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

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