Theoretical thermodynamic analysis of a closed-cycle process for the conversion of heat into electrical energy by means of a distiller and an electrochemical cell

TL;DR

This paper presents a thermodynamic analysis of a heat-to-electricity conversion device using a distiller and electrochemical cell, showing potential efficiencies approaching Carnot limits and improvements with multiple effects and high boiling point elevation solutions.

Contribution

It provides a theoretical framework for a closed-cycle heat-to-electricity conversion process, including efficiency limits and design improvements.

Findings

Efficiency approaches Carnot limit at fixed pressure.

Multiple effects increase overall efficiency.

High boiling point elevation solutions reduce the number of effects needed.

Abstract

We analyse a device aimed at the conversion of heat into electrical energy, based on a closed cycle in which a distiller generates two solutions at different concentrations, and an electrochemical cell consumes the concentration difference, converting it into electrical current. We first study an ideal model of such a process. We show that, if the device works at a single fixed pressure (i.e. with a ``single effect''), then the efficiency of the conversion of heat into electrical power can approach the efficiency of a reversible Carnot engine operating between the boiling temperature of the concentrated solution and that of the pure solvent. When two heat reservoirs with a higher temperature difference are available, the overall efficiency can be incremented by employing an arrangement of multiple cells working at different pressures (``multiple effects''). We find that a given efficiency can be achieved with a reduced number of effects by using solutions with a high boiling point elevation.