PV System Mechanical Design Flashcards Preview

NABCEP Entry Level > PV System Mechanical Design > Flashcards

Flashcards in PV System Mechanical Design Deck (32):
1

You check the polarity of the PV output before applying ______ to ______.

PV power to an inverter, a charge controller, batteries, or a load

2

The battery bank for a battery backup utility-interactive PV system is located in a harsh environment with temperature and humidity extremes. What are the most likely effects on the battery's state of charge?

Undercharged in cold weather and overcharged in hot weather

3

A 1/4" x 3 1/2" lag screw that has a 3" thread is used to attach an L- bracket to an asphalt-shingle roof. If the combined thickness of the L- bracket, shingles, and roof membrane is 3/4", and if the screw penetrates directly into a roof truss made of Southern Yellow Pine into a properly sized pilot hole, then what is the withdrawal resistance?

773 Ohms

4

In a PV system, which equipment is colored in green?

The grounding conductors

5

If your magnetic compass is in San Francisco, CA and is showing that your array is aiming to the heading of 189 degrees, what is the azimuth of solar (true) south?

-24 degrees

6

In DC PV systems, what is the function of bare copper?

It's usually not carrying substantial current

7

Of the following site assessment tools, which are most often needed to determine optimal array placement?

- sun path analyzer

- pliers 

- Inclinometer 

- compass

- voltmeter

Compass, inclinometer, and sun path analyzer

8

A PV array for a utility-interactive system is to be ground-mounted on a hill 1,000 feet from the point of utility connection. It uses a 240 V inverter, and a single string of 1W modules operates between 300 and 550 volts DC. There is a small building halfway between the array location and the utility point of connection. To minimize wire size, increase performance, and ensure consistent operation, where should the inverter be installed?

At the utility point of connection

9

What does green mean in an AC system?

Ground

10

Under what conditions does thin-film PV respond less than polycrystalline PV?

Heat and shading

11

What is the required minimum working space width in front of a 48 V lead acid battery bank?

30" or the width of the battery bank, whichever is greater

12

Areas of low wind, latitude greater than 30 degrees, and minimal daytime summer cloud cover are optimal conditions for what?

Two-axis tracking mount

13

A PV array for a utility-interactive system is to be ground-mounted on a hill 1,000 ft from the point of utility connection. The single string of 1W modules operates between 300 and 550 volts DC. The inverter is a 240 V inverter. There is a small building halfway between the array location and the utility point of connection. The utility point connection will do what for the inverter?

Minimize wire size, increase performance, and ensure consistent operation.

14

What is the cost advantage of thin-film?

Can be cheaper per watt to produce

15

PV systems located far south should do what to optimize performance?

Increase the tilt angle

16

Four PV modules, each with an area of 10 ft2, are to be mounted with a stand-off mount secured to a metal seam roof with L-brackets. If the modules can withstand a load of 75 lbs/ft2, and it is desired to support the full load with one lag screw in each bracket, and each screw has a withdrawal resistance of 300 lb/in2 including a safety factor of 4, the minimum screw thread length to penetrate would be...

1.67"

17

A proposed PV installation site has an unobstructed south-facing roof area of 60 m2. If thin-film modules with six watts-per-square-foot power output at STC are to be installed on 50% of the roof, then the maximum available PV array output power (based on the sum of module ratings) at STC will be...

1900 watts

18

As it relates to PV system mechanical design, the closer you are to the north, what action will optimize performance?

Decrease your tilt angle

19

A small conductor between the array and the inverter is a characteristic of a 500 V DC PV array and gives it an advantage over what kind of array?

A 48 V DC array of the same wattage

20

What is distributed generation?

Smaller systems produce electricity close to consumption needs

21

What is the most important consideration of mounting PV arrays on residential rooftops with regard to energy production?

Shading

22

30 inches, or the width of the battery bank, is the required minimum for what?

Working space width in front of a 48 V lead acid battery bank

23

Shading is the most important consideration for what?

For mounting PV arrays on residential rooftops with regard to energy production

24

It is important to have what in coastal areas where the air contains salt spray?

Stainless-steel hardware

25

When many smaller systems produce electricity that meets consumption needs, what is it called?

Distributed generation

26

In DC PV systems, what is usually NOT carrying substantial generation?

Bare copper

27

Arrays are common components in what?

All PV systems

28

Stainless-steel hardware is most important in which areas?

Coastal areas where the air contains salt spray

29

A compass, inclinometer, and sun path analyzer are site assessment tools used for what?

Determining the optimal array placement

30

Before applying PV power to either an inverter, a charge controller, batteries, or a load, one should first do what?

Check the polarity of the PV output

31

Heat and shading have what effect on thin-film PV?

Decreased responsiveness, compared to polycrystalline PV

32

What kind of PV system promises to be cheaper per watt to produce?

Thin-film