Performance improvement of the ocean thermal energy conversion using R1234ZEZ/R1233ZDE in an organic Rankine cycle

Min-Hsiung Yang and Rong-Hua Yeh

Energy, 2025, vol. 327, issue C

Abstract: For sustainable development, ocean thermal energy conversion (OTEC) provides an abundant renewable energy source. Two eco-friendly refrigerants with ultra-low global warming potential and zero ozone depletion potential, R1234ZEZ and R1233ZDE, are used as the components of the ORC working fluid mixture. The net power output, Wnet, and levelized energy cost, LEC, of the OTEC system are optimized with respect to the mass fractions of mixture, α, temperature variations in seawater between the condenser and evaporator's inlets and outputs, ΔT7-8 (ΔT9-10), and mass flowrates of deep seawater, mds. The OTEC system using a mixture of R1234ZEZ/R1233ZDE at an optimal mass fraction of 0.25 achieves a maximum net power output that is 19.96 % higher than that of pure R1234ZEZ and 18.65 % higher than that of pure R1233ZDE. The minimum levelized energy cost of the system utilizing R1234ZEZ/R1233ZDE (30/70 wt%) is lower than R1234ZEZ and R1233ZDE by 7.73 % and 13.81 %, respectively. In addition, for the mass flowrate of deep seawater operating in the range between 8 × 103 and 2 × 104 kg/s, a maximum Wnet of 4881.49 kW for the system with R1234ZEZ/R1233ZDE is obtained at the corresponding mds = 2 × 104 kg/s, α = 0.253, and ΔT7-8 = ΔT9-10 = 5.07 °C, and a minimum LEC of 0.203 $/kW-h is achieved at the corresponding mds = 1.2 × 104 kg/s, α = 0.31, and ΔT7-8 = ΔT9-10 = 4.31 °C.

Keywords: Working fluid; Mass flowrate of deep seawater; Net power output; Levelized energy cost; Ocean thermal energy conversion; Organic Rankine cycle (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:327:y:2025:i:c:s0360544225020456

DOI: 10.1016/j.energy.2025.136403

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