Glossary of Terms - U & V

• U.S. Department of Energy (DOE) - The DOE managers programs of research, development and commercialization for various energy technologies, and associated environmental, regulatory and defense programs. DOE announces energy policies and acts as a principal advisor to the President on energy matters.
• U.S. Environmental Protection Agency (EPA) - The EPA administers federal environmental policies, enforces environmental laws and regulations, performs research, and provides information on environmental subjects. The agency also acts as chief advisor to the President on U.S. environmental policy and issues.
• Ultimate Analysis - A procedure for determining the primary elements in a substance (carbon, hydrogen, oxygen, nitrogen, sulfur, and ash).
• Ultrahigh Voltage Transmission - Transporting electricity over bulk-power lines at voltage greater than 800 kilovolts.
• Ultraviolet - Electromagnetic radiation in the wavelength range of 4 to 400 nanometers. vacuum evaporation-The deposition of thin films of semiconductor material by the evaporation of elemental sources in a vacuum.
• Unbundling - Disaggregating electric utility service into its basic components and offering each component separately for sale with separate rates for each component. For example, generation, transmission and distribution could be unbundled and offered as discrete services.
• Uncertainties - Uncertainties are factors over which the utility has little or no foreknowledge, and include load growth, fuel prices, or regulatory changes. Uncertainties are modeled in a probabilistic manner. However, in the Detailed Workbook, you may find it is more convenient to treat uncertainties as "unknown but bounded" variables without assuming a probabilistic structure. A specified uncertainty is a specific value taken on by an uncertainty factor (e.g. 3 percent per year for load growth). A future uncertainty is a combination of specified uncertainties (e.g. 3 percent per year load growth, 1 percent per year real coal and oil price escalation, and 2.5 percent increase in housing starts).
• Underlying - The stock, commodity, futures contract, or cash index against which the futures or options contract is valued.
• Uniform System of Accounts - Prescribed financial rules and regulations established by the Federal Energy Regulatory Commission for utilities subject to its jurisdiction under the authority granted by the Federal Power Act.
• Unit Energy Consumption (UEC) - The annual amount of energy that is used by the electrical device or appliance.
• Universal Service - Electric service sufficient for basic needs (an evolving bundle of basic services) available to virtually all members of the population regardless of income.
• Unserved or Unmet Energy - The average energy that will be demanded but not served during a specified period due to inadequate available generating capacity.
• Upgrade - Replacement or addition of electrical equipment resulting in increased generation or transmission capability.
• Uprate - An increase in the rating or stated measure of generation or transfer capability.
• Useful Heat - Heat stored above room temperature (in a solar heating system).
• Useful Thermal Output - The thermal energy made available for use in any industrial or commercial process, or used in any heating or cooling application, i.e., total thermal energy made available for processes and applications other than electrical generation.
• Utility - A regulated entity which exhibits the characteristics of a natural monopoly. For the purposes of electric industry restructuring "utility" refers to the regulated, vertically-integrated electric company. "Transmission utility" refers to the regulated owner/operator of the transmission system only. "Distribution utility" refers to the regulated owner/operator of the distribution system which serves retail customers.
• Utility-Earned Incentives - Costs in the form of incentives paid to the utility for achievement in consumer participation in DSM programs. These financial incentives are intended to influence the utilityÌs consideration of DSM as a resource option by addressing cost recovery, lost revenue, and profitability.
• Utility-Interactive Inverter - An inverter that can function only when tied to the utility grid, and uses the prevailing line-voltage frequency on the utility line as a control parameter to ensure that the PV system's output is fully synchronized with the utility power.
• Utilization Factor - The ratio of the maximum demand of a system or part of a system to the rated capacity of the system or part of the system.
• U-Value (see Coefficient of Heat Transmission) - The reciprocal of R-Value. The lower the number, the greater the heat transfer resistance (insulating) characteristics of the material.
• Vac - Volts ac
• Vacuum Evaporation - The deposition of thin films of semiconductor material by the evaporation of elemental sources in a vacuum.
• Vacuum Zero - The energy of an electron at rest in empty space; used as a reference level in energy band diagrams.
• Valence Band - The highest energy band in a semiconductor that can be filled with electrons.
• Valence State - valence level energy, bound state--Energy content of an electron in orbit about an atomic nucleus.
• Valley Filling - Valley filling is a form of load management that increases or builds, off-peak loads. This load shape objective is desirable if a utility has surplus capacity in the off-peak hours. If this strategy is combined with time-or-use rates, the average rate for electricity can be lowered.
• Variable Costs - Costs, such as fuel costs, that depend upon the amount of electric energy supplied.
• Variable Prices - Prices that vary frequently. Prices that are not stable.
• Variable-Speed Wind Turbines - Turbines in which the rotor speed increases and decreases with changing wind speed, producing electricity with a variable frequency.
• Variation Margin - Payment made on a daily or intraday basis by a clearing member to the clearinghouse to cover losses created by adverse price movement in positions carried by the clearing member, calculated separately for customer and proprietary positions.
• Vega - The sensitivity of an option's value to a change in volatility.
• Vertical Integration - An arrangement whereby the same company owns all the different aspects of making, selling, and delivering a product or service. In the electric industry, it refers to the historically common arrangement whereby a utility would own its own generating plants, transmission system, and distribution lines to provide all aspects of electric service.
• Vertical Multijunction (VMJ) Cell - A compound cell made of different semiconductor materials in layers, one above the other. Sunlight entering the top passes through successive cell barriers, each of which converts a separate portion of the spectrum into electricity, thus achieving greater total conversion efficiency of the incident light. Also called a multiple junction cell. See 'multijunction device'; 'split-spectrum cell.'
• Vertical-Axis Wind Turbine (VAWT) - A type of wind turbine in which the axis of rotation is perpendicular to the wind stream and the ground.
• Visible Radiation - The visible portion of the electromagnetic spectrum with wavelengths from 0.4 to 0.76 microns
• Vmp - Voltage at maximum power
• Voc - Open-circuit voltage
• Volatility - The market's price range and movement within that range. The direction of the price move, whether up or down, is not relevant. Historic volatility indicates how much prices have changed in the past and is derived by using daily settlement prices for futures. Implied volatility measures how much the market thinks prices will change in the future, and is obtained from daily settlement prices for options. A measurement of the price fluctuation of an underlying instrument that takes place over a certain period of time. The relative rate at which the price of a commodity moves up and down; found by calculating the annualized standard deviation of daily change in price.
• Volt - A unit of electrical pressure. It measures the force or push of electricity. Volts represent pressure, correspondent to the pressure of water in a pipe. A volt is the unit of electromotive force or electric pressure analogous to water pressure in pounds per square inch. It is the electromotive force which, if steadily applied to a circuit having a resistance of one ohm, will produce a current one ampere.
• Voltage - The amount of electromotive force, measured in volts, that exists between two points.
• Voltage at Maximum Power (Vmp) - The voltage at which maximum power is available from a module. [UL 1703]
• Voltage Reduction - Any intentional reduction of system voltage by 3 percent or greater for reasons of maintaining the continuity of service of the bulk electric power supply system.
• Volt-amperes - The volt-amperes of an electric circuit are the mathematical products of the volts and emperes of the client.