Lecture Notes: Solar Energy (Topic 6.8)

Objectives

• Describe how solar energy is used to generate power.
• Describe the environmental effects of generating solar electricity.
• Practice explaining trends in data.

Key Concepts

Passive Solar Energy

• Definition: Utilizing the sun's heat without mechanical or electronic equipment.
• Examples:
  • Solar Oven: Reflective material concentrates sun's energy to heat dishes.
  • Sustainable Building Design:
    • Double-paned Windows: Trap sun's energy to warm interiors.
    • Southern-facing Windows: Capture winter sun for natural heating.
    • Roof Overhangs: Block summer sun to keep interiors cool.
    • Deciduous Shade Trees: Provide shade in summer, allow sun in winter.
    • Dark-colored Floors/Walls: Absorb and convert sunlight into heat.

Active Solar Energy

• Definition: Using mechanical/electric equipment to capture sun's energy.
• Methods:
  • Photovoltaic (PV) Cells: Convert sunlight directly into electricity.
  • Solar Water Heater: Uses solar energy to heat water or liquid for home heating.
  • Concentrating Solar Thermal (CST): Uses mirrors to concentrate sunlight to generate steam for electricity.

Photovoltaic Cells (Solar Panels)

• Mechanism:
  • Photons hit semiconductor material (e.g., silicon), creating an electric circuit.
  • Electricity can power appliances or be sent back to the grid for rebates.
  • Challenge: Intermittency (not available 24/7) and storage issues (duck curve).

Concentrating Solar Thermal (CST)

• Process:
  • Mirrors (heliostats) focus sunlight on a central tower.
  • Superheated liquid (e.g., molten salt) used to generate steam and electricity.
  • Drawbacks: Habitat destruction, risk to birds.

Solar Energy Infrastructure

• Rooftop vs. Community Solar:
  • Rooftop Solar:
    • Reduces individual carbon footprint.
    • Does not require additional land.
  • Community Solar (Solar Farms):
    • Large-scale power generation.
    • Potential for habitat loss and fragmentation.

Environmental Pros and Cons

Pros

• No air pollutants or greenhouse gases during electricity generation.
• Renewable resource.
• No mining of fossil fuels for electricity.

Cons

• Mining Impact:
  • Extraction of semiconductor metals can cause habitat destruction and pollution.
  • Silicon is finite.
• Habitat Loss: Due to both mining and solar farm installations.

Practice FRQ

• Explain the relationship between the tracking ability of a solar PV system and its energy production.