Preliminary Design and Transient Simulation of a Nuclear-Solar Hybrid System Using an Open-Air Brayton Cycle

Abstract During the energy transition period, global governments are dedicated to develop renewable energy to address environmental challenges. Solar energy has intrinsic problems such as intermittency and volatility. Conversely, nuclear energy boasts stability and low-carbon features. Therefore, this work proposes a new concept of a nuclear-solar hybrid system (NSHS), which shows promise in improving the grid penetration of renewable energy. A 1 MWt Heat Pipe-cooled nuclear reactor (HPR) is coupled with Concentrating Solar Power (CSP) and Thermal Energy Storage (TES) units using an open-air Brayton cycle (OBC). For the micro HPNR, the point kinetic (PK) model considering temperature feedback effects is used to model nuclear power evolution. For the high-temperature heat pipe, a heat transfer limit-based variable resistance model is developed to represent the main features of this high-efficiency thermal device. A secondary solar salt circuit comprises two TES tanks, a solar receiver, and a secondary heat exchanger. Finally, a composite control strategy is proposed to manage the operation of the hybrid energy system, where the nuclear and solar parts are responsible for base-load and peak-load, respectively. The mentioned components and models of the NSHS are integrally constructed using the MATLAB/Simulink environment. A transient simulation of the NSHS is conducted during a typical sunny day. The reactor thermal power varies from 1 MW to 800 kW due to temperature feedback. The volumes of the two TES tanks change due to varying solar radiation and electricity demands. Over the whole year, the total generated power is 2635.6 MWh, resulting in a total energy efficiency of 22.9%.