Solar PV: Theory, Calculations and NABCEP Exam Preparation

The sun provides energy as light and heat, powered by hydrogen fusing into helium through thermonuclear reactions under gravity.

Investigate extraterrestrial solar radiation and the solar constant, noting values around 1353–1377, and how Earth's elliptical orbit causing ±1.7% variation informs calculations for solar pv system design.

Explore how terrestrial solar radiation interacts with the atmosphere, distinguishing direct beam, diffuse, and global components, and examine how air mass and albedo influence surface irradiance.

Determine peak sun hours by dividing the day’s total solar irradiance energy by 1000 W/m^2, recognizing that peak sun equals one hour when irradiance reaches 1000 W/m^2 under standard conditions.

Define solar irradiance as solar radiation per unit area, used as a reference input to evaluate a solar system's output, noting sun cycles and sun distance affecting irradiation.

Use solar radiation data and maps to estimate the yield for planned work, drawing on global horizontal irradiation data, high-resolution charts, and color-coded maps of irradiance.

Explore solar time and the equation of time, showing how solar noon differs from 12 p.m. local time due to longitude, meridians, and time zones, with a correction graph.

Analyze how tilt and azimuth angles affect solar radiation and pv output. The optimal tilt equals latitude, while azimuth and climate influence annual energy production.

Understand magnetic declination, the angle between magnetic north and true north, varying by location and time, and adjust compasses using a revolving bezel with National Center for Environmental Information calculator.

Explore atoms and Bohr models, electron transitions, and how photons cause emission or absorption, enabling conduction via conduction and valence bands and band gaps in semiconductors.

Explore silicon structure and doping, including donor states that create free electrons and holes, and how phosphorus and boron dopants influence the conduction and valence bands and charge carriers.

Explore how photon absorption excites electrons across a band gap, creating electron-hole pairs in a p-n junction, generating drift and field currents, and producing open circuit voltage under illumination.

Analyze current, voltage, and power curves of solar PV modules, including open-circuit voltage and maximum power point. Learn how irradiance and temperature shift operating points along constant load lines.

Explore efficiency and fill factor to assess solar module performance, using power output and input, irradiance, area, and max power point metrics (Vmp, Imp) with Voc and Isc.

Explain how bypass diodes protect a photovoltaic module from shaded cells by bypassing groups of cells, preventing power loss and overheating, with installation in a back junction box.

Explore PV module labels, including nameplate electrical ratings, maximum overcurrent device ratings for module protection, open circuit and operating voltages under standard test conditions, and fire classification and certification notes.

Explain standard test conditions for solar modules—1000 W/m^2, air mass 1.5, 35°C—and compare to nominal operating conditions at 800 W/m^2, air mass 1.5, ambient 20°C and nominal operating cell temperature.

Identify key components of solar PV systems—modules, mounting racks, connectors, cables, inverter, battery storage, and BOS—plus safety, disconnects, OCPD, and layout considerations for rooftop design.

Examine major conductor types, copper, aluminum, acsr, aa, and their solid or stranded forms, sizing systems, capacity, voltage and temperature ratings, insulation, and pv color coding.

Understand grounding and bonding in PV circuits, including main bonding jumper, equipment grounding conductor, and grounding electrode conductor, and how fault current travels via least impedance path to trip breakers.

Explore essential electrical fittings for solar PV installations—connectors, couplings, grounding bushings, strain reliefs, and LB conduit bodies—along with NEC 690 labeling, working clearances, and grounding practices.

Learn safety in solar pv systems by addressing high dc voltage, dc arcs, grounding, rapid shutdown, arc fault protection, labeling, and PPE under OSHA and NEC 690.

Identify and apply major standards and codes for solar PV systems, including NEC 690, UL listings, IEEE 1547, IEC 61215, and NFPA fire and building codes.

Identify the correct earthing cable color as green or green with yellow stripes, instead of red, blue, or black, for proper earth connections.

This lecture explains the color scheme for a 120/240 V split-phase with high-leg delta, indicating orange as the high leg and blue and black for other conductors in residential applications.

Calculate solar power from irradiance and module specs by multiplying each module's nominal power by the count and applying efficiency, using 1000 w/m^2 irradiance and siac condition.

Calculate total output for ten 400-watt PV modules under 800 w/m2 irradiance, using the STC reference of 1000 w/m2 and an irradiance ratio of 0.8.

The lecture explains multimode inverters can operate as standalone or interactive systems, accepting input from PV and energy storage, and can also connect to the grid when available.

Explore sun path charts that map sun position using solar elevation (altitude) and azimuth angles, aiding shading analysis and PV system design.

Select the correct solar PV system type for home with backup power, distinguishing interactive, stand-alone, multi-model, and hybrid options, and noting multi-model provides energy storage or direct backup.

Explore residential rooftop mounting methods for solar PV, comparing leg-based and screw-based systems with flashing, and learn how securing PV modules to the roof structure prevents water intrusion.

Explore how a solar system uses a charge controller to regulate battery charging and how an inverter converts DC to AC, including transformers and PWM basics.

The PV cable interconnects PV modules into strings to connect to the inverter, while a green grounding cable provides a common grounding line.

Calculate the system voltage and current for ten PV modules connected in series under STC, assuming ideal inverter and no losses, using open-circuit and maximum power data.

Calculate the ac output of a 150 kilowatt dc solar pv system with 11% system losses and 96% inverter efficiency to yield about 128 kilowatts ac.

Transformers convert high voltage to low voltage and low current while preserving power between primary and secondary windings, enabling transmission at high voltage and distribution to 120 or 220-volt residences.

Calculate the minimum number of modules in series to keep the array voltage within the inverter range of 250 to 600 V at elevated temperature, which requires eight modules.

Irradiance is the solar power per unit area, measured in watts per square meter, with about 1000 W/m^2 at sea level and 1361 W/m^2 at the top of the atmosphere.

Ground the aluminum frames and mounting hardware of pv modules by connecting them to the building's grounding system, and understand how grounding interacts with inverter connections and lightning protection.

Learn how bypass diodes limit shading effects on series-connected PV cells, keeping some modules productive when others are shaded and preventing overheating.

Identify the maximum power point on the IV characteristic curve of a PV module by considering load conditions and inverter wiring; short circuits yield zero voltage.

Explore the albedo phenomenon and how reflected irradiance from surfaces adds to direct and diffuse components, boosting PV module output.

Use temperature and its coefficient to calculate changes in maximum system voltage, not ground, power, or resistance; open-circuit voltage increases as temperature decreases and decreases as temperature rises.

Identify the maximum fuse rating of a PV module by reading the back-label, which shows the fuse value (for example 15 A), rather than relying on inverter or disconnect guesses.

Connect four strings of ten modules in parallel to the inverter, so the MPPT input voltage remains the same as a single string, about 41 V.

Learn how a charge controller drives a 12-volt lead-acid battery through bulk, absorption, and float stages, with charging voltage near 14 volts to reach full charge.

Explain that in a supply-side connection, inverter output is constrained by the service entrance cable sizing and the main disconnect sizing, not by the pv module size.

Identify which wire characteristics cause greater voltage drop: longer and thinner conductors increase resistance and voltage drop, while shorter and wider conductors decrease it.

Calculate the maximum PV power from the total area of 25 m^2 at 19% efficiency under 1000 W/m^2 irradiance.

sealed valve-regulated lead-acid batteries are maintenance-free, as hydrogen is managed by a pressure-relief vent and recombination; only terminal cleaning is required, with no water top-ups or equalization charging.

Interconnecting a grid-tied solar system requires permission from utility authorities. City, county, or state bodies do not approve the grid interconnection.

This lecture shows that a digital multimeter is the best tool to verify that solar PV modules wired in series are connected correctly before connecting to the combiner or inverter.

An undersized PV system fails to provide enough charging to the battery, leading to undercharging and ultimately decreased battery life.

Size a 12 v battery bank by energy: 2400 w for 1 h requires two 12 v 100 ah batteries in parallel.

Determine how many 12-volt, 100 Ah batteries are needed to power a 400 W load for three hours via a 120 V inverter with no losses.

Explore glass mounting and fixed orientation mounting, and learn how tilting adjustments optimize seasonal solar radiation to maximize module power.

OSHA dictates ladder safety with a maximum slope of 1:4 and a top extends at least 3 feet above the surface; for a 16‑foot height, ladder length is 19 feet.

Safety concerns forbid placing a disconnect in bathrooms or toilets, even if readily accessible.

Identify electric shock as the most likely hazard when working with PV systems, and review safety practices, PPE, and MCE connectors to prevent arcing and heat-related risks on rooftops.

Enlarging solar cell size increases the current and module power by capturing more irradiance, while module size alone does not raise current and temperature has minimal impact.

Calculate power units by converting a 250 watt load to kilowatts, then apply energy equals power times time to find kilowatt hours and the duration in days.

Compute the resistance in a basic 120-volt AC circuit using a 2.5-amp current by applying the relation R = V / I.

Stc watts are the nominal rating of a solar module under standard test conditions, calculated as vmp × imp at 25 °c and 1000 w/m².

Calculate the STC system power for 10 modules with 1.2 m^2 area and 19% efficiency under 1000 W/m^2 irradiance; the result is about 2280 watts, excluding system losses.

Learn how to size the circuit breaker for a temporary on-grid interactive inverter with a 20 amp output, using standard NBC/NSC ratings of 15, 20, 30, or 60 amps.

Micro-inverters attach to individual PV modules, converting DC to AC and allowing independent orientation. They reduce shading impact and feed the grid via a common bus-bar.

Explain standard test conditions (STC) for solar modules—1000 W/m2 irradiance, 25°C cell temperature, AM 1.5—and contrast them with real-world operating conditions and CEC/PTC considerations.

Determine inter-row spacing for PV modules using solar elevation and azimuth angles, and the modules' dimensions. Understand how December 21 worst-case shading shapes spacing calculations.

Explain how current in a conductor creates a magnetic field and how inductance is defined as the ratio of voltage to the rate of change of current.

Troubleshooting a PV system on a hot summer day reveals that rising module temperature lowers voltage, dropping inverter input below the minimum range due to too few modules.

Describe the OSHA mandatory condition to use fall protection when working at heights of six feet or more, following offshore safe practices.

Install OSHA safety nets near the working level, not more than 30 feet below the surface, to provide fall protection for workers at six feet or more.

Identify OSHA stairway requirements based on elevation thresholds—19 inches or more, with additional considerations for heights over 30 inches and four or more steps.

analyze high voltage safety classifications, noting class b and class g hazards for low water applications, and examine glass and glossy materials for penetration, impact, and electrical works.

Examine the OSHA question on current needed to cause painful shock, focusing on ten million pairs and the progression from slight shocks to heart rhythm disruption.

Set the optimum tilt angle for a northern hemisphere off-grid pv system in summer to latitude minus 15 degrees; winter uses latitude plus 15.