Thermodynamic and economy analysis of solid oxide electrolyser system for syngas production

A pressurized solid oxide electrolyser (SOE) system for syngas production is analyzed. The system is modeled and analyzed considering energy and exergy aspects. The main consideration is to quantify the effect of operating pressure on the system performance when syngas is used for synthetic diesel production. At elevated pressures methanation reaction within the electrolyser causes internal production of methane from syngas. The results show that methane fraction increase from almost zero percent to 14% at 25 bar. Since methane is not a favorable outcome of this system, elevated pressure has adverse effect on the total system performance and consequently system efficiency drops by about 20% points by increasing the electrolyser operating pressure from atmospheric to 25 bar. This effect also results in higher levelized cost of syngas at elevated pressures. Effects of other operating parameters like temperature and utilization factor on the syngas production rate and system performance are also explored. In addition, relative irreversibility of each component is estimated. It is concluded that the solid oxide electrolyser has the highest relative irreversibility amongst other system components which can be minimized by changing operating temperature. At last but not least, levelized cost of produced syngas is estimated.