Earth Science

Natural Resources

Obtaining Energy Resources

Study Tip
In any type of reaction, energy is always conserved. For instance, the energy before a reaction is equal to the energy after plus the energy lost.

What is Net Energy?

  • Net energy is the difference between usable energy and amount of energy used to acquire it.
  • Resources that are accessible and easy to use can provide a high net energy because not much energy is needed to obtain them.
Study Tip
In any type of reaction, energy is always conserved. For instance, the energy before a reaction is equal to the energy after plus the energy lost.
Study Tip
The same way a person may cast a shadow over another person when they stand under the sun, planets or celestial bodies that have aligned themselves cast shadows over one another as well.

Available Energy and Energy Output

  • The Net-Energy Ratio is the amount of available energy related to the amount of energy needed to produce it. The ratio is found through the following formula:
    Units of Energy Available
    Units of Energy Input

Net-Energy Ratios for Common Energy Sources
Energy Source
Net-energy Ratio
Solar Energy
5.8
Natural Gas
4.9
Petroleum
4.5
Coal-fired Electricity
2.5-5.1
Offshore drilling plant
Offshore drilling requires a lot of energy in order to obtain the resource of oil.

Energy Efficiency

  • Energy efficiency is measured through how much useful work can be extracted from a unit of energy.
  • An efficient energy source is able convert a large percentage of its energy into useful work.
  • When converting energy from one form to another, some of the energy will be lost to heat.
  • For example, when you are converting coal into electric energy,

Chemical Potential Energy in Coal Electrical Energy + Heat Energy

  • High energy efficiency is desired because they waste less energy, preserve energy resources longer, and keep costs low.
Concept Check
  • What is net energy?
  • What relationship is displayed in a net-energy ratio?
  • What happens when converting energy from one form to another?