Geothermal desalination
Template:Desalination Geothermal desalination refers to the process of using geothermal energy to power the process of converting salt water to fresh water. The process is considered economically efficient, and while overall environmental impact is uncertain, it has potential to be more environmentally friendly compared to conventional desalination options.<ref name=":1">Template:Cite journal</ref> Geothermal desalination plants have already been successful in various regions, and there is potential for further development to allow the process to be used in an increased number of water scarce regions.<ref name=":0">Template:Cite journal</ref>
Process explanationEdit
Desalination is the process of removing minerals from seawater to convert it into fresh water. Desalination is divided into two categories in terms of processes: processes driven by thermal energy and processes driven by mechanical energy.<ref name=":3">Template:Cite journal</ref> Geothermal desalination uses geothermal energy as the thermal energy source to drive the desalination process.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
There are two types of geothermal desalination: direct and indirect.<ref name=":1" /><ref name=":3" /> Direct geothermal desalination heats seawater to boiling in an evaporator, then transferring to a condenser.<ref name=":4">Template:Cite book</ref> In contrast, indirect geothermal desalination converts geothermal energy into electricity which is then used for membrane desalination.<ref name=":4" /> If the geothermal energy is used indirectly, it can be used to generate power for the water desalination process, as well as excess electricity that can be used for consumers.<ref name=":5">Template:Cite journal</ref> Similarly, if the geothermal energy is used directly, the excess geothermal energy can be used to drive heating and cooling processes.<ref name=":5" />
ApplicationsEdit
CurrentEdit
One use of geothermal desalination is in producing fresh water for agriculture.<ref name=":7">Template:Cite journal</ref> One example of agricultural applications of geothermal energy is the Balcova-Naridere Geothermal Field (BNGF) in Turkey.<ref name=":7" /> However, arsenic and boron, two potentially toxic elements, have been found in the geothermal water used to generate electricity.<ref name=":7" /> Since the construction of the geothermal desalination plant in this region, these toxic elements have contaminated freshwater wells, rendering this water unusable for agriculture.<ref name=":7" /> Due to the increase in contamination in the surrounding environment, this project is not considered a success.<ref name=":7" />
Another use of geothermal desalination is the production of drinking water, as shown by the Milos Island Project in Greece, which relied entirely on geothermal energy to produce desalinated water.<ref name=":3" /> This plant was constructed because geothermal energy is readily available in this region, as Milos Island is located in a volcanic region, which makes using geothermal energy a viable way to power the desalination of salt water.<ref name=":3" /> The Milos Island plant utilizes a combination of direct and indirect desalination.<ref name=":3" /> Unlike the BNGF project, this is considered a success as it produced drinkable water without polluting the environment at a low cost using only geothermal energy.<ref name=":3" />
Future potentialEdit
Research indicates geothermal desalination can be implemented in some regions with water scarcity, as it is a relatively low cost solution to increasing available fresh water.<ref name=":0" /> In particular, two regions that have ample geothermal resources and are experiencing water scarcity are California and Saudi Arabia.<ref name=":0" /> Because these regions already have existing desalination plants, implementation of geothermal desalination plants would be relatively easy.<ref name=":0" />
Furthermore, as the technology for producing geothermal energy improves, geothermal desalination will become possible in more regions.<ref name=":0" /> Technologies that are currently being developed will allow the geothermal water used to produce energy to be the water that becomes desalinated.<ref name=":0" /> This will allow regions that are not close to an ocean to perform geothermal desalination, which will widely expand the potential for regions to perform geothermal desalination.<ref name=":0" />
Environmental impactsEdit
Much of the environmental impact in the geothermal desalination process stems from the use of geothermal energy, not from the desalination process itself. Geothermal desalination has both environmental benefits and drawbacks.<ref name=":1" /> One benefit is that geothermal energy is a renewable resource and emits fewer greenhouse gasses than non-renewable energy sources. Another benefit to the environment is that geothermal energy has a smaller land footprint compared to wind or solar energy.<ref name=":8">Template:Cite journal</ref> More specifically, the land usage required for geothermal desalination site has been estimated to be 1.2 to 2.7 square terameters are required for each megawatt of energy produced.<ref name=":0" />
One environmental drawback is due to geothermal desalination being an energy intensive process; the energy consumption ranges from about 4 to 27 kWh per square meter of the desalination plant.<ref name=":1" /> Moreover, some researchers are concerned that due to lack of regulation on carbon dioxide (Template:CO2) emissions from geothermal plants, particularly in the United States, there are significant detrimental Template:CO2 emissions from these plants that are not being measured.<ref name=":2">Template:Cite journal</ref> Geothermal power has been found to leak toxic elements such as mercury, boron, and arsenic into the environment, meaning geothermal desalination plants are a potential health hazard for their surrounding environment. Ultimately though, the long term environmental consequences of geothermal power desalination plants are still not clear.<ref name=":2" />
Economic factorsEdit
Geothermal energy is not dependent on day or night cycles and weather conditions, meaning it has a high-capacity factor, which is a measure of how often a plant is running at maximum power.<ref name=":8" /> This provides a stable and reliable energy supply.<ref name=":8" /> This also means that geothermal desalination plants can operate in any weather condition at any time of day.<ref name=":8" /> In terms of capacity, the United States, Indonesia, Philippines, Turkey, New Zealand, and Mexico accounted for 75% of the global geothermal energy capacity.<ref name=":9">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It would be the most economically feasible to perform geothermal desalination in these countries due to their geothermal energy capacity.<ref name=":9" />
For membrane desalination specifically, using geothermal energy reduces cost compared to using other energy sources.<ref name=":0" /> This is because geothermal power is traditionally produced at a competitive cost compared to other energy sources including fossil fuels; a 2011 study estimates the cost to be $0.10/kWh.<ref name=":0" /> Specifically, the US Department of Energy has estimated that geothermal desalination can produce desalinated water at a cost of $1.50 per cubic meter of desalinated water.<ref name=":0" />
HistoryEdit
The exact origins of geothermal desalination are unclear; however some early work is credited to Leon Awerbuch, a scientist working in Research & Development at the Bechtel Group at the time, who proposed the process of using geothermal energy for water desalination in 1972.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref> In 1994, a prototype that used geothermal energy to power desalination was built by Caldor-Marseille.<ref name=":32">Template:Cite journal</ref> This prototype was able to produce a few cubic meters of desalinated water per day.<ref name=":32" /> In 1995, a geothermal desalination prototype plant was built in Tunisia, which is one of the earliest documented cases of a geothermal desalination plant. Its capacity was three cubic meters of water per day, which could meet the needs of the surrounding communities. The cost of water was estimated to be $1.20 per cubic meter.<ref>Template:Cite book</ref>