Evaluation of the Economic and Environmental Performance of Low-Temperature Heat to Power Conversion using a Reverse Electrodialysis – Multi-Effect Distillation System

Abstract

In the examined heat engine, reverse electrodialysis (RED) is used to generate electricity from the salinity difference between two artificial solutions. The salinity gradient is restored through a multi-effect distillation system (MED) powered by low-temperature waste heat at 100 °C. The current work presents the first comprehensive economic and environmental analysis of this advanced concept, when varying the number of MED effects, the system sizing, the salt of the solutions, and other key parameters. The levelized cost of electricity (LCOE) has been calculated, showing that competitive solutions can be reached only when the system is at least medium to large scale. The lowest LCOE, at about 0.03 €/kWh, is achieved using potassium acetate salt and six MED effects while reheating the solutions. A similar analysis has been conducted when using the system in energy storage mode, where the two regenerated solutions are stored in reservoir tanks and the RED is operating for a few hours per day, supplying valuable peak power, resulting in a LCOE just below 0.10 €/kWh. A life-cycle assessment has been also carried out, showing that the case with the lowest environmental impact is the same as the one with the most attractive economic performance. Results indicate that the material manufacturing has the main impact; primarily the metallic parts of the MED. Overall, this study highlights the development efforts required in terms of both membrane performance and cost reduction, in order to make this technology cost effective in the future.

Electrodialytic Processes: Market Overview, Membrane Phenomena, Recent Developments and Sustainable Strategies

“…SWRO-MCDI-RED was investigated at lab scale and showed better performances and lower energy consumption (by 17%) when compared to two-pass RO [ 258 ]. The eco-efficiency evaluation of a multi-effect distillation (MED)-RED process recycling low-temperature waste heat showed promising results when comparing with other sustainable technologies [ 303 ].…”

Energy Recovering Using Regenerative Braking in Diesel–Electric Passenger Trains: Economical and Technical Analysis of Fuel Savings and GHG Emission Reductions

“…Table 4. Studied cases and their characteristics [36]. In the above table, cases 1, 2, and 3 are related to trips in a cold climate.…”

“…There are five cold months for case 1 (London), with average temperatures between 6 and 10 • C. The cold temperature effect is evaluated at 0% additional charge per year [36]. For case 2 (Montreal), there are seven months subject to cold temperature effects.…”

“…For case 2 (Montreal), there are seven months subject to cold temperature effects. The average temperature varies from −9 to 10 • C. The cold temperature effect is evaluated at approximately 3.84% additional charge per year [36]. In case 3 (Schefferville), 10 months are known to have cold episodes where the average temperatures range between −24 and 9 • C. The cold temperature effect is evaluated at approximately 11.22% additional charge per year [37].…”

Heat to Hydrogen by Reverse Electrodialysis—Using a Non-Equilibrium Thermodynamics Model to Evaluate Hydrogen Production Concepts Utilising Waste Heat

“…To reach sufficient efficiencies for the industrialisation of the technology, both ion-exchange membranes and process design need to be optimised [33]. Optimisation potentials have been elaborated in previous investigations on REDHE for electricity generation [34][35][36][37][38], and for hydrogen production [24,[39][40][41]. The choice of electrolyte composition, regeneration technology and ion-exchange membrane performance have been identified as particularly important influencing factors [32,39,42].…”