Main content area

HIGH-EFFICIENT reversible solid oxide fuel cell coupled with waste steam for distributed electrical energy storage system

Giap, Van-Tien, Kang, Sanggyu, Ahn, Kook Young
Renewable energy 2019 v.144 pp. 129-138
computer software, electric power, energy density, exergy, fuel cells, fuels, hydrogen, models, renewable energy sources, steam, temperature, wastes
Recently, the penetration of renewable energy into the power sector has dramatically increased; thus, electrical energy storage (EES) systems with long duration time, high capacity, and high energy density are essential. Reversible solid oxide fuel cell (RSOFC) systems have become a promising candidate for this important role. In this study, a new RSOFC system coupled with waste steam considering the compatibility between charge and discharge modes is proposed. A lumped model of RSOFC stack was integrated into EBSILON®Professional commercial software for system analysis. Parametric studies were conducted to examine the effects of fuel composition, waste steam temperature, and steam conversion ratio on three system round-trip efficiency types: reference system round-trip efficiency (ηRT1), electrical round-trip efficiency (ηRT2), and exergy round-trip efficiency (ηRT3). Base case calculation shows that the system round-trip efficiencies ηRT1, ηRT2, and ηRT3 are 37.9%, 53.8% and 49.6%, respectively. In the parametric analysis, as hydrogen volume concentration in the hydrogen-steam mixture in the SOEC mode was increased from 10% to 60%, ηRT1 and ηRT2 increased, reaching a maximum value of 54.2% and 38.7% at 30% and 40% of H2 concentration, respectively. The exergy round-trip efficiency had the same trend as ηRT2 and reaches maximum value of 50.1%. The waste steam temperature had a small effect on all round-trip efficiency types. The increase in steam conversion ratio relatively improved ηRT1 and ηRT3, but negligibly influences ηRT2. The proposed system provided a solution for upgrading the EES system performance via integrating a RSOFC system with low exergy waste steam. The efficiencies ηRT2 and ηRT3 were much higher than ηRT1 because of the use of waste steam. The exergy round-trip efficiency with consideration of waste steam exergy was a good indicator of system performance.