Figure 5: 50 MWei, net power cycle with sea water cooling, efficiency (steam -> el, net): 32.8%. Size of Solar Field and Gas Boiler

The gas share depending on solar field size and boiler size is given in figure 7. The operation mode of the boiler described above is assumed.

65%

60%

55%

50%

45%

40%

35%

30%

25%

20%

15%

10%

5%

0%

12%

11%

10%

9%

8%

7%

Solar Field Size [m2]

□ 11%-12% □ 10%-11%

□ 9%-10%

□ 8%-9%

□ 7%-8%

<Gas boiler [MW. h]

Figure 8: Mean annual efficiency DNI -> net solar electricity depending on solar field size and gas boiler capacity

Solar Field >
Size [m2]

Gas boiler [MWth]

Figure 7: Gas share depending on gas boiler size [MWth] and solar field size [m2]

3500

3000

2500

2000

1500

1000

500

Solar Field Size

□ 3000-3500

□ 2500-3000

□ 2000-2500

□ 1500-2000

□ 1000-1500

■ 500-1000

■ 0-500

Gas boiler [MWth]

Figure 9: Full load hours

00 50

0 (solar only)

[m2]

Although the efficiency is not necessarily the decisive criteria to judge a power technology, figure 8 still shows that the primary solar energy DNI can be converted into electricity with higher efficiency in hybrid operation. On the one hand this is attributable to higher steam cycle efficiency due to lower part load losses, on the other hand the so-called »lower dumping« due to a necessary minimal mass flow for the turbine (20% of nominal mass flow assumed) is reduced as well.