For the economic analysis an emerging market for solar tower plants is assumed with concentrator costs of 132 €/m2 for a 120 m2 glass-metal heliostat. The receiver costs are 16 k€/m2, 33 k€/m2 and 37.5 k€/m2 for the low, medium and high temperature receiver.

The investment costs for the conventional part (power block incl. BOP) are 560 €/kW for the Mercury system and 510 €/kW for the PGT10 Combined Cycle system.

For the detailed cost calculations a 2nd generation plant is considered. The engineering cost for gas turbine solarisation are shared between 10 similar plants, and the plant is operated remotely in a ‘virtual park’ of 4 similar plants with a high degree of automation. For the calculation of levelized electricity costs (LEC) a debt rate of 75% at 4.2% interest rate is assumed. Other financial parameters are: common equity rate of 25% at 14% rate of return, 2.5% inflation rate, 12 years debt payback time, 20 years plant lifetime.

The results of the LEC calculations for the stand-alone option can be found in [9]. The total LEC range from about 6.3 €cent/kWh to 20 €cent/kWh depending on power level, capacity factor and solar share. The solar incremental LEC are calculated as the additional costs compared to the generation at a market price of 4 €cent/kWh divided by the incremental solar generated electricity. They range from about 12.8 €cent/kWh to 41.4 €cent/kWh for the 2nd generation plants in daytime operation (Table 2).. For the largest system a total LEC of 8.6 €cent/kWh at a solar share above 50% is calculated.

Relating the solar LEC to the annual amount of CO2 that can be avoided3 when operating the hybrid plant instead of the pure fossil reference plant, the CO2-avoidance costs can be calculated for each individual plant. For the higher power level a value well below 200 €/ton CO2 can be reached.

a CO2 production from natural gas of 200 kg/MWh LHV is assumed.