PV test
what value of solar irradiance is most commonly used to rate the output of pv modules and arrays?
1000 watts per meter squared
What are the typical Ac output voltages of an inverter?
120v or 240v single phase units with power outputs up to 10KW, while 208 and 480v are available from around 10kw up to a few MW.
What is an inverter?
A device that converts DC power to AC power.
The NEC defines a PV array as what ? (it is in the codebook!)
A mechanically integrated assembly of modules or panels with a support structure and foundation, tracker, and other components as req. to form a dc or ac power producing unit.
What is a Photovoltaic cell (solar cell) ?
A semiconductor device that converts sunlight into DC electricity.
The orientation of PV arrays is defined by their ______ and ______ angles.
Array tilt angle and array azimuth angle
What is the inverter in an interactive PV system required to do when utility service voltage is lost?
Automatically de-energize its output to the connected electrical production and distribution network( also know as utility)
Equipment other than major components in a PV system are referred to as_________ components.
Balance of system
Eight specifications that are required by the NEC on every pv module label (690.51)
IN codebook 690.51
what is the optimal orientation for maximum annual energy production of a flat-plate collector?
IT is an azimuth angle of due south and a tilt angle close to the latitude.
what terms are used to describe solar energy?
Insolation-the amount of solar radiation reaching a given area. irradiation-the total amount of solar energy accumulated on an area over time. Peak sun hours
Inverters used in utility-interactive PV systems must be _____?
Listed and identified for interactive
Inverters listed to UL std. 1741 are intended to be installed in accordance with What?
NFPA 70 NEC and manufactures instructions.
The electrical contacts on the top surface of a silicon solar cell are typically what polarity?
Negative Note: meaning the contacts on the bottom of a solar cell must be positive.
Only inverters and AC modules ______ and _____ as _____ shall be permited in grid tied PV systems.
Only inverters and AC modules LISTED and identified as interactive shall be permited in grid tied PV systems.
IF shading of an array is on the south end what is the best thing to do to fix the problem?
Options for dealing with shading include trimming or transplanting trees or moving the array. in this situation moving the array a few feet to the north may reduce or eliminate this problem
What is a solar energy technology that uses the unique properties of certain semiconductors to directly convert solar radiation into electricity?
Photovoltaics
The availability of low power DC lamps make pv energy ideal for remote lighting applications. Lighting needs are greatest at night, what kind of storage is a necessary part of these installations?
Power storage- Most commonly in the form of batteries NOTE: PV systems can be used to light billboards, highways, information signs, parking lots, and marinas.
Which pv system application in the UNited states generates the most power?
Residential and commercial utility interactive applications.
What are the primary differences between static solid-state inverters and rotating generators?
Rotating generators can act as loads. While inverters can-not. Inverters have no moving part. While rotating generators do.
What type of PV system operates autonomously and supplies power to electrical loads independent of the utility grid?
Stand-Alone system
Some charge controllers protect a battery from excessively deep discharges by disconnecting what?
System Loads
What were the first terrestrial application for photovoltaics?
Telecommunication systems
What primary effect does solar irradiance have on the electrical output of a solar cell?
The current increases proportional to the irradiance.
For stand alone inverters what is the ac and dc power typically hooked up to?
The dc input for stand alone inverters is connected directly to the battery bank, and the ac output is connected to a distribution panel to power the Ac loads.
The voltage divided by the current for any point on an I-V curve represents what?
The load resistance required to operate on the I-V curve at that point
what is solar irradiance?
The power of solar radiation per unit area. (W/m2) As solar irradiance changes its affects voltages and outputs. Solar irradiance is an instantaneous value meaning the measurement is constantly changing. It is used to evaluate the output of solar energy utilization equipment at a given point in time( PV modules power output)
What effect does increasing operating temperature have on a typical silicon solar cell output?
The voltage decreases slightly and the current increases slightly.
Why are PV systems are extremely reliable and last a long time with minimal maintenance?
There are no Moving parts in the system.
what is the difference in determing the output of a battery based inverter and a utility-interactive inverter?
Utility interactive inverter output is determined by the dc input from the array, while battery based inverter output is determined by the load.
What is a battery based inverter?
are used in stand alone PV systems and operate directly from battery banks as there input source. DC input corresponds to nominal battery bank voltages, usually 12v, 24v or 48v.
Photovoltaic systems use wafers, primarily made of _______ , that are sensitive to sunlight and produce a small direct current when exposed to light
crystalline silicon
Typical pv modules are connected in ______ to achieve a desired voltage output, then connected in _______ to build power output.
series, parallel
How do utility interactive inverters work?
they draw power directly from pv arrays and operate in parallel with the utility grid.
In pv systems what are the functions of an inverter?
to convert dc power from battery banks or PV arrays to AC power for AC loads or export to the utility grid.
Solar energy is commonly expressed in units of?
watt hours per sqaure meter. (wh/m2) or kilowatt hours per square meter, (kw/m2)
