Equipment and components
Photovoltaic cell
Also known as: solar cell, PV cell.
Definition
The photovoltaic cell is the basic unit that produces electricity from light. A solar panel is made up of many cells connected together. Most are silicon, monocrystalline or polycrystalline, and each generates a small voltage.
The phenomenon that makes it work is the photovoltaic effect: when photons of light strike the silicon, they free electrons; the junction between two layers of silicon with different doping creates an electric field that pushes those electrons in a specific direction, and that ordered movement is the current. There is no combustion, no moving parts and no material consumed.
A silicon cell generates around half a volt, a voltage useless on its own. That is why dozens of cells are connected in series inside a single panel: their voltages add up to a workable value. Current modules usually use cells cut in half (half-cut), an arrangement that reduces internal resistance losses and limits the effect of partial shading.
Cell efficiency — the percentage of light energy it converts into electricity — is what determines how many watts fit into a square metre of roof. It is a relevant figure when space is scarce; when there is roof to spare, cost per watt matters more than efficiency.
The essentials of Photovoltaic cell
- It works by the photovoltaic effect: light frees electrons in the silicon.
- A silicon cell produces around 0.5 V.
- Cells are connected in series inside the panel to add voltage.
- Half-cut cells reduce losses and tolerate shading better.
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Frequently asked questions about Photovoltaic cell
What is the difference between a cell, a panel and a system?
The cell is the smallest unit that generates electricity; the panel is the set of cells encapsulated in a module; the system is the complete set of panels, inverter, structure, protections and wiring that delivers usable alternating current to your electrical installation.
Do cells generate electricity from heat?
No: they generate from light, not from heat. In fact heat harms them, because silicon loses efficiency as cell temperature rises. A cool, clear day is better for producing than a very hot day with the same radiation.
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