Solar PV Exam Prep Notes

Solar PV Concepts

Irradiance

• Density of radiation incident on a given surface.
• Typically expressed in watts per square meter (W/m²).

Insulation vs. Irradiance

• Insulation is irradiance over time (e.g., over a year).

Radiant Energy (Art)

• Instant energy.
• The maximum amount of energy that can be released in an extreme or flash situation.

Maximum Power Point (MPP)

• On the IV curve (relationship between current and voltage), MPP is the point where maximum power can be produced.

Solar Panel Production Tolerances

• Solar panels have production tolerances, e.g., plus or minus 5% (or 3%).

Insulated Gate Bipolar Transistor (IGBT)

• IGBT stands for Insulated Gate Bipolar Transistor.

Standard Testing Conditions (STC)

• Standard testing conditions are used to rate solar panels.

Open Circuit Voltage (Voc) vs. Voltage at MPP (Vmpp)

• Open circuit voltage rating is higher than voltage at MPP.
• Analogy: A garden hose with a sprayer. When the hose is firm and full of pressure (maximum voltage), no current is flowing. Once you start spraying water (current flowing), the voltage drops slightly.
• STC: 1000 watts per meter squared and a cell temperature of 25 degrees Celsius.

Panel Connections: Parallel vs. Series

• Parallel: Panels connected in parallel approximately double the current.
  • Connecting positive to positive and negative to negative increases current.
  • Voltage remains consistent.
  • Analogy: A garden hose splitter. The total flow (e.g., 10 gallons per minute) is divided among the hoses.
• Series: Connecting solar panels in series connects positive to negative. This configuration increases voltage.

MC4 Connectors

• It is not recommended to mix MC4 compatible connectors from different brands.
• This is because proper intermatability and low resistance connections cannot be guaranteed.

IGBT Location

• IGBTs are located in specific assemblies within the system.

Array Brain Tracking System Motor

• The array brain tracking system uses a three-phase motor.

Medium Voltage Transformer

• Medium voltage transformers step voltage up or down.
• Typical medium voltage: Hundreds of volts (e.g., 32kV to 36kV).

Solar Site Components: Smallest to Largest

1. Cell (smallest physical object, ~0.5V)
2. Module (multiple cells in series)
3. Panel (multiple modules, sometimes cells, in series)
4. String (multiple panels in series)

• Modules and panels are sometimes used interchangeably.
• Bypass diodes are often present in junction boxes (e.g., three modules with three bypass diodes).

Switch Behavior

• The duration for which a switch is open or closed affects average voltage and current.

High Voltage (HV) Gloves Exchange Frequency

• Near employees (NextEra Energy Resources): Exchange every six months, based on the test date stamped on the gloves. If out of date but sealed in plastic, they can be used once and then must be retested.
• FPL employees (Florida Power & Light): Exchange every one month.
• Canadians: Exchange every three months.