Parametric study of thermodynamic and cost performance of thermal energy storage coupled with nuclear power

Abstract

Thermal energy storage for nuclear power can increase the flexibility of low carbon baseload power plants and facilitate greater use of renewable energy sources. The thermodynamic performance and cost of approaches to integrate thermal energy storage with a 1050 MW nuclear power plant are compared in a parametric study over practical ranges of charge/discharge durations, peaking power and round-trip efficiency of the storage. Conceptual designs for sensible and latent heat storage modules are presented. The results quantify for the first time how different options for thermal energy storage affect technical performance of a nuclear power plant and are interpreted to identify the most efficient options and operating conditions. The three configurations are distinguished by charge and discharge operation. Configuration I charges the storage via high-pressure steam supply and discharges steam to the low-pressure turbine. Configuration II charges via high–pressure steam and discharges preheated condensate to the steam generator. Configuration IIII charges via low-pressure steam and discharges steam to a secondary Rankine cycle. The diurnal energy production ratio, or capacity factor, versus peaking power, and storage material cost are the metrics used to compare configurations. Configuration III, which does not require changes to the primary cycle turbines and thus has no detrimental impact on the efficiency of baseload operation, has the highest energy production ratio of 0.99. Energy production ratio increases as charging duration and discharge power are reduced. Configurations I and III can provide peaking power more than 1.5 times the baseload plant. Configuration II is limited to a peaking power of less than 1.1 times that of baseload and is cost effective in this range, albeit with lower energy production ratio than configuration III. Sensible heat storage in a rock bed is more economical than latent heat storage due to the relatively high cost of eutectic salt mixtures with appropriate melt temperatures. Keywords: thermal storage, nuclear, thermodynamic, sensible heat, latent heat