Energy, Exergy, Economic and Environmental Analysis of a Solar-Assisted Multi-Generation System Based on SOFC-GT Waste Heat Recovery with LNG as the Cold Source

Solid oxide fuel cell (SOFC) can directly and efficiently convert chemical energy into electricity without additional pollutants, which is a very promising power generation technology. It is often combined with a gas turbine (GT) as an SOFC-GT combined cycle to achieve higher efficiency. However, there is still abundant waste heat in the exhaust of the SOFC-GT combined cycle. Therefore, supercritical carbon dioxide (sCO₂) Brayton cycle and organic Rankine cycle (ORC) are often used as the bottoming cycle to further recover the exhaust waste heat. As a promising solar energy utilization technology, solar power tower (SPT) is often combined with sCO₂ Brayton cycle to generate electricity. The use of this technology is very helpful in reducing the use of traditional fossil fuels. This paper integrates SOFC-GT with SPT, using sCO₂ and ORC as bottoming cycles, LNG as the cold source, and introduces a proton exchange membrane (PEM) electrolyzer to form a novel solar-assisted SOFC-GT multi-generation system, which can simultaneously achieve power generation, heating, cooling, and hydrogen production. In order to evaluate the performance of the proposed system, mathematical modeling of the system is conducted from the perspectives of energy, exergy, economy, and environment. The impact of key thermodynamic parameters of the system on its performance is analyzed and discussed. The influence trends of key thermodynamic parameters on system performance are summarized, and the reasons for their changes are analyzed. Under the given parameter conditions, a case of the proposed system is analyzed in detail from the aspects of system output, exergy flow distribution, and subsystem cost distribution.