glossary of Terms on Water Energy
activated shelf life — The period of time, at a specified temperature, that a charged battery can be stored before its capacity falls to an unusable level.
activation voltage's) — The
voltage's) at which a charge controller will take action to protect the batteries.
adjustable set point — A feature allowing the user to adjust the voltage levels at which a charge controller will become active.
alternating current (AC) — A type of electrical current, the direction of which is reversed at regular intervals or cycles. In the United States, the standard is 120 reversals or 60 cycles per second. Electricity transmission networks use AC because voltage can be controlled with relative ease.
ampere (amp) — A unit of electrical current or rate of flow of electrons.
ampere-hour (Ah/AH) — A measure of the flow of current (in >amperes) over one hour; used to measure battery capacity.
anode — The positive electrode in an electrochemical cell (battery). Also, the earth or ground in a cathodic protection system. Also, the positive terminal of a diode.
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base load — The average amount of electric power that a utility must supply in any period.
battery — Two or more electrochemical cells enclosed in a container and electrically interconnected in an appropriate series/parallel arrangement to provide the required operating voltage and current levels. Under common usage, the term battery also applies to a single cell if it constitutes the entire electrochemical storage system.
battery available capacity — The total maximum charge, expressed in ampere-hours, that can be withdrawn from a cell or battery under a specific set of operating conditions including discharge rate, temperature, initial state of charge, age, and cut-off voltage.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 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 — The simplest operating unit in a
storage battery. It consists of one or more positive electrodes or plates, an electrolyte that permits ionic conduction, one or more negative electrodes or plates, separators between plates of opposite polarity, and a container for all the above.
battery cycle life — The number of cycles, to a specified depth of discharge, that a cell or battery can undergo before failing to meet its specified capacity or efficiency performance criteria.
battery life — The period during which a cell or battery is capable of operating above a specified capacity or efficiency performance level. Life may be measured in cycles and/or years, depending on the type of service for which the cell or battery is intended.
bypass channel — A structure in a dam that provides a route for fish to move through or around the dam without going through the turbine units. The bypass channel is the part of a system that includes a conduit built into the dam to pass fish.
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cell (battery)
— A single unit of an electrochemical device capable of producing
direct voltage by converting chemical energy into electrical energy. A
battery usually consists of several cells electrically connected
together to produce higher voltages.
cell junction — The area of immediate contact between two layers (positive and negative) of a photovoltaic cell. The junction lies at the center of the cell barrier or depletion zone.
charge — The process of adding electrical energy to a battery.
charge controller — A component of a photovoltaic system that controls the flow of current to and from the battery to protect it from over-charge and over-discharge. The charge controller may also indicate the system operational status.
charge factor — A
number representing the time in hours during which a battery can be
charged at a constant current without damage to the battery. Usually
expressed in relation to the total battery capacity, i.e., C/5
indicates a charge factor of 5 hours.
conductor — The material through which electricity is transmitted, such as an electrical wire, or transmission or distribution line.
converter — A unit that converts a direct
current (dc)) voltage to another dc voltage.
cubic feet per second (CFS) — The rate at which water is flowing. One cfs is equal to about 450 gallons per minute.
cutoff voltage — The voltage levels (activation) at which the charge controller disconnects the photovoltaic array from the battery or the load from the battery.
cycle — The discharge and subsequent charge of
a battery.
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deep-cycle battery — A battery with large plates that can withstand many discharges to a low state-of-charge.
deep discharge — Discharging a battery to 20% or less of its full charge capacity.
direct current (DC) — A type of electricity transmission and distribution by which electricity flows in one direction through the conductor, usually relatively low voltage and high current. To be used for typical 120 volt or 220 volt household appliances, DC must be converted to alternating current, its opposite.
discharge — The withdrawal of electrical energy from a battery.
discharge rate — The rate, usually expressed in
amperes or time, at which electrical current is taken from the battery.
distributed generation — A popular term for localized or on-site power generation.
distributed power —
Generic term for any power supply located near the point where the
power is used. Opposite of central power.
distributed systems — Systems that are installed at or near the location where the electricity is used, as opposed to central systems that supply electricity to grids. A residential
draft tube — A tube or pipe which forms the exit path for water coming from a water turbine.
drawdown — Releasing water from a hydroelectric project to lower the reservoir elevation. Drawdowns are used for energy production or to create additional space in the reservoir to hold back floodwaters; to reduce the cross-sectional area of the reservoir, increasing the current to aid downstream fish passage; and to expose normally submerged structures for maintenance.
duty rating — The amount of time an inverter (power conditioning unit) can produce at full rated power.
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electric circuit — The path followed by electrons from a power source (generator or battery), through an electrical system, and returning to the source.
electric current — The flow of electrical energy (electricity) in a conductor, measured in amperes.
electrical grid — An integrated system of electricity distribution, usually covering a large area.
electricity — Energy resulting from the flow of charge particles, such as electrons or ions.
electrochemical cell — A device containing two conducting electrodes, one positive and the other negative, made of dissimilar materials (usually metals) that are immersed in a chemical solution electrolyte) that transmits positive ions from the negative to the positive electrode and thus forms an electrical charge. One or more cells constitute a battery.
electrode — A conductor that is brought in conducting contact with a ground.
Electrolyte — A nonmetallic (liquid or solid) conductor that carries current by the movement of ions (instead of electrons) with the liberation of matter at the electrodes of an electrochemical cell.
energy — The capability of doing work; different forms of energy can be converted to other forms, but the total amount of energy remains the same.
energy audit — A survey that shows how much energy used in a home, which helps find ways to use less energy.
energy density — The ratio of available energy per pound; usually used to compare storage batteries.
equalization — The process of restoring all cells in a battery to an equal state-of-charge. Some battery types may require a complete discharge as a part of the equalization process.
equalizing charge — A continuation of normal battery charging, at a voltage level slightly higher than the normal end-of-charge voltage, in order to provide cell equalization within a battery.
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fish ladder — A series of ascending pools, similar to a staircase, that enables fish to migrate up the river past dams. Also called a fishway.
float charge — The voltage required to counteract the self-discharge of the battery at a certain temperature.
float service — A battery operation in which the battery is normally connected to an external current source; for instance, a battery charger which supplies the battery load under normal conditions, while also providing enough energy input to the battery to make up for its internal quiescent losses, thus keeping the battery always up to full power and ready for service.
flow —The volume of water passing a given point during a unit of time. Typically expressed as cubic feet per second, or
CFS. Also known as "flow rate" or "discharge."
forebay — The part of a dam’s reservoir that is immediately upstream of the powerhouse.
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gassing — The evolution of gas from one or more of the electrodes in the cells of a battery. Gassing commonly results from local action self-discharge or from the electrolysis of water in the electrolyte during charging.
gassing current — The portion of charge current that goes into electrolytical production of hydrogen and oxygen from the electrolytic liquid. This current increases with increasing voltage and temperature.
gatewell — The slot on the upstream face of a concrete dam where hydraulic gates are stored when not used to close the turbine intakes.
generating capacity — The maximum power that a power plant, such as a hydroelectric dam, can produce under specific conditions.
Gigawatt (GW) — A unit of power equal to 1 billion Watts; 1 million kilowatts, or 1,000 megawatts.
grid-connected system — A home energy system in which the current being generated is connected to the power meter and the power grid for storage and use.
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head — Water pressure created by gravity in a hydroelectric system. The head pressure is determined by the
vertical distance water must fall under the influence of gravity. It is measured either in feet or in units of pressure such as pounds per square
inch (PSI).
head pond — A pond that is used to store water for a hydroelectric project.
high voltage disconnect — The voltage at which a charge controller will disconnect the photovoltaic array from the batteries to prevent overcharging.
hybrid system — A home energy system which uses more than one source of electricity generation, such as combining microhydro electric generation with solar energy generation.
hydraulic capacity — The maximum amount of water that can go through the powerhouse at a project.
hydro — Having to do with water.
hydroelectric — Electricity which is generated by the force of water through an electric turbine.
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inverter — A device that converts direct current electricity to alternating current either for stand-alone systems or to supply power to an electricity grid.
intake —The entrance to a water turbine unit in hydroelectric system.
intake shaft — A tube or pipe that connects to the piping or penstock which brings the water into the turbine
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joule — A metric unit of energy or work; 1 joule per second equals 1 watt or 0.737 foot-pounds; 1 Btu equals 1,055 joules.
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kilowatt (kW) — A standard unit of electrical power equal to 1000 watts, or to the energy consumption at a rate of 1000 joules per second.
kilowatt-hour (kWh) — 1,000 thousand watts acting over a period of 1 hour. The kWh is a unit of energy. 1 kWh=3600 kJ.
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lead-acid battery — A general category that includes batteries with plates made of pure lead, lead-antimony, or lead-calcium immersed in an acid electrolyte.
life-cycle cost — The estimated cost of owning and operating a microhydro system for the period of its useful life.
liquid electrolyte battery — A battery containing a liquid solution of acid and water. Distilled water may be added to these batteries to replenish the electrolyte as necessary. Also called a flooded battery because the plates are covered with the electrolyte.
load — The demand on an energy producing system; the energy consumption or requirement of a piece or group of equipment. Usually expressed in terms of amperes or watts in reference to electricity.
load circuit — The wire, switches, fuses, etc. that connect the load to the power source.
load current (A) — The current required by the electrical device.
load resistance — The
resistance presented by the load.
low voltage cutoff (LVC) — The voltage level at which a charge controller will disconnect the load from the battery.
low voltage warning — A warning buzzer or light that indicates the low battery voltage set point has been reached.
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maintenance-free battery — A sealed battery to which water cannot be added to maintain electrolyte level.
megawatt (MW ) — 1,000 kilowatts, or 1 million watts; standard measure of electric power plant generating capacity.
megawatt Hour — 1,000 kilowatt-hours or 1 million watt-hours.
multi-stage controller — A charging controller unit that allows different charging currents as the battery nears full state_of_charge.
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National Electrical Code (NEC) — Contains guidelines for all types of electrical installations in the U.S. Most states require that NEC codes be followed when installing a microhydro system.
nickel cadmium battery — A battery containing nickel and cadmium plates and an alkaline electrolyte.
nominal voltage — A reference voltage used to describe batteries, modules, or systems (i.e., a 12-volt or 24-volt battery, module, or system).
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ohm — A measure of the electrical resistance of a material equal to the resistance of a circuit in which the potential difference of 1 volt produces a current of 1 ampere.
overcharge — Forcing current into a fully charged battery. The battery will be damaged if overcharged for a long period.
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peak load — The maximum energy demand or load in a specified time period.
Pelton turbine — A form of impulse turbine or water wheel, consisting of a row of double cup-shaped buckets arranged round the rim of a wheel and actuated by one or more jets of water playing into the cups at high velocity.
penstock — The pipe leading from the water intake to the hydraulic turbine.
power conditioning — The process of modifying the characteristics of electrical power (for e.g., inverting direct current to alternating current).
power conversion efficiency — The ratio of output power to input power of the inverter.
powerhouse — That part of a hydroelectric system where the turbine-generators are housed and where power is produced by the action of the water on the turbine blades..
PSI gauge — A gauge used in hydroelectric systems which measure the water pressure in units of pounds per square inch..
pulse-width-modulated (PWM) wave inverter — A type of power inverter that produce a high quality voltage.
pumped storage — A hydroelectric project designed to store electrical energy on a short-term basis. A pumped storage project is typically used to store electricity during nighttime periods of low demand for use during daily peak demand periods.
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rated battery capacity — The term used by battery manufacturers to indicate the maximum amount of energy that can be withdrawn from a battery under specified discharge rate and temperature.
regulator — Prevents overcharging of batteries by controlling charge cycle-usually adjustable to conform to specific battery needs.
resistance (R) — The property of a conductor, which opposes the flow of an electric current resulting in the generation of heat in the conducting material. The measure of the resistance of a given conductor is the electromotive force needed for a unit current flow. The unit of resistance is ohms.
run of the river site — A microhydro site which has low head (2 to 10 feet) but uses much of the river's flow.
runner blade — A blade in a water turbine which is pushed by the force of the water.
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sealed battery — A battery with a captive electrolyte and a resealing vent cap, also called a valve-regulated battery. Electrolyte cannot be added.
self-discharge — The rate at which a battery, without a load, will lose its charge.
shallow-cycle battery — A battery with small plates that cannot withstand many discharges to a low state-of-charge.
shelf life of batteries — The length of time, under specified conditions, that a battery can be stored so that it keeps its guaranteed capacity.
short-circuit current (Isc) — The current flowing freely through an external circuit that has no load or resistance; the maximum current possible.
shunt controller — A charge controller that redirects or shunts the charging current away from the battery. The controller requires a large heat sink to dissipate the current from the short-circuited photovoltaic array. Most shunt controllers are for smaller systems producing 30 amperes or less.
sine wave inverter — An inverter that produces utility-quality, sine wave power forms.
single-stage controller — A charge controller that redirects all charging current as the battery nears full state-of-charge.
sluiceway — A channel designed to collect ice and debris in the river before they get into the turbine units and cause damage.
spillbay — Releasing water out the spillbays rather than through the turbine units. The spillbay is the dam’s safety valve. Without it, excess water can damage the dam’s structure or overflow the dam.
standby current — This is the amount of current (power) used by the inverter when no load is active (lost power). The efficiency of the inverter is lowest when the load demand is low.
state-of-charge (SOC) — The available capacity remaining in the battery, expressed as a percentage of the rated capacity.
storage dam — A dam with a large reservoir that can hold water over from the annual high-water season to the following low-water season.
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tailrace — The canal or channel that carries water that is discharged by the water turbine./P>
total AC load demand — The sum of the alternating current loads. This value is important when selecting an inverter.
transformer — An electromagnetic device that changes the voltage of alternating current electricity.
trickle charge — A charge at a low rate, balancing through self-discharge losses, to maintain a cell or battery in a fully charged condition.
Turgo turbine — A type of impulse water turbine in which the hub is surrounded by a series of curved vanes.
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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 microhydro turbine system's output is fully synchronized with the utility power.
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varistor — A voltage-dependent variable resistor. Normally used to protect sensitive equipment from power spikes or lightning strikes by shunting the energy to ground.
volt (V) — A unit of electrical force equal to that amount of electromotive force that will cause a steady current of one ampere to flow through a resistance of one ohm.
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 photovoltaic module.
voltage protection — Many inverters have sensing circuits that will disconnect the unit from the battery if input voltage limits are exceeded.
voltage regulation — This indicates the variability in the output voltage. Some loads will not tolerate voltage variations greater than a few percent.
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watt — 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).
waveform — The shape of the phase power at a certain frequency and amplitude.
water turbine — An electric
turbine which is powered by the force of water.
weir method — An approach for measuring water flow in which is diverted in a stream or river and the water depth upstream from the blockade or weir is measured.
wet shelf life — The period of time that a charged battery, when filled with electrolyte, can remain unused before dropping below a specified level of performance.
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zero head turbine — A water turbine which is designed to be submerged in a fast moving stream or river and relies completely on flow for extracting energy.
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Harris Water Turbine