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Solar-powered desalination system requires no extra batteries

(news.mit.edu)
130 points bentocorp | 2 comments | 17 Nov 24 22:06 UTC | HN request time: 0.415s | source
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terramars ◴[18 Nov 24 14:42 UTC] No.42172669[source]▶
This is a questionable way to present what's an excellent project and hopefully soon to be commercialized technology. The big deal here is it's a presumably installation ready application of EDR for desalination instead of RO which most systems use. This is a big deal because the membranes use electricity instead of pressure as the filter, which means everything can run at low, normal plumbing, pressures instead of the crazy high pressure RO stuff. For seawater it's borderline whether or not it will match RO for performance, but for lower salinity groundwater and industrial wastewater, it should be significantly higher performance for the same power as well as lower maintenance and capex.

The no batteries thing is basically irrelevant to the innovation, and in fact Genius Water already offers no battery RO systems, also with questionable benefit (as well as being difficult to work with).

I run a solar and water focused EPC in East Africa and will hopefully be working with these guys in the future when they're off the ground with a commercial system. The potential is extremely high, particularly if the maintenance overhead and operational complexity can come down in practice.

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1. hedora ◴[18 Nov 24 15:16 UTC] No.42173073[source]▶
Yeah; the solar part is really questionable. In an installation without batteries, they’d need an additional large tank to store excess daytime output.

Without such a tank, they’d need to somehow power the thing at night, which means a big battery, just like RO.

Also, the article suggests the power input needs to be steady and they use a computer to run it at higher rates when the battery would be charging.

Assuming there is a small battery or power grid (as both systems require), you could oversize an RO system and then change its duty cycle to keep the batteries at (say) 80% to prevent the solar production from curtailing. Round-tripping electricity through our home battery loses about 20%.

So, the “advantage” boils down to two questions that the article doesn’t answer: (1) what are the relative energy efficiencies of this system (in theory) vs RO? If the new system is 20% worse, RO wins, regardless of this optimization (2) what is the relative equipment cost vs. max throughput? (Since both setups assume oversizing to get better solar utilization).

I’d also like to know if the new system requires plastic, since the RO membrane probably leaches all sorts of nasties into its output.

I do like the fact that they are focusing on brackish water. We have this problem even in the coastal US (in the form of water softener output), and I’m sure they could sell a premium alternative to RO as a way to get scaling advantages on the manufacturing of the equipment.

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2. cryptonector ◴[18 Nov 24 17:51 UTC] No.42174901[source]▶
Tanks are fairly cheap, and you'll need one anyways. But yeah, the solar angle is not what's interesting here. It's the electrodialysis.