An exergoeconomic and normalized sensitivity based comprehensive investigation of a hybrid power-and-water desalination system

Abstract

Cogeneration of power-and-water is one of the potential solutions for ever-rising energy and freshwater demand. These systems have shown superior thermodynamic and economic performance compared to their standalone counterparts because of processes synergy and shared utilities resources. The current study investigates a multi-effect distillation system operated on bleed-out steam from the last stages of low-pressure steam turbine of a combined cycle gas turbine power plant (CCGT + MED). For this purpose, a component-based exergoeconomic investigation integrated with normalized sensitivity analysis for energy, exergy, and economic evaluation. The performance indicators include specific fuel consumption, thermal efficiency, exergy destruction, exergy efficiency, stream cost, and product cost (electricity and freshwater). The analysis showed that the cogeneration scheme reduced the electricity cost by 16.8% and freshwater production cost by 24.5% compared to the standalone power plant and MED systems. Moreover, the payback period for the MED system is calculated as 2.59 years with freshwater selling at $1.6 /m3. The sensitivity analysis showed that the electricity and the freshwater production cost are the most sensitive to gas turbine efficiency, fuel cost, and fuel heating value with normalized sensitivity coefficients of 1.71, 0.86, and 0.80 for electricity and 0.76, 0.42 and 0.40, for freshwater cost, respectively. While the other parameters such as interest rate, cost index factor, steam turbine efficiencies etc. showed a remarkably low impact on the cost of the products.