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Renewable energy comes from natural sources that are constantly replenished — unlike fossil fuels, which took millions of years to form. The key sources are: Solar, Wind, Hydro, Geothermal, and Biomass / Biogas.
Photovoltaic (PV) cells convert sunlight directly into electricity using the photoelectric effect. When photons from the sun hit a semiconductor (usually silicon), they knock electrons loose, creating an electric current. Solar panels are made of many PV cells connected together. Beyond panels, concentrated solar power (CSP) uses mirrors to focus sunlight to generate steam and drive turbines.
Wind turbines use the kinetic energy of moving air to spin large blades connected to a generator. Offshore wind farms benefit from stronger, more consistent winds. Hydroelectric power harnesses flowing or falling water — a dam stores water at height (potential energy), releasing it through turbines (kinetic → electrical). Micro-hydro systems can power remote villages with small streams.
Biogas from Organic Waste: Food scraps, animal manure, and agricultural waste undergo anaerobic digestion by bacteria to produce methane gas — which can fuel generators or be fed into gas grids.
Aluminium Recycling & Energy Savings: Recycling aluminium uses only 5% of the energy of smelting new metal. That energy saving can be redirected elsewhere.
Piezoelectric Tiles: Tiles embedded with piezoelectric materials generate small electrical charges when people walk over them — useful in high-traffic public spaces.
Microbial Fuel Cells: Bacteria breaking down waste in landfill or sewage can be harnessed to produce electricity directly via biological fuel cells.
Geothermal energy taps heat from the Earth's crust — hot springs, steam vents, and deep drilling access temperatures exceeding 300°C. Iceland powers 90% of its homes with geothermal. Ocean energy includes tidal (exploiting the gravitational pull of the moon) and wave energy converters that bob or flex with wave action to generate electricity.
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