Amps (I): The unit of measure that indicates how much
electricity flows through a conductor. It is like using cubic feet per second
to measure the flow of water. For example, a 1,200-watt, 120-volt hair dryer
pulls 10 amperes of electricity current. (amps = watts/volts)
Balance of System (BOS) components: The parts of the
photovoltaic system other than the PV array: switches, controls, meters, power-conditioning
equipment, supporting structure for the array and storage components, if any.
Batteries, see Storage: Batteries are often sold with
a PV system. The primary purpose is to store the electricity not immediately
used, which could be used at some later time. With net metering, the value of
batteries is less because the utility grid basically acts as a storage facility.
For a reliable generation system that can function independent of the utility
grid, however, batteries may be a viable component to the total system. Back-up
generators may be included in a system to provide power when the PV system is
not operating, and are generally included when systems are not grid connected.
Neither batteries nor generators are eligible for rebate money.
Building Integrated Photovoltaics:A
term for the design and integration of PV into the building envelope, typically
replacing conventional building materials. BIPV often integrates PV cells into
vertical facades, such as in window glazing; into roofing systems, replacing
traditional roofing materials and into shading structures that cover windows.
Data Acquisition System (DAS):A key part of the DATA
COLLECTION SYSTEM which has the function of collecting analog and digital signals,
converting the analog signals to digital,multiplexing the signals, doing arithmetic
and logical operations, and storing measured and calculated values.Depending
on the specific manufacturer's model, the DAS may have its own display and printing
devices built in (e.g., data loggers).
Data Collection System: A complete system for collecting,
analyzing, storing, and displaying measured and calculated data. It consists
of sensors, signal conditioning, cabling, and the DAS.
Gigawatt: One billion watts or one million kilowatts
Grid: The network of ac power transmission lines and
transformers used in central power systems.Grid power means utility power.
Grid-tied system: Grid-connected
or utility-interactive PV systems are designed to operate in parallel with and
interconnected with the electric utility grid. The primary component in grid-connected
PV systems is the inverter, or power conditioning unit (PCU). The PCU converts
the DC power produced by the PV array into AC power consistent with the voltage
and power quality requirements of the utility grid, and automatically stops
supplying power to the grid when the utility grid is not energized. A bi-directional
interface is made between the PV system AC output circuits and the electric
utility network, typically at an on-site distribution panel or service entrance.
This allows the AC power produced by the PV system to either supply on-site
electrical loads, or to back feed the grid when the PV system output is greater
than the on-site load demand. At night and during other periods when the electrical
loads are greater than the PV system output, the balance of power required by
the loads is received from the electric utility This safety feature is required
in all grid-connected PV systems, and ensures that the PV system will not continue
to operate and feed back onto the utility grid when the grid is down for service
or repair.
Interconnection Agreement: An agreement entered into
with the local utility (PG&E) allowing for net-metering a photovoltaic,
wind or fuel cell system to the utility grid.
Inverter:A power conversion device which changes dc
voltage input to an ac voltage output. A power conversion device which changes
dc voltage inGrid-connected or utility-interactive PV systems are designed to
operate in parallel with and interconnected with the electric utility grid.
The primary component in grid-connected PV systems is the inverter, or power
conditioning unit (PCU). The PCU converts the DC power produced by the PV array
into AC power consistent with the voltage and power quality requirements of
the utility grid, and automatically stops supplying power to the grid when the
utility grid is not energized. A bi-directional interface is made between the
PV system AC output circuits and the electric utility network, typically at
an on-site distribution panel or service entrance. This allows the AC power
produced by the PV system to either supply on-site electrical loads, or to back
feed the grid when the PV system output is greater than the on-site load demand.
At night and during other periods when the electrical loads are greater than
the PV system output, the balance of power required by the loads is received
from the electric utility This safety feature is required in all grid-connected
PV systems, and ensures that the PV system will not continue to operate and
feed back onto the utility grid when the grid is down for service or repair.
put to an ac voltage output.
Kilowatts : (equal to 1,000
watts)1000 watts. A unit of measure of the amount of electricity needed to operate
given equipment. For example, one kW is enough power to illuminate 10 light
bulbs at 100 watts each. (volts x amps = watts)
Kilowatts AC (or Peak KW):
Maximum generating capacity of photovoltaic system. Term used in performance
rating of PV cells, modules, and arrays, usually at sunlight intensity of 1000
W/m2 with an average cell temperature of 25°C.
Kilowatts DC (nameplate): Size
of the photovoltaic system, based on the sum of the nameplate module wattages.
The power of a PV system will be lower than the kilowatts DC due to dust and
dirt, ambient temperature, conversion losses (going from DC to AC), wire losses,
orientation, tilt and shading.
Kilowatt-hours: The amount
of kW produced over a period of time, or one kilowatt of electricity supplied
for one hour. For example, a one kW system, if operating at full capacity for
5 hours will produce 5 kWh of electricity.
Net-metering: Net Metering
is a billing arrangement between Pacific Gas & Electric and customers who generate
their own electricity with photovoltaic or wind systems, by which the excess
electricity produced using your own generating equipment is fed back onto the
utility grid and is deducted from your electric bill.
Off-grid system: System installed
in households, typically in remote areas, that are not connected to the utility
grid. Requires a means to store electricity (most commonly a lead-acid battery).
Also called "stand-alone photovoltaic power system".
Output (of a PV system): The amount of electricity a
PV system produces. Dust and dirt, ambient temperature, conversion losses (going
from DC to AC), wire losses, orientation, tilt and shading all effect the output
of a PV system.
Photovoltaic Cell: A device that produces electricity
from light. Cells are the building block for modules.
Photovoltaic Module: A number of PV cells connected
together,sealed with an encapsulant, and having a standard size and output power;
the smallest building block of the power generating part of a PV array.
Photovoltaic Array: A group of photovoltaic panels.
Polycrystalline Silicon: Silicon which has solidified
rapidly enough to produce many small crystals which are arbitrarily arranged.
This type of cell has grain boundaries, randomly oriented, visible on the active
surface. Compare to Monocrystalline Silicon and Amorphous Silicon.
Stand Alone PV System:A type
of PV system that is not connected to an auxiliary power source or a PV system
that operates independently of the electric utility lines. It usually contains
one or more batteries, but many pumping systems comprise only the PV array and
the inverter. Also known as an "off-grid PV system"
Storage: Storage refers to saving surplus electricity
produced by a PV system. Generally batteries are used as storage devices.
Tilt Angle: The angle which the plane of a PV module
makes relative to the horizontal plane.
Tracking Equipment: Structure that houses PV modules
and that can automatically follow the sun across the sky throughout the day
to maximize output.
Turn-key photovoltaic products/services
: Typically refers to a solar contractor that handles most/all of the stages
of a photovoltaic installation, including design, engineering, product supply
and installation.
Volts (V): A unit of measure of the force, or 'push,'
given the electrons in an electric circuit. One volt produces one ampere of
current when acting on a resistance of one ohm.
