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

Water treatment, particularly desalination is a major global electricity user. Normally, electricity is produced via fossil fuel that has transportation and environmental impacts of pollution and carbon dioxide production. A recent investigation on the Red Sea coast of Saudi Arabia showed that there is high potential for development of hot dry rock geothermal energy that can be used to produce base-load electricity without use of fossil fuels. In order to increase efficiency and to reduce the cost of this energy extraction method, two desalination methods have been linked to geothermal electricity generation using the waste heat instead of venting steam to ambient. The water recovered from the well collection system will initially have a temperature of about 270 ˚C under pressure and will flash to steam before passing through the electricity generation turbine with a subsequent second pass through the turbines (steam temperature still high after first pass). The waste steam after electricity generation still has a temperature of 100 ˚C (hfg >2400 kJ/kg) so it can be used to desalinate seawater using the multiple-effect distillation process. After use in this desalination process, the condensate has a temperature ranging from 70 to 90 ˚C which allows it to be used a third time to feed an adsorption desalination (AD) unit. This unit produces both distilled water and a stream of chilled water. The distilled water from the AD unit is then split with some water going into the energy recovery system (for use in the injection and recovery wells) and the remainder utilized for drinking water. The chilled water is used to run the facility air-conditioning system and to enhance steam condensation. To balance seasonal water and electricity demands and to further improve plant efficiency, a conventional seawater reverse osmosis desalination plant along with an aquifer storage and recovery facility would also be constructed at the facility. This geothermal energy to electricity-desalination campus concept could be used at a large number of global sites in lieu of using hydrocarbon fuels.