Solar Integrated Unit to Reduce Power and Cooling Penalty of a Natural Gas Combined Cycle Plant integrated with a Carbon Capture System
Authors: Mohammed Ali Saif W. , Ahmed Sahib S. , Ghayadh Nabeel A. 
Published: December 2020

Integrating solar assisted plant with a carbon capture unit to provide the required reboiler heat duty has been recently investigated extensively to reduce the negative impact of carbon capture unit on plant performance. However, using solar assisted plant to provide the required energy in the reboiler of the stripper leads to increase plant’s condenser duty unfavorably. In the present study, two novel configurations have been proposed for a concentrated solar assisted power plant to generate the required reboiler duty in the stripper of a post-combustion carbon capture unit (PCCC-SAPP) in a (630 MWe) natural gas combined cycle (NGCC) power plant to reduce both the condenser duty and power penalty of the plant simultaneously. In the present study, both the solar plant and plant’s low-pressure steam (LPS) are contributing to deliver the required reboiler thermal energy in the first method while the extraction is from the cooling system load in addition to the solar plant in the second method. Solar contribution factor (SCF) is the main criteria which has been used to evaluate the findings. Condenser duty with its associated water requirements, power penalty, and the required solar field land area are the parameters which have been investigated in the preset study. It has been found that the second configuration method has better impact on the performance of the plant and its associated cooling system than the first configuration method where zero power penalty is consumed in the second configuration as well as reducing the condenser duty with its related water usage amounts. In addition, it was shown that raw water withdrawal and consumption amounts in term of (gal/min)/MWnet decrease with increasing SCF in the first configuration where raw water withdrawal and consumption amounts are 7.23 (gal/min)/MWnet, and 5.17 (gal/min)/MWnet at SCF equals to 0 while these amounts reach to 6.74 (gal/min)/MWnet and 4.82 (gal/min)/MWnet at SCF of 0.95 respectively. On the other hand, these amounts increase with increasing SCF in the second configuration where water withdrawal and consumption values approach 6.75 (gal/min)/MWnet, and 4.92 (gal/min)/MWnet at SCF equals to 0 while the amounts are equal to 7.93 (gal/min)/MWnet and 5.81 (gal/min)/MWnet at SCF equals to 0.95 respectively despite that condenser duty is increasing in the both methods. This comes from the fact that the net produced power is increasing in the first scenario with SCF while it keeps constant in the second scenario. Furthermore, the relationship between the solar field’s required land area and solar direct normal irradiation (DNI) was investigated in the present paper under four different SCF; 0.2, 0.4, 0.6, and 0.8. It was found that reducing the solar field’s required land area requires increase in the DNI and decrease in the SCF where the reboiler heat duty is constant in the PCCC and the relationship is almost exponential. The validation was performed with an American governmental report (NETL, 2015) showing that the presented results has a significant agreement with the report.