Lawrence Berkeley National Laboratory

This study links a model of thermal energy storage (TES) performance to a subsystem model with heat exchangers that cool down the storage at night; this cool storage is used to precool the air flow for a power plant air-cooled condenser during peak day temperatures. The subsystem model is also computationally linked to a model of Rankine cycle power plant performance to predict additional power the plant could generate due to the additional cooling. The model was used to explore the effects of varying phase change material (PCM) melt temperature and the energy input and rejection control settings with the goal of maximizing efficiency for a 50 MW power plant operating in the desert regions of Nevada for an average summer day. The results suggest that the kWh output of the modeled plant can be increased by up to 3.25% during the heat input/cold extraction period, and a cost analysis estimates that the TES system has the potential to provide additional revenue of up to $686,000 per year, depending on electricity cost and parameter choices.