Environmental Engineering Reference
In-Depth Information
Concentrator bowl
Concentrator bowl
Stirling unit
Stirling unit
Elevation
bearing
Elevation
bearing
Stirling supporting structure
Stirling supporting structure
Annular
mounting
structure
Annular
mounting
structure
Elevation
drive
guide
Elevation
drive
guide
Pedestal
Pedestal
Azimuth
drive
Azimuth
drive
Azimuth
drive
guide
Azimuth
drive
guide
Electrical
cabinet
Electrical
cabinet
Foundation
Foundation
Fig. 5.20
Dish/Stirling systems (Distal II)
5.4.1
Technical description
Within the following explanations, the technology of dish/Stirling power plants
including all related components is discussed.
5.4.1.1
System components
Parabolic concentrator (dish).
The parabolically shaped concave mirror (dish)
concentrates sunlight onto a focal spot. The size of this spot depends on concen-
trator precision, surface condition and focal distance. Common concentrators
achieve concentration ratios between 1,500 and 4,000. Common maximum diame-
ters amount to 25 m.
With regard to concentrator design facetted paraboloids (i.e. consisting of indi-
vidual segments) and full-surface paraboloids are distinguished.
-
For facetted concentrators several mirror segments are mounted on a mounting
structure. The segments are supported and oriented individually. Such mirror
segments may either consist of glass mirrors or media covered with reflecting
foil or thin-glass mirrors.
-
For full-surface concentrators the entire concentrator surface is shaped parabo-
lically by a forming process. For instance, a pre-stressed metallic or plastic
membrane is attached on both sides onto a stable ring (stretched membrane
technology). Subsequently, it is transformed into the desired shape via a form-
ing process (e.g. by water load) and stabilised via a specific vacuum. Such low-
weight metal membrane designs provide full-surface concentrators with high
rigidity and high optical quality. As an alternative, the facets may also consist
of sandwich elements made of fibre-glass reinforced epoxy resin with thin-
glass mirrors glued onto them /5-20/.
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