How Does Photovoltaics Work?

Photovoltaics (PV) converts sunlight directly into electrical energy. In this article we explain the fundamental principles, from the microscopic process inside the solar cell to the complete system on your roof.

The Photoelectric Effect

The foundation of every solar cell is the photoelectric effect, which was explained by Albert Einstein in 1905 (for which he later received the Nobel Prize).

How it works:

1. Light absorption: Sunlight consists of photons (particles of light). When a photon strikes the silicon surface of the solar cell, it transfers its energy to an electron.

2. Electron release: The energised electron breaks free from its bond in the silicon crystal and becomes a “free” electron.

3. Charge separation: Through a built-in electric field (p-n junction), the freed electrons are separated from the remaining “holes”.

4. Current flow: When we connect the solar cell to an external circuit, electrons flow through this circuit — we have generated electric current!

From Cell to Module

A single solar cell typically delivers about 0.5 volts. To achieve usable voltages, many cells are connected in series:

• Cells to strings: Multiple cells are connected in series to form “strings”
• Strings to modules: Multiple strings are connected in parallel to form a module
• Modules to system: Multiple modules make up the complete PV system

Components of a PV System

A typical PV system consists of:

1. Solar modules: Convert light into direct current
2. Inverter: Converts direct current into alternating current (230V)
3. Mounting system: Secures the modules to the roof
4. Wiring: Connects all components
5. Meter: Measures the generated and fed-in electricity
6. Optional: Battery storage: Stores surplus electricity

Efficiency of Modern Solar Cells

Efficiency indicates how much of the incident solar energy is converted into electrical energy:

Cell type	Typical efficiency
Monocrystalline	19-22%
Polycrystalline	15-18%
Thin-film	10-13%
PERC	20-23%
HJT/TOPCon	21-24%

Frequently Asked Questions about Photovoltaics

How does a solar cell work in simple terms?

Sunlight consists of photons that strike the silicon surface and free electrons. A built-in electric field (p-n junction) separates the positive and negative charges. Electrons flow through an external circuit — we use this current. This process is called the photoelectric effect.

Does photovoltaics work without direct sunlight?

Yes! Solar cells also use diffuse light in overcast conditions and then generate 10-30% of their maximum output. Even under heavy cloud cover, electricity is produced. However, the total yield depends heavily on the number of sunshine hours.

What does the inverter do in a PV system?

The inverter converts the direct current (DC) from the solar modules into alternating current (AC, 230V) that your household appliances require. It also handles grid management, yield monitoring and protects the system during grid disturbances.

How long does a photovoltaic system last?

Modern PV systems have a lifespan of over 25-30 years. Manufacturers typically guarantee 80-90% of rated output after 25 years. Annual degradation is only 0.3-0.5%. The inverter typically needs replacing after 10-15 years.

What roof orientation is best for photovoltaics?

South-facing orientation with a 30-35 degree pitch delivers the highest annual yield. East-west systems achieve about 85-90% of the south-facing yield, but distribute generation more evenly across the day — ideal for high self-consumption. Use our PV calculator for your individual situation.

Conclusion

Photovoltaics is a mature and reliable technology for electricity generation. Modern modules achieve efficiencies of over 20% and have a lifespan of more than 25 years.

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Further reading:

• What module types are there?
• How does an inverter work?
• What affects the yield of a PV system?