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

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

Brine utilisation for cooling and salt production in wind-driven seawater greenhouses:Design and modelling

Brine disposal is a major challenge facing the desalination industry. Discharged brines pollute the oceans and aquifers. Here is it proposed to reduce the volume of brines by means of evaporative coolers in seawater greenhouses, thus enabling the cultivation of high-value crops and production of sea salt. Unlike in typical greenhouses, only natural wind is used for ventilation, without electric fans. We present a model to predict the water evaporation, salt production, internal temperature and humidity according to ambient conditions. Predictions are presented for three case studies: (a) the Horn of Africa (Berbera) where a seawater desalination plant will be coupled to salt production; (b) Iran (Ahwaz) for management of hypersaline water from the Gotvand dam; (c) Gujarat (Ahmedabad) where natural seawater is fed to the cooling process, enhancing salt production in solar salt works. Water evaporation per face area of evaporator pad is predicted in the range 33 to 83 m3/m2·yr, and salt production up to 5.8 tonnes/m2·yr. Temperature is lowest close to the evaporator pad, increasing downwind, such that the cooling effect mostly dissipates within 15 m of the cooling pad. Depending on location, peak temperatures reduce by 8–16 °C at the hottest time of year