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3.2 Energy Analysis 77

of free energy or free enthalpy during chemical processes. Only if the latter is
negative – thus delivered by the system – a reaction can take place voluntarily. Only
the free energy can be converted, for example, into electricity, the remainder is
dissipated as heat.
Energy dissipated as ‘waste heat’ can be economically used, within an appropriate
infrastructure, for heating purposes (also for cooling). 42) The overall efficiency
including the use of heat can be much higher (approximately 0.8) than the
efficiency that refers to electrical or mechanical energy (work) alone.

3.2.2
Cumulative Energy Demand (CED)

3.2.2.1 Definition
44)
The determination of the cumulative energy demand (CED ) is used in compara-
43)
tive assessments of the primary energy demand of technical processes and product
systems. Prior to standardisation, this value was called energy equivalent value. 45)
Following a somehow clumsy, but exact nomenclature, the VDI recommends
according to guideline 4600 (see also ):
46)
The Cumulative Energy Demand KEA 47) (CED) states the entire demand, valued
as primary energy, which arises in connection with production, use and disposal of
an economic good or which may be attributed to it in a causal relation. This energy
demand represents the sum of Cumulative Energy Demands for production, use
and disposal of the economic good.
In VDI 4600, the common expression ‘product’ in LCA, according to ISO 14040,
which includes goods and services, is replaced by ‘economic good’. As a formula,
the definition can be presented as follows:
KEA = KEA + KEA + KEA E (3.3)
N
H
whereby the subscripts refer to H = production (Herstellung), N = use including
maintenance (Nutzung), and E = disposal (Entsorgung). Because of this formula,
life cycle thinking can be perceived. The transportation is not assessed separately,
but included in the definitions of concepts and sub-concepts. The same applies for
‘production and auxiliary materials, consumables and production facilities’.

3.2.2.2 Partial Amounts
The CED consists of different amounts that include energy consumption in the
narrow sense, and the content of energy resources and other materials with calorific

42) Depending on the perspective, a refrigerator is always also an oven; this technique is applied in
so-called passive houses.
43) VDI, 1997; ecoinvent 1, 2004a (Chapter 2).
44) Kl¨ opffer, 1997.
45) Kindler and Nikles, 1980.
46) Mauch and Schaefer, 1996.
47) KEA = Kumulierter Energieaufwand. In the following, the German acronyms KEA, and so on
are used, as in the English version of VDI 4600 VDI (1997).