A key feature of a solid particle system is the extraordinary wide temperature range of its heat transfer and storage medium (HTM). Such a system is therfore highly flexible regarding the selection of temperature levels.
The increased temperature allows the integration of advanced high efficiency steam power cycles, e. g. with modern 620°C steam power blocks. Moreover, the temperature spread between upper and lower particle temperature can be optimized in a wide range.
A recent study evaluated modular solar tower plants with solid particles as HTM, with maximum HTM temperatures of up to 1,000°C. The study looked at the impact of the lower and upper HTM temperature on the levelized cost of electricity (LCOE). In the study, 14 solar tower modules in total, each with a design point thermal power of 50MW and a storage system for 12 hours, are providing heated particles to a central steam power block.
The scheme bewow shows such a solar tower module.
The results show a significant impact of the HTM temperature selection, mainly governed by the HTM temperature difference (see figure below).
A high temperature difference results in a reduced LCOE. The most important factors for this reduction are the cost savings in particle inventory, storage containment, and particle steam generator. The reduction is partially offset by an increase in heliostat field and tower cost, resulting from lower heliostat field and receiver efficiencies.