AC Systems

Alternating current. Electrical energy which reverses its direction at regular intervals.

AC Daily Power Budget- The daily amount of watts your AC appliances use.

AC Inverter and Battery Power Allowance- Running an inverter draws a small amount of power from your battery. So does keeping power stored. The inverter and battery allowance in your power calculations help make certain enough power will be produced to keep your battery from running in the red.

Adjusted Total Daily Power Budget- A total daily power budget may be changed to meet certain situations. For instance, if you spend only weekends at a house, then your adjusted total daily power budget will be lower. Adding a generator to your system also reduces your total daily power budget. The adjusted daily power budget provides the figure that determines the size of your solar electric power system.

Air mass- A measure of distance that light travels through the earth's atmosphere.

Ampere or amp- Electric current is measured in amperes or amps.

Amp Hours- The number of amps used or produced in a given hour equals the number of hours. Batteries are rated in amp hours.

Array- A group of solar electric modules connected together in a power system.

Battery Bank- A group of batteries wired together to store power in a solar electric system. Allows you to use the stored power at night, on cloudy days or to run more power than the array can produce at one time.

Cell efficiency- The ratio of the electrical energy produced by a photovoltaic cell (under full sun conditions) to the energy from sunlight falling upon the cell.

Centrifugal (Water Pumping)- Rotating outward, away from the center, as in centrifugal force.

Charge controller- A component that controls the flow of current to and from the battery subsystem to protect the batteries from overcharge and overdischarge. The charge controller may also monitor system performance and provide system protection.

Current- The rate of flow of an electric charge. Current is measured in amps.

DC- Direct current. Electrical energy flowing in one direction and of substantially constant value.

DC Daily Power Budget- The number of watts your DC appliances use daily.

Direct radiation- Light that has traveled in a straight path from the sun (also referred to as beam radiation). An object in the path of direct radiation casts a shadow on a clear day.

Design tilt- The tilt of the array at which design and sizing calculations are made. Often the design tilt is optimized for energy output under prescribed conditions.

Fall (Water Pump/Hydro Sections)- The vertical descent of water, usually measured in vertical feet. Also called "head".

Fill factor- The ratio of maximum power to the product of open-circuit voltage and short-circuit current. Fill factor is the "squareness" of the I-V curve shape.

Flat-plate array- A photovoltaic array in which the incident solar radiation strikes a flat surface and no concentration of sun light is involved.

Flow Rate- Speed at which water moves.

GPM- Gallons per minute.

Grid-connected- An energy producing system connected to the utility grid. (Also called utility-interactive).

Grounding- Connection to a large conducting body (such as the earth), which is used as common return for an electrical circuit and as an arbitrary zero potential.

Ground Mount- A piece of equipment upon which solar modules are mounted.

Head- See "Fall".

Hertz or HZ- The frequency of electrical current described in cycles per second. Appliances in the U.S. use 60 HZ. Appliances in other countries generally use 50 HZ.

Holes- Vacancies where electrons would normally be in a perfect crystalline structure.

Hybrid system- A power system consisting of two or more power generating subsystems (e.g. the combination of a wind turbine and a photovoltaic system).

Hydroelectricity- Electricity created by water power.

Hydrometer- An instrument used to measure state-of-charge (voltage) of a battery.

Insolation- The amount of sunlight reaching an area. Usually expressed in watts per square meter per day.

Inverter- An Appliance used to convert independent DC power into standard household AC current.

Junction box-A protective enclosure into which wires or cables are led and connected.

Kilowatt or KW- a thousand watts. (See Watts.)

LED- Light emitting diode. These lights are often used to indicate low power on modern electronic equipment.

Line Loss- Voltage drop over the length of electric line wire. Line loss robs your system of power when wire is too small for the load being run through the line or when voltage is too low for the distance the power must travel.

Load- Electrical power beignn consumed at any given moment. The load that an electric generating system supplies varies greatly with time of the day and to some extent season of year. Also, in an electrical circuit, the load is any device or appliance that is using power.

mA- Milliamps, 1000 MA = 1 amp.

Module- A number of photovoltaic cells electrically wired together, usually in a sealed unit of convenient size for handling and assemling into panels and arrays

Nominal operating cell temperature (NOCT)- The photovoltaic cell junction temperature corresponding to nominal operating conditions in a standard reference environment of 1 KW per sqr m irradiance, 20 degrees C ambient air temperature, 1 m/s wind, and electrically open circuit.

Panel- Anumber of modules wired together, which in turn, can be wired to other panels to form an array.

Parallel Wiring- A system of wiring, for solar electric modules of batteries, which increases amperage. Parallel wiring is "+ to +" (positive to positive) and " – to – " (negative to negative).

Peak sun hours- The equivalent number of hours at peak sun conditions (i.e., 1 KW per sqr m) that produces the same total insolation as actual sun conditions.

Photovoltaic- Converting light into electricity. Photo means "light" voltaic means "electric". Often referred to as "PV" for short. More commonly referred to as "solar electric".

Photovoltaic cell- The basic device that converts light into electricity; the building block of photovoltaic modules.

p-n junction- The junction formed at the interface between two differently doped layers of semiconductor material, one layer being doped with a positive-type dopant, the other with a negative-type dopant. An electric field is established at the p-n junction which gives direction to the flow of light-stimulated electrons.

PSI- Pounds per square inch.

Self-Regulating- Some modules have a special circuitry which keeps the battery from overcharging. This means that no controller is needed when the self-regulating module is properly matched to battery storage capacity.

Series Wiring- A system of wiring, for solar electric modules or batteries, which increases voltage. Series wiring is + to – (positive to negative).

Single-Crystal Silicon- Many solar chargers use single-crystal solar cells as they are the most efficient cell on the market. Pure silicon is grown into crystalline ingots which are cut into thin slices to make solar electric cells. These cells are then soldered together to meet the charger’s voltage and current requirements.

Solar Cell- The smallest basic solar electric device which generates electricity when exposed to light.

Solar Electric- The preferred term used to describe something which uses sunlight to produce electricity. "Photovoltaic" is the more technical term.

Thin-Film Silicon- The tiny solar chargers found in calculators and wristwatches are solar thin-film. Thin-film solar chargers are made by spreading a micro-thin layer of silicon on glass and creating the voltage and current circuits using laser technology. Thin-film chargers are produced in sizes from the microscopic calculator chip, up to the 1’x4’ power module.

Total Daily Power Budget- In a DC system, the daily amount of watts your DC appliances use, plus the battery power allowance. In a DC and AC system, the daily amount of watts DC and AC appliances use, plus battery and inverter power allowances.

Voltage or Volts- Voltage is the rating of the amount of electrical pressure that causes electricity to flow in the power line. If electricity were water, voltage would measure the amount of pressure at the faucet.

Watts- A watt is a measurement of total electrical power. Volts x amps = watts.

Watt Hour- The quantity of electrical energy used or produced when one watt is used for one hour.