How Solar Panels Work

4 min read

Solar panels are a technology that converts sunlight into electricity by using cells called "photovoltaic cells," which are often made of silicon, a semiconductor material. When sunlight falls on these cells, the light is absorbed and converted directly into electrical energy in the form of direct current (DC) [1].

Basic Mechanism of Action:

1. Absorption of Sunlight: Photons from sunlight fall on the photovoltaic cells, and their energy is transferred to the electrons within the silicon material.
2. Release of Electrons: After absorbing the photons, the electrons gain enough energy to be released from the silicon atoms, becoming free to move.
3. Formation of Electrical Current: An electric field is created inside the solar cells that directs the movement of electrons in a specific direction, forming a direct electrical current.
4. Current Conversion: The resulting direct current is sent to an inverter, which converts it into alternating current (AC) suitable for powering household appliances or feeding into the electrical grid [2].

The Photovoltaic Effect and the Role of Silicon

The photovoltaic effect is the phenomenon in which electrons are emitted from the surface of a material when exposed to light with sufficient energy. In solar cells, this effect represents the basis of the electricity generation process, where sunlight photons release electrons from the silicon [1].

The role of silicon in the solar cell:

• A semiconductor material that controls the movement of electrical charges.
• When doped with precise impurities, it forms two layers: one rich in electrons (negative charge) and another containing positively charged "holes."
• The interaction between these two layers creates an internal electric field that pushes the released electrons toward the negative pole, generating an electrical current.

Types of Solar Panels

• Monocrystalline: Made from a single pure silicon crystal, characterized by high efficiency (17-22% or more), dark color, and higher cost due to the complex manufacturing process.
• Polycrystalline: Made from several combined crystals, lower efficiency (15-17%), often blue in color and lower in cost.

Function of the Inverter and Batteries

The inverter converts the direct current (DC) produced by the panels into alternating current (AC) usable in homes and grids. As for batteries, they are not necessary in grid-tied systems (the most common system), where excess energy is fed into the grid and electricity is drawn when needed. In standalone or hybrid systems, however, batteries are essential for storing energy for use when sunlight is unavailable [1].

Panel Efficiency and Influencing Factors

Panel efficiency is the ratio of sunlight converted into electricity, typically ranging between 15% and 22%. Factors that reduce panel production:

• High Heat: Every increase in temperature above 25°C reduces efficiency by approximately 0.3%-0.5% per degree.
• Accumulation of Dust and Dirt: Reduces light access and lowers production by 5%-25% depending on the severity of pollution.
• Shading: Even partial shade significantly harms production.
• Panel Tilt Angle: An improper angle reduces light reception.
• Weather Conditions: Clouds, fog, and smoke reduce the intensity of the inspiring radiation.
• Panel Degradation: Losing about 0.5%-1% of efficiency annually [1].

Estimating the Number of Panels for an Average Home in a Sunny Country

1. Calculate your daily electricity consumption in kilowatt-hours (kWh).
2. Determine the number of peak sun hours in your region (usually 5-7 hours in sunny areas).
3. Choose the capacity of a single panel (e.g., 400 Watts).
4. Calculate the daily production of one panel, accounting for losses (usually 20%).
5. Calculate the number of panels = Daily Consumption / Actual Production of one panel.

Example: For a daily requirement of 20 kWh, with 6 peak sun hours, 400W panels, and 20% losses, the number of panels ≈ 11 panels [1].

Lifespan and Maintenance

• The lifespan of panels exceeds 20-25 years with low degradation, often reaching 30 years or more.
• Maintenance is simple and includes cleaning the panels periodically to remove dust and dirt, visual inspection to detect cracks or damage, and performance monitoring to ensure efficient operation.
• Electrical inspection of the inverter and wiring is recommended every few years by a specialist.

Summary of Key Points

• Panels work by converting sunlight into direct current (DC) electricity via the photovoltaic effect in silicon cells.
• Monocrystalline panels are more efficient and more expensive than polycrystalline ones.
• The inverter converts direct current to alternating current (AC) for home use.
• Batteries are necessary only for off-grid or hybrid systems.
• Factors such as heat, dirt, and shading reduce efficiency.
• The number of panels depends on consumption, peak sun hours, and panel capacity.
• The lifespan is long and maintenance is simple but essential to maintain performance.

Sources: [1], [2]