Posted: Feb 14, 2020 12:10 pm
by GrahamH
This may be a form of
Multiple-effect distillation
Multiple-effect distillation (MED) works through a series of steps called "effects".[10] Incoming water is sprayed onto pipes which are then heated to generate steam. The steam is then used to heat the next batch of incoming sea water.[10] To increase efficiency, the steam used to heat the sea water can be taken from nearby power plants.[10] Although this method is the most thermodynamically efficient among methods powered by heat,[11] a few limitations exist such as a max temperature and max number of effects.
https://en.wikipedia.org/wiki/Desalinat ... onsumption

At much lower temperature. Inflowing seawater could cool the condensers and be pre-heat ahead of the next stage of evaporator. If solar heating is added at each stage, and each condenser is cooled by inflow, you might get some efficiency gains compared to a single stage solar distillation system. Still such a series of stages must have a lower thermal gradient in each stage so there would be diminishing returns. Each stage, input to output, will be less efficient with a warm condenser than if the condenser was at the lowest possible temperature (seawater temperature).

The most efficient technique seems to be reverse osmosis at 3 - 5.5 kWh.m3 which might be run using a solar powered electrical pump.

https://en.wikipedia.org/wiki/Desalinat ... onsumption

Assuming PV generation of 300W/m2 (a crude guestimate)

0.3/5.5 -> 0.0545m3/h or ~12 gallon/m2/h in full sun.

So, ignoring the silly efficiency numbers, it doesn't seem too far fetched to run desalination plant on solar energy

Although RO is not maintenance free, according to Wikipedia.