Glossary-1

Glossary

ACCESS CHARGE: A charge paid by all market participants withdrawing energy from the ISO controlled grid. The access charge will recover the portion of a utility's transmission revenue requirement not recovered through the variable usage charge. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

ACTIVE SOLAR ENERGY SYSTEM: A system designed to convert solar radiation into usable energy for space, water heating, or other uses. It requires a mechanical device, usually a pump or fan, to collect the sun's energy. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

ADJUSTMENT BID: A bid that is used by the ISO to adjust supply or demand when congestion is anticipated. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

ADVERSE HYDRO: Water conditions limiting the production of hydroelectric power. In years having below-normal levels of rain and snow, and in seasons having less-than-usual runoff from mountain snowpack, there is then less water available for hydro energy production. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

AGGREGATOR: Any entity, such as a marketer, broker, public agency city, county or special district that combines the loads of multiple end use customers in negotiating the purchase of electricity, the transmission of electricity and other related services to these customers. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

ALCOHOL FUELS: Liquid chemicals made from renewable resources such as locally grown crops and even waste products. They contain a certain combination of hydrogen, carbon and oxygen that qualifies them as fuels. Methanol and ethanol are two types of alcohol fuels used in cars. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

ALTERNATING CURRENT (AC): Flow of electricity that constantly changes direction between positive and negative sides. Almost all power produced by electric utilities in the United States moves in current that shifts direction at a rate of 60 times per second. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

ALTERNATIVE ENERGY: Alternative energy is an umbrella term that refers to any source of usable energy intended to replace fuel sources (fossil fuels and nuclear energy) without the undesired consequences of high carbon dioxide emissions -- the major contributing factor of global warming. Examples of alternative energy include wind power and solar polar. (SOURCE: AeroVironment Energy, http://www.avinc.com/glossary)

ANCILLARY SERVICES: The services other than scheduled energy that are required to maintain system reliability and meet WSCC/NERC operating criteria. Such services include spinning, non-spinning, and replacement reserves, voltage control, and black start capability. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

AVERAGE COST: The revenue requirement of a utility divided by the utility's sales. Average cost typically includes the costs of existing power plants, transmission, and distribution lines, and other facilities used by a utility to serve its customers. It also included operating and maintenance, tax, and fuel expenses. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

AVERAGE DEMAND: The energy demand in a given geographical area over a period of time. For example, the number of kilowatt-hours used in a 24-hour period, divided by 24, tells the average demand for that period. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

BASE LOAD UNIT: A power generating facility that is intended to run constantly at near capacity levels, as much of the time as possible. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

BASE LOAD: The lowest level of power production needs during a season or year. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

BASELINE FORECAST: A prediction of future energy needs which does not take into account the likely effects of new conservation programs that have not yet been started. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

BATTERY: A device that stores energy and produces electric current by chemical action. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

BLACK START: A black start is the process of restoring a power station to operation without relying on the external electric power transmission network. (SOURCE: DOE Energy Storage Database, http://www.energystorageexchange.org/application/glossary)

CAPACITY (Electric utility): The maximum amount of electricity that a generating unit, power plant or utility can produce under specified conditions. Capacity is measured in megawatts and is also referred to as the NAMEPLATE RATING. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

COMPRESSED AIR ENERGY STORAGE (CAES): Off-peak electrical energy is used to compress air into underground storage reservoirs for storage until times of peak or intermediate electricity demand. Wind power offers a good opportunity for charging CAES storage. The storage is typically underground in natural aquifers, depleted oil or gas fields, salt caverns, or excavated or natural rock caverns. To generate power, the compressed air is first heated and then passed through a turbine. (SOURCE: CEPE, http://www.cepe.ethz.ch/publications/Semadeni_Glossary_Energy_Storage.pdf)

ELECTRIC GRID: A large interconnection of both generation and transmission electrical subsystems to facilitate efficient distribution of electricity to consumers and businesses. (SOURCE: Southern California Edison, http://www.sce.com/PowerandEnvironment/PowerGeneration/SanOnofreNuclearGeneratingStation/glossaryofterms.htm)

ELECTRIC SUPPLY CAPACITY: Depending on the circumstances in a given electric supply system, energy storage could be used to defer and/or to reduce the need to buy new central station generation capacity and/or to ‘rent’ generation capacity in the wholesale electricity marketplace. (SOURCE: DOE Energy Storage Database, http://www.energystorageexchange.org/application/glossary)

ELECTRIC SUPPLY RESERVE CAPACITY - NON-SPINNING: Generation capacity that may be offline, or that comprises a block of curtailable and/or interruptible loads, and that can be available within 10 minutes. Unlike spinning reserve capacity, non-spinning reserve capacity is not synchronized with the grid (frequency). Non-spinning reserves are used after all spinning reserves are online. (SOURCE: DOE Energy Storage Database, http://www.energystorageexchange.org/application/glossary)

ELECTRIC SUPPLY RESERVE CAPACITY – SPINNING: Generation capacity that is online but unloaded and that can respond within 10 minutes to compensate for generation or transmission outages. ‘Frequency-responsive’ spinning reserve responds within 10 seconds to maintain system frequency. Spinning reserves are the first type used when a shortfall occurs. (SOURCE: DOE Energy Storage Database, http://www.energystorageexchange.org/application/glossary)

ELECTRICAL SWITCHYARD: a facility where electricity from the electrical generator is transferred to the electric grid. (SOURCE: Southern California Edison, http://www.sce.com/PowerandEnvironment/PowerGeneration/SanOnofreNuclearGeneratingStation/glossaryofterms.htm)

ENERGY RESERVES: The portion of total energy resources that is known and can be recovered with presently available technology at an affordable cost. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org) EPAct: The Energy Policy Act of 1992 addresses a wide variety of energy issues. The legislation creates a new class of power generators, exempt wholesale generators (EWGs), that are exempt from the provisions of the Public Utilities Holding Company Act of 1935 and grants the authority to FERC to order and condition access by eligible parties to the interconnected transmission grid. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

FEDERAL ENERGY REGULATORY COMMISSION (FERC): An independent regulatory commission within the U.S. Department of Energy that has jurisdiction over energy producers that sell or transport fuels for resale in interstate commerce; the authority to set oil and gas pipeline transportation rates and to set the value of oil and gas pipelines for ratemaking purposes; and regulates wholesale electric rates and hydroelectric plant licenses. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

FLYWHEELS: Consist of heavy symmetrical or cylindrical masses of steel or composite material that store mechanical energy by rotation. Almost frictionless, the masses rotate around a titanium axle with magnetic bearings at about 50,000 revolutions per minute. The rotating masses are used in conjunction with a dynamo to generate electricity on demand. Flywheels can be attached to a machine to regulate its speed or variation in motion. (SOURCE: CEPE, http://www.cepe.ethz.ch/publications/Semadeni_Glossary_Energy_Storage.pdf)

FOSSIL FUEL: Oil, coal, natural gas or their by-products. Fuel that was formed in the earth in prehistoric times from remains of living-cell organisms. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

FREQUENCY REGULATION: Frequency regulation involves moment-to-moment reconciliation of the supply of electricity and the demand for electricity. The reconciliation is done every few seconds. So at any given moment, if electricity demand exceeds supply then the supply is increased to meet demand. And, if demand is less than supply then the supply is decreased. (SOURCE: DOE Energy Storage Database, http://www.energystorageexchange.org/application/glossary)

GIGAWATT (GW): One thousand megawatts (1,000 MW) or, one million kilowatts (1,000,000 kW) or one billion watts (1,000,000,000 watts) of electricity. One gigawatt is enough to supply the electric demand of about one million average California homes. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

GIGAWATT-HOUR (GWH): One million kilowatt-hours of electric power. California generated about 290,000 gigawatt-hours of electricity in 2004. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

GRID ARCHITECTURE: The layout of transmission and distribution systems of an electricity grid connects power generation plants through thousands of branches to feeder lines reaching into homes, buildings, and industries. Redundant branches between transmission lines provide a redundant system, which assure the smooth flow of power to the distribution lines. (SOURCE: CEPE, http://www.cepe.ethz.ch/publications/Semadeni_Glossary_Energy_Storage.pdf)

GRID CONNECTED COMMERCIAL (RELIABILITY & QUALITY): The electric reliability application entails use of energy storage to provide highly reliable electric service. In the event of a complete power outage lasting more than a few seconds the storage system provides enough energy to a) ride through outages of extended duration or b) to complete an orderly shutdown of processes, c) transfer to on-site generation resources. The electric power quality application involves use of energy storage to protect loads downstream against short duration events which affect the quality of power delivered to the load. Some manifestations of poor power quality include: • variations in voltage magnitude, (e.g., short-term spikes or dips, longer-term surges, or sags) • variations in the primary 60 cycles/sec frequency at which power is delivered • low power factor (voltage and current excessively out of phase with each other) • harmonics, (i.e., the presence of currents or voltages at frequencies other than the primary frequency) • interruptions in service, of any duration, from a fraction of a second to minutes (SOURCE: DOE Energy Storage Database, http://www.energystorageexchange.org/application/glossary) GRID

ENERGY STORAGE: Grid Energy Storage is a power grid that is used to manage the flow of electricity. (SOURCE: AeroVironment Energy, http://www.avinc.com/glossary)

INTERMITTENCY OF RENEWABLE ENERGY SOURCES: Fluctuating availability of the energy source due to the variation of natural services of terrestrial or solar systems. (SOURCE: CEPE, http://www.cepe.ethz.ch/publications/Semadeni_Glossary_Energy_Storage.pdf)

ISO/RTO (INDEPENDENT SYSTEM OPERATOR/REGIONAL TRANSMISSION ORGANIZATION): The ISO or RTO that manages the grid where the energy storage system is installed, if applicable. In the areas where an ISO is established, it coordinates, controls, and monitors the operation of the electrical power system, usually within a single US State, but sometimes encompassing multiple states. RTOs typically perform the same functions as ISOs, but cover a larger geographic area. (SOURCE: DOE Energy Storage Database, http://www.energystorageexchange.org/application/glossary)

KILOWATT (kW): One thousand (1,000) watts. A unit of measure of the amount of electricity needed to operate given equipment. On a hot summer afternoon a typical home, with central air conditioning and other equipment in use, might have a demand of four kW each hour. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

LOAD: The amount of electric power supplied to meet one or more end user's needs. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

LOAD FACTOR: A percentage that denotes the difference between the amount of electricity a consumer used during a given time span and the amount that would have been used if the usage had stayed at the consumer's highest demand level during the whole time. The term also is used to mean the percentage of capacity of an energy facility -- such as power plant or gas pipeline -- that is utilized in a given period of time. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

LOAD MANAGEMENT: Steps taken to reduce power demand at peak load times or to shift some of it to off-peak times. This may be with reference to peak hours, peak days or peak seasons. The main thing affecting electric peaks is air-conditioning usage, which is therefore a prime target for load management efforts. Load management may be pursued by persuading consumers to modify behavior or by using equipment that regulates some electric consumption. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

LOSSES (Electric utility): Electric energy or capacity wasted in the normal operation of a power system. Some kilowatt-hours are lost in the form of waste heat in electrical equipment such as substation conductors. LINE LOSSES are kilowatts or kilowatt-hours lost in transmission and distribution lines under certain conditions. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

MEGAWATTS (MW): standard measure of electrical power. One megawatt equals one million watts or a thousand kilowatts.(SOURCE: Southern California Edison, http://www.sce.com/PowerandEnvironment/PowerGeneration/SanOnofreNuclearGeneratingStation/glossaryofterms.htm)

NON-DEPLETABLE ENERGY SOURCES: Energy not obtained from energy sources that can run out. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

PEAK LOAD: The highest electrical demand within a particular period of time. Daily electric peaks on weekdays occur in late afternoon and early evening. Annual peaks occur on hot summer days. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

PUMPED HYDROELECTRIC STORAGE: Commercial method used for large-scale storage of power. During off-peak times, excess power is used to pump water to a reservoir. During peak times, the reservoir releases water to operate hydroelectric generators. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

QUALIFYING FACILITY: QFs are non-utility power producers that often generate electricity using renewable and alternative resources, such as hydro, wind, solar, geothermal or biomass (solid waste). QFs must meet certain operating, efficiency, and fuel-use standards set forth by the Federal Energy Regulatory Commission (FERC). If they meet these FERC standards, utilities must buy power from them. QFs usually have long-term contracts with utilities for the purchase of this power, which is among the utility's highest-priced resources. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

RAMPING: Changing the loading level of a Generating Unit in a constant manner over a fixed time (e.g., Ramping up or Ramping down). Such changes may be directed by a computer or manual control. (SOURCE: DOE Energy Storage Database, http://www.energystorageexchange.org/application/glossary) ?

RATED POWER: The total possible output from the energy storage system, expressed in kW. (SOURCE: DOE Energy Storage Database, http://www.energystorageexchange.org/application/glossary) REGULATION: The service provided by generating units equipped and operating with automatic generation controls that enables the units to respond to the ISO's direct digital control signals to match real-time demand and resources, consistent with established operating criteria. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

RELIABILITY: Electric system reliability has two components-- adequacy and security. Adequacy is the ability of the electric system to supply the aggregate electrical demand and energy requirements of the customers at all times, taking into account scheduled and unscheduled outages of system facilities. Security is the ability of the electric system to withstand sudden disturbances such as electric short circuits or unanticipated loss of system facilities. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

RENEWABLES CAPACITY FIRMING: Use of storage to mitigate rapid output changes from renewable generation due to: a) wind speed variability affecting wind generation and b) shading of solar generation due to clouds. It is important because these rapid output changes must be offset by other “dispatchable” generation. (SOURCE: DOE Energy Storage Database, http://www.energystorageexchange.org/application/glossary)

RENEWABLE ENERGY: Resources that constantly renew themselves or that are regarded as practically inexhaustible. These include solar, wind, geothermal, hydro and wood. Although particular geothermal formations can be depleted, the natural heat in the earth is a virtually inexhaustible reserve of potential energy. Renewable resources also include some experimental or less-developed sources such as tidal power, sea currents and ocean thermal gradients. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

RENEWABLE ENERGY TIME-SHIFT: Centralized or distributed Electric Energy Time Shifting specifically related to the uncontrollable nature of renewable generation. (SOURCE: DOE Energy Storage Database, http://www.energystorageexchange.org/application/glossary)

RENEWABLE PORTFOLIO STANDARD (RPS): Renewable Portfolio Standard. The requirement that IOUs must contract a percent of there load with renewable energy. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

RENEWABLE RAW MATERIAL: Biomass that is only harvested to an extent that allows a (natural) regeneration. It is used for energetic or other purposes (e.g. as a construction material). (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

RENEWABLE RESOURCES: Renewable energy resources are naturally replenishable, but flow-limited. They are virtually inexhaustible in duration but limited in the amount of energy that is available per unit of time. Some (such as geothermal and biomass) may be stock-limited in that stocks are depleted by use, but on a time scale of decades, or perhaps centuries, they can probably be replenished. Renewable energy resources include: biomass, hydro, geothermal, solar and wind. In the future they could also include the use of ocean thermal, wave, and tidal action technologies. Utility renewable resource applications include bulk electricity generation, on-site electricity generation, distributed electricity generation, non-grid-connected generation, and demand-reduction (energy efficiency) technologies. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

SOLAR ENERGY: Heat and light radiated from the sun. Solar radiation reaching the earth and its use for the production of electricity and heat. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

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. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

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. (SOURCE: California Energy Commission, http://www.consumerenergycenter.org)

VOLTAGE SUPPORT: To manage "reactance" at the grid system level, grid system operators rely on an ancillary service called ‘voltage support’. The purpose of voltage support is to offset reactive effects so that grid system voltage can be restored or maintained. The purpose of voltage support is to offset reactive effects so that grid system voltage can be restored or maintained. "Reactance" occurs because equipment that generates, transmits, or uses electricity often has or exhibits characteristics like those of inductors and capacity ors in an electric circuit. (SOURCE: DOE Energy Storage Database, http://www.energystorageexchange.org/application/glossary)

WIND ENERGY: Wind energy is a converted form of solar energy and is mainly used today to generate electricity. As the sun's radiation heats different parts of the earth at different rates it causes portions of the atmosphere to warm differently. As a result, hot air rises, reducing the atmospheric pressure at the earth's surface, and cooler air is drawn in to replace it. The result is wind. (SOURCE: AeroVironment Energy, http://www.avinc.com/glossary)