Performance analysis of a underwater power transcritical CO2 cycle system prototype

The energy system of deep-sea underwater equipment is the core element supporting its operation. High energy density, high safety and stability are the key indicators to measure the performance of the system. In view of the lack of highly adaptable secondary loops for underwater equipment,this paper established a 100 kW-class regenerative reheat transcritical CO2 cycle underwater power system prototype. The performance test of the entire process from standby to power generation was completed for the first time under the conditions of simulated deep-sea cold source (<2 °C) and micro-reactor heat source (>500 °C). The results showed that its actual cycle thermal efficiency reached 22.7 %, the power generation was 97.6 kW, the cold source fluctuation of ±1 °C was acceptable, and the system flow rate fluctuates by only 0.725 %/°C with sudden changes in seawater temperature. In addition, the supporting power density of the liquid storage tank is 1 MW/m3, which is equivalent to the total CO2 volume of all major components of the system except the pipeline, and can realize the working medium adjustment of the entire system from standby to long-term multi-operating conditions.The innovatively developed seal-cool self-reflow fan system consumes 2 % of the power generation and has a volume of 1/10 of the turbine generator. This study presents the first experimental demonstration of transcritical CO2 cycle's multidimensional compatibility with underwater power systems, providing substantial empirical support for existing research. The threefold advantages demonstrated - enhanced energy conversion efficiency, exceptional system reliability, and robust environmental adaptability - collectively establish this technology as a groundbreaking solution for underwater power applications.