Solar PV: Theory, Calculations and NABCEP Exam Preparation

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.

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.

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.

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.

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.

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.

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.

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.

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 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.

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

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.

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.

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

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.

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.

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.

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

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

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.

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.

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.

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.

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.