| Balance Of System | Represents all components and costs other than the photovoltaic modules/array. It includes design costs, land, site preparation, system installation, support structures, power conditioning, operation and maintenance costs, indirect storage, and related costs. |
| Balance Of System (BOS) | Parts or components of a photovoltaic system other than the photovoltaic array or other generating equipment. |
| Balanced Schedule | A Scheduling Coordinator’s schedule is balanced when generation, adjusted for transmission losses, equals demand. |
| Ballast | A circuit used to condition and stabilize an electric current, for example, in a fluorescent light. |
| Balneology | using hot spring mineral water for therapy. This is perhaps the oldest use of natural geothermal waters. |
| Band Gap | In a semiconductor, the energy difference between the highest valence band and the lowest conduction band. |
| Band Gap Energy (Eg) | The amount of energy (in electron volts) required to free an outer shell electron from its orbit about the nucleus to a free state, and thus promote it from the valence to the conduction level. |
| Barrel | In the petroleum industry, a barrel is 42 U.S. gallons. One barrel of oil has an energy content of 6 million British thermal units. It takes one barrel of oil to make enough gasoline to drive an average car from Los Angeles to San Francisco and back (at 18 miles per gallon over the 700-mile round trip). |
| Barrels Per Day Equivalent (Bpd-Equivalent) | A unit of measure that tells how much oil would have to be burned to produce the same amount of energy. |
| Barrier Energy | The energy given up by an electron in penetrating the cell barrier; a measure of the electrostatic potential of the barrier. |
| Base Load | The lowest level of power production needs during a season or year. |
| Base Load Unit | A power generating facility that is intended to run constantly at near capacity levels, as much of the time as possible. |
| Base Rate | That portion of the total electric or gas rate covering the general costs of doing business unrelated to fuel expenses. |
| 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. |
| Batch Solar Hot Water Heater | The simplest of solar hot water systems. A tank of water within a glass-covered insulated enclosure aimed at the sun. Water is heated in the tank and then flows to the load or an auxiliary water heater. |
| Battery | A single electric cell, or group of connected cells, that produces a direct electric current. |
| Battery Available Capacity | The total maximum charge, expressed in ampere-hours, that can be withdrawn from a cell or battery under a specific set of operating conditions including discharge rate, temperature, initial state of charge, age, and cut-off voltage. |
| Battery Bank | A group of batteries which stores excess electrical energy for later use. |
| Battery Capacity | The maximum total electrical charge, expressed in ampere-hours, which a battery can deliver to a load under a specific set of conditions. |
| Battery Cell | An individual unit of a battery that can store electrical energy and is capable of furnishing a current to an external load. For lead-acid batteries the voltage of a cell (fully charged) is about 2.2 volts dc. A battery may consist of a number of cells. |
| Battery Charger | A device used to charge a battery by converting (usually) mains voltage AC to a DC voltage suitable for the battery. Chargers often incorporate some form of regulator to prevent overcharging and damage to the battery. |
| Battery Cycle Life | The number of times a battery can be discharged and charged before it fails. |
| Battery Energy Capacity | The total energy available, expressed in watt-hours (kilowatt-hours), which can be withdrawn from a fully charged cell or battery. The energy capacity of a given cell varies with temperature, rate, age, and cut-off voltage. This term is more common to system designers than it is to the battery industry where capacity usually refers to ampere-hours. |
| Battery Energy Storage | Energy storage using electrochemical batteries. The three main applications for battery energy storage systems include spinning reserve at generating stations, load leveling at substations, and peak shaving on the customer side of the meter. |
| Battery Life | The period during which a cell or battery is capable of operating above a specified capacity or efficiency performance level. With lead-acid batteries, end-of-life is generally considered when a fully charged cell can deliver only 80 percent of its rated capacity. Beyond this state of aging, deterioration and loss of capacity begins to accelerate rapidly. Life may be measured in cycles or years, depending on the type of service for which the cell or battery is intended. |
| Battery Self Discharge | Energy loss by a battery not under load. |
| Battery Self-Discharge | Energy loss by a battery that is not under load. |
| Battery State Of Charge (SOC) | The charge status as a percentage of full charge |
| Benzene | A type of colorless liquid hydrocarbon that can be used as a motor fuel. Its chemical symbol is C6H6. |
| Betz Limit | The theoretical maximum energy that a wind generator can extract from the wind—59.6 percent. |
| Bi-Fuel Vehicle | A vehicle with two separate fuel systems designed to run on either fuel, using only one fuel at a time. These systems are advantageous for drivers who do not always have access to an alternative fuel refueling station. Bi-fuel systems are usually used in light-duty vehicles. One of the two fuels is typically an alternative fuel. |
| Bi-Gas | A process being developed as a means of making synthetic gas from coal. The synthetic gas would be intended to substitute for natural gas in meeting industrial and home energy needs. |
| Bilateral Contract | A two-party agreement for the purchase and the sale of energy products and services. |
| Bioconversion | Processes that use plants or micro-organisms to change one form of energy into another. For example, an experimental process uses algae to convert solar energy into gas that could be used for fuel. |
| Biodiesel | a biodegradable transportation fuel for use in diesel engines that is produced through the transesterfication of organically- derived oils or fats. It may be used either as a replacement for or as a component of diesel fuel. |
| Bioenergy | the energy from biomass (organic matter)—can be used directly for heat or to power a generator to produce electricity. Biomass can also be chemically converted into a fuel oil or liquid fuels. |
| Biofuels (Biomass Fuels) | Biomass converted directly to energy or converted to liquid or gaseous fuels, such as ethanol methane, and hydrogen. |
| Biomass | Any organic matter available on a renewable basis, including agricultural crops, wastes, and residues; wood, wood wastes, and residues; animal wastes and municipal wastes; and aquatic plants. |
| Biosphere | The zone at and adjacent to the earth’s surface where all life exists; all living organisms of the earth. |
| Bipv | Building Integrated Photovoltaics. As the name suggests, this is where PV modules are integrated in to the building construction materials as on integrated unit. |
| BIPV (Building-Integrated Photovoltaics) | A term for the design and integration of photovoltaic (PV) technology into the building envelope, typically replacing conventional building materials. This integration may be in vertical facades, replacing view glass, spandrel glass, or other facade material; into semitransparent skylight systems; into roofing systems, replacing traditional roofing materials; into shading "eyebrows" over windows; or other building envelope systems. |
| Bituminous Coal | Soft coal containing large amounts of carbon. It has a luminous flame and produces a great deal of smoke. |
| Blackout | The total loss of electric power supplied by the electric company. |
| Blade | The energy capturing, aerodynamically designed part of a wind turbine, which interacts directly with the wind. |
| Blocking Diode | A diode used to prevent current flow in an undesirable direction e.g. From the rest of the PV array to a failed module or from the battery to the PV array when current generation is low. |
| Boiler | A closed vessel in which water is converted to pressurized steam. |
| Boiling Point | temperature at which a single substance, such as water, changes from a liquid to a gas (steam) under normal atmospheric pressure. The boiling point at which water transitions to steam is 212°F (100°C). Some liquids boil at a lower temperature than water – a principle utilized in binary power plants. Boiling point is also affected by pressure. The greater the pressure, the higher the boiling point. This principle is put to work in geothermal (flash) power plants when superheated (hotter than boiling) geothermal water is brought up wells. The hot water flashes to steam when the pressure is released as it reaches the surface. This phenomenon also occurs naturally, resulting in such features as geysers. |
| Boiling Water Reactor | (BWR) A nuclear power unit in which water used as a coolant is allowed to boil at the core. The resulting steam may be used to drive electric turbines. |
| Bora | A cold wind that blows from the north or northeast across the lands around the Adriatic Sea. This wind is named after Boreas. |
| Boreas | The North Wind in Greek mythology. (“Aquilo” in Latin.) |
| Boron (B) | The chemical element commonly used as the dopant in photovoltaic device or cell material. |
| Bottled Gas | The liquified petroleum gases propane and butane, contained under moderate pressure (about 125 pounds per square inch and 30 pounds per square inch respectively), in cylinders. |
| Bottoming Cycle | A means to increase the thermal efficiency of a steam electric generating system by converting some waste heat from the condenser into electricity rather than discharging all of it into the environment. |
| Boule | A sausage-shaped, synthetic single-crystal mass grown in a special furnace, pulled and turned at a rate necessary to maintain the single-crystal structure during growth. |
| Brake | Device for stopping a wind turbine. This can be an electric brake that shorts the output of the turbine (dynamic braking), or a mechanical brake that physically stops the rotation, as with a brake drum and shoe. |
| Breaker | A manually operable switching device that also automatically opens a circuit in the event of overcurrent. |
| Breeder | A nuclear reactor that produces more fuel than it consumes. The breeder, invented in the United States, is used as a power source in several European countries. |
| Breeze | Wind classified as light, gentle, moderate, fresh, or strong. To see the corresponding wind speeds for each of these, look at the Beaufort Scale above. |
| British Thermal Unit (Btu) | The amount of heat energy required to raise one pound of water from a temperature of 60 degrees F to 61 degrees F at one atmosphere pressure. One Watt hour equals 3,413 BTU. |
| Broker | A retail agent who buys and sells power. The agent may also aggregate customers and arrange for transmission, firming and other ancillary services as needed. |
| Brownout | A temporary reduction of voltage supplied by the electric company. Typically causes lights to dim. |
| BTU (British Thermal Unit) | Measurement of heat energy. 1 BTU is the amount of energy it require to heat 1 pound of water from 60 to 61 degrees Fahrenheit. 1W = 3413BTU. |
| Building Envelope | The assembly of exterior partitions of a building which enclose conditioned spaces, through which thermal energy may be transferred to or from the exterior, unconditioned spaces, or the ground |
| Bulk Charge | The initial phase of battery charging, when the largest amount of energy is put into the battery. |
| Bulk Power Supply | Often this term is used interchangeably with wholesale power supply. In broader terms, it refers to the aggregate of electric generating plants, transmission lines, and related-equipment. The term may refer to those facilities within one electric utility, or within a group of utilities in which the transmission lines are interconnected. |
| Busbar | In electric utility operations, a busbar is a conductor that serves as a common connection for two or more circuits. It may be in the form of metal bars or high-tension cables. |
| Buss | An electrical connection component that can accept multiple cables or wires. Also bus, bus bar, or busbar |
| Buster | A sudden and violent cold wind that blows across Australia from the south. In parts of Australia it is referred to as a “southerly buster” or a “brickfielder.” |
| Butane | A hydrocarbon gas found in the earth along with natural gas and oil. Butane turns into a liquid when put under pressure. It is sold as bottled gas. It is used to run heaters, stoves and motors, and to help make petrochemicals. |
| Buy Through | An agreement between utility and customer to import power when the customer’s service would otherwise be interrupted. |
| Buyer | An entity that purchases electrical energy or services from the Power Exchange (PX) or through a bilateral contract on behalf of end-use customers. |
| Bypass Diode | A diode connected across one or more solar cells in a photovoltaic module such that the diode will conduct if the call(s) change polarity. |
