Glossary of Terms - W, X, Y & Z

• Waste-to-Energy - This is a technology that uses refuse to generate electricity. In mass burn plants, untreated waste is burned to produce steam, which is used to drive a steam turbine generator. In refuse-derived fuel plants, refuse is pre-treated, partially to enhance its energy content prior to burning.
• Water Jacket - A heat exchanger element enclosed in a boiler. Water is circulated with a pump through the jacket where it picks up heat from the combustion chamber after which the heated water circulates to heat distribution devices. A water jacket is also an enclosed water-filled chamber in a tankless coiled water heater. When a faucet is turned on water flows into the water heater heat exchanger. The water in the chamber is heated and transfers heat to the cooler water in the heat exchanger and is sent through the hot water outlet to the appropriate faucet.
• Water Source Heat Pump - A type of (geothermal) heat pump that uses well (ground) or surface water as a heat source. Water has a more stable seasonal temperature than air thus making for a more efficient heat source.
• Water Turbine - A turbine that uses water pressure to rotate its blades; the primary types are the Pelton wheel, for high heads (pressure); the Francis turbine, for low to medium heads; and the Kaplan for a wide range of heads. Primarily used to power an electric generator.
• Water Wall - An interior wall made of water filled containers for absorbing and storing solar energy.
• Water Wheel - A wheel that is designed to use the weight and/or force of moving water to turn it, primarily to operate machinery or grind grain.
• Watt (W) - The unit of electric power, or amount of work (J), done in a unit of time. One ampere of current flowing at a potential of one volt produces one watt of power. The electrical unit of power. The rate of energy transfer equivalent to 1 ampere flowing under a pressure of 1 volt at unity power factor. The rate of energy transfer equivalent to one ampere under an electrical pressure of one volt. One watt equals 1/746 horsepower, or one joule per second. It is the product of Voltage and Current (amperage).
• Watt-hour (Wh) - An electrical energy unit of measure equal to 1watt of power supplied to, or taken from, an electric circuit steadily for 1 hour. A unit of electricity consumption of one Watt over the period of one hour.
• Wattmeter - A device for measuring power consumption.
• Wave Power - The concept of capturing and converting the energy available in the motion of ocean waves to energy.
• Waveform - The shape of the curve graphically representing the change in the ac signal voltage and current amplitude, with respect to time.
• Wavelength - The distance between similar points on successive waves.
• West Texas Intermediate - A grade of crude oil deliverable against the New York Mercantile Exchange light, sweet crude oil contract. Nominally, the benchmark crude of the U.S. oil industry.
• Western systems Coordinating Council (WSCC) - One of the ten regional reliability councils that make up the North American Electric Reliability Council (NERC).
• Wet Barrel - A physical barrel of crude oil or refined product as opposed to a "paper barrel."
• Wet Gas - Natural gas containing condensable hydrocarbons.
• Wheeling - The process of transmitting electricity over one or more separately owned electric transmission and distribution systems. (See Wholesale and Retail Wheeling.)
• Wheeling Service - The movement of electricity from one system to another over transmission facilities of intervening systems. Wheeling service contracts can be established between two or more systems.
• Wholesale Bulk Power - Very large electric sales for resale from generation sources to wholesale market participants and electricity marketers and brokers.
• Wholesale Competition - A system whereby a distributor of power would have the option to buy its power from a variety of power producers, and the power producers would be able to compete to sell their power to a variety of distribution companies.
• Wholesale Power Market - The purchase and sale of electricity from generators to resellers (who sell to retail customers) along with the ancillary services needed to maintain reliability and power quality at the transmission level.
• Wholesale Sales - Energy supplied to other electric utilities, cooperatives, municipals, and Federal and State electric agencies for resale to ultimate consumers.
• Wholesale Transition - The sale of electric power from an entity that generates electricity to a utility or other electric distribution system through a utility's transmission lines.
• Wholesale Transmission Services - The transmission of electric energy sod, or to be sold, at wholesale in interstate commerce.
• Wholesale Wheeling - The wheeling of electric power in amounts and at prices that generally have been negotiated in longterm contracts between the generator and a distributor or very large consumer of power.
• Wind Energy - Energy available from the movement of the wind across a landscape caused by the heating of the atmosphere, earth, and oceans by the sun.
• Wind Energy Conversion - A process that uses energy from the wind and converts it into mechanical energy and then electricity.
• Wind Energy Conversion System (WECS) or Device - An apparatus for converting the energy available in the wind to mechanical energy that can be used to power machinery (grain mills, water pumps) and to operate an electrical generator.
• Wind Generator - A WECS designed to produce electricity.
• Wind Power Plant - A group of wind turbines interconnected to a common utility system through a system of transformers, distribution lines, and (usually) one substation. Operation, control, and maintenance functions are often centralized through a network of computerized monitoring systems, supplemented by visual inspection. This is a term commonly used in the United States. In Europe, it is called a generating station.
• Wind Resource Assessment - The process of characterizing the wind resource, and its energy potential, for a specific site or geographical area.
• Wind Speed - The rate of flow of the wind undisturbed by obstacles.
• Wind Speed Duration Curve - A graph that indicates the distribution of wind speeds as a function of the cumulative number of hours that the wind speed exceeds a given wind speed in a year.
• Wind Speed Frequency Curve - A curve that indicates the number of hours per year that specific wind speeds occur.
• Wind Speed Profile - A profile of how the wind speed changes with height above the surface of the ground or water.
• Wind Turbine - A term used for a wind energy conversion device that produces electricity; typically having one, two, or three blades.
• Wind Turbine Rated Capacity - The amount of power a wind turbine can produce at its rated wind speed, e.g., 100 kW at 20 mph. The rated wind speed generally corresponds to the point at which the conversion efficiency is near its maximum. Because of the variability of the wind, the amount of energy a wind turbine actually produces is a function of the capacity factor (e.g., a wind turbine produces 20% to 35% of its rated capacity over a year).
• Wind Velocity - The wind speed and direction in an undisturbed flow.
• Windmill - A WECS that is used to grind grain, and that typically has a high-solidity rotor; commonly used to refer to all types of WECS.
• Windpower Curve - A graph representing the relationship between the power available from the wind and the wind speed. The power from the wind increases proportionally with the cube of the wind speed.
• Windpower Profile - The change in the power available in the wind due to changes in the wind speed or velocity profile; the windpower profile is proportional to the cube of the wind speed profile.
• Winter Peak - The greatest load on an electric system during any prescribed demand interval in the winter season or months.
• Wire (Electrical) - A generic term for an electrical conductor.
• Wires Charge - A broad term which refers to charges levied on power suppliers or their customers for the use of the transmission or distribution wires.
• Work Function - The energy difference between the Fermi level and vacuum zero. The minimum amount of energy it takes to remove an electron from a substance into the vacuum.
• Working Fluid - A fluid used to absorb and transfer heat energy.
• Wound Rotor Motors - A type of motor that has a rotor with electrical windings connected through slip rings to the external power circuit. An external resistance controller in the rotor circuit allows the performance of the motor to be tailored to the needs of the system and to be changed with relative ease to accommodate system changes or to vary the speed of the motor.
• Writer - The seller of an option. Also known as the grantor of the option.
• Yaw - The rotation of a horizontal axis wind turbine around its tower or vertical axis.
• Yield - 1) A measure of the annual return on an investment expressed as a percentage. 2) The proportion of heavy or light products which can be derived from a given barrel of crude oil.