Energy recovery is necessary to make desalting cost-competitive.
The principle of the FTC is to take the salt out of the water, as opposed to reverse osmosis which takes the water out of the salt. After some time during the operation of the FTC, the electrodes will become saturated with salt. At this time, the capacitor will have to be discharged to remove the adsorbed salt. One way to discharge the capacitor of both its electronic and ionic charge is to simply short circuit the electrode leads through a resistive element. The designs discussed below feature energy recovery to make the FTC technology extraordinarily energy-efficient.