitization scheme, the legislature or utility commission orders customers to pay a surcharge as part of their electric bill. That surcharge must be paid within the utility's original service territory, regardless of who supplies the electricity to customers.
• Seebeck Effect - The generation of an electric current, when two conductors of different metals are joined at their ends to form a circuit, with the two junctions kept at different temperatures.
• Selective Absorber - A solar absorber surface that has high absorbtance at wavelengths corresponding to that of the solar spectrum and low emittance in the infrared range.
• Selective Surface Coating - A material with high absorbtance and low emittance properties applied to or on solar absorber surfaces.
• Self Discharge - The rate at which a battery, without a load, will lose its charge.
• Self-Generation - A generation facility dedicated to serving a particular retail customer, usually located on the customer's premises. The facility may either be owned directly by the retail customer or owned by a third party with a contractual arrangement to provide electricity to meet some or all of the customer's load.
• Seller's Market - A condition of the market in which there is a scarcity of goods available and hence sellers can obtain better conditions of sale or higher prices. Opposite of buyer's market.
• Semiconductor - Any material that has a limited capacity for conducting an electric current. Certain semiconductors, including silicon, gallium arsenide, copper indium diselenide, and cadmium telluride, are uniquely suited to the photovoltaic conversion process.
• Senate Committee on Energy and Natural Resources - This committee has jurisdiction on: coal production, distribution and utilization; energy policy; energy research, conservation, and development; hydroelectric power; irrigation; mineral conservation; nonmilitary development of nuclear energy; solar energy systems; and over territorial possessions, including trusteeships of the United States.
• Senate Subcommittee on Energy Research, Development, Production and Regulation - This committee has jurisdiction on the oversight and legislative responsibilities for: coal, nuclear, and non-nuclear energy commercialization projects; DOE National Laboratories; global climate change; new technologies research and development; commercialization of new technologies including, solar energy systems; Federal energy conservation programs; energy information; and utility policy.
• Sensible Cooling Effect - The difference between the total cooling effect and the dehumidifying effect.
• Sensible Cooling Load - The interior heat gain due to heat conduction, convection, and radiation from the exterior into the interior, and from occupants and appliances.
• Sensible Heat - The heat absorbed or released when a substance undergoes a change in temperature.
• Sensible Heat Storage - A heat storage system that uses a heat storage medium, and where the additional or removal of heat results in a change in temperature.
• Serial Expiration - Options on the same underlying futures contract which expire in more than one month. NYMEX Division platinum options have serial expiration.
• Series - A configuration of an electrical circuit in which the positive lead is connected to the negative lead of another energy producing, conducting, or consuming device. The voltages of each device are additive, whereas the current is not.
• Series - All options of the same class which share a common strike price.
• Series Connection - A way of joining photovoltaic cells by connecting positive leads to negative leads; such a configuration increases the voltage.
• Series Regulator - Type of battery charge regulator where the charging current is controlled by a switch connected in series with the PV module or array.
• Series Resistance - Parasitic resistance to current flow in a cell due to mechanisms such as resistance from the bulk of the semiconductor material, metallic contacts, and interconnections.
• Service Agreement - The initial agreement and any supplements thereto entered into by the Transmission Customer and the Transmission Provider for service.
• Service Area - The territory a utility system is required or has the right to supply electric service to ultimate customers.
• Service Drop - The lines running to a customer's house. Usually a service drop is made up of two 120 volt lines and a neutral line, from which the customer can obtain either 120 or 240 volts of power. When these lines are insulated and twisted together, the installation is called triplex cable.
• Service Life - The length of time a piece of equipment can be expected to perform at its full capacity.
• Service Territory - This is the state, area or region served exclusively by a single electric utility.
• Settling Price - The price established by the Exchange settlement committee at the close of each trading session as the official price to be used by the clearinghouse in determining net gains or losses, margin requirements, and the next day's price limits. The term "settlement price" is often used as an approximate equivalent to the term "closing price." The close in futures trading refers to a brief period at the end of the day, during which transactions frequently take place quickly and at a range of prices immediately before the bell. Therefore, there frequently is no one closing price, but a range of prices. The settlement price is derived by calculating the weighted average of prices during that period.
• Shading Coefficient - A measure of window glazing performance that is the ratio of the total solar heat gain through a specific window to the total solar heat gain through a single sheet of double-strength glass under the same set of conditions; expressed as a number between 0 and 1.
• Sheathing - A construction element used to cover the exterior of wall framing and roof trusses.
• Short - 1) The market position of a futures contract seller whose sale obligates him to deliver the commodity unless he liquidates his contract by an offsetting purchase. 2) A trader whose net position in the futures market shows an excess of open sales over open purchases. 3) The holder of a short position. 4) In the options market, the position of the seller of a call or a put option. The short in the options market is obliged to take a futures position if he is assigned for exercise. Opposite of long.
• Short Circuit - An electric current taking a shorter or different path than intended.
• Short Circuit Current - The current flowing freely through an external circuit that has no load or resistance; the maximum current possible.
• Short Selling - Selling a contract with the idea of delivering or of buying to offset it at a later date.
• Short the Basis - The purchase of futures as a hedge against a commitment to sell in the cash or spot markets. See hedging.
• Short Ton - A unit of weight equal to 2,000 pounds.
• Short-Circuit Current (Isc) - The current flowing freely from a photovoltaic cell through an external circuit that has no load or resistance; the maximum current possible.
• Shunt Regulator - Type of a battery charge regulator where the charging current is controlled by a switch connected in parallel with the PV generator. Overcharging of the battery is prevented by shorting the PV generator.
• Shutter - An interior or exterior movable panel that operates on hinges or slides into place, used to protect windows or provide privacy.
• Siding - A construction element applied to the outermost surface of an exterior wall.
• Siemens Process - A commercial method of making purified silicon.
• Sigma Heat - The sum of sensible heat and latent heat in a substance above a base temperature, typically 32 degrees Fahrenheit.
• Silicon (Si) - A chemical element, atomic number 14, semimetallic in nature, dark gray, an excellent semiconductor material. A common constituent of sand and quartz (as the oxide). Crystallizes in face-centered cubic lattice like a diamond. The most common semiconductor material used in making photovoltaic devices.
• Sine Wave - The type of alternative current generated by alternating current generators, rotary inverters, and solid-state inverters.
• Single Phase Line - This carriers electrical loads capable of serving the needs of residential customers, small commercial customers, and streetlights. It carrier a relatively light load as compared to heavy duty three phrase constructs.
• Single-Crystal Material - In reference to solar photovoltaic devices, a material that is composed of a single crystal or a few large crystals.
• Single-phase - A generator with a single armature coil, which may have many turns and the alternating current output consists of a succession of cycles.
• Sizing - The process of designing a solar system to meet a specified load given the solar resource and the nominal or rated energy output of the solar energy collection or conversion device.
• Small Power Producer (SPP) - Under the Public Utility Regulatory Policies Act (PURPA), a small power production facility (or small power producer) generates electricity using waste, renewable (water, wind, and solar), or geothermal energy as a primary energy source. Fossil fuels can be used, but renewable resource must provide at least 75 percent of the total energy input. (See Code of Federal Regulations, Title 18, Part 292.)
• Smart Window - A term used to describe a technologically advanced window system that contains glazing that can change or switch its optical qualities when a low voltage electrical signal is applied to it, or in response to changes in heat or light.
• Sodium Lights - A type of high intensity discharge light that has the most lumens per watt of any light source.
• Solar Access or Rights - The legal issues related to protecting or ensuring access to sunlight to operate a solar energy system, or use solar energy for heating and cooling.
• Solar Air Heater - A type of solar thermal system where air is heated in a collector and either transferred directly to the interior space or to a storage medium, such as a rock bin.
• Solar Altitude Angle - The angle between a line from a point on the earth's surface to the center of the solar disc, and a line extending horizontally from the point.
• Solar Array - A group of solar collectors or solar modules connected together.
• Solar Energy - Electromagnetic energy transmitted from the sun (solar radiation). The amount that reaches the earth is equal to one billionth of total solar energy generated, or the equivalent of about 420 trillion kilowatt-hours.
• Solar Energy Industries Association (SEIA) - A national trade association of solar energy equipment manufacturers, retailers, suppliers, installers, and consultants.
• Solar Energy Research Institute (SERI) - A federally funded institute, created by the Solar Energy Research, Development and Demonstration Act of 1974, that conducted research and development of solar energy technologies. Became the National Renewable Energy Laboratory (NREL) in 1991.
• Solar Mass - A term used for materials used to absorb and store solar energy.
• Solar Module (Panel) - A solar photovoltaic device that produces a specified power output under defined test conditions, usually composed of groups of solar cells connected in series, in parallel, or in series-parallel combinations.
• Solar One - A solar thermal electric central receiver power plant ("power tower") located in Barstow, California, and completed in 1981. The Solar One had a design capacity of 10,000 peak kilowatts, and was composed of a receiver located on the top of a tower surrounded by a field of reflectors. The concentrated sunlight created steam to drive a steam turbine and electric generator located on the ground.
• Solar Power Satellite - A solar power station investigated by NASA that entailed a satellite in geosynchronous orbit that would consist of a very large array of solar photovoltaic modules that would convert solar generated electricity to microwaves and beam them to a fixed point on the earth.
• Solar Radiation - A general term for the visible and near visible (ultraviolet and near-infrared) electromagnetic radiation that is emitted by the sun. It has a spectral, or wavelength, distribution that corresponds to different energy levels; short wavelength radiation has a higher energy than long-wavelength radiation.
• Solar Spectrum - The total distribution of electromagnetic radiation emanating from the sun. The different regions of the solar spectrum are described by their wavelength range. The visible region extends from about 390 to 780 nanometers (a nanometer is one billionth of one meter). About 99 percent of solar radiation is contained in a wavelength region from 300 nm (ultraviolet) to 3,000 nm (near-infrared). The combined radiation in the wavelength region from 280 nm to 4,000 nm is called the broadband, or total, solar radiation.
• Solar Thermal Electric Systems - Solar energy conversion technologies that convert solar energy to electricity, by heating a working fluid to power a turbine that drives a generator. Examples of these systems include central receiver systems, parabolic dish, and solar trough.
• Solar Thermal Parabolic Dishes - A solar thermal technology that uses a modular mirror system that approximates a parabola and incorporates two-axis tracking to focus the sunlight onto receivers located at the focal point of each dish. The mirror system typically is made from a number of mirror facets, either glass or polymer mirror, or can consist of a single stretched membrane using a polymer mirror. The concentrated sunlight may be used directly by a Stirling, Rankine, or Brayton cycle heat engine at the focal point of the receiver or to heat a working fluid that is piped to a central engine. The primary applications include remote electrification, water pumping, and grid-connected generation.
• Solar Thermal Systems - Solar energy systems that collect or absorb solar energy for useful purposes. Can be used to generate high temperature heat (for electricity production and/or process heat), medium temperature heat (for process and space/water heating and electricity generation), and low temperature heat (for water and space heating and cooling).
• Solenoid - An electromechanical device composed of a coil of wire wound around a cylinder containing a bar or plunger, that when a current is applied to the coil, the electromotive force causes the plunger to move; a series of coils or wires used to produce a magnetic field.
• Solenoid Valve - An automatic valve that is opened or closed by an electromagnet.
• Solid Fuels - Any fuel that is in solid form, such as wood, peat, lignite, coal, and manufactured fuels such as pulverized coal, coke, charcoal, briquettes, pellets, etc.
• Solidity - In reference to a wind energy conversion device, the ratio of rotor blade surface area to the frontal, swept area that the rotor passes through.
• Sour Gas - Natural gas found with a sufficiently high quantity of sulfur to require purifying prior to shipment or use.
• Sour or Sweet Crude - Industry terms which denote the relative degree of a given crude oil's sulfur content. Sour crude refers to those crudes with a comparatively high sulfur content, 0.5% by weight and above; sweet refers to those crudes with sulfur content of less than 0.5%.
• Source Energy - All the energy used in delivering energy to a site, including power generation and transmission and distribution losses, to perform a specific function, such as space conditioning, lighting, or water heating. Approximately three watts (or 10.239 Btus) of energy is consumed to deliver one watt of usable electricity.
• Southeasterm Electricity Reliability Council (SERC) - One of the ten regional reliability councils that make up the North American Electric Reliability Council (NERC).
• Southwest Power Pool (SPP) - One of the ten regional reliability councils that make up the North American Electric Reliability Council (NERC).
• Spark Spread - The spark spread reflects the costs or anticipated costs of producing power from a specific facility. It can be used as a method of converting millions of Btus to megawatt hours and vice versa, and thus relates well to the electricity and natural gas futures contracts. The spread is simply the heat rate (a proxy for efficiency) of a specific generating unit or power system (the number of Btus needed to make one kilowatt hour of electricity), multiplied by the cost of energy expressed as dollars per British thermal units (Btus). For example, if it takes 10,000 Btus to make one kilowatt hour of electricity, the formula can be simplified by multiplying the price per million Btus (MMBtu) by 10 to equate one MMBtu of natural gas to one megawatt hour (Mwh) of electricity. The usefulness of the spread evaluation is dependent on the market price for power which reflects the relationship of the supply and demand for power, not the efficiencies of the generating units. Other costs affecting the price of power using the spark spread evaluation include those of gas transportation, power transmission, plant operations and maintenance, and fixed costs. Because the electricity futures contract is specified in lots of 736 megawatt hours, and the natural gas futures contracts are specified in units of 10,000 million Btus, one power contract equates to 0.736 natural gas contracts.
• Specific Gravity - The ratio of the density of a substance at 60 degrees Farenheit to the density of water at the same temperature.
• Specific Heat Capacity - The quantity of heat required to change the temperature of one unit weight of a material by one degree.
• Specific Humidity - The weight of water vapor, per unit weight of dry air.
• Specific Volume - The volume of a unit weight of a substance at a specific temperature and pressure.
• Specifications - 1) Contract terms specified by the Exchange. 2) Term referring to the properties of a given crude oil or refined petroleum product, which are "specified" since they often vary widely even within the same grade of product. In the normal process of negotiation, seller will guarantee buyer that the product or crude to be sold will meet certain specified limits. Generally, the major properties of oil that are guaranteed are API gravity, sulfur, pour point, viscosity, and BS&W.
• Spectral Energy Distribution - A curve illustrating the variation or spectral irradiance with wavelength.
• Spectral Irradiance - The monochromatic irradiance of a surface per unit bandwidth at a particular wavelength, usually expressed in Watts per square meter-nanometer bandwidth.
• Spectral Reflectance - The ratio of energy reflected from a surface in a given waveband to the energy incident in that waveband.
• Speculative Position Limit - The maximum position, either net long or net short, in one commodity futures or options, or in all futures or options of one commodity combined, which may be held or controlled by an entity without a hedge exemption as prescribed by an exchange or the Commodity Futures Trading Commission.
• Speculator - A trader who hopes to profit from the specific directional price move of a futures or options contract, or commodity.
• Spillway - A passage for surplus water to flow over or around a dam.
• Spinning Reserve - That reserve generating capacity running at a zero load and synchronized to the electric system.
• Split Spectrum Photovoltaic Cell - A photovoltaic device where incident sunlight is split into different spectral regions, with an optical apparatus, that are directed to individual photovoltaic cells that are optimized for converting that spectrum to electricity.
• Split-the-savings - The basis for settling economy-energy transactions between utilities. The added cost of the supplier are subtracted from the avoided costs of the buyer, and the difference is evenly divided.
• Spot - Term which describes one-time open market case (CHANGE TO CASH) transaction, where a commodity is purchased "on the spot" at current market rates. Spot transactions are in contrast to term sales, which specify a steady supply of product over a period of time.
• Spot Month - The futures contract closest to maturity. The nearby delivery month.
• Spot Purchases - A single shipment of fuel or volumes of fuel, purchased for delivery within 1 year. Spot purchases are often made by a user to fulfill a certain portion of energy requirements, to meet unanticipated energy needs, or to take advantage of low fuel prices.
• Spread (Futures) - The simultaneous purchase and sale of futures contracts for different months, different commodities, or different grades of the same commodity.
• Spread (Options) - The purchase and sale of options which vary in terms of type (call or put), strike prices, expiration dates, or both. May also refer to an options contract purchase (sale) and the simultaneous sale (purchase) of a futures contract for the same underlying commodity.
• Sputtering - A process used to apply photovoltaic semi-conductor material to a substrate by a physical vapor deposition process where high-energy ions are used to bombard elemental sources of semiconductor material, which eject vapors of atoms that are then deposited in thin layers on a substrate.
• Stability - The property of a system or element by virtue of which its output will ultimately attain a steady state. The amount of power that can be transferred from one machine to another following a disturbance. The stability of a power system is its ability to develop restoring forces equal to or greater than the disturbing forces so as to maintain a state of equilibrium.
• Stable Prices - Prices that do not vary greatly over short time periods.
• Stack (Heat) Loss - Sensible and latent heat contained in combustion gases and vapor emitted to the atmosphere.
• Staebler-Wronski effect - The tendency of the sunlight to electricity conversion efficiency of amorphous silicon photovoltaic devices to degrade (drop) upon initial exposure to light.
• Stagnation Temperature - A condition that can occur in a solar collector if the working fluid does not circulate when sun is shining on the collector.
• Stall - In reference to a wind turbine, a condition when the rotor stops turning.
• Stand-Alone (PV system) - An autonomous or hybrid photovoltaic system not connected to a grid. May or may not have storage, but most stand-alone systems require batteries or some other form of storage.
• Stand-Alone Generator - A power source/generator that operates independently of or is not connected to an electric transmission and distribution network; used to meet a load(s) physically close to the generator.
• Stand-Alone Inverter - An inverter that operates independent of or is not connected to an electric transmission and distribution network.
• Standard Air - Air with a weight of 0.075 pounds per cubic foot with an equivalent density of dry air at a temperature of 86 degrees Fahrenheit and standard barometric pressure of 29.92 inches of mercury.
• Standard Conditions - In refrigeration, an evaporating temperature of 5 degrees Fahrenheit (F), a condensing temperature of 86 degrees F., liquid temperature before expansion of 77 degrees F., and suction temperature of 12 degrees F.
• Standard Cubic Foot - A column of gas at standard conditions of temperature and pressure (32 degrees Fahrenheit and one atmosphere).
• Standard Industrial Classification (SIC) Code - Standardized codes used to classify businesses by type of activity they engage in.
• Standard Rate - The basic rate customers would take service under if they were not on real-time pricing.
• Standard Reporting Conditions (SRC) - A fixed set of conditions (including meteorological) to which the electrical performance data of a photovoltaic module are translated from the set of actual test conditions. [ASTM E 1036]
• Standard Test Conditions (STC) - Conditions under which a module is typically tested in a laboratory: (1) Irradiance intensity of 1000 W/square meter (0.645 watts per square inch), AM1.5 solar reference spectrum, and (3) a cell (module) temperature of 25 degrees C, plus or minus 2 degrees C (77 degrees F, plus or minus 3.6 degrees F). [IEC 1215]
• Standby Facility - A facility that supports a utility system and is generally running under no load. It is available to replace or supplement a facility normally in service.
• Standby Heat Loses - A term used to describe heat energy lost from a water heater tank.
• Standby Service - Support service that is available, as needed, to supplement a consumer, a utility system, or to another utility if a schedule or an agreement authorizes the transaction. The service is not regularly used.
• Starting Torque - The torque at the bottom of a speed (rpm) versus torque curve. The torque developed by the motor is a percentage of the full-load or rated torque. At this torque the speed, the rotational speed of the motor as a percentage of synchronous speed is zero. This torque is what is available to initially get the load moving and begin its acceleration.
• State of Charge (SOC) - The available capacity remaining in the battery, expressed as a percentage of the rated capacity.
• Static Pressure - The force per unit area acting on the surface of a solid boundary parallel to the flow.
• Steam Electric Plant (Conventional) - A plant in which the prime mover is a steam turbine. The steam used to drive the turbine is produced in a boiler where fossil fuels are burned.
• Steam Turbine - A device that converts high-pressure steam, produced in a boiler, into mechanical energy that can then be used to produce electricity by forcing blades in a cylinder to rotate and turn a generator shaft.
• Stirling Engine - A heat engine of the reciprocating (piston) where the working gas and a heat source are independent. The working gas is compressed in one region of the engine and transferred to another region where it is expanded. The expanded gas is then returned to the first region for recompression. The working gas thus moves back and forth in a closed cycle.
• Stocks - A supply of fuel accumulated for future use. This includes coal and fuel oil stocks at the plant site, in coal cars, tanks, or barges at the plant site, or at separate storage sites.
• Stock-Type Settlement - A settlement procedure in which the purchase of a contract requires immediate and full payment by the buyer to the seller. In stock-type settlement, the actual cash profit or loss from a trade is not realized until the position is liquidated. NYMEX Division energy and platinum options have this type of settlement procedure, which differs from that in the futures market where gains and losses are realized on a daily basis.
• Stoichiometric Ratio - The ratio of chemical substances necessary for a reaction to occur completely.
• Stoichiometry - Chemical reactions, typically associated with combustion processes; the balancing of chemical reactions by providing the exact proportions of reactant compounds to ensure a complete reaction; all the reactants are used up to produce a single set of products.
• Stop Limit Order - An order that goes into force as soon as there is a trade at the specified stop price. The order, however, can only be filled at the limit price or better. The stop price and the limit price can be the same or different. The stop price is the price level specified in the order.
• Stop-Loss - A resting order designed to close out a losing position when the price reaches a level specified in the order. It becomes an at-the-market order when the "stop" price is reached. Individuals also use stops to enter the market when the prices reach a specified level.
• Storage Capacity - The amount of energy an energy storage device or system can store.
• Storage Hydropower - A hydropower facility that stores water in a reservoir during high-inflow periods to augment water during low-inflow periods. Storage projects allow the flow releases and power production to be more flexible and dependable. Many hydropower project operations use a combination of approaches.
• Straddle (Futures) - Also known as a spread, the purchase of one futures month against the sale of another futures month of the same commodity. A straddle trade is based on a price relationship between the two months.
• Straddle (Options) - The purchase or sale of both a put and a call having the same strike price and expiration date. The buyer of a straddle benefits from increased volatility, and the seller benefits from decreased volatility.
• Stranded Benefits - Special collection programs, renewable energy and demand side management programs, lifeline rates and other utility resources funded by a monopoly utility that may not be funded if the utility's competition does not have smaller costs.
• Stranded Commitment - Assets and contracts associated with shifting to competition which are above market prices and result in non-competitive conditions for the utility.
• Stranded Investment (Costs and Benefits) - An investment in a power plant or demand side management measures or programs, that become uneconomical due to increased competition in the electric power market. For example, an electric power plant may produce power that is more costly than what the market rate for electricity is, and the power plant owner may have to close the plant, even though the capital and financing costs of building the plant have not been recovered through prior sales of electricity from the plant. This is considered a Stranded Cost. Stranded Benefits are those utility investments in measures or programs considered to benefit consumers by reducing energy consumption and/or providing environmental benefits that have to be curtailed due to increased competition and lower profit margins.
• Stranded/Strandable Costs - These are costs inherent in the existing electric utility industry rendered potentially unrecoverable in a competitive market.
• Strangle - An options position consisting of the purchase or sale of put and call options having the same expiration but different strike prices.
• Strategic Conservation - Strategic conservation results from load reductions occurring in all or nearly all time periods. This strategy can be induced by price of electricity, energy-efficient equipment, or decreasing usage of equipment.
• Strategic Load Growth - A form of load building designed to increase efficiency in a power system. This load shape objective can be induced by the price of electricity and by the switching of fuel technologies (from gas to electric).
• Strike Price - The price at which the underlying futures contract is bought or sold in the event an option is exercised. Also called an exercise price.
• Strip - The simultaneous purchase (or sale) of futures positions in consecutive months. The average of the prices for the futures contracts bought (or sold) is the price level of the hedge. A six-month strip, for example, consists of an equal number of futures contracts for each of six consecutive contract months. Also known as a calendar strip.
• Subbituminous Coal - Subbituminous coal, or black lignite, is dull black and generally contains 20 to 30 percent moisture. The heat content of subbituminous coal ranges from 16 to 24 million Btu per ton as received and averages about 18 million Btu per ton. Subbituminous coal, mined in the western coal fields, is used for generating electricity and space heating.
• Substation - A facility used for switching and/or changing or regulating the voltage of electricity. Service equipment, line transformer installations, or minor distribution or transmission equipment are not classified as substations.
• Sulfation - A condition that afflicts unused and discharged batteries; large crystals of lead sulfate grow on the plate, instead of the usual tiny crystals, making the battery extremely difficult to recharge.
• Sulfur - An element that is present in some oil and gas as an impurity in the form of its various compounds.
• Sulfur - One of the elements present in varying quantities in coal which contributes to environmental degradation when coal is burned. In terms of sulfur content by weight, coal is generally classified as low (less than or equal to 1 percent), medium (greater than 1 percent and less than or equal to 3 percent), and high (greater than 3 percent). Sulfur content is measured as a percent by weight of coal on an Ïas received or a Ïdry (moisture-free, usually part of a laboratory analysis) basis.
• Summer Peak - The greatest load on an electric system during any prescribed demand interval in the summer.
• Sun Path Diagram - A circular projection of the sky vault onto a flat diagram used to determine solar positions and shading effects of landscape features on a solar energy system.
• Superconducting Magnetic Energy Storage (SMES) - SMES technology uses the superconducting characteristics of low-temperature materials to produce intense magnetic fields to store energy. SMES has been proposed as a storage option to support large-scale use of photovoltaics and wind as a means to smooth out fluctuations in power generation.
• Superconductivity - The abrupt and large increase in electrical conductivity exhibited by some metals as the temperature approaches absolute zero.
• Supplementary Heat - A heat source, such as a space heater, used to provide more heat than that provided by a primary heating source.
• Supplier - A person or corporation, generator, broker, marketer, aggregator or any other entity, that sells electricity to customers, using the transmission or distribution facilities of an electric distribution company.
• Supply Side - Technologies that pertain to the generation of electricity.
• Support - In technical analysis, a price area where new buying is likely to come in and stem any decline.
• Surplus - Excess firm energy available from a utility or region for which there is no market at the established rates.
• Swamp Cooler - A popular term used for an evaporative cooling device.
• Swap - A custom-tailored, individually negotiated transaction designed to manage financial risk, usually over a period of one to 12 years. Swaps can be conducted directly by two counterparties, or through a third party such as a bank or brokerage house. The writer of the swap, such as a bank or brokerage house, may elect to assume the risk itself, or manage its own market exposure on an exchange. Swap transactions include interest rate swaps, currency swaps, and price swaps for commodities, including energy and metals. In a typical commodity or price swap, parties exchange payments based on changes in the price of a commodity or a market index, while fixing the price they effectively pay for the physical commodity. The transaction enables each party to manage exposure to commodity prices or index values. Settlements are usually made in cash.
• Swept Area - In reference to a wind energy conversion device, the area through which the rotor blades spin, as seen when directly facing the center of the rotor blades.
• Switching Station - Facility equipment used to tie together two or more electric circuits through switches. The switches are selectively arranged to permit a circuit to be disconnected, or to change the electric connection between the circuits.
• Synchronous Generator - An electrical generator that runs at a constant speed and draws its excitation from a power source external or independent of the load or transmission network it is supplying.
• Synchronous Inverter - An electrical inverter that inverts direct current electricity to alternating current electricity, and that uses another alternating current source, such as an electric power transmission and distribution network (grid), for voltage and frequency reference to provide power in phase and at the same frequency as the external power source.
• Synchronous Motor - A type of motor designed to operate precisely at the synchronous speed with no slip in the full-load speeds (rpm).
• Synthetic Futures - A position created by combining call and put options. A synthetic long futures position is created by combining a long call option and a short put option for the same expiration date and the same strike price. A synthetic short futures position is created by combining a long put and a short call with the same expiration date and the same strike price.
• System (Electric) - Physically connected generation, transmission, and distribution facilities operated as an integrated unit under one central management, or operating supervision.
• System Peak Demand - The highest demand value that has occurred during a specified period for the utility system.
• Systems Benefits Charge - This is a per-customer charge intended to recover the costs of utility demand-side management reach and development, renewable resources or low-income programs.