Extended operating range of PCM steam generators

For steam-driven industrial processes, Latent Heat-Thermal Energy Storages are a promising option to increase their flexibility regarding fluctuating renewable energies. This work provides the foundation for the quantitative analysis of control strategies for such phase change material steam generators and their practical system integration in once-through operation. Experiments are conducted in a self-built, one-kilowatt-scale single-tube test rig with extensive measurement equipment and precise fluid control, employing water/steam as the heat transfer fluid and PLUSICE A133 as the phase change material. Tests at different mass flow rates and pressures of the HTF show the strong correlation between the mass flow rate of the HTF and the storage power in practice. In addition, it is found that a reduction in the mass flow rate significantly increases the effective capacity during charging and discharging: By halving the mass flow rate during charging, it can be increased from 62 % to 77 % at a pressure level of 6.7 bar and from 3 % to 21 % at a pressure level of 3.0 bar. An increased pressure level can further increase the usable capacity of the storage material. The experimental results thus prove the effectiveness and relevance of considering heat transfer fluid control aspects already in the storage design process. Furthermore, the validation of a numerical storage design model shows that the peak power during charging can be accurately predicted by the model with deviations <3 %. With sufficiently long charging processes, also the simulated transient power profiles and outlet temperatures of the heat transfer fluid can be used reliably for storage design. • Integration of PCM steam generators into applications • Detailed analysis of storage control strategies • Precise power control • Enhanced material efficiency • Validation of numerical storage design model