Proposal and performance assessment of novel combined ORC and HDD cogeneration systems

In this paper, four combined cogeneration systems including the Humidification-Dehumidification Desalination (HDD) and Organic Rankine Cycle (ORC) are investigated from thermodynamic and economic viewpoints. In the first scenario, the outlet water flow of ORC condenser enters the HDD directly as feed water. In the second scenario, the temperature of ORC condenser outlet water rises in a heat exchanger by the ORC evaporator heat source outlet flow before entering the HDD. In the third scenario, the ORC evaporator heat source outlet flow passes through a heat exchanger to heat the HDD feed water. The fourth scenario is a combination of scenarios (I) and (III) so that it contains both of them in one configuration. In all the scenarios the ORC waste heat either from its condenser or evaporator is utilized. Results show that the ORC with toluene produces more power and that scenarios (IV) and (II) produce more desalinated water compared to the other scenarios. It is also observed that, compared to seven working fluids, using n-heptane as a working fluid in these two scenarios results in the highest distilled water production rate. It is concluded that the least distilled water unit cost is achieved by the scenarios (I) and (II), respectively and that using n-heptane, among the other working fluids, brings about the least unit cost for produced distilled water.