Techno-economic analysis of two-tank and packed-bed rock thermal energy storages for foil-based concentrating solar collector driven cogeneration plants

Concentrated solar power driven systems using thermal energy storage technology are an attractive solution for medium-scale dispatchable cogeneration plants. Recently, a novel concentrating solar collector system using a micro-structured polymer foil-based solar collector, with a potential of large cost reduction compared with current solar collector systems, was proposed. A techno-economic analysis of two-tank indirect storage, two-tank direct storage and packed-bed rock storage, respectively, for the foil-based solar field driven cogeneration plant is presented in this paper. The objectives are to identify the most suitable energy storage technology and to identify the optimal design for such system. Three different heat transfer fluids and two different rocks are considered in the analysis. The effects of solar field heat transfer fluid's operating and cost parameters on the selection of storage system are studied. The results suggest that the packed-bed rock (considering quartzite rock) thermocline storage with Therminol 55 as heat transfer fluid is the preferred option, attaining a minimum levelized cost of electricity and fresh water of 0.103 €/kWh_e and 0.995 €/m³, respectively, for Antofagasta, Chile. The levelized costs of electricity and water are about 11.2% and 11.9% lower, respectively, compared to those of the conventional two-tank indirect storage based plant.