APES 6.8 Solar Energy

Enduring Understanding:

  • Humans use energy from a variety of sources, resulting in positive and negative consequences.

Learning Objective:

  • Describe the use of solar energy in power generation.
  • Describe the effects of the use of solar energy in power generation on the environment.

Essential Knowledge:

  • Photovoltaic solar cells capture light energy from the sun and transform it directly into electrical energy.  Their use is limited by the availability of sunlight.
  • Active solar energy systems use solar energy to heat a liquid through mechanical and electric equipment to collect and store the energy captured from the sun.
  • Passive solar energy systems absorb heat directly from the sun without the use of mechanical and electric equipment, and energy cannot be collected or stored.
  • Solar energy systems have low environmental impact and produce clean energy, but they can be expensive.  Large solar energy farms may negatively impact desert ecosystems.

Types

Photovoltaic

  • Transforms sunlight directly into electricity
Process
  • When sunlight hits the various components in the photovoltaic cell, it releases electrons
  • As the electrons flow, it creates (or is,) electricity
Positives
  • Generates electricity
  • Can reduce habitat destruction with strategic installation
  • Large- and small-scale applications
    • Off the grid electricity
Negatives
  • Use is limited by the availability of sunlight
  • Limited lifespan of nonrenewable PV cells
  • Expensive
  • Solar farms may negatively impact fragile desert ecosystems if installed there

Active/Concentrated Solar

  • Uses mechanical and electric equipment to transfer solar heated liquid to transfer heat or create electricity
Process
  • Liquid is heated by concentrated solar beams
    • Beams are concentrated by reflective surfaces
  • This water evaporates and turns into steam, turning a turbine, fueling a generator
  • Electricity is produced
  • This can also produce heat to be distributed wherever needed
    • Like a home, water tank, etc.
Positives
  • Generates heat and electricity
  • Large- and small-scale applications
Negatives
  • Expensive
  • Requires maintenance
  • Solar farms may negatively impact desert ecosystems
  • Solar farms require high solar intensity to maximize efficiency

Passive Solar

  • Heat is directly absorbed from the sun without mechanical or electric equipment
Process
  • Essentially, sunlight comes in from windows and heats the indoors
    • Its important, however, that the windows face the right direction to maximize sunlight
    • An overhang is also necessary to block higher elevation sunlight that would heat too much
  • This also requires good insulation and high thermal mass in the floors
Positives
  • Relatively inexpensive
  • Low maintenance
Negatives
  • Some aspects are difficult to implement retroactively
  • Energy cannot be collected or stored
  • Only heats, does not produce electricity