Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman Thermo-economic evaluation of a hybrid solar-conventional energy supply in a zero liquid discharge wastewater treatment plant Ahmadreza Najafi, Ali Jafarian ⁎ , Jamal Darand Department of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran ARTICLE INFO Keywords: Thermo-economic Hybrid solar-conventional energy supply Wastewater treatment Brine concentrator Crystallizer Zero liquid discharge plant ABSTRACT In this paper, thermo-economic evaluation of hybrid solar-conventional energy supply in a zero liquid discharge plant has been conducted. The zero liquid discharge plant includes a brine concentrator and a crystallizer. Brine concentrator and crystallizer utilize falling film and forced circulation evaporators respectively. The plant was studied thermo-economically in capital of Iran, Tehran city weather conditions. The plant performance and economics were investigated in four design (winter, spring, summer and autumn design) conditions based on the seasonal weather data and compared with the conventional energy supply system. It was concluded that the design proposed based on average weather conditions shows no economic advantage over the conventional design; due to accounting for financial aids and subsides for the fuel cost at 0.05 $/m 3 ,affecting the steam and water costs. However, a parametric study demonstrated that if the financial aids associated with the fuel are disregarded, it will have a pronounced effect on the cost of steam and produced water. 1. Introduction Today, the need for recycling industrial wastewater is one of the most important problems in society; and due to the faster growing population, and subsequently, the growing industries, it is deemed even more necessary [1]. In addition to environmental problems and water shortage, energy is considered another important reason in industrial wastewater management [2]. Therefore, thermodynamic study and economic analysis of water and power cogeneration plants in the scope of industrial wastewater can demonstrate the feasibility of different methods to resolve the aforementioned issues [3]. One of the solutions to water scarcity is recycling and concentration of the industrial was- tewater. Desalination is the process to remove the dissolved salts to produce fresh water. Multi-effect distillation (MED) and multistage flash distillation (MSF) are among the most important processes to produce fresh water. Although desalination processes have succeeded in slightly improving the water scarcity problem, they require ex- pensive investments due to their high energy consumption [4]. Because of the rising fuel costs, environmental contaminant and greenhouse gas emission, using fossil fuels to setup the aforementioned processes are not efficient options [5]. Regarding the problems with fossil fuels, re- newable energy resources seem like an appropriate alternative [6]. Among renewable energy resources, using solar energy has a lot of advantages, especially in areas with high sunlight, such as the Middle East [7]. Accordingly, a lot of researches have been carried out on using solar energy for desalination. Shaobo et al. [8] provided an improved MSF design based on “Pinch” technology. Sharaf et al. [9] studied two configuration of multi effect distillation-vapor compression in both economic and thermo- dynamic aspects. Their studies showed that for a 4545 m 3 /day design, water would be priced at 2.1 and 1.5 $/m 3 for multi effect distillation- thermal vapor compression (MED-TVC), and multi effect distillation- mechanical vapor compression (MED-MVC), respectively. Palenzuela et al. [10] studies different configuration of parabolic trough solar power plants with distillers designs in arid environments. In one of the designs, they used a low-temperature distiller in the place of the con- denser in a solar power plant, and studied the optimization of this de- sign by evaluating the turbine discharge. Bataineh [11] studied the yearly operation of a MED-MVC in Jordan. He demonstrated that highest efficiency of the system is achieved by placing the collectors towards south, and solar fraction change has negligible variation in saturated vapor production. Delgado et al. [12] demonstrated in their thermoeconomic study of a solar powered reverse osmosis and MED- TVC seawater desalination plant, that highest system efficiency is achieved when the reverse osmosis unit is connected to the local power grid. Kouta et al. [13] provided an entropy, exergy, and cost analyses of a solar driven cogeneration systems using supercritical CO 2 Brayton cycles and multiple effect evaporation with a thermal vapor https://doi.org/10.1016/j.enconman.2019.03.059 Received 20 December 2018; Received in revised form 18 March 2019; Accepted 19 March 2019 ⁎ Corresponding author. E-mail address: jafarian@modares.ac.ir (A. Jafarian). Energy Conversion and Management 188 (2019) 276–295 0196-8904/ © 2019 Elsevier Ltd. All rights reserved. T