| Summary: | As increasingly complex and capital-intensive energy supply
and conversion systems are developed to exploit more dilute and inaccessible energy resources, larger quantities of indirect
energy, embodied in the form of inputs of goods and services,
are needed to build and operate such systems. Concern has arisen that market imperfections, including research and development subsidies and tax concessions to the energy industry,
could result in an energy system being selected as financially
viable, while requiring more energy in external inputs (i.e., non-feedstock energy) than it could produce.
In response to these concerns, net energy analysis (NEA) has recently been developed as a technique which identifies and quantifies all energy inputs to energy supply and conversion
systems, including the indirect energy embodied in goods and services. By providing this information, NEA may be used to establish whether a system is indeed a net yielder of energy, and to compare its overall efficiency of energy use to that of alternative systems.
While NEA does not presently take into account the depletion
of non-fossil stock energy resources, qualitative differences in energy forms, and intertemporal aspects of energy flows, there are various means of avoiding these problems
or making partial allowances for them. Furthermore, although a number of boundary problems relating to NEA have been identified, most of them are also common to economic analysis.
It has been stated that NEA should be judged according to the relative significance of indirect energy requirements since this is the only new component that the technique adds to the information base of the energy field. Studies to date have shown that the quantity of indirect energy requirements relative to feedstock flows is quite insignificant in many current energy supply and conversion systems. However, the relative importance
of indirect energy requirements may increase considerably in the future, particularly as an increasing proportion of our energy is derived from renewable flows instead' of depletable feedstocks.
A case study involving a net energy analysis of the Revel-stoke hydroelectric project was carried out to examine the applicability of this technique at a practical level and the results were compared with those of other net energy analyses. The project was calculated to pay back the quantity of energy invested in its capital facilities in less than 6 months, with a net energy return of more than 126 times the total amount of external energy put into the construction and operation of the project over its lifetime. Reliability of results could be most improved by a more up-to-date data base, and a further disaggregation of the commodity profile used as a basis for calculations.
While net energy analysis has many potential applications, including the analysis of energy conservation measures to see if they achieve net energy savings, the technique has not been widely used in practice due to its relative immaturity and a
general uncertainty as to its role in the overall decisionmaking
process. Net energy analysis, in providing a quantitative description of the energy requirements of energy systems, is not intended to be used as an evaluative technique or to provide
a single set of decision-making criteria. Instead, the energy-related impacts of a decision must be weighed ; against its environmental, socio-economic, and political impacts. Although such tradeoffs can be presented within the framework of benefit-costs analyses, no simple rules for the relative weighting given to net energy considerations can be formulated. Exercises of this nature are inherently value-based and should ultimately be made at the political rather than the bureaucratic
level. === Applied Science, Faculty of === Community and Regional Planning (SCARP), School of === Graduate
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