Resource, environmental and economic considerations in the development of a Reverse Electrodialysis Heat Engine

The RED Heat Engine operates as a closed-loop RED system, where limited amounts of artificial saline solutions are used as working fluids. The solutions exiting from the RED unit are regenerated by means of a separation step, which uses low-temperature heat as its energy source. Essentially the system converts low-grade heat to electricity. There are two main alternative regeneration strategies: (i) extract solvent from the high salinity solution and move it to the low salinity solution or (ii) extract salt from the low salinity solution and move it to the high salinity solution. In this thesis are considered the Multi-effect distillation (MED) and the Membrane Distillation (MD) under the solvent extraction strategy, while the use of thermolytic salts with distillation and absorption columns are considered for the solute extraction option. This thesis studied the RED Heat Engine perspectives in terms of: • the sources that can provide the heat necessary for running the system, indicating the characteristics that the system should have to match the market requirements • the life-cycle impacts, providing evidence for the environmental credentials of the technology, compared to alternative electricity supply options, and providing direction to system designs with the minimum environmental impacts. • economic performance, improving the understanding of the factors that affect it, including the design options, operational choices as well as the development over time of the key components in terms of performance and cost