Numerical modeling of discharge modes and evaluation of the major characteristics of latent heat thermal energy storage at a nuclear power plant

Abstract

Under conditions of uneven power consumption schedules, construction of renewable power plants and low maneuverability of nuclear power plants (NPPs), combining NPPs with latent heat thermal energy storage systems (LHTES) can improve efficiency and maneuverability of NPPs. Combination of the LHTES with an additional low-capacity steam turbine will allow not only meeting peak electricity loads, but also increase the NPP safety by additional reservation of its own needs using this multifunctional turbine in emergency situations of complete blackouts. A scheme for combining a PCM-based thermal storage system with a two-circuit nuclear power plant is proposed, where the LHTES is charged with part of fresh steam from steam generators in the night hours of off-peak loads in the power grid and heating feed water above the nominal temperature during the peak loads. Non-stationary heat transfer between the heat storage material and feed water during the LHTES discharge was modeled using the finite volume method. The design characteristics of the LHTES as part of the NPP and the weight-size parameters of the thermal accumulator have been determined. The rational phase change material and the types of finned tubes have been determined. A solution has been proposed to ensure stable water temperature at the outlet of the PCM-based thermal accumulator during its discharge within the NPP that will significantly increase efficiency of its performance. Heat losses from the LHTES to the environment during the day have been calculated.