Solar Technician Interview Questions and Answers

How does a solar panel produce electricity?

Solar cells made of silicon convert sunlight directly into DC electricity (the photovoltaic effect). Cells are connected inside the panel to give a usable voltage, and an inverter converts the DC to AC for the building or the grid.

What are Voc and Isc?

Voc is the open-circuit voltage: the panel's voltage with nothing connected. Isc is the short-circuit current: the current when its terminals are shorted. Both are on the panel's label and datasheet, and they are used to check a string and to size the inverter and protection.

How to say it: Read them off a real panel label if you can; interviewers like that.

What happens when you connect panels in series and in parallel?

In series, voltages add and the current stays that of one panel. In parallel, currents add and the voltage stays that of one panel. A string is panels in series; strings may then be paralleled.

What is the difference between mono and poly panels?

Monocrystalline cells are cut from a single silicon crystal, look uniformly dark and are more efficient. Polycrystalline cells are made from many crystals, look bluish and speckled, and are a little less efficient.

What does shading do to a panel?

Shade on even part of a panel can cut the output of the whole string. Bypass diodes in the junction box limit the loss, but the best fix is to place panels where nothing shades them during the main sun hours.

What is the difference between on-grid, off-grid and hybrid systems?

On-grid (grid-tied) works with the utility supply and has no batteries; it stops when the grid fails, for safety. Off-grid runs on batteries and works without the grid. Hybrid has batteries and a grid connection, so it can run loads during a power cut.

How to say it: Mention that an on-grid inverter switches off in a power cut so linemen are safe: that is anti-islanding.

What does MPPT mean?

Maximum Power Point Tracking: the inverter or charge controller keeps adjusting the operating voltage so the panels give the most power as sunlight and temperature change.

What is net metering?

With an on-grid rooftop system, a bidirectional meter records both the power taken from the grid and the extra solar power sent to it, and the bill is for the difference. The electricity company (DISCOM) installs or approves the meter.

Which direction and tilt do panels face in India?

Facing south, with a tilt roughly equal to the site's latitude as a starting point, unless the design says otherwise. A flat-roof structure is designed for that angle and for wind load.

What are the main parts of a rooftop system?

Panels, mounting structure, DC cables with MC4 connectors, DC combiner or junction box with fuses, DC isolator and surge protection, inverter, AC distribution box with breaker and SPD, earthing, and the meter.

How do you check a string before connecting the inverter?

Check polarity, then measure the open-circuit voltage of the string with a multimeter and compare it with the expected value (panels in series × Voc, adjusted for temperature). Check insulation and earthing as the procedure says, then connect.

Why is earthing important in a solar system?

It protects people from shock if insulation fails and protects equipment from lightning and surges. The panel frames and structure, the inverter and the surge protection devices are all earthed as per the design.

How should panels be cleaned?

With clean water and a soft brush or cloth, early in the morning or in the evening when the panels are cool, without detergents that leave a film and without standing on the panels. Dust lowers output, so plants clean on a schedule.

Why is DC from solar dangerous, and what safety do you follow?

Panels produce voltage whenever light falls on them, so a string stays live even with the inverter off, and a DC arc does not stop on its own like AC. Isolate with the DC isolator, never disconnect MC4 connectors under load, cover panels or work in low light where the procedure says so, use insulated tools and gloves, and wear a harness on roofs.

How to say it: Say "isolate, verify with a meter, then touch". It is the answer they want.

What is the usual practical test?

Commonly: identify parts and read a panel label, connect panels in series and in parallel and measure voltage and current, crimp an MC4 connector, or wire a small system with a charge controller and battery.