Isothermal Organic Rankine Cycle (ORC) driving Reverse Osmosis (RO) desalination: Experimental investigation and case study using R245fa working fluid

Abstract

In many regions of the world, groundwater salinity contributes to the growing fresh water deficit. Desalination of saline water via reverse osmosis (RO) could be driven by Organic Rankine cycle (ORC) engines, exploiting readily available low-grade heat (e.g. solar or waste heat). However, the specific energy consumption (SEC) of conventional ORC-RO systems is quite high, while the ORC efficiency is significantly low at low temperatures. To improve on the efficiency and SEC of brackish ground water desalination processes, a novel isothermal ORC driven batch RO desalination system was experimentally investigated, using R245fa working fluid. Results showed about a half of the energy requirement of conventional ORC-RO desalination systems. A case study indicated that the system can be potentially employed in recovering waste heat from a bakery facility to produce about 0.4 L of fresh water per kg of baked food.