Environmental Engineering Reference
In-Depth Information
Table 1.3
Primary Energy, Final Energy and Effective Energy
Term
Definition
Type of energy or energy source
Primary energy
Original energy, not yet
e.g. crude oil, coal, uranium,
processed
solar radiation, wind
Final energy
Energy in the form that
e.g. gas, fuel oil, petrol, electricity,
reaches the end user
hot water or steam
Effective energy
Energy in the form used by
e.g. light, radiator heat, driving
the end user
force of machines or vehicles
majority is 'lost'. The
efficiency
,
, describes the conversion quality and is
given by:
profitable energy
efficiency
η
=
(1.3)
expended energy
The average thermal power station in countries such as Germany has an
efficiency of around 34 per cent. Two thirds of the expended energy disappears
as waste heat. This means that only one third remains as electricity.
Technical conversion of energy has different conversion stages: primary
energy, final energy and effective energy. These stages are explained in Table
1.3.
Going back to the example, it has to be emphasized that the calculated
thermal energy (see equation (1.2)) is the effective energy, and the values given
in Figure 1.1 are final energy. The comparison of energy efficiency should,
instead, be based on primary energy when considering different energy carriers
such as gas and electricity. The primary energy source for generating electricity
is the coal, gas or uranium used in conventional power plants. Natural gas
used for boiling water is also a type of final energy. The transport of natural
gas to the consumer causes some losses, but these are much lower than the
Heating water
31%
(97 Wh)
Effective energy
Primary energy source
Natural gas
100%
(311 Wh)
Final energy
gas
90%
(280 Wh)
Waste water
59%
(183 Wh)
Losses
10%
(31 Wh)
Figure 1.2
Energy Conversion Chain and Losses for Water Heating with a
Gas Cooker
