Chapter 7 Summary
This chapter covers the process of sizing a PV system. Several sizing worksheets are available
to the system designer and installer in addition to software and simulation programs. Before
sizing the system, a site analysis must be done and the system type should be selected. System
sizes will depend on budget, whether you are installing a standalone or utility-interactive PV
system. Also, the electrical demand will need to be determined by completing a load analysis
based on various loads.
Derating factors need to be assessed based on various system losses and their values.
These derating factors will have an affect on total AC power output measured in kilowatt-
hours (kWh). By using software and simulation tools, these losses can be easily calculated and
accounted for prior to installation.
Lastly, the size of inverters, batteries, and arrays needs to be carefully calculated according
to electrical load and module specifications. You must be familiar with sizing worksheets and
how they work. Otherwise, it will be difficult to accurately determine the size and configura-
tion of the PV system you wish to design and install.
Key ConCeptS and termS
Derating
Load analysis
PVWatts
Chapter 7 aSSeSSment
PV System Sizing Principles
1. In most cases, PV battery systems should be sized according to the three lowest months of
insolation and the highest load demand.
A. True
B. False
2. A utility-interactive PV system does not have to provide for all of the daily energy load
needs.
A. True
B. False
3. Most residential solar systems fall within what KW range?
A. 10–16 KW
B. 1–8 KW
C. 20–26 KW
D. 90–96 KW
4. A(n) is an estimate of electric consumption based on the number of
electronic and inductive devices; the devices’ daily use averages with energy consumption.
136
REVIEW GUIDE FOR THE NABCEP ENTRY-LEVEL EXAM
5. is the process of determining the impact of operational and
environmental factors on equipment or system ability to operate at 100 percent of its
nameplate, rated operational rating, or rated performance and shows that performance as a
fractional loss for the system. For example, a 5 percent deration factor would result in a 95
percent system multiplier.
6. In what area does PVWatts work?
A. All around the world
B. Only in North America
C. Only in the Northern Hemisphere
D. Only in the Southern Hemisphere
7. The size of the array directly affects the size of the battery needed for a standalone PV
system.
A. True
B. False
8. The size of the will depend upon the watts it will have to convert from
DC to AC, the estimated surge watts, and which type of waveform (square, sine, modified
sine) it will have to accommodate.
9. The load profile lists the total AC and DC watts that will be used in a building.
A. True
B. False
10. Which of the following is the most common type of battery used in standalone PV systems?
A. Nickel-cadmium
B. Vented
C. Lead-acid
D. Iron-cadmium
11. An appropriately sized inverter will not allow the client to use multiple high-energy devices
simultaneously.
A. True
B. False
12. Battery capacity is usually measured in which of the following units?
A. Amp hours
B. Watt-hours
C. Kilowatt-hours
D. Autonomy hours
13. What three pieces of information do you need to know to determine the size of the
inverter? (Choose three.)
A. Total AC watts required
B. DC system voltage
C. Estimated starting/surge loads
D. The sun’s azimuth angle
CHAPTER 7 PV System Sizing Principles 137

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