This paper reports a performance assessment of advanced CSP power plants. The CSP system analyzed is based on parabolic troughs, CO2 heat transfer fluid and thermocline thermal storage systems. The use of CO2 instead of the more conventional thermal oil as heat transfer fluid (550 °C instead of 400 °C) can allow to increase the steam cycle conversion efficiency, whereas the use of thermocline storage systems allows to store and recover the thermal energy at constant temperature. However, the increase of the CO2 temperature reduces the efficiency of the solar field whereas the use of solid materials leads to some problems related to the utilization of the storage volume capacity. The performance of CSP systems have been evaluated by means of specifically developed simulation models for the solar collector, solid storage system and the steam power plant. In particular, the operating parameters of the steam cycle (steam pressure and temperature, steam extraction) have been optimized according to the different temperature and composition of the heat transfer fluid. Moreover, the performance of the CSP system was evaluated with reference to different values of solar module and storage capacity as a function of the solar radiation. The results of the performance assessment show that the enhancement of the steam cycle efficiency overcomes the efficiency reduction of the solar field. The analysis carried out with reference to the solar radiation of Cagliari demonstrate that the annual efficiency of the CSP power plant decreases with increasing values of both solar module and thermal storage capacity. On the contrary, the annual net energy production from solar increases with increasing values of these parameters. With reference to a solar module equal to 1.5 and a thermal storage capacity of 4-6 hours, the CSP efficiency ranges from 18% to 19%. Moreover, the annual energy production of a 50 MW CSP plant is around 140-150 GWh/yr (that is 3.000 hour/yr).
Impianti solari termodinamici operanti con collettori parabolici lineari e fluidi gassosi ad alta temperatura. Parte 1
CAU, GIORGIO;COCCO, DANIELE;PETROLLESE, MARIO;PUDDU, PIERPAOLO
2012-01-01
Abstract
This paper reports a performance assessment of advanced CSP power plants. The CSP system analyzed is based on parabolic troughs, CO2 heat transfer fluid and thermocline thermal storage systems. The use of CO2 instead of the more conventional thermal oil as heat transfer fluid (550 °C instead of 400 °C) can allow to increase the steam cycle conversion efficiency, whereas the use of thermocline storage systems allows to store and recover the thermal energy at constant temperature. However, the increase of the CO2 temperature reduces the efficiency of the solar field whereas the use of solid materials leads to some problems related to the utilization of the storage volume capacity. The performance of CSP systems have been evaluated by means of specifically developed simulation models for the solar collector, solid storage system and the steam power plant. In particular, the operating parameters of the steam cycle (steam pressure and temperature, steam extraction) have been optimized according to the different temperature and composition of the heat transfer fluid. Moreover, the performance of the CSP system was evaluated with reference to different values of solar module and storage capacity as a function of the solar radiation. The results of the performance assessment show that the enhancement of the steam cycle efficiency overcomes the efficiency reduction of the solar field. The analysis carried out with reference to the solar radiation of Cagliari demonstrate that the annual efficiency of the CSP power plant decreases with increasing values of both solar module and thermal storage capacity. On the contrary, the annual net energy production from solar increases with increasing values of these parameters. With reference to a solar module equal to 1.5 and a thermal storage capacity of 4-6 hours, the CSP efficiency ranges from 18% to 19%. Moreover, the annual energy production of a 50 MW CSP plant is around 140-150 GWh/yr (that is 3.000 hour/yr).
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