Note

The importance of the ratio of Energy Returned over Energy Invested cannot be overstated; however, different researchers have included different items in the energy invested term. This may be satisfactory depending upon the use to which the concept is to placed; but, only the method recommended on this blog results in a ratio that can be used to determine sustainability of the technology*. 

 

* To establish sustainability, it is necessary to include some items in the energy-invested term that are normally not thought of as investments. For example, the cost of sequestering such carbon dioxide as will be produced by the energy technology under investigation should be added to the energy-invested term because sustainability requires that our society survive (until astronomical events intervene). In this thought experiment, the living expenses of every citizen who is working to keep the energy flowing and his dependents must be added to the energy invested. If his contribution is something like playing the cello in an orchestra, it may be a little hard to see the connection; but it is relatively easy to distinguish freeloaders, especially those who do nothing the purpose of which is not to get a larger piece of the pie for himself, his family, his friends, or his employer.  The cost of living of freeloaders expressed in energy units must be taken from the net energy, EX, not added to the energy invested, EI. This will be made much clearer in terms of a scientific thought experiment.