A self-condensing CO2 power system for widely adaptive underwater conditions

Haotian Yin, Lingfeng Shi, Yonghao Zhang, Xiaocun Sun, Zirui Wu, Jintao He, Hua Tian and Gequn Shu

Energy, 2024, vol. 313, issue C

Abstract: In the underwater environment, a nuclear-powered CO₂-based transcritical recuperative power cycle can effectively utilize the low temperature of seawater to achieve high-efficiency. To address the challenge of non-condensable working fluids in the epipelagic zone, a self-condensing subloop offers an effective solution. This study introduces a configuration for a self-condensing CO₂-based transcritical recuperative power cycle, establishes a thermodynamic model, investigates the negative impacts of the self-condensing subloop, and analyzes its operational strategies at various underwater depths. Results indicate, when CO₂ can condense in the cooler, the subloop consumes between 17.4 % and 36.9 % of generated power, which decreases as seawater temperatures rise at a cooler pressure of 8.5 MPa. Since the high heat capacity of the heat source, increasing turbine inlet temperature and pressure significantly improves system efficiency. Activation of the self-condensing subloop enhances power output with higher storage tank temperatures. Furthermore, when seawater temperatures exceed 23.4 °C, a linear functional relationship between seawater temperature and optimal cooler pressure is specifically proposed, which effectively optimizes system power output. The study recommends activating the self-condensing subloop when CO2 at cooler outlet exceed 28 °C, broadening applicable temperature range of transcritical power cycle systems in the ocean. Methods in this research include first-principle modeling and optimization.

Keywords: Carbon dioxide; Transcritical rankine cycle; Self-condensing; Underwater power generation (search for similar items in EconPapers)
Date: 2024
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:313:y:2024:i:c:s0360544224036120

DOI: 10.1016/j.energy.2024.133834

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