Electricity Essentials
This electrical quantity is measured in volts and represents the “pressure” that pushes current through a circuit.
What is voltage?
The angle between the PV module surface and the horizontal ground is known as this.
What is the tilt angle?
This unit measures how much electric charge a battery can supply over time.
What are amp-hours (Ah)?
The first step before performing electrical maintenance is to disconnect and isolate the energy source, also known as this.
What is Lockout-Tagout (LOTO)?
The term for the total measure of solar energy received on an area over a period of time, often expressed in kWh/m2/day, is:
(A) Irradiance (B) Albedo (C) Zenith Angle (D) Insolation
If a light draws 2 amps on a 120-volt circuit, its power draw is this many watts.
What is 240 watts? (P = 120 × 2)
A module with 20 % efficiency and an area of 2 m² produces this much power at STC.
What is 400 W? (2 × 1,000 × 0.20)
A 12 V, 100 Ah battery stores this many watt-hours of energy.
What is 1,200 Wh? (12 × 100)
According to OSHA, fall protection must be used when working at this height or higher on construction sites.
What is 6 feet?
The device that converts DC electricity from PV modules into usable AC electricity for homes and businesses.
What is an inverter?
The unit that measures electrical resistance.
What is the ohm (Ω)?
If each module is 42 Vmp and you want a 420 V string, you’ll connect this many modules in series.
What is 10 modules? (420 ÷ 42)
If a 24 V inverter runs at 10 A for 4 hours, it consumes this much energy.
What is 960 Wh? (24 × 10 × 4)
PV module frames and metal racking must be connected to this system to prevent shock hazards.
What is the equipment grounding system?
What is the purpose of an Equalization charge cycle, used only for flooded lead-acid batteries?
(A) Monitor state-of-charge (B) Prevent thermal runaway (C) Stir the electrolyte and break down sulfation (D) Provide a rapid bulk charge
A 1,500-watt space heater on a 120-volt circuit draws this many amps.
What is 12.5 amps? (1,500 ÷ 120)
A 6 kW array with a system derating factor of 0.82 will have this approximate AC output at peak sun.
What is 4.92 kW? (6 × 0.82)
The charging stage that restores about 80 % of a lead-acid battery’s capacity.
What is the bulk charge stage?
This device is required on grid-tied systems to ensure safe disconnection from the utility grid.
What is an AC disconnect (utility disconnect)?
The total solar energy available on a tilted PV surface combines direct beam, diffuse sky, and ground-reflected light. Together, these form what type of radiation?
What is global solar radiation?(Correct — G = beam + diffuse + reflected.)
A 240-volt water pump drawing 4 A operates for 3 hours. It consumes this much energy in kilowatt-hours.
What is 2.88 kWh? (240×4×3 = 2,880 Wh = 2.88 kWh)
A site gets 5.5 PSH/day. A 7 kW PV system (after derate 0.88) will produce about this much energy per day.
What is 33.9 kWh/day? (7 × 0.88 × 5.5 = 33.88)
A lithium battery rated at 5 kWh is cycled once daily at 90 % depth of discharge. It delivers this many kWh per day.
What is 4.5 kWh? (5 × 0.9)
When lifting heavy solar modules onto a roof, this safe lifting principle should always be followed.
What is “lift with your legs, not your back”?
When calculating the maximum number of modules per string for a cold climate, the voltage calculation must be rounded:
(A) Up, to ensure proper MPPT voltage (B) Down, to prevent over-voltage damage to the inverter (C) To the nearest whole number (D) Based on the inverter's maximum MPPT current