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Diagram of how the geothermal energy would be used for energy production, and two types of desalination (MED and AD). Red lines indicate hot water, while blue lines are cooled water. At the end of the process, it would be available for consumers and aquifer storage, and the water could be used in air conditioning for the plant. The whole theoretical system is carbon-neutral. Credit: Courtesy of Thomas Missimer. Credit: Geological Society of America
Water shortages are hitting some areas of the world hard, and with increasing global temperatures, more regions may be experiencing drought conditions.
Countries such as Saudi Arabia rely on desalinating plants to provide drinking water to their residents, producing 5 million cubic meters of desalinated water per day. The method requires a high amount of energy, which can not be used in the world.
Researchers have been working on renewable energy sources, and reduce the need for traditional fossil fuel-powered methods. Now, new research presents an untapped resource for powering desalination: geothermal energy.
"We're searching the world right now for better methods, low carbon methods, to create energy," says Thomas Missimer, of Florida Gulf Coast University. "Geothermal is one of those types of energies."
Missimer says geothermal provides energy in two ways: wet rock and dry rock. Wet areas, like Iceland, use the hot water from deep in the earth to provide energy to move turbines and produce energy. But this type of geothermal heat is rare.
On the other hand, dry rock geothermal potential is more wide-spread globally. Missing California, North Africa, and the Red Sea region-to heat water can be used to produce energy.
Dry rock geothermal methods are currently being used in the world for energy production, but Missimer says that heat can be used in more efficient ways, especially with desalination. Details of the new research constructing a geothermal energy-water campus will be presented on Monday at the 2018 Geological Society of America Annual Meeting in Indianapolis, Indiana.
Usually, geothermally heated to the ground, it is converted to steam, that steam powers a turbine to create electricity, then it is heated to the atmosphere while it is still hot-still over 100 degrees Celcius in most cases. Instead of venting, the team wants to use that hot steam in their desalination processes.
The first desalination process is a multiple effect distillation (MED), which requires hot water (above 100 degrees Celsius), but the second process, adsorption desalination (AD), says Missimer. As the steam moves through the system, it is still effective for powering desalination. "Now you have an efficient system where you have captured the power of generation, MED and AD."
At the end of the desalination process, Missimer says that distilled water and chilled water are the final products. While the distilled water can be consumed, the water is reused-the cool water can be recycled through the plant to help with air conditioning.
Lastly, the researchers propose to store excess water in aquifers for later use, which Missimer says is a future energy saver. "By storing some of that excess water, you are required to be in the system."
The benefits of a carbon dioxide system are more important than fossil fuels. It also has an economic benefit. "If you look at saving Saudi Arabia, saving 6 million barrels of oil a day, $ 100 has barrel-that's a bloody fortune," says Missimer.
Missimer says it is even more effective than a solar-powered plant, because it can be run 24 hours a day, compared to just daylight hours. He adds that the benefits really come with the efficiency of operation. "In a facility like this, if it's run properly, you're not consuming a resource," says Missimer, adding that the heat keeps flowing and is renewable.
For now, the idea is theoretical and has not been put into practice. But Missimer adds that the individual parts of the plant and the technology have been around for a while-it has not been combined. "We've learned that sometimes you do not need new technology to make advances," he says. "Sometimes it's piecing together old technology in a constructive way to provide more efficient operation." He and his colleagues are hoping to put their carbon-neutral ideas into practice in the near future.
Explore further:
Researchers pilot system using electrodialysis to produce safe drinking water
More information:
Linking Geothermal Electricity Generation with Multiple Desalination Process and Aquifer Storage and Recovery: A Method to Reduce Fossil Fuels Use and the Carbon Footprint of Many Global Regions. Geological Society of America Abstracts with Programs. Flight. 50, No. 6
DOI: 10.1130 / abs / 2018AM-320494, https://gsa.confex.com/gsa/2018AM/webprogram/Session45325.html
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