High-temperature thermal energy storage enabling a second life for existing fluidized bed boilers with a high efficiency (HIGHWAY)

Retrofitting existing fossil-fired fluidized bed power plants with high-temperature thermal energy storage systems is a promising approach for the flexible CO2-free provision of electricity and heat. This project studies the potential of thermal storage use with existing fluidized bed power plants through a pilot scale testing unit. Unit charge and discharge cycles are tested using a thermal energy storage system, which utilizes an electric air heater powered by renewable electricity. Inside the storage, the heated air is passed through a bed of particles where heat transfer takes place between the hot air and the bed. During the discharge process, cold air is fed into the bed and the heat is transferred from the hot particles to the air, which is fed into a water-steam cycle to generate superheated steam.

Different numerical models (steady state, dynamic and CFD models) are developed, validated through experimental data, and applied to design modifications. The concept is evaluated in terms of electrical efficiency, economic viability and environmental and social impact.

Goals

The project aims to modify existing fluidized bed plant components to integrate a high-temperature thermal energy storage system and maximize round-trip efficiency. Technical solutions for heat supply, air circulation, and optimal storage design are identified and validated through laboratory and pilot-scale testing, establishing the operating window and cyclic performance of the integrated system. Advanced modeling tools will be developed to predict scale-up behavior, dynamic performance, and gas–solid fluid dynamics. Finally, the project will assess the market potential, economic and environmental impacts, and overall flexibility and efficiency of the retrofitted power plant.