Environmental Engineering Reference
In-Depth Information
electrical output during the day closely correlates with solar radiation. Neverthe-
less, there is a certain updraft that can be utilised for power generation even dur-
ing some night hours. This becomes also obvious in Fig. 5.31 showing the charac-
teristic curve of such a plant exemplarily for the same day shown in Fig. 5.30.
This graphic also outlines that the updraft speed as well as the electrical power
provision is directly proportional to global radiation.
In the year 1987, the plant was operated for a total of 3,197 h; this corresponds
to a mean daily operating time of 8.8 h. This was achieved by a fully automated
plant management which ensured automatic start-up of the plant and synchronisa-
tion with the power grid, once the flow speed exceeded a certain value (typically
2.5 m/s).
In spite of the absolutely positive operating results, confirming the calculated
data, the test plant was completely dismantled after a storm at the end of the
1980s.
60
60
9
9
Updraft speed (best fit straight line)
Electric capacity (best fit straight line)
Updraft speed (best fit straight line)
Electric capacity (best fit straight line)
8
8
50
50
7
7
40
40
6
6
5
5
30
30
4
4
20
20
3
3
Measured updraft speed
Measured electric capacity
Measured updraft speed
Measured electric capacity
2
2
10
10
1
1
0
0
0
0
0
0
100
100
200
200
300
300
400
400
500
500
600
600
700
700
800
800
900
900
1,000
1,000
1,100
1,100
Global radiation in W/m
2
Global radiation in W/m
2
Fig. 5.31
Solar radiation and capacity of the Manzanares prototype (example: measured
data at 8
th
June 1987)
Large solar updraft tower power plants.
In spite of the big differences between
dimensions of the pilot plant in Manzanares and projected 200 MW plants, ther-
modynamic parameters are quite similar: Taking, for instance, the temperature rise
and the flow speed inside the collector, the Manzanares plant has a temperature
rise of up to 17 K and a speed of up to 12 m/s, whereas the calculated mean values
for a 200 MW plant are 18 K or 11 m/s /5-33/.
Fig. 5.32 illustrates the results of a simulation calculation of such a 200 MW
plant for a site with pronounced seasons. It shows a period of four days for every
season. This plant thus also operates night and day without additional heat stor-
age, even though the output power is reduced during the night, especially in win-
ter.
Although various big solar updraft tower power plant projects have been de-
veloped, e.g. in India and Australia, to date no commercial plant has been built.
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