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A- General Engineering License > Photovoltaic & Solar Thermal Systems > Flashcards

Photovoltaic & Solar Thermal Systems Flashcards

1
Q

A photovoltaic system is?

A

An electrical system consisting of a PV module array and other electrical components needed to convert solar energy into electricity usable loads.

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2
Q

What is a solar energy collector?

A

Is a device designed to absorb solar radiation and convert it to another form, usually heat or electricity.

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3
Q

What are two common types of collectors?

A
  1. Flat-plate collector - absorbs solar energy on a flat surface without concentrating i.
  2. Concentration Collector - enhances solar energy by focusing on a smaller area through reflective surfaces.
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4
Q

Concentrating Solar Power (CSP)

A

Uses mirrors and lenses to reflect and concentrate solar radiation from a large area onto a small area.

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5
Q

Three main styles of CSPs?

A
  1. Trough Collectors
  2. Dish Collectors
  3. Power Towers
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6
Q

Solar Irradiance

A

The power of solar radiation per unit area (power per unit area or W/m^2) [speed]

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7
Q

Solar Irradiation

A

The total amount of solar energy accumulated on an area over time (watt-hours per square meters). Principal data needed for sizing and estimating the performance of PV systems. [distance]

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8
Q

Formula for solar irradition:

A 
H = E x t
H = solar irraditation (Wh/m^2)
E = average solar irradiance (W/m^2)
t = time (hr)
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9
Q

Insolation

A

The solar irradiation received over a period of time, typically one day.
- Solar Energy per Unit Area

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10
Q

Pyranometer

A

Is a sensor that measures the total global solar irradiance in a hemispherical field of view. Often used to monitor solar radiation incident on flat plate type arrays.

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11
Q

Pyreheliometers

A

Is a sensor that measure only direct solar radiation in the field of view of the solar disk (5.7 degrees). Used on sun-tracking device.

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12
Q

Solar declination

A

The angle between the equatorial plane and rays of the sun. (Positive angle when Northern Hemisphere is tilted toward the sun)

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13
Q

Incidence Angle

A

The angle between the sun’s rays and a line perpendicular to the array surface. Maximum solar radiation is received when the incidence angle is 0 degrees.

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14
Q

Charge control is required by the NEC if the array current is equal to __ or more of the rated battery capacity in ampere-hours.

A

3%

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15
Q

Blocking Diode

A

A diode used to block reverse flow of current into a photovoltaic source circuit.

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16
Q

Diversion Charge Controller

A

Equipment that regulates the charging process of a battery by diverting power from energy storage to direct-current or alternating-current loads or to an interconnected utility service.

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17
Q

Equipment such as raceways, cables, etc can be located above or below electrical equipment but must not extend more than ____ inches into the equipment’s working space.

A

6 inches

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18
Q

What is the minimum depth of a ground rod electrode in contact with soil?

A

8 feet (NEC 690.4)

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19
Q

What is “depth of discharge” as it relates to a battery?

A

Depth of discharge is a measurement of the battery status - not related to usable capacity.

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20
Q

The grounded PV conductor size 6AWG or less used for wiring from the combiner box to the inverter must be what color?

A

White, gray or any color with 3 white stripes.

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21
Q

A residence has a 200A service panel with a 150A main circuit breaker to the utility. What is the highest rated inverter continuous AC output that can be backed into this main service point?

A

Sum of OCPD supplying power to busbar must not exceed 120% of the busbar rating.
Supply power maximum = 1.2 x 200 240A
Maximum from solar = 240-150=90A

NEC 705.12

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22
Q

The center of the grip of the operating handle of an over current protection device when at it’s highest position cannot be higher:

A

6ft -7in

NEC 404.8(A)

23
Q

What formula is used to estimate the PV source circuit or output circuit voltage?

A

Vmax = Voc x Nm x Ct

Nm = number of series-connected modules
Ct = low-temperature voltage correction factor
24
Q

Maximum current for PV source circuits?

A

125% of the sum of the short-circuit current rating of parallel-connected modules/

25
Q

Ampacity

A

The current that a conductor can carry continuously under the conditions of use without exceeding its temperature rating

26
Q

How is conductor size chosen?

A

For PV source circuits, conductors must be sized to handle at least 125% of the maximum current. This is an addition to the 125% used to estimate the maximum current under high irradiance.

27
Q

Cubic feet to Gallon Conversion

A

1 CF = 7.5 gallons

28
Q

The highest average winter insolation will fall on a solar module with a tilt angle equal to :

A

The location’s latitude plus 15 degrees

Hint:

The sun is lower in the sky, so to create a more perpendicular angle, you increase the angle (from horizontal)

29
Q

What is standard test Conditions (STC)?

A

Cell module temperature at 25C, Air Mass of 1.5 and irradiance of 1000 W/m2

30
Q

What is the approximate percentage that the maximum power voltage changes based on temperature?

A

0.5% per C

31
Q

Article 690.5 requires what to be installed when a PV array is installed on a roof of a dwelling?

A

Ground fault protection device to detect and interrupt high currents that can create a fire hazard.

32
Q

If the total nominal voltage of a battery bank exceeds ____ , then the batteries shall not be installed in conductive cases.

A

48V

33
Q

Minimum spacing between rows of modules at a tilt angle?

A

3 x height of top of the adjacent module

34
Q

The potential uplift force of a strong wind is?

A

50 pounds per square foot (psf)

35
Q

As a rule of thumb, crystalline silicon modules with 10% efficiency will generate?

A

100 watts per square foot

36
Q

A fuse protecting the conductors must also be rated at?

A

1.25 x the continuous current or 1.56Isc.

Fuse rating is rounded up to the next highest value.

37
Q

What is the maximum system voltage for a DC system?

A

PV system open-circuit voltage multiplied by the correction factor in table 690.7

38
Q

Table for nominal ampacities of insulated copper conductors?

A

310.16 and 310.17

39
Q

Table for ampacity correction factors for high temperatures?

A

310.16

40
Q

Table for ampacity correction factors for number of conductors?

A

310.15 (B)(2)(a)

41
Q

Formula for nominal ampacity when a minimum conductor size must be determined from maximum circuit current.

A

Inom = Imax/ (CFtemp x CFconduit)

42
Q

NEC recommended maximum voltage drop?

A

3%

43
Q

Calculate voltage drop?

A

Voltage drop = operating current x conductor resistance x length

44
Q

Interrupting Rating

A

The maximum current that an over current protection device is able to stop without being destroyed or causing an electric arc.

45
Q

A power source operating over what temperature corrected maximum open circuit voltage must have one grounded conductor?

A

50V

46
Q

For AC/DC systems, the separate grounding rod does not need to be directly bonded to the other electrodes if the array is how far away from the premises wiring electrode?

A

6’

47
Q

Ground Fault

A

The undesirable condition of current flowing through the grounding conductor.

48
Q

When ground fault protection is not used, the equipment grounding conductor is sized for?

A

Twice the temperature and conduit fill derated ampacity of the circuit’s current-carrying conductors.

49
Q

When ground fault protection is used, PV circuit equipment grounding conductors are sized in accordance?

A

Article 250 establishes the minimum size for equipment grounding conductors based on the over current protection rating for the circuit

50
Q

Surge Arrestor

A

A device that protects electrical devices from transients (voltage spikes).

51
Q

Can a surge arrestor be installed in an ungrounded system?

A

No, they rely on a connection to ground to dissipate surges

52
Q

Battery systems of greater than ___ volts must include a disconnect to divide the system into segments of ____ volts or less for maintenance.

A

48 volts and 48 volts

53
Q

Flooded, lead-acid batteries in these battery banks may not have ____ cases or be installed on ____ racks that come within ____ of the top of the cases.

A

Conductive, metal, 6”

A- General Engineering License (13 decks)

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