Solar Thermal Power Plants - Renewable Energy: Technology, Economics and Environment - page 209

ring truss assembly which is characterised by high stiffness and contour accuracy.
The front side of the shell is covered with thin-glass mirror to constantly achieve a
high reflectivity of approximately 94 %.

12 12 12 12 12 12

10 10 10 10 10 10

8 8 8 8 8 8

6 6 6 6 6 6

4 4 4 4 4 4

In the afternoon In the afternoon Am Nachmittag Am Nachmittag Am Nachmittag Am Nachmittag Start-up in the forenoon Start-up in the forenoon Start up am Vormittag Start up am Vormittag Start up am Vormittag Start up am Vormittag

2 2 2 2 2 2

0 0 0 0 0 0

0 0 0 0 0 0 100 100 100 100 100 100 200 200 200 200 200 200 300 300 300 300 300 300 400 400 400 400 400 400 500 500 500 500 500 500 600 600 600 600 600 600 700 700 700 700 700 700 800 800 800 800 800 800 900 900 900 900 900 900 1000 1000 1000 1000 1000 1000

Direct radiation in W/m² Direct radiation in W/m²

Direktstrahlung in [W/m²] Direktstrahlung in [W/m²] Direktstrahlung in [W/m²] Direktstrahlung in [W/m²]

Fig. 5.23 Characteristic curve of 10 kW dish/Stirling systems

5.4.2 Economic and environmental analysis

The following explanations are aimed to assess dish/Stirling systems according to
economic and environmental parameters.

Economic analysis. The power generation costs for the described dish/Stirling
plants are calculated in line with the assessment method applied throughout this
topic. According to this, the costs for construction and operation are calculated
and distributed in the form of annuities over the technical lifetime of the plant.
Specific power generation costs are calculated on the basis of these annual depre-
ciations and the generated electric energy. Unless otherwise indicated, a technical
lifetime of 20 years and an interest rate of 4.5 % have been assumed.
Since such plants are exclusively installed in areas of a high share of direct ra-
diation a reference site of an annual direct radiation total of 2,700 kWh/m 2 has
been assumed.
The main technical data of the assessed 10 kW dish/Stirling system of the
EuroDish type are indicated in Table 5.11.

Investments. Dish/Stirling systems have been tested in continuous operation in the
USA and in Spain for more than 15 years. Nevertheless, still they are not com-
mercially available. To approximately quantify the investments, published data of
suppliers are used. By doing this we need to bear in mind that the investment costs
of trial plants differ tremendously from the values of commercial systems manu-