8.1.2 Degraded Energy

Non isolated systems such as the human body or the economy must be imported or injected by energy from outside. Yet for the system to maintain their internal order they must export degraded energy to the outside.

Degraded energy is energy that becomes unavailable which means it is no longer able to produce work.

Degraded energy has a connection with the second law of thermodynamics.
The second law of thermodynamics states that the entropy of a closed or isolated system always increases. This means that all available energy is used up and there is no more potential for further useful work. The system becomes disordered and also degraded. This is also called the Entropy Law.

Physical, chemical, and electrical energy can be completely changed into heat. While the reverse (heat into physical energy, for example) cannot be fully accomplished without outside help or without an inevitable loss of energy in the form of irretrievable heat. This does not mean that the energy is destroyed; it means that it becomes unavailable for producing work. This (as we know) is called entropy. Therefore we can conclude that the degradation of energy is due to the ever increasing levels of entropy in the universe, as all forms of energy, over a long period of time, are transformed into heat.

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This is a Sankey diagram that represents the flow of energy. The diagram illustrates where the lost of energy (degraded energy) is going after it is no longer able to produce work or usable to the system.


  1. "Entropy and the Laws of Thermodynamics." 1996. Pricipia Cybernetica Web. 25 Mar. 2009 <http://dieoff.org/page17.htm>.
  2. Wackernagel, and Rees. "OUR ECOLOGICAL FOOTPRINT." Energy, Entropy, Economics, and Ecology. New Society Pub. 25 Mar. 2009 <http://pespmc1.vub.ac.be/ENTRTHER.html>.
  3. "Degraded Energy." Energy, Power Generation and Power Sources. 25 Mar. 2009 <http://www.shs.issaquah.wednet.edu/teachers/fowler/Energy,%20Power%20Generation%20and%20Power%20Sources_files/frame.htm>.