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Solar desalination dome promises record-low water price

Solar desalination dome promises record-low water price

Scaling up concentrating solar power

A new solar dome technology claiming to produce desalinated water cheaper than traditional methods is hoping to put Saudi Arabia’s new NEOM vision on the global water map.

Called “solar dome”, the decentralised solution uses concentrating solar power (CSP) technology to treat seawater.

With a predicted price of $0.34/m3, the team behind it claim the solution will be considered “significantly lower” than desalination plants using reverse osmosis (RO) membrane methods.

Developed at Cranfield University, UK company Solar Water will work with NEOM to develop the first project on a 26,500 km2 area in northwestern Saudi Arabia.

The first project is expected to be completed by the end of 2020.

How the “solar dome” works

Claimed to be 100 per cent carbon neutral, the process involves piping seawater under a “glass-enclosed aqueduct system”, which heats the water as it travels into the dome.

These structures, made from glass and steel, will vary in size from 20m to 120m, according to the company.

An array of parabolic mirrors, or “heliostats” that surround the sphere, concentrate the solar radiation onto the dome.

This transfers the heat to boil the seawater, creating a “cauldron effect” where the water is superheated. After evaporation, steam condensate is then piped as freshwater to reservoirs and irrigation channels.

Secondary treatment will then be necessary to create drinking water. More details on the process can be seen in the video below:

Interestingly, NEOM claims the process can also operate at night as solar energy generated throughout the day can be stored, suggesting energy storage or battery capabilities.

Another big claim is that this arrangement will “reduce the total amount of brine that is created”, as “no brine is discharged into the sea”.

With the by-product from desalination labelled as “one of the world’s greatest environmental challenges”, it raises the question of what happens to the concentrated brine?

Solar Water said it would gather at the bottom of the dome’s basin to be extracted and sold commercially.

This includes commercial by-products for industrial use, including lithium batteries, grit for roads, fertiliser or detergents.

Industry reaction on social media

Speaking to Aquatech Global, desalination industry veteran Leon Awerbuch said it’s currently difficult to assess the reality of the dome as very little technical information has been made available.

Speaking to Aquatech Global Events, he said: “The price of 0.34 $/m3 with high recovery is extremely ambitious, but there isn’t any information on energy recovery. Inside the dome, there could be scale deposition if they use high-temperature steam to focus on seawater. So there are challenges, I hope NEOM has experienced advisors.”

Awerbuch posted the dome announcement on LinkedIn, sparking mixed comments about whether the promised low price included capital costs (CAPEX), or was just the operating cost (OPEX).

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