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Dry rock geothermal methods are currently being used in parts of the world for energy production, but Missimer says that the 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 water from the ground is converted to steam, that steam powers a turbine to create electricity, then the heated water is vented to the atmosphere while it's still hot—still over 100 degrees Celcius[sic] in most cases. Instead of venting, the team wants to use that hot steam in their desalination processes.
The first desalination process is multiple effect distillation (MED), which requires hot water (above 100 degrees Celsius), but the second process, adsorption desalination (AD), can be run on cooler water, says Missimer. As the steam moves through the system and cools, it is still effective for powering desalination. "Now you have an efficient system where you have conserved the latent heat that you've captured in the ground through three processes: turbine electricity generation, MED and AD."
At the end of the desalination process, Missimer says that distilled water and chilled water (from the AD process) are the final products. While the distilled water can be consumed, even the chilled water is reused—the cool water can be recycled through the plant to help with air conditioning.
(Score: 2) by stretch611 on Tuesday November 06 2018, @08:08PM (1 child)
Ok, I'm a software developer... not a chemist or engineer... So I am not sure if I am missing something in my reasoning here or not, but I think I have an obvious answer.
If you have geothermal turning heated ground water into steam vapor, wouldn't the easy way to produce desalinated water be to just cool down the steam vapor? A metal tube with cool air inside inserted into the flow of the hot steam vapor should allow water to condense on the outside and drip down into a gathering pool of fresh clean water.
If you need more desalinated water, just let some salt water drip down into the geothermal vent for it to heat up and create more steam vapor. The only issue I foresee with this approach is that if too much salt accumulates at the bottom, heating efficiency can be reduced, but if a simple method can be used to remove the salt buildup you should be ok.
Now with 5 covid vaccine shots/boosters altering my DNA :P
(Score: 0) by Anonymous Coward on Tuesday November 06 2018, @09:38PM
Yes, this works in principle. Instead of cooling the vapor as you describe, though, it would be more efficient to use a heat pump to move energy from hot steam into the water-to-be-vaporized. Such a heat pump could be powered by some clean energy source such as geothermal or solar.