Design and performance of a multistage fluidised bed heat exchanger for particle-receiver solar power plants with storage

- A general method for designing a multistage FB HEX for hot particles heat recovery is presented.
- Temperature difference 100 °C higher than current molten salt storage technology can be achieved.
- A particle HEX for a 50 MWe solar plant with a two-stage Rankine cycle operating at 535 °C is designed.
- Thermal efficiency of 99.3% and a global heat exchange efficiency of 49.7% can be achieved.
- It is a design tool applicable for similar devices.

This paper presents an analytical model of a multistage fluidised bed heat exchanger for particle-based solar power plants. This model was developed as an applicable design tool for similar devices. It enables a parametric analysis of the heat exchanger performance to be conducted as a function of the operating specifications of the plant power block, the heat exchanger geometry and the fluidised bed properties, among other parameters. A 50 MWe solar plant with a two-stage Rankine cycle operating at 535 °C was used to analyse the heat exchanger design. The results indicate that for the proposed application, improvements in the thermal behaviour mostly depend on the addition of preheating and superheating stages. The most efficient configuration includes seven fluid bed stages with a thermal efficiency of 99.3% and a global heat exchange efficiency of 49.7%. With such a configuration, a maximum solid temperature difference of 387 °C may be achieved between the heat exchanger entrance and its exit for particle inlet temperature of 650 °C, thus enabling the best utilization of the thermal energy stored in the solid particles.