Solar (PV & thermal)

Photovoltaic Cells

How do PV cells work ?

• When light energy strikes the solar cell , electrons are knocked loose from the atoms in the semiconductor material.
• If electrical conductors are attached to the positive and negative sides, forming an electrical circuit, the electrons can be captured in the form of an electric current that is, electricity

P-N Junction Solar Cells

Silicon Structure

• Crystal of pure silicon (lattice) ‘doped’ with impurity
  • element with more e in outer shell than Si means e free to move (negatively charged Si – n-type)
  • element with less e in outer shell than Si means overall shortage of e (positively charged Si – p-type)
• n-type & p-type Si in contact with each other
• e move across from n to p via junction
• light energy pushes e across junction and, if an electrical circuit is made between the two silicon types, e will flow through it

Solar Power – Different Technology Available

• Solar thermal systems
  • Non concentrating (passive)
  • Concentrating (active)
    • Troughs, dishes, linear Fresnel, towers & heliostat
  • Storing Solar thermal
• Photovoltaic cell types
  • Monocrystalline
  • Polycrystalline
  • Amorphous

Passive (non concentrating) Solar Thermal

• Domestic water heating
• Pool heaters
• Space heating
• Water processes for industrial heating
• Agricultural drying

Concentrating Solar Thermal

• absorbs & collects solar radiation
• mirrors reflect & concentrate sunlight
• receivers collect solar energy convert it to heat energy
  • Heat → Steam → Turbine → Generator → Electricity
• Parabolic trough
  • ~ 80 MW
• Solar dish / engine
  • ~ (325 MW)

Parabolic Trough Solar Collectors

Linear Fresnal Reflector (LFR)

• Fresnel: flat lens made of a number of concentric rings, to reduce spherical aberration.
  • ~ 2 MW

Tower & heliostat

• in development phase
  • ~ 200 MW

Concentrating Solar Thermal
Storage

Hybrid Solar Thermal Power Plants

Other Solar Thermal Technologies