Introduction

Sun as source of energies
  • Sun is the main source of energy on Earth
  • Provides light and heat
  • Direct use: solar devices
  • Indirect use: wind, hydro, biomass
  • Fossil fuels are ancient solar energy
  • Few sources are non-solar

The Sun Itself

Nuclear fusion in Sun
  • Energy from nuclear fusion
  • Hydrogen fuses to form helium
  • 4 hydrogen → 1 helium nucleus
  • Mass loss converted to energy
  • Releases huge light and heat
  • Process lasts billions of years

Direct Use of Solar Energy

Direct solar devices
  • Sunlight used directly
  • No intermediate process
  • Examples: panels, cookers, heaters
  • Clean and renewable
  • Reduces fuel dependency
  • Eco-friendly technology

Solar Panels

Solar panels
  • Photovoltaic cells
  • Direct sunlight → electricity
  • Made of silicon
  • Produces DC current
  • Used on roofs and plants
  • Renewable & clean

Solar Cooker

Solar cooker
  • Cooks using only sunlight
  • Mirrors focus sun rays
  • Black surface absorbs heat
  • Glass traps heat
  • Saves cooking fuel
  • Eco-friendly

Solar Water Heater

Solar water heater
  • Absorbs sunlight in collectors
  • Heats water directly
  • Provides hot water
  • Installed on rooftops
  • Saves electricity/gas
  • Renewable source

Indirect Forms of Solar Energy

Indirect solar sources
  • Sun drives most energy forms
  • Wind from uneven heating
  • Hydro from water cycle
  • Biomass from plants
  • Fossil fuels ancient solar
  • Few exceptions exist

Wind Energy

Wind formation
  • Uneven heating by Sun
  • Hot air rises, cold moves in
  • Creates wind flow
  • Wind turns turbines
  • Generates electricity
  • Clean renewable source

Hydro Energy

Water cycle
  • Sun evaporates water
  • Forms clouds and rain
  • Rivers flow downhill
  • Turns turbines in dams
  • Produces electricity
  • Renewable energy

Biomass Energy

Biomass cycle
  • Plants store solar energy
  • Through photosynthesis
  • Wood, dung, waste used
  • Burned or made into biogas
  • Releases stored energy
  • Renewable if replanted

Fossil Fuels

Fossil fuel formation
  • From ancient plants
  • Captured sunlight long ago
  • Buried under earth
  • Heat & pressure formed coal/oil/gas
  • Burning releases energy
  • Non-renewable

Exceptions to the Rule

Non-solar sources
  • Not all energy from Sun
  • Nuclear: uranium fission
  • Geothermal: Earth's core heat
  • Tidal: Moon's gravity
  • These are minor sources