How does solar power work?

A solar module is built from silicon cells with two semiconductor layers: an n-type layer with surplus electrons and a p-type layer with electron vacancies, meeting at the p-n junction. When a photon with sufficient energy hits the cell, it frees an electron and creates an electron-hole pair.

The built-in electric field at the junction pushes electrons one way and holes the other, producing a voltage across the terminals. Connect the terminals through an external circuit and the electrons flow — that current is the photovoltaic effect at work.

• A standard silicon cell produces roughly 0.6–0.7 V open-circuit, so many cells are wired in series inside one module.
• Current output is roughly proportional to the irradiance reaching the module surface.
• Voltage falls as cell temperature rises, so the same module delivers less power on a hot, still day than at standard test conditions.

Modules are wired in series into strings to raise DC voltage before reaching the inverter. The inverter does two critical jobs: maximum power point tracking (MPPT) so each string always delivers as much power as the current conditions allow, and inversion of DC into a sine-wave AC output synchronised with the grid in frequency (50 Hz), voltage and phase angle.

AC output then passes through the distribution board and meter and supplies the plant's loads. Any shortfall is drawn from the grid; any surplus is exported, unless the system is configured for zero export.

• String inverters: the standard choice for commercial rooftops, each unit managing several independent MPPTs.
• Central inverters: used on utility-scale solar farms and floating PV projects.
• Optimisers or micro-inverters: useful where the roof has local shading or several orientations.
• Zero-export control caps inverter output so nothing is fed back when the system is licensed for self-consumption only.

• Modules and mounting structure, engineered for wind load and roof structure.
• DC combiner with fuses, surge protection and isolators for safe maintenance.
• Inverter, AC panel, main breaker and residual current protection.
• Metering, export-limitation device and current sensors at the connection point.
• Remote monitoring that logs yield per minute/hour and raises string or inverter alarms.
• Optionally a BESS to shift midday generation into other hours.

A standard grid-tied system disconnects during a grid outage (anti-islanding) to protect line workers; keeping loads alive requires a hybrid configuration with storage.

Two projects with identical installed capacity can produce noticeably different energy. The main drivers are local irradiance, roof orientation and tilt, operating temperature, shading, soiling and electrical design quality.

• Irradiance: check the project coordinates on the Global Solar Atlas before fixing the design.
• Orientation and tilt: south-facing roofs give the highest annual yield in Vietnam; east-west layouts spread output across the day.
• Temperature: module output falls with the temperature coefficient (typically around −0.3%/°C), so ventilation under the array matters.
• Shading and soiling: partial shade can drag down a whole string if string design is poor.
• System losses: cabling, connections, transformer, inverter efficiency and maintenance downtime.