Machines · machine
Photovoltaic Cell
Power source · 1954
- Year
- 1954
- Kind
- Power source
- Materials
- Polysilicon grown from the purest quartz on Earth, silver contacts, glass, aluminium frames.
- Efficiency
- 20–24 % for commercial modules; the single-junction limit is about 33 %.
- Used In
- Rooftops, deserts, satellites; the fastest-growing source of electricity.
- Power Density
- About 200 W per square metre in full sun.
- Cycle
- None
How It Works
A photon knocks an electron loose in a silicon junction; the built-in field at the junction sweeps it one way, and a current flows with no moving parts, no fuel and no noise. Bell Labs' first cell was 6 %; the sunlight is free, so the cost of the cell is everything.
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