Physics for Sustainable Energy Notes

Physics for Sustainable Energy

Introduction

  • Humans require energy for various activities like heating, cooling, and transportation.
  • Conventional energy sources include wood, coal, biomass, and fossil fuels.
  • Fossil fuels (non-renewable energy) are formed over millions of years from decayed plants and sea creatures buried and subjected to Earth's pressure and heat.
  • Increasing population and improving living standards are driving up energy demand.
  • Fossil fuel reserves are limited and expected to deplete soon.
  • Finding alternative energy sources is necessary.

Renewable Energy

  • Green energy (renewable energy) is naturally obtained from the environment and can be replenished.
  • Examples:
    • Solar energy
    • Wind energy
    • Tidal Energy
    • Geothermal energy
    • Biomass

Solar Energy

  • Solar energy is radiant light and heat from the sun, harnessed through technologies like solar heating, photovoltaics, and artificial photosynthesis.
  • Solar thermal power uses sunlight to heat water or buildings.
Solar Cells
  • A solar cell (photovoltaic cell) converts light energy directly into electricity via the photovoltaic effect.
  • Solar cells are building blocks of solar panels.
  • Common configuration: large-area p-n junction made from silicon.
  • An n-type dopant is diffused into one side of a p-type wafer (or vice versa).
  • Metal contacts are made for electrical connection on both sides.
  • Anti-reflection coating prevents light energy loss due to reflection.
Basic Working Principle of Solar Cells
  • Based on the photovoltaic effect: potential difference generated by separating electrons and holes in the built-in electric field of a p-n junction.
  • Light photons with energy higher than eV<em>oceV<em>{oc} or band gap (E</em>g)(E</em>g) enter the junction through a thin p-type layer.
  • Incident light disrupts thermal equilibrium and creates electron-hole pairs.
  • Free electrons move to the n-type side, and holes move to the p-type side.
  • Light energy supplies energy to create electron-hole pairs.
  • Electrons require