The TS unit of REDHE exhibits a high level of flexibility. Luo et al. [
5] proposed a REDHE, i.e., thermal-driven electrochemical generator (TDEG), which adopted a distillation column as the TS unit. They primarily focused on investigating the potential of ammonium bicarbonate (NH
4HCO
3) solutions for electricity generation in TDEG. The results indicated that the ionic flux and energy efficiency of the RED stack employing NH
4HCO
3 solutions could respectively reach 88% and 31% under the optimal condition. Regrettably, relevant studies concerning the whole performance of the REDHE were not conducted in their work. Giacalone et al. [
6] constructed the first world laboratory-scale REDHE which consisted of a stripping column as the TS unit and a RED unit. They operated the REDHE for up to 55 h to demonstrate its feasibility and stability, and the highest exergy efficiency of it was equal to 1.1% for the case of 0.05−1.9 mol/L NH
4HCO
3 solutions. Long et al. [
7] adopted membrane distillation (MD) as the TS unit which was combined with a RED stack to form a REDHE, and the whole performance of it was investigated. The results showed that a larger MD feed sodium chloride (NaCl) concentration induces a greater electrical efficiency which reaches 1.15% operating between 20 and 60 °C with the MD feed NaCl concentration of 5 mol/kg. Micari et al. [
8] provided a perspective analysis for MD-RED heat engine, and the energetic efficiency of the REDHE could reach to 2.8% (corresponding to the exergy efficiency of about 16.5%) when highly performance RED membranes and future MD module were employed. Tamburini et al. [
9] integrated a multi-effect distillation (MED) system with the RED stack to create a MED-RED heat engine. They employed a simplified model to analyze the performance of the REDHE and determined that the current state-of-the-art performances of RED and MED could achieve a maximum energetic efficiency of 5%. Hu et al. [
10] presented a comprehensive thermodynamic analysis of a MED-RED heat engine, revealing that the system could achieve an energy conversion efficiency of 1.01% when the effect number of MED was set to 10. Palenzuela et al. [
11] conducted a performance analysis on a MED-RED heat engine, obtaining a maximum thermal efficiency of 1.4% for the case of current membranes and up to about 6.6% thermal efficiency assuming ideal membrane properties. Ortega-Delgado et al. [
12] performed an extensive exergy analysis on a REDHE with MED and identified the MED unit as the primary source of exergy destruction, resulting in an overall exergy efficiency of 24% for the REDHE when high-performance membranes were utilized. They also boosted the performance of the MED-RED heat engine, and the maximum thermal efficiency of the REDHE reached 9.4% by employing potassium acetate solution and adopting high-performing ion-exchange membranes (IEMs) [
13]. Olkis et al. [
14] integrated adsorption desalination (AD) with RED stack in REDHE and investigated the efficiencies of 277 salts and 10 adsorption materials, achieving an exergy efficiency of up to 30% for the REDHE. After that, they [
15] implemented simulation analyses on different heat integration scenarios for the REDHE using validated models for both RED and dynamic AD based on experimental data, demonstrating that the exergy efficiency could reach up to 15%, while its energy efficiency could reach up to 0.55%. Liu et al. [
16] employed a generator as the TS unit of REDHE, and simulated the REDHE system adopting lithium bromide (LiBr) solution as working fluid by Aspen Plus® 11. They found that under respective conditions, the maximum energy efficiency achievable by this particular configuration was determined to be around 6.05%. Afterwards, they experimentally investigated its performance through a laboratory-scale REDHE [
17]. However, the results showed that the actual energy efficiency of the REDHE approached to 0%, which extremely deviated from the theoretical result mentioned above. Besides, they conducted a prospect analysis, which indicated that the energy efficiency of the REDHE had a capacity to reach 2.6% by employing IEMs with high permselectivity under high concentration conditions.