8.1 Energy Sources

• Specific Energy and Energy Density of Fuel Sources

  • Specific energy and energy density are vital for quantifying the energy released during combustion.

  • Specific energy: energy per unit mass (energy/mass).

  • Energy density: energy per unit volume (energy/volume).

  • Sankey Diagrams and Energy Degradation

  • Cyclical processes are needed for continuous conversion of thermal energy to work.

  • Some energy is lost to the surroundings, termed degraded energy.

  • Sankey diagrams visually represent energy flows.

8.2 Thermal Energy Transfer

• Conduction, Convection, and Thermal Radiation

  • Conduction and convection require a medium; radiation can transfer through a vacuum.

• Black-Body Radiation

  • A black body absorbs all incident electromagnetic radiation.

  • Black-body radiation follows the Stefan-Boltzmann law.

• Albedo and Emissivity

  • Albedo

    • Measures the ratio of total scattered (reflected) radiation to total incident radiation.

    • Influenced by season, latitude, and terrain.

  • Emissivity

    • Objects radiate a fraction compared to a black body.

    • Emissivity = power per unit area radiated by the object / power per unit area radiated by a black body at the same temperature.

• The Solar Constant

  • Amount of energy falling on 1m^2 of Earth's atmosphere per second.

  • Solar constant is approximately 1366 W/m^2.

• The Greenhouse Effect

  • Greenhouse Gasses

    • Absorb infrared radiation due to natural frequencies.

  • Mechanism

    • Incoming solar radiation takes the form of ultraviolet and visible radiation.

    • Greenhouse gasses trap infrared radiation, leading to the greenhouse effect.

  • Chain Reaction

    • Global warming reduces ice/snow cover, affecting albedo.

    • Carbon dioxide solubility in the sea decreases, increasing atmospheric carbon dioxide.

  • Effects

    • Rising mean sea levels, extreme weather events.

• Energy Balance in the Earth Surface–Atmosphere System

  • Describes how incoming solar energy is used and returned to space.

  • Balanced energy flow maintains a constant Earth temperature.