Seawater Desalination via Waste Heat Recovery from Generator of Wind Turbines: How Economical Is It to Use a Hybrid HDH-RO Unit?

Abstract

Over recent years, the concept of waste heat recovery from the generators of wind turbines for driving a thermal-driven desalination system was introduced, and its advantages were highlighted. However, any selection of a bottoming thermal-driven desalination system among different existing technologies should be taken under consideration before making an ultimate recommendation. Unfortunately, no comprehensive comparison is available in the literature to compare the performance as well as the cost aspects of using the waste thermal energy of the generator of a wind turbine for desalinating seawater, comparing them with those of a layout where the power of the wind turbine is directly supplied to a mechanically driven desalination system for the same amount of drinkable water production. This study aims at analyzing the economic aspects of waste heat recovery from the generators of wind turbines for seawater desalination via the humidification-dehumidification (HDH) approach, versus the reverse osmosis (RO) unit. For this purpose, a closed-air water-heater HDH unit, directly coupled with a RO unit (called a hybrid HDH-RO unit) is employed, in which thermal energy is provided by the heat dissipating from the generator of the wind turbine while its power is supplied directly by the wind turbine. The energetic and exergetic performance, along with the cost aspects of a hybrid HDH-RO unit driven by the wind turbine, are compared with those of a solo RO unit. The results of the study were extended for six different types of wind turbines, and we concluded that the unit cost associated with the freshwater produced by the waste heat recovery approach is astronomically higher than that of the solo RO system for all wind turbine models, and hence is not practically feasible. It was found that more power can be recovered from the discarded brine from the solo RO unit than the hybrid HDH-RO unit. In addition, the solo RO desalination system, working directly with the power of the wind turbine, has a less complex configuration, and hence its investment cost rate is significantly lower than that needed for setting up an HDH-RO unit. At high wind speeds, however, the cost penalty associated with the freshwater produced by the HDH-RO unit decreases, but it is still huge. Among all screened wind turbines, the GW-136/4.8 is most appealing in terms of greater power generation, but its investment cost rate is the highest among all models due to its high rated power value. However, the freshwater unit cost of the GW-136/4.8 is significantly lower than the values obtained for other models. Finally, the two locations of Manjil and Zabol are selected as a benchmark and the results of the simulation are extended for these locations.