Alkali Metal Nitrates Promoted MgO Composites with High CO₂ Uptake for Thermochemical Energy Storage

Abstract

Thermochemical energy storage (TCES) by means of reversible chemical reactions represents a promising strategy for harnessing renewable energy and recovering industrial waste heat. In this work, alkali metal nitrate promoted MgO composites were synthesized, and the MgO−CO 2 working pair was suggested as an alternative candidate for harvesting intermediatetemperature industrial waste heat. However, it remains unclear how operating parameters would affect the heat storage density, and the long-term cycling stability of the alkali metal nitrate promoted MgO composites under harsh conditions close to practical application scenarios needs to be clarified. The objectives of this work are to expound the effects of operating parameters on TCES performance and to evaluate the long-term cycling stability of the alkali metal nitrate promoted MgO composites. With increasing NaNO 3 content, the heat storage density of NaNO 3 −MgO increases dramatically first and then exhibits no significant change. With rising carbonation temperature, the heat storage density of the 10NaNO 3 −MgO composite increases first and then declines marginally, while it increases with the increasing CO 2 partial pressure. Doping alkali metal nitrate eutectic mixtures adversely affects the heat storage density. 10NaNO 3 −MgO exhibits a high heat storage density of 2291 kJ/kg at 340 °C in 100% CO 2 . The 10NaNO 3 −MgO and 10(K−Na)NO 3 −MgO composites suffer a significant decline in heat storage density within 10 consecutive cycles, while 10(Li−Na)NO 3 −MgO retains good stability with a slight decrease of heat storage density from 1073 to 770 kJ/kg in 50% CO 2 . The desired 10(Li−Na)NO 3 −MgO is suggested as a promising material for TCES application.

Dynamic CO2 sorption on MgO-based sorbent in the presence of CO and H2O at elevated pressures

“…The mechanism of enhanced CO 2 sorption in alkali metal nitrate saltspromoted MgO is based on the phase transition of nitrate salts to molten state above its melting temperature, where the dissolution of CO 2 and MgO into molten nitrate salts can be facilitated [21,22,27]. On the other hand, further temperature increase above the melting temperature results in decreasing CO 2 solubility as well as preventing MgCO 3 formation due to its exothermic reaction [28]. Therefore, an optimal temperature for CO 2 sorption kinetics exists, which depends on the composition and eutectic point of alkali metal nitrate mixtures.…”

Evaluation of Thermochemical Energy Storage Performance of Fe-/Mn-Doped, Zr-Stabilized, CaO-Based Composites under Different Thermal Energy Storage Modes

“…Concentrated solar power (CSP) plants offer the possibility of large-scale electricity generation from solar energy. , However, they cannot effectively bridge the gap between supply and demand because of the inherent intermittency and unstable nature of solar irradiation. , Hence, it is necessary to configure an efficient and cost-effective thermal energy storage (TES) system for CSP plants . TES technologies are mainly divided into three types, including sensible heat storage, latent heat storage, − and thermochemical energy storage. ,, Currently, heat-conduction oil or molten salt is commonly selected as the heat storage materials in the TES systems for most commercial CSP plants to achieve the continuous generation of electricity …”