Multi-criteria optimisation of integrated power systems for low-environmental impact

ABSTRACT

This paper presents a multi-criteria optimization of integrated power systems. Five power configurations that combines the solid oxide fuel cell (SOFC), gas turbine cycle (GTC), steam turbine cycle (STC), organic Rankine cycle (ORC), absorption refrigeration cycle (ARC), and carbon capture and sequestration (CCS) as SOFC-GTC, SOFC-GT-STC, SOFC-GT-ST-ORC, SOFC-GT-ST-OR-ARC, and SOFC-GT-ST-OR-AR-CCS were proposed, modeled, and analyzed. The proposed plants were further subjected to the Technique for Order of Preference by Similarity to the Ideal Solution (TOPSIS) optimization with technical and socio-economic parameters as the decision criteria. Important results suggest that the power of the proposed systems are within 207–281 MW, while energy and exergy efficiencies are in the range of 42.93–58.13% and 42.49–57.54%, respectively. The exergy destruction rate is within 206–322.9 MW. Furthermore, SOFC-GT-ST-OR-AR-CCS that integrates all the investigated power cycles, including the carbon capture proposes a CO₂ emission factor of 0.029 ton/MWh, as against 0.332–0.401 ton/MWh for the other configurations. Unit cost of energy (UCOE) for all systems are within $0.059–0.141 per kWh, with the SOFC-GT-ST-OR-AR-CCS having the highest UCOE. The cost of CO₂ avoidance of $110 per ton of CO₂ suggests the minimum carbon tax that will make SOFC-GT-ST-OR-AR-CCS economically competitive with the best configuration that is without carbon capture. Also, the carbon capture integrated power system has the least efficiency of 42.93% because a portion (73.5 MW) of the power generation was used in the carbon capture process. Nonetheless, the TOPSIS results suggest that at 0.7312, the SOFC-GT-ST-OR-AR-CCS is closest to the ideal solution, when compared to the other configurations which fall within 0.2238–0.7312. It is suggested that policies in Nigeria should promote (i) the integration of CCS technology in power generation; (ii) the retrofitting of simple cycle power plants with medium- and low-grade thermal power technologies; and (iii) dual-fuel power plants (natural gas and biomass) to harness the benefit of carbon neutrality in biomass and good energy density in natural gas.

KEYWORDS:

• low-emission future
• integrated power systems
• multi-criteria optimization
• low
• medium and high grade energy
• carbon capture
• biomass energy

Nomenclature

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Acknowledgments

The first author acknowledged the PhD partial sponsorship by the World Bank through the Africa Centre of Excellence Centre for Oilfield Chemicals Research (ACE-CEFOR), University of Port Harcourt. However, the findings do not necessarily reflect the policies of the ACE-CEFOR.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the ACE-CEFOR, University of Port Harcourt