Osmotic Steam Condenser

A steam engine's efficiency depends primarily on the pressure differential between it's intake and it's exhaust.

The typical way of providing a low pressure exhaust for a steam engine is to route the used steam into a condenser, which removes heat to turn the steam into water, and then use a pump to remove the condensed water, and a compressor to remove any air that leaked into the condenser.

This idea is to provide a low pressure exhaust for a steam engine using a different method. Namely, route the used steam across an osmotic membrane, and pump salt water across the other surface of the membrane. There is no condensate, so no pump is needed to remove that; a compressor is, however needed, for the same reason as it is needed with a condenser.

The salt water's affinity for fresh water will pull the steam through the membrane, in a manner identical to that which occurs in an pressure retarded osmosis power plant.

This method should require less salt water to remove a given amount of steam than if we were merely using that water to condense the steam by removing heat.

Furthermore, it should be able to operate at lower steam pressure than a condenser, producing a more efficient steam engine.

A disadvantage is that it doesn't produce condensate, which means that water for the steam engine must be continually resupplied.

The ideal location for a power plant using this method would therefor be the same as the ideal location of an osmotic power plant -- close to both a wastewater treatment plant and a desalination plant.

The wastewater plant produces water that's quite pure (but which (at least in America) can't legally be used as drinking water) and is thus ideal to be fed to the steam engine's boiler with minimal treatment, while the desalination plant produces concentrated salt brine, which has greater steam removal ability than mere seawater.