Nomenclature
To avoid confusion with other forms of analysis and to rigorously define concepts, an emergy nomenclature has been developed that defines terms, units, and ratios used in emergy evaluations. The following table shows terms, abbreviations, definitions and units related to emergy, summarized from the literature.
| Term | Definition | Abbreviation | Units |
|---|---|---|---|
| Extensive Properties | |||
| Emergy | The amount of available energy of one type (usually solar) that is directly or indirectly required to generate a given output flow or storage of energy or matter. | Em | seJ (solar equivalent Joules) |
| Emergy Flow | Any flow of emergy associated with inflowing energy or materials to a system/process. | R=renewable flows; N= nonrenewable flows; F= imported flows; S= services |
seJ*time−1 |
| Gross Emergy Product | Total emergy annually used to drive a national or regional economy | GEP | seJ*yr−1 |
| Product-related Intensive Properties | |||
| Transformity | Emergy investment per unit process output of available energy | Τr | seJ*J−1 |
| Specific Emergy | Emergy investment per unit process output of dry mass | SpEm | seJ*g−1 |
| Emergy Intensity of currency | Emergy investment per unit of GDP generated in a country, region or process | EIC | seJ*curency−1 |
| Space-related Intensive Properties | |||
| Emergy Density | Emergy stored in a volume unit of a given material | EmD | seJ*volume−3 |
| Time-related Intensive Properties | |||
| Empower | Emergy flow (released, used) per unit time | EmP | seJ*time−1 |
| Empower Intensity | Areal Empower (emergy released per unit time and area) | EmPI | seJ*time−1*area−1 |
| Empower Density | Emergy released per unit time by a unit volume (e.g. a power plant or engine) | EmPd | seJ*time−1*volume−3 |
| Selected Performance Indicators | |||
| Emergy released (used) | Total emergy investment in a process (measure of a process footprint) | U= N+R+F+S (see Fig.1) |
seJ |
| Emergy Yield Ratio | Total emergy released (used up) per unit of emergy invested | EYR= U/(F+S) (see Fig.1) |
== |
| Environmental Loading Ratio | Total nonrenewable and imported emergy released per unit of local renewable resource | ELR= (N+F+S)/R (see Fig.1) |
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| Emergy Sustainability Index | Emergy yield per unit of environmental loading | ESI= EYR/ELR (see Fig.1) |
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| Renewability | Percentage of total emergy released (used) that is renewable. | %REN= R/U (see Fig.1) |
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| Emergy Investment Ratio | Emergy investment needed to exploit one unit of local (renewable and nonrenewable) resource. | EIR= (F+S)/(R+N) (see Fig.1) |
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