NABCEP Entry Level Study Guide

Frage	Antworten
Solar radiation	Radiant energy emitted by the sun
Solar irradiance	Solar radiation that has reached Earth's surface. Power per unit area produced by the Sun. W/m^2 Measure of how much solar power you are getting at your location.
Solar irradiation	Solar irradiance integrated over time. Wh/m^2
Solar insolation	The amount of solar irradiation per day Wh/m^2/day
Solar constant	The long-term average of the total solar irradiance. Quantifies the amount of radiation energy that arrives from the sun at the outermost layers of the atmosphere. 1.353 kW/m^2
Air mass	The path length which light takes through the atmosphere normalized to the shortest possible path length (when the sun is directly overhead). AM=1/cos(angle from the vertical). When sun is overhead, air mass=1.
Ecliptic plane	Plane in which the Earth orbits the Sun
Equatorial plane	Plane containing Earth's equator and extending outward into space
Pyranometer	Measures global radiation in an area. Measures both direct and diffuse (reflected) radiation
Solar declination	An angle between the equatorial plane and rays of the sun
Solstice	When the sun will raise to either the highest or lowest path possible
Equinox	The sun will move across the sky for the same amount of time everywhere in the world
Solar time	Corresponds with the sun's position in the sky. Noon solar time is when the sun is highest in the sky
Solar altitude angle	The vertical angle between the sun and the horizon
Solar azimuth angle	The horizontal angle between a reference direction (typically due south) and the sun
Solar window	The area between the path of the sun at summer solstice and the path of the sun at winter solstice.
Array tilt angle	The vertical angle between horizontal and the array surface
Array azimuth angle	The horizontal angle between a reference direction and the direction an array surface faces
Solar incidence angle	The angle between the sun's rays and a line perpendicular to the array surface
Energy equation	Energy=power x time
V=	volts, V=IR
I=	amps, current, amperes
R=	resistance, ohms
W=	watts, power W=VI
Isc=	short circuit current. When you have all current and no voltage (wires are crossed/shorted)
Voc=	Voltage Open Circuit. When you have all voltage and no current (wires not touching/open circuit)
Imp=	Current Maximum Power
Vmp=	Voltage Maximum Power
Imp x Vmp =	STC watts
STC	Standard Test Conditions. Irradiance at STC=1,000 watts/m^2. Temp is 25C. 1.5 atmosphere spectrum of light. Does not take heat from irradiance into account.
MPPT	M
Wiring in series increases ________, wiring strings in parallel increases ________.	voltage, current
120% rule	Busbar * 1.2 must be greater than or equal to the main breaker + backfeed (solar) breaker
Max current on PV source circuit=	Isc * 1.25, because sometimes we can get 1,250 watts per m^2 of irradiance
DC PV conductor sizing	Compare Isc * 1.56 and Isc * 1.25 and conditions of use, then pick the biggest conductor of the two.
What kind of wire is white?	Grounded current carrying conductor, usually negative.
What kind of wire is green or bare?	Grounding and non-current carrying for grounding equipment for safety
What kind of wire is black?	Hot ungrounded current carrying conductor
Wire sizes	Bigger wires have smaller numbers. Small wire=AWG 16, large=000
Temperature correction factors for cold temperatures	Two ways: -PV mfg (?) gives temp coefficient of Voc (ex: 0.33%/deg. C). Multiply by delta deg C from 25 C for increase Voc in cold temp -If no coefficient from mfg, use table 690.7 (?) and multiply Voc by temp factor (If record low temp =-40C, correction factor is 1.25. If 40 Voc module @ 0C, 40V*1.25=50 Voc
Calculate circuit breaker size.	Inverter output max current * 1.25=circuit breaker size (round up)
Calculate battery sizing given days of autonomy and depth of discharge.	If you use 10 kWh/day, 3 days of autonomy, 50% depth of discharge: 10 kWh * 3 days = 30 kWh 30 kWh / .5 depth of discharge = 60 kWh in battery bank Then derate for other things
Peak sun	jk
Peak sun hours	jk
Consequences of array shading and best practices for minimizing shading and preserving output	Minimizing shading: take 3 times height of modules b/t modules Distance between rows= height * cos(azimuth)/tan(altitude)
Spacing distances	jk
Five key electrical output parameters	Voc: open circuit voltage Isc: short circuit current Vmp: max power voltage Imp: max power current Pmp: max power point Label on an I-V curve (current-voltage): Isc is high A, no V, Voc is high V, no A, and Imp and Vmp meet at the maximum power point.
Performance rating and measurement conditions	STC: 25 C, 1,000 w/m^2 SOC: 1,000 w/m^2 & nom (NOCT) temp NOCT: 800 w/m^2, 20 C, wind speed 1 m/s PTC
Overcurrent protection	jk
Conduit and raceway systems	jk
Switchgear	jk
Junction and combiner boxes	Combiner boxes: overcurrent protection for modules and conductors. Combines series strings in parallel. Need one per series string, and it needs a DC disconnect
Terminators	jk
Connectors	jk
De-rating factors and system losses	jk
Major components of a PV system	jk
A fall protection system must be in place for all work done at heights in excess of _______.	6 feet
A circuit breaker performs the same function as ______.	a fuse, a switch, and over-current protection
What typically trips a breaker?	Not voltage...need more info
Between the main pane and the inverter, you have _______.	an AC disconnect
Between the array and the inverter, you have _______.	2 of the following are correct: a DC disconnect, an AC disconnect, sometimes a charge controller
KNOW HOW TO READ A SUN DIAGRAM	ok
2 phase is...	what is it
Utility interconnection is done in this order:	PV, charge controller, battery, inverter, grid
In California, magnetic North is pointing....?	More east than true north, BECAUSE...?
The critical design month is the worst case scenario where the load and the _______ are used to size the PV system	insolation data
If you combine solar and wind energy in an off-grid system, it is ______.	hybrid
Irradiance proportionally affects	amperage, NOT voltage
The further north you are, the better it is to	increase your tilt angle (match the latitude)
Temporarily shorting the output terminals of a PV module will	have no effect on the module
KNOW HOW TO READ A SUN PATH DIAGRAM	ok
When the sun sets on summer solstice, it is the farthest ______ that it will ever set.	north
The best way to increase your PV output is to	switch from stand alone to interactive (tracking?)
What factor inhibits higher voltages in PV?	hot weather
Linear current boosters	are commonly used in direct pumping applications and drop voltage
Irradiance is measured in	watts per square meter
The length of time a load is on...	is proportional to the energy used
Equinox	is the same day everywhere in the world at the same time
Ideal altitude and azimuth orientations for PV arrays	Year-round use: Summer only: Winter only:
What is the rule of thumb for estimating daily and yearly output for a PV array?	1,000 kW per installed kW per year
Calculate the efficiency of a PV module.	Efficiency=Pmp/solar irradiance * area (m^2)
How to calculate appropriate distance between modules	Distance between modules = height of modules * cos(az angle between solar az and array az)/tan(sun altitude angle)
Why is DC current more dangerous that AC?	It is constant and more difficult to break
Ideal angle (altitude) of collector =	complimentary angle of sun chart's altitude
Charge controller	Purpose is to prevent overcharging battery, prevent reverse current flow, protect equipment from high voltage.

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