Simulation Modelling and Techno-Economics of Supercritical Carbon Dioxide Recompression Closed Brayton Cycle

In recent years, there has been global interest in meeting targets relating to energy affordability and security while taking into account greenhouse gas emissions. This has heightened major interest in potential investigations into the use of supercritical carbon dioxide (sCO2) power cycles. Climate change mitigation is the ultimate driver for this increased interest;other relevant issues include the potential for high cycle efficiency and a circular economy. In this study, a 25 MWe recompression closed Brayton cycle (RCBC) has been assessed, and sCO2 has been proposed as the working fluid for the power plant. The methodology used in this research work comprises thermodynamic and techno-economic analysis for the prospective commercialization of this sCO2 power cycle. An evaluated estimation of capital expenditure, operational expenditure, and cost of electricity has been considered in this study. The ASPEN Plus simulation results have been compared with theoretical and mathematical calculations to assess the performance of the compressors, turbine, and heat exchangers. The results thus reveal that the cycle efficiency for this prospective sCO2 recompression closed Brayton cycle increases (39% - 53.6%) as the temperature progressively increases from 550˚C to 900˚C. Data from the Aspen simulation model was used to aid the cost function calculations to estimate the total capital investment cost of the plant. Also, the techno-economic results have shown less cost for purchasing equipment due to fewer components being required for the cycle configuration as compared to the conventional steam power plant.

Dynamic simulation of a space gas-cooled reactor power system with a closed Brayton cycle

Space nuclear reactor power(SNRP)using a gas-cooled reactor(GCR)and a closed Brayton cycle(CBC)is the ideal choice for future high-power space missions.To investigate the safety characteristics and develop the control strategies for gas-cooled SNRP,transient models for GCR,energy conversion unit,pipes,heat exchangers,pump and heat pipe radiator are established and a system analysis code is developed in this paper.Then,analyses of several operation conditions are performed using this code.In full-power steady-state operation,the core hot spot of 1293 K occurs near the upper part of the core.If 0.4$reactivity is introduced into the core,the maximum temperature that the fuel can reach is 2059 K,which is 914 K lower than the fuel melting point.The system finally has the ability to achieve a new steady-state with a higher reactor power.When the GCR is shut down in an emergency,the residual heat of the reactor can be removed through the conduction of the core and radiation heat transfer.The results indicate that the designed GCR is inherently safe owing to its negative reactivity feedback and passive decay heat removal.This paper may provide valuable references for safety design and analysis of the gas-cooled SNRP coupled with CBC.

Preliminary Design Study on Concentrated Solar Power PVRs to Operate with RCBC

Parabolic through concentrators and parabolic dish concentrators followed by a PVR （pressurized volumetric receiver） are proposed, studying the performance behavior of a RCBC （regenerative closed Brayton cycle） operating with helium or hydrogen. A pressurized gas such as helium circulates along the volumetric receiver, capturing the concentrated thermal solar energy to be further converted into electric power via a thermal cycle. The overall efficiency of the plant has been computed under variable parameters to determine the operating conditions for which efficiency and specific power are acceptable. As consequence of the proposed analysis, it is concluded that direct coupling between volumetric receivers and thermal engines renders high efficiency while avoiding an intermediate heat transfer medium.