Pendulum clocks are an old fashioned way of keeping time. The pendulum swings back and forth, converting energy from kinetic to potential and back expending very little energy. A series of weights slowly tick down on their cords to replenish what little energy is lost in the pendulum operation.
back-and-forth motion might be ideal for use in saltworks, to increase evaporation by increasing the surface area of water exposed to air.
Some humidifier designs consist of a series of discs, which spin partially submersed in water. airborne dust particles attach to the wet discs, and then dissolve into the water, as the air is humidified.
So, with this idea, the wet discs are spun by the motion of the pendulum. Gears up the ratio, so that the discs actual spin about 2 full rotations with each swing of the pendulum.
There is an extra concern about potential microbes, like legionaire's disease, being released into the air in the mist, as well as scaling.
But, if worse comes to worse, all parts that actually touch water can be made corrosion-proof, and the seawater can be acidified before entering the pendulum tanks. Accomplishing seawater acidification can be done by seament electroaccretion-- eletrolytic reactions with cause magnesium hydroxide and calcium carbon to precipitate, leading to a more acidic process water. This will mean no scale, and no microbes.
the bitterns cannot be dumped back into the ocean if acidic, but they should be processed for potassium anyway in my opinion.