TERM DEFINITION ac motor an electric motor designed to operatre from alternating current. active solar generally refers to a system which uses the sun's energy through direct conversion to electricity alternating current (ac) "an electrical current inwhich the current periodically reverses its direction of flow. Most household electrical systems use ac current rated at 120volts and 60 cycles per second, where 1 cycle refers to 2 complete reverses in direction of the flow." alternator an electrical generator which produces alternating current ammeter a device used for measuring current flow at any point in an electrical circuit amp hour "a unit of measurement which quantifies an amount of current flow for an amount of time. For ex. a current of 1 amp drawn from a battery for 10 hours would consume 10 amp-hrs of charge from the battery. Fundamentally, a measurment of electrical charge." ampacity refers to the highest amount of electrical current which may flow through a conductor (wire) safely ampere (a) a measure of electrical current quantifying the amount of electrical charge (coulombs) passing a point per unit of time (1 amp = 1coulomb/sec) amplitude generally refers to the maximum and minimum voltage attained by an alternating or pulsed current in each complete cycle or pulse of that current anode "the electrode within the cell which undergoes the chemical process of oxidation. Electrically, the anode is the cell's positive terminal." antenna "a metal rod, wire, or bunch of wires used for radiating or receiving radio waves" AWG "American Wire Gauge, a set of standards specifying the diameter of wire" ballast "a circuit used to stabilize an electric current, for example, in a fluorescent light" battery a group of interconnected electrochemical cells. Single cells are considered to be a battery if they are used alone. blocking diode an electronic device inserted between the PV panels and the batteries which blocks electrons from leaking from the batteries to the panels after dark BTU British Thermal Unit: a unit of energy commonly used in heating applications. 1 watt-hr = 3.413 BTU buss any conductor into which voltage is supplied and from which many lines to household loads extend cathode "the electrode within the cell which undergoes the chemical process of reduction. Electrically, the cathode is negative terminal of the cell." charge controller / regulator a device which regulates the voltage of a battery. These may be used to assure a battery is not overcharged and/or overly discharged. charge rate "the amount of energy per unit time that is being added to the battery, commonly expressed as the ratio of rated capacity to charge duration in hours" continuous output rating refers to the maximum amount of power an inverter may deliver to a load (or loads) for a sustained period of time. current "refers to electrical current, i.e. the flow of the electrons, electricity" cycle one complete charge/discharge cycle of the battery DC brushless motor an electric motor using permanent magnets and operable from direct current electricity. deep cycle battery a battery designed to regularly discharge 80 percent of its capacity before recharging. depth of discharge or cycle the amount of energy withdrawn from a battery or cell expressed as a percentage of its rated capacity DHW Domestic Hot Water: refers to any system which provides hot water for household use digital multimeter (DMM) "a device with multiple electrical measurement capabilities, such as: voltage, amperage, resistance, etc., commonly usable for both ac and DC circuits and has a digital readout " diode a semiconductor device which allows electrical current to flow through it in only one direction direct current (DC) an electrical current which flows in one direction only discharge rate the amount of energy per unit time that is being drained from the battery duty cycle "refers to the fraction of time a device or load actually draws current in a unit of time, for ex. a load that draws current for 5 seconds out of every 10 seconds has a 50% duty cycle" efficiency "refers to the effectiveness of a device to convert energy from one form to another, or to transfer energy from one body to another. Ex. a solar cell which converts 1/10 of the sun's energy which strikes its surface to electricity has an efficieny of 10%." electricity the flow of electrons electrolysis the breaking down of a chemical compound into simpler compounds or elements by the passage of electricity through the chemical compound electrolyte the medium of ion transport within within an electrochemical cell. It provides a path for electron transfer between the anode and cathode of the cell. electromagnetic radiation (EMR) "magnetic radiation produced by a changing electrical current, such as alternating current (ac)" electron a fundamental particle of an atom which carries an electrical charge of 1.6exp-19 coulombs. energy "an attribute of a system or entity which quantifies the amount of work which that system or entity could do (potential energy) or is doing (kinetic energy), measured in joules." energy density a ratio of a battery or cell's capacity to either its volume or weight. Volumetric energy density is expressed in watt-hrs/cubic in. Weight energy density is expressed in watt-hrs/pound. engine "a machine which converts energy into mechanical force or motion. Sources of energy include: heat, chemical reaction, nuclear, potential energy of elevated water, etc. " equilizing charge a controlled overcharge of an already full battery to restore all the individual cells within the battery to the same state of charge FCC "Federal Communications Commission: Determine the rules and regulations governing the use of radio, television, and many other mediums of communication" feathering "in wind generators, this refers to an adjustment of the blades so that they catch less wind. This can prevent damage to the windplant in high winds." flow in hydro-electric terms flow refers to the quantity of water supplied to a water source or exiting a nozzle per unit of time. Commonly measured in gallons per minute. Fluorescent light "an electric lamp coated on its inner surface with phosphor and containing mercury vapor. When bombarded with electrons, the vapor emits ultraviolet light which, in turn, causes the phosphor to emit visible light." fuse an electrical device which is designed to break a circuit and halt current flow when the current in the circuit excedes the maximum considered to be safe for the conductors or devices in the circuit generator a device which converts mechanical energy into electrical energy governer "a device which limits the output of another device, such as a wind generator" grid refers to electricity produced and delivered by a commercial power utility ground rod (electrode) "a metal rod (typically 5/8"" diameter) which is driven into the earth (typically 8' deep) and is electrically connected to the negative line and/or any large metal parts of an electrical circuit." head "the difference in elevation, in feet, between a source of water and the location at which the water from that source may be used" heat pump "a device typically used for heating and cooling of buildings. When cooling, a heat pump works like a refrigerator. When heating, it also works like a frig, except the heat produced (as from the cooling coils on the frig) is used to heat a space" hertz cycles per second. Generally refers to the number of complete cycles of the sinusoidal ac waveform per second hydro-electricity any electricity which is generated by the flow of water incandescent light an electric lamp which is evacuated or filled with an inert gas and contains a filament (commonly tungsten). The filiment emits visible light when heated to extreme temperatures by passage of electric current through it. insolation "the amount of solar energy striking a surface, measured in watts per square meter (SI)" inverter "a device which converts DC voltage/current (typically 12, 24, or 48 VDC) to ac voltage/current (typically 120/240 vac)" jack pump a submerged pump mechanically activated by a rod at the well head. joule the standard unit of energy (SI) light emitting diode (LED) a semiconductor device composed of a pn junction designed such that electrons emit visible light during their migration across the junction line/wire loss refers to the voltage or power lost due to the resistance of any wire (or wires) in any electrical circuit linear current booster (lcb) an electronic circuit that matches PV output directly to a motor. Used in array direct water pumping. load "refers to any electrical device which draws electrical current from a voltage source, for ex. any household appliance" lumen a unit of measurement quantifying the amount of light emitted from a light source micro-hydro hydro plants producing more than 100 watts and less than 2000 watts motor a device which converts electrical energy into mechanical energy nano-hydro any hydro plant which produces less than 100 watts National Electric Code (NEC) an organization which determines the legal standards for household wiring with safety as the prime objective ohm the unit which quantifies a material's resistance to electrical flow open circuit voltage refers to the voltage difference of two points in a circuit when the two points are electrically disconnected from each other parallel connection and electrical circuit with more than one possible path for electronic flow passive solar "refers to any use of the sun's energy in a manner which is found in nature. For ex., heating a thermal mass (a concrete wall or slab, for instance) during the day, and using the stored heat in that mass to warm a greenhouse or home at night." peak watts (Wp) the maximum power a device produces or consumes pen stock the area where water is collected and fed into the pipe of a hydro system. phantom load "a device which consumes power even its power switch is off, such as the digital clock on a VCR" photovoltaic (PV) "refers to any device which produces free electrons when exposed to light. When these electrons are properly gathered, a potential difference (voltage) may be produced by the device, for ex. a solar cell produces approx. one half volt in full sun." pipe loss "the amount of energy or pressure lost, due to friction with the inside surface of a pipe, when water flows through a pipe" polycrystalline cell "a wafer of silicon with a multi-grained structure. All grains have the same atomic crystal lattice, however, each grain has a unique orientation in space thereby producing a unique reflection of light, resulting in a ""patchy"" appearance. " power "describes the rate of energy use per unit time, measured in watts, i.e. 1watt = 1joule/sec" pulse width modulation "when speaking of pulsed (or alternating) current, this the intentional variation of the time duration of each pulse (or each half cycle)" PV array two or more photovoltaic panels wired in series and/or parallel quartz-halogen light an incandescent lamp filled with halogen gas. radiotelephone a two way radio system that enbales use of a regular telephone but with radio instead of wires. rated capacity "the amount of charge which may be stored in a battery, commonly expressed in amp-hrs." renewable energy Any type of energy which may be renewed by natural ecological cycles or appropriate management practices resistance "refers to the resistance of a material to the flow of electrons, measured in ohms" resistor a device with a known amount of resistance used in electrical circuits RF (radio frequency) "any radiation of a frequency which may be recieved or radiated by radios. Common usage: RF interference; refers to the interference of radio frequency radiation with the operation of devices or appliances such as televisions, computers, etc." RMS "Root-Mean-Square: defines a time averaged value of a sinusoidally varying parameter such as ac current, voltage, or power. " rotor the blades of a windplant which are shaped to spin when exposed to wind thereby harnessing the wind's energy self-discharge the tendency of all electrochemical cells to lose energy. Self-discharge represents energy lost to internal chemical reactions within the cell. series connection an electrical circuit with only one possible path for electronic flow series regulator a device which prevents overcharging of a battery by disconnecting the charging current as the battery voltage approaches some upper limit short circuit current refers to the current which passes between two points in a circuit when the points are electrically connected with a conductor with essentially zero resistance shunt a resistive load through which electricity is diverted. Often the resistance of a shunt is known precisely and is used to determine amperage by measuring the voltage across it and using Ohm's law (I = V/R) shunt regulator a device which prevents overcharging of a battery by diverting some (or all) of the charging current to a resistive load when the battery voltage reaches some upper limit single crystal cell "a wafer of silicon which has a perfect, continuous, crystal lattice (on the atomic level)" site evaluation "an estimation of a location for its potential for solar, hydro, or wind power." solar cell "one silicon (or other semiconductor) wafer, appropriately processed and electrically connected for gathering free electrons. Generally, many wafers are connected in series and assembled in a photovoltaic panel." solar cooker "a device which converts the sun's energy to heat energy, which then used to cook food" state of charge (SOC) "a ratio, expressed in percent, of the energy remaining in a battery in relation to its capacity when full" surge capacity refers to the maximum amount of ac power a inverter may deliver to a load (or loads) for a short period of time switch a common device which breaks an electrical circuit thereby halting the flow of electricity through the circuit thin film "a PV manufacturing technique where silicon is vapor deposited, a few molecules thick, onto another material (usually steel)." tracker any device used direct a PV array towards the sun trash rack a large strainer at the input to a hydro system. Used to remove debris from the water before it enters the pipe. turbine "an engine which produces rotary motion through reaction or impulse, or both, with fluid under pressure. In hydro systems, the resultant rotary motion is usually used to drive an alternator generator." volt (V) the unit of measurement which quantifies the difference in the strength of the electric field of two points -often referred to as electrical potential difference or potential difference. voltmeter a device for measuring the voltage difference between any two points in an electrical circuit watt "a fundamental unit of measurement of power, 1 watt = 1joule/sec" watt hour "a unit of measurement quantifying an amount of power used, or absorbed, for an amount of time. A load which consumes 1 watt for 10 hours uses 10 watt-hrs. Fundamentally, a measurement of energy." windings "refers to the coils of wire in a electro-magnet, commonly found in generators and motors"