Introduction and Structure - Renewable Energy: Technology, Economics and Environment - page 16

of steam power plants. Therefore, this power plant type is of decreasing impor-
tance.
− Gas and steam power plant. A gas turbine power plant can be ideally combined
with a steam turbine power plant. Within such gas and steam power plants the
hot exhaust gases released from the gas turbine are transferred to a heat recov-
ery boiler which generates superheated steam for a steam process. The so-
called gas and steam plants allow achieving efficiencies of above 58 %.
The provision of electrical energy by such conventional power plants is character-
ised by corresponding costs. They are briefly discussed in the following. How-
ever, first one hard coal-fired steam power plant and one natural gas-fired gas and
steam power plant designed according to state-of-the-art technology (i.e. new
plant construction) are defined.
− For the hard coal-fired steam power plant with an electrical capacity of
600 MW and a mean annual efficiency of 45 % (Table 1.4) pulverised coal-
firing is assumed. This power plant thus represents plants to be built under
European conditions in the years to come. Furthermore a typical application for
medium load power generation of roughly 5,000 full load hours per year has
been assumed.

Table 1.4 Technical and economic parameters of the investigated power generation sys-
tems based on fossil fuel energy

Hard coal-fired
power plant

Natural gas-fired
power plant

Fuel
Power plant type
Nominal electric capacity

Hard coal
Pulverised coal firing
600
30
45

Natural gas
GaS a
600
25
58

in MW

Technical life time in a

Annual mean system efficiency in % (net)

Full load hours in h/a 5,000

24,000

5,000
18,600 Fuel consumption in TJ/a

a Gas and steam power plant.
− As a further characteristic option to generate power from fossil energy carriers
a gas-fired gas and steam turbine power plant also of a block size of 600 MW
and an annual mean efficiency of roughly 58 % is assessed (Table 1.4). Also
for this case medium load power generation (approximately 5,000 full load
hours) is assumed.
For the comparison of the economic figures of these power generation technolo-
gies with generation technologies based on renewable sources of energies (e.g.
wind power plants), for conventional technologies mean and not maximum full
load hours are assumed; from a technical viewpoint, for the latter they are consid-
erably higher and could reach 8,000 hours per year and more (a maximum of
8,760 h/a is theoretically possible). Power generation by renewable energies, by
contrast, always depends on the availability of the renewable energy source (e.g.