Photovoltaic (PV) Systems:
Photovoltaic systems use solar cells to convert sunlight directly into electricity. The cells are made of semiconducting materials and generate electricity when exposed to sunlight. The simplest solar cells power small electronic devices like watches and calculators. The solar cells do not store electricity – they just generate electric current when sunlight is available – but batteries are often included as part of the complete PV system. In a rooftop PV system, the electricity generated by a multitude of solar cells is channeled into an inverter and converted into a usable alternating current (AC) power source.
Wind Systems:
For hundreds of years, people have captured the energy of the wind, using windmills to grind grain and pump water. The modern equivalent of windmills – wind turbines – capture the wind using two or three propeller-like blades mounted on a shaft to form a rotor. When the wind blows, the combination of lift and drag spins the rotor like a propeller, and the turning shaft spins a generator to make electricity.
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