Thermochemical energy storage of concentrated solar power by Integration of the calcium looping process and a CO2 power cycle

摘要

Energy storage is the main challenge for a deep penetration of renewable energies into the gridto overcome their intrinsic variability. Thus, the commercial expansion of renewable energy,particularly wind and solar, at large scale depends crucially on the development of cheap,efficient and non-toxic energy storage systems enabling to supply more flexibility to the grid.The Ca-Looping (CaL) process, based upon the reversible carbonation/calcination of CaO, is oneof the most promising technologies for thermochemical energy storage (TCES), which offers ahigh potential for the long-term storage of energy with relatively small storage volume. Thismanuscript explores the use of the CaL process to store Concentrated Solar Power (CSP). A CSPCaLintegration scheme is proposed mainly characterized by the use of a CO2 closed loop for theCaL cycle and power production, which provides heat decoupled from the solar source andtemperatures well above the ~550ºC limit that poses the use of molten salts currently used tostore energy as sensible heat. The proposed CSP-CaL integration leads to high values of plantglobal efficiency (of around 45-46%) with a storage capacity that allows for long time gapsbetween load and discharge. Moreover, the use of environmentally benign, abundantlyavailable and cheap raw materials such as natural limestone would mark a milestone on theroad towards the industrial competitiveness of CSP.