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410 A COmpREHENSIvE GUIDE TO SOLAR ENERGy SySTEmS

FIGURE 21.2 Mean EROI (and standard error) for thermal fuels. Adapted from Hall CAS. Energy return on investment:
a unifying principle for biology, economics, and sustainability. Springer Nature, Lecture Notes in Energy, vol. 36. Cham:
Springer International Publishing AG; 2017; Lambert J, Hall CAS, Balogh S, Gupta A, Arnold M. Energy, EROI, and quality
of life. Energy Policy 2014;64:153–67. For explanation and detailed references please see Hall CAS, Lambert JG, Balogh
SB. EROI of different fuels and the implications for society. Energy Policy 2014;64:141–52.

in the standard analysis and constitute what can be called “extended boundary analysis.”
This allows for a comparison among different fuels and resources as well as a procedure
for undertaking other approaches an analyst might want to control. Among the protocols
outlined by murphy and Hall are those of correcting for energy quality, for example, the
difference between thermal energy versus electricity for coal. A very basic procedure for
an EROI analysis of any fuel or system as adapted from Hall [18] and murphy and Hall [14]
is as follows:
1. State objectives.
2. Create a flow diagram and identify system boundaries—all direct, indirect, and
embodied energy inputs and outputs should be included, as well as the boundaries
used for analysis or sensitivity analysis.
3. Quantify all appropriate inputs and outputs within system boundaries.
4. Identify and convert financial flows if necessary—in the case where direct flow
measurements are not available and financial information must be used, the data
needs to be converted to energy units using an energy intensity value.
5. Make the calculation—at minimum a standard EROI value should be calculated.
6. Choose method of energy quality adjustments as part of sensitivity analysis.