PV System Mechanical Design

Question 1

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

Answer 1

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

Question 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?

Answer 2

Undercharged in cold weather and overcharged in hot weather

Question 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?

Answer 3

773 Ohms

Question 4

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

Answer 4

The grounding conductors

Question 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?

Answer 5

-24 degrees

Question 6

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

Answer 6

It’s usually not carrying substantial current

Question 7

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

• sun path analyzer
• pliers
• Inclinometer
• compass
• voltmeter

Answer 7

Compass, inclinometer, and sun path analyzer

Question 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?

Answer 8

At the utility point of connection

Question 9

What does green mean in an AC system?

Answer 9

Ground

Question 10

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

Answer 10

Heat and shading

Question 11

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

Answer 11

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

Question 12

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

Answer 12

Two-axis tracking mount

Question 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?

Answer 13

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

Question 14

What is the cost advantage of thin-film?

Answer 14

Can be cheaper per watt to produce

Question 15

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

Answer 15

Increase the tilt angle

Question 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…

Answer 16

1.67”

Question 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…

Answer 17

1900 watts

Question 18

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

Answer 18

Decrease your tilt angle

Question 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?

Answer 19

A 48 V DC array of the same wattage

Question 20

What is distributed generation?

Answer 20

Smaller systems produce electricity close to consumption needs

Question 21

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

Answer 21

Shading

Question 22

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

Answer 22

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

Question 23

Shading is the most important consideration for what?

Answer 23

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

Question 24

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

Answer 24

Stainless-steel hardware

Question 25

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

Answer 25

Distributed generation

Question 26

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

Answer 26

Bare copper

Question 27

Arrays are common components in what?

Answer 27

All PV systems

Question 28

Stainless-steel hardware is most important in which areas?

Answer 28

Coastal areas where the air contains salt spray

Question 29

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

Answer 29

Determining the optimal array placement

Question 30

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

Answer 30

Check the polarity of the PV output

Question 31

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

Answer 31

Decreased responsiveness, compared to polycrystalline PV

Question 32

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

Answer 32

Thin-film