Solar-Powered Rankine Cycle Assisted by an Innovative Calcium Looping Process as an Energy Storage System

Abstract

Solar energy is an intermittent resource, and thus an energy storage system is required for practical applications of the collected solar irradiance. This work deals with the integration of a thermo-chemical energy storage (TCES) system based on the calcium looping (CaL) process with a concentrated solar tower power (CSP) plant. The objective of this work is the integration of a conventional 320 MWe Rankine cycle with a direct calcination for energy harvesting. Particularly, this work addresses the use of CO 2 as the working fluid of a compressed-gas energy storage (CGES) system for hybrid energy storage with the CaL process. The hybrid TC/CG-ES (thermo-chemical/compressed-gas energy storage) system can increase the competitiveness of the CSP with respect to conventional fossil-based power plants leading to a reduction in CO 2 emissions. The thermal integration with the calcium looping (CaL) system is optimized by means of the pinch analysis methodology. The obtained results show a reduction in the electrical efficiency of about four percentage points with respect to the conventional Rankine power cycle without the CSP unit: the net electrical efficiency reduces from 43.7% to 39.5% while the global (thermal and electrical) efficiency of the plant reaches the peak value of 51.5% when low enthalpy energy is recovered (e.g., district heating network, district cooling network). This paper highlights the importance of the thermochemical CaO based material. With a conversion of CaO to CaCO 3 of 80% the storage efficiency is defined as the ratio of the energy released during the carbonation and the CO 2 expansion to the energy collected by the solar field and required during the CO 2 compression, which is 87.3%.

An Innovative Calcium Looping Process as Energy Storage System Integrated With a Solar-Powered Supercritical CO2 Brayton Cycle

“…In addition, we supposed that the CaO sorbent deactivates at a large number of carbonation/calcination cycles. The CaO conversion is set at 70% (Chen et al, 2012), and the make-up flow is considered negligible, as reported elsewhere (Cannone et al, 2020).…”

“…The s-CO 2 Brayton cycle is integrated into the STP, replacing the current water-steam Rankine cycle analyzed in our previous work (Cannone et al, 2020) and the air Brayton cycle (Bryner et al, 2016). The CO 2 acts as heat transfer fluid and the working fluid as well.…”

“…Nevertheless, the direct expansion of CO 2 at the exit of the carbonator reactor is not recommended because it may contain solid particles that would damage the blades of the turbines downstream. In the last work, we have performed a conventional Rankine cycle integrated by a solar calciner to improve the efficiency of the system (Cannone et al, 2020). As a result, net electric efficiency and gross (electric and thermal) efficiency were estimated, respectively, equal to 39.5 and 51.5%.…”

Recent Advances in Thermochemical Energy Storage via Solid–Gas Reversible Reactions at High Temperature

“…Several of them have demonstrated attractive performances for TCES application, such as CaO/CaCO 3 , SrO/SrCO 3 or BaO/BaCO 3 [33]. Calcium-Looping (CaL) technology in particular, coupled with CSP, is being thoroughly studied for adaptation to TCES power plant (Equation ( 2)) [3,12,[34][35][36][37][38]. This reversible cycle requires operating temperatures between 850 and 950 • C.…”

A Review on CO2 Capture Technologies with Focus on CO2-Enhanced Methane Recovery from Hydrates

“…The majority of data available for post-combustion capture plants are based on MEA solvents. Several technologies have been developed for post-combustion processes (e.g., Calcium Looping [30,31] and membrane separation [Section 3.4]). Although they offer a future reduction of capture costs, they have not yet been developed for large capture plants.…”