Energy Forms and Sources

Energy

  • Defined as the capacity to do work.

  • Power is the rate at which energy is consumed.

Sustainable Development

  • Meets present needs without compromising future generations' ability to meet their needs.

Sustainable Energy

  • Renewable energy: Naturally regenerated over a short time scale.

    • Derived from solar energy (directly or indirectly) or other natural energy flows.

  • Energy efficiency: Reduction in energy used per unit service.

  • Promotes energy sources that:

    • Are not depleted with continuous use.

    • Have low emissions.

    • Pose minimal health hazards or social injustice.

Forms of Energy

  • Kinetic Energy: Energy possessed by moving objects.

    • KE =
      ewcommand{\frac}[2]{{\frac{#1}{#2}}} \frac{1}{2} mv^2 (m = mass, v = speed)

  • Thermal Energy: Kinetic energy of vibrating particles in matter; dependent on temperature.

    • Average translational kinetic energy: 32kBT=12mv2\frac{3}{2} k_B T = \frac{1}{2} mv^2

  • Gravitational Potential Energy: Energy stored due to an object's height above a reference.

    • PE=mghPE = mgh (m = mass, g = gravitational acceleration, h = height)

  • Electrical Energy: Associated with electrical forces, movement of electrons (electric current).

    • Power = Voltage × Current

  • Electromagnetic Energy: Energies released by stars, including radio waves, light, X-rays, gamma rays, etc.

  • Nuclear Energy: Energy bound in the nuclei of atoms; released in nuclear fission (reactors) or fusion (Sun).

Conversion and Efficiency

  • Efficiency: Ratio of useful output to input, expressed as a percentage.

    • η=Useful outputinput×100%\eta = \frac{\text{Useful output}}{\text{input}} \times 100 \%

Types of Energy Sources

  • Non-Renewable: Fossil fuels, nuclear.

  • Renewable: Solar, wind, hydro, biomass, tidal, ocean, geothermal.

Fossil Fuels

  • Coal, oil/petroleum, natural gas.

  • Limited resource.

Renewable Energy Examples

  • Solar: Thermal (solar concentrators) or electrical (photovoltaics).

  • Wind: Harnessed by wind turbines.

  • Hydro: Kinetic energy of water driving turbines.

    • Run of river, Dam.

  • Biomass: Chemical energy in non-fossil, carbon-containing materials.

  • Ocean, Tidal, Wave: Still in demonstration stage, expensive.

  • Geothermal: Ground-based heat energy.

Primary Energy

  • Energy in natural resources before conversion (e.g., coal, crude oil, sunlight).

Secondary Energy

  • Energy converted from primary sources into usable forms (e.g., electricity, refined petroleum products).