Thermally coupled pumped thermal energy storage system for a renewable powered ammonia production: Performance assessment and optimal sizing

The paper investigates the ability of a pumped thermal energy storage system, coupled with renewable energy generators, to meet the electrical and thermal demands of an ammonia production plant. A steady-state model of an industrial-scale Haber-Bosch process is first developed to quantify the electrical and thermal energy demands and to identify high-temperature waste heat streams suitable for recovery. A tailored pumped thermal energy storage configuration is then designed and simulated. The storage system performance is characterized through a parametric analysis with respect to the compression ratio and the relative sizing of the charging and discharging power ratings. The resulting performance maps are then embedded into an optimization model for sizing the renewable generation and storage subsystems while minimizing the total system cost. Results show that the optimal configuration is strongly influenced by the maximum allowed share of grid electricity: allowing a 10% grid contribution reduces the total cost by about 50% compared to the fully renewable case and leads to a costeffective design in which the power rating of the pumped thermal energy storage system in discharging mode is equal to the nominal electrical demand of the ammonia plant, while the charging power is approximately 1.5 times the discharging power. Compared with a reference configuration without pumped thermal energy storage, the proposed system reduces total cost by approximately 3-10%, depending on grid contribution and design parameters.