Comment by rtkwe
3 days ago
Correct it's massively energy intensive to filter the salt out the newest best ideas still use ~2 KWh/m3 of water and that's a lab system in perdue that batches the process instead of having it run continuously which is why current RO desalination systems require so much energy.
For a real world comparison, the Perth desalination plant claims ~4kWh/m3.
California pays other states to take its excess solar energy. Power for a project like this isn't the issue, actually building the system is the issue.
> California pays other states to take its excess solar energy
Intermittently. Essential services like water (with expensive fixed costs) aren’t a good fit for absorbing variable supply.
> Power for a project like this isn't the issue
California has the country’s most expensive power [1] in part due to policymakers constantly assuming it’s free.
[1] https://www.electricchoice.com/electricity-prices-by-state/
They wouldn't if you switched just Urban water use from natural sources to desalination. To do that you need to replace the ~5 million acre feet of water, ~6,167,400,000 m3, that goes into the Urban bucket which is all of the water used to keep people alive, clean, and all industrial uses of water. [0] That comes to ~ 12BkWh of energy needed to scale up batched reverse osmosis to take over just the life and job required water needs which is about 25% of the total solar power generated in all of 2025 via grid-scale solar farms. CA does export some during the day due to excess solar but is still a net importer of power.
[0] p2 of https://cwc.ca.gov/-/media/CWC-Website/Files/Documents/2019/...
Those are the numbers I was looking for - that means that (ignoring build-out costs) total desalination for CA would be on the order of 10% of the 3 gorges dam yearly output (max).
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> it's massively energy intensive to filter the salt out the newest best ideas still use ~2 KWh/m3 of water
Am I alone in thinking that doesn't sound like a lot? That would be something on the order of 10% of what major cities charge for tap water?
A scaled down perspective is….
The most efficient commercial desalinator for boats is 32 Watts a gallon.
Do you mean 32 Watt-hours / gallon?
Hard to say. The spec sheet calls out 4 Amps for the 12 Volt system or 32 Watts for a single gallon.
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