Thermal desalinator

The Thermal desalinator is a water production building that converts steam into fresh water. It is most useful when a factory already has access to waste steam from sources such as power plants, exhaust scrubbers, or arc furnaces, since that steam can be recovered instead of being discarded. The building supports multiple recipes, including high steam, low steam, and depleted steam, which makes it a flexible option for turning otherwise reusable heat into water.

Its main tradeoff is between water output, steam quality, and where the energy cost is paid. High steam produces more water than low steam, but it also consumes much more energy, making it a poor choice compared with siphoning low steam from an existing power system. Depleted steam is the cheapest recipe in terms of direct electrical demand, but it shifts the burden onto the electrical grid because the desalinator itself uses power and then needs additional electrical generation to replace the steam energy that would otherwise have been produced elsewhere.

A key detail is that steam is not entirely “lost” when used for water recovery. Every unit of steam can be turned into 0.75 water by a cooling tower for free, so the apparent output of a desalinator can be misleading if the steam could have been cooled instead. This is especially important for depleted steam: although a desalinator using depleted steam may appear very productive, part of that water would have been available anyway through cooling towers. In practice, the net gain is lower than the raw recipe output suggests.

• Depleted steam is the most electrically demanding option, even though it uses the least direct power at the building itself, because the lost steam energy must still be replaced.
• Low steam is generally more efficient than high steam for desalination, since high steam gives only a small increase in water output for a much larger increase in energy cost.
• The most practical use case is often to route waste steam from existing systems into desalinators, rather than creating steam solely for desalination.
• When comparing designs, the real question is not only how much water the building outputs, but how much extra water it provides beyond what a cooling tower would have recovered anyway.

For planning purposes, the thermal desalinator is best treated as a steam recovery building rather than a standalone water source. It is strongest in integrated industrial layouts where steam is already being produced continuously, and where the player can balance the tradeoff between fuel usage, electrical demand, and water supply.