Comparative 4E analysis for solar desalinated water production by utilizing organic fluid and water

In this paper design and analysis of energy, exergy, economic and the environmental impacts (4E) of direct twostage reverse osmosis (RO) system have been optimized for supplying Miarkelar water, north of Iran using multiobjective optimization. In this city, water has been provided for a period of 20 years and at the end of this period water is supplied for a population of 12,125 people. The calculation was based on the Caspian Sea water maximum TDS up to 13,000 ppm and permeate production of 4000 m3/day. The results present that optimal recovery and final price per cubic meter are respectively 76% and 0.37$. Feed water should be 10 °C preheated in power generation cycle condenser. Power needed for pumping is 362 kW. Based on these data, the organic fluids R290 and R717 have been selected for Organic Rankine Cycle (ORC), which have negligible environmental impacts than other fluids. Energy and exergy analysis was done according to this selection. Finally, considering the optimal design of a solar farm being matched with the HRSG with known Pinch and Approach temperatures, the results indicated that, R290 has the lowest desalinated water production cost compared with water and R717 and its cost is 0.568$ per cubic meter. © 2015 Elsevier B.V. All rights reserved.

This paper focuses on designing a system with minimal environmental impacts and water supply capability for Miarkela. RO system has been selected with respect to these criteria. At first, the system was optimized by GA. Then the power generation cycle of optimized RO system was chosen according to these facts: 1- Preheating increases the desalinated water flow rate. 2- Usual condensers operate within 10 °C cooling water temperature difference. The results indicate that organic fluid utilization reduces HRSG construction costs. This cost reduction is due to the saturation temperature decrease and thus, a supposed high Pinch temperature for them. To design a power generation cycle with water as working fluid, HRSG should comprise three heat exchangers to achieve favorable steam quality. The superheater produces high temperature steam for the turbine to generate desirable work. Yet organic fluids have enough steam quality to enter the turbine whereas they are saturated at the HRSG outlet. That Fig. 13. Price changes of designed HRSG and pumps with respect to fluid type.