Use of geothermal energy for seawater desalination in the Galápagos Islands, Ecuador

Abstract

The lack of reliable sources of potable water is a health and social problem in the Galápagos. The presence of geothermal resources in the islands opens a window of opportunity for the development of a geothermal energy-driven desalination system. Analysis on the available research studies on three shield volcanoes located on the western side of Isabela Island, reveals that Alcedo Volcano presents the most active hydrothermal system with a liquid-dominated reservoir. This type of system is suitable to achieve the separation of nearly salt-free fresh water by implementing a Single Stage Flash Geothermal desalination system (SSF-G). The concept implies the use of geothermal brine from a separator unit as the heat input source for desalination, while producing electricity from the steam to power the plant totally detached from the grid. Results from a thermodynamic model and exergy analysis of the system, using Engineering Equation Solver (EES) software, show that the geothermal resource can be successfully coupled to this desalination method. It also reveals that most of the energy received from the well, exits the plant while still containing substantial exergy, which can be used to perform usable work by the system.

As a result of irreversibilities, exergy destruction occurs in all the heat exchangers of the desalination process. As the area under study is within a National Park, the impacts of the plant need to be considered especially. An accounting framework that measures social, environmental and financial performance in terms of sustainability was undertaken in this study. It indicates that an improvement in water quality on Isabela Island, using geothermal energy, would have significant positive impacts on these dimensions of performance. Detailed geophysical studies using AC resistivity methods, and an exploratory drilling campaign is needed to achieve more conclusive information about the feasibility of this project. The results, collected from these studies will help obtaining more information regarding the cap rock, host rock, and hydrothermal alteration of the geothermal prospects located in the Island.