One of the main differences between concentrating solar power (CSP) and other renewable energy technologies is the potential for Thermal Energy Storage (TES) integrated into a CSP plant. The concept of thermal storage is simple: throughout the day, excess heat produced is diverted to a storage material. When electricity production is required after sunset, the stored heat is released into the steam cycle and the plant continues to produce electricity. All CSP plants have some ability to store heat energy for short periods of time and thus have a “buffering” capacity that allows them to smooth electricity production considerably and eliminate the short-term variations other solar technologies exhibit during cloudy days. ThermoChemical Storage (TCS) involves the exploitation of the heat effects of reversible chemical reactions for the “storage” of solar heat. Among gas-solid reactions proposed for such an approach the utilization of a pair of redox reactions involving multivalent solid oxides has several inherent advantages that make it attractive for large-scale deployment.
The new concept introduced in the RESTRUCTURE Project is instead of using packed or fluidized beds of the redox material as the heat storage medium, to employ porous monolithic structures made entirely or partially from the redox oxide materials. The idea stems from a number of technical achievements materialized in previous co-operations among consortium members, that have to do on the one hand with the demonstration of the capability of several multivalent oxide-based redox systems to be used in thermochemical storage cycles for storing and releasing heat in CSP plants and on the other hand with the development and demonstration of advanced structured ceramic receivers/reactors for performing either efficient solar heat exchange or solar–aided thermochemical redox reactions. The proposed concept combines the successfully demonstrated technologies of ceramic volumetric receivers and structured solar reactors and promotes them one step further to the development of an integrated receiver/reactor/heat exchanger configuration with enhanced heat storage characteristics, through a series of innovations to be implemented concerning new reactor/heat exchanger designs, enhanced incorporation of redox materials in the reactor’s structure, improved redox material compositions and utilization of industrial wastes as raw materials for the oxide redox systems synthesis.
The RESTRUCTURE consortium has been created with the rationale to have the capability of addressing real practical needs of the CSP industry like the particular requirement for effective heat storage, not only by the implementation of innovative ideas and solutions and validation of their merit by on-site, pilot-scale, solar power plant operation, but by their fast scale-up and commercialization as well.
The RESTRUCTURE Project is co-funded from European Commission’s 7th Framework Programme (FP7) via the Energy Call (FP7-ENERGY-2011-1, Theme 2011.2.5.1: Thermal energy storage for CSP plants, Project Number 283015). It started on November 1st, 2011 and will last for four years.