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Life cycle energy analysis (LCEA) is an approach in which all energy inputs to a product are accounted for, not only direct energy inputs during manufacture, but also all energy inputs needed to produce components, materials and services needed for the manufacturing process. Early expression used for the approach is energy analysis.
By life cycle energy analysis the total life cycle energy input is established.
Life cycle analysis of energy production
When performed on the production of energy commodities itself, such as nuclear energy, photovoltaic electricity or high quality petroleum products, it is recognised that considerable energy has been lost during the production process. Net energy content is the final energy content of the energy product minus all energy input expended during the extraction and conversion processes, directly or indirectly.
A controversial early result of LCEA claimed that during manufacture of solar cells more energy is invested than can be recovered by operation of the solar cell during its lifetime. The result was refuted.
Criticism
A criticism of the energy analysis approach is that it is an attempt to eliminate monetary cost analysis, that is replace the currency by which economic decisions are made with an energy currency.
A problem that energy analysis method can not resolve is that different energy forms (heat, electricity, chemical energy etc.) have different quality and value even in natural sciences, as a concequence of the two main laws of thermodynamics. A thermodynamic measure of the quality of energy
is exergy. According to the first law of thermodynamics, all energy inputs should be accounted with equal weight, whereas by the second law diverse energy forms should be accounted by different values.
The conflict is resolved in one of the following ways:
- value difference between energy inputs are ignored,
- arbitrary assignment of a value ratio, e.g. a Joule of electricity is 2.6 times more valuable than a Joule of heat or fuel input,
- the analysis is supplemented by economic (monetary) cost analysis.
References
- Thomas,J.A.G., ed: Energy Analysis, ipc science and technology press & Westview Press, 1977, ISBN 0-902852-60-4 or ISBN 0-89158-813-2
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