3 ms·

There's lots to unpack here why this isn't workable at scale. 1) Renewable energy product still has a cost associated with it, even if it is at times, excess.

by Maxion 3y ago

There's lots to unpack here why this isn't workable at scale. 1) Renewable energy product still has a cost associated with it, even if it is at times, excess. 2) That excess capacity, and the times when there's more energy produced than consumed might not match with water demand. 3) There definitely isn't, and won't be, enough excess renewable capacity to distill even a fraction of the fresh water consumed. 4) This means that you still have to calculate a per kWh cost for the energy consumed to distill salt water to fresh water. The average kWh might not be the same as the market average kWh price, since if you make your distillation plants oversized so you can utilize any spare energy production, but there will still be a price. 5) This price will most likely mean that the per gallon cost of distilled water will be higher than RO, or water pumped through a pipeline. Desalination is still an extreme measure taken when all other forms of fresh water are cost prohibitive.

jeffbee 3y ago
With the amount of curtailed energy this year in California, using a state-of-the-art RO process, we could have desalinated about 880k acre-feet of water. This is roughly enough water for all domestic urban water use statewide for about half the year. It is already close to penciling out and our energy resources are still expanding.
jjk166 3y ago
> 1) Renewable energy product still has a cost associated with it, even if it is at times, excess. This cost is already paid for in the infrastructure. You're not going to tear down extra solar panels when demand is low just to reinstall them an hour later. > 2) That excess capacity, and the times when there's more energy produced than consumed might not match with water demand. Water can be stored very easily in large quantities and over long periods of time. Replenishing an aquifer in the summer will still help you even when the dry season is winter. > 3) There definitely isn't, and won't be, enough excess renewable capacity to distill even a fraction of the fresh water consumed. You don't need to distill 100% of freshwater, you just need to make up the difference between what is naturally available and what is used. The difference is generally small, especially when combined with water conservation methods. California's water shortfall could be covered by using just 6% of it's current annualized electricity generating capacity for desalination. > 4) This means that you still have to calculate a per kWh cost for the energy consumed to distill salt water to fresh water. The average kWh might not be the same as the market average kWh price, since if you make your distillation plants oversized so you can utilize any spare energy production, but there will still be a price. You would presumably locate your desalination plant in an appropriate location and operate it at appropriate times such that your cost per kwh is substantially below normal market rate. > 5) This price will most likely mean that the per gallon cost of distilled water will be higher than RO, or water pumped through a pipeline. RO would be desalination. A pipeline is still taking water from somewhere else, the price depending heavily on where you're getting it from and the geography between you and the source. In many cases there isn't a suitable freshwater source to pull from. Certainly there are no fresh water sources so limitless and readily accessible as the world's oceans.

by Maxion 3y ago

jeffbee 3y ago

With the amount of curtailed energy this year in California, using a state-of-the-art RO process, we could have desalinated about 880k acre-feet of water. This is roughly enough water for all domestic urban water use statewide for about half the year. It is already close to penciling out and our energy resources are still expanding.

jjk166 3y ago

> 1) Renewable energy product still has a cost associated with it, even if it is at times, excess. This cost is already paid for in the infrastructure. You're not going to tear down extra solar panels when demand is low just to reinstall them an hour later. > 2) That excess capacity, and the times when there's more energy produced than consumed might not match with water demand. Water can be stored very easily in large quantities and over long periods of time. Replenishing an aquifer in the summer will still help you even when the dry season is winter. > 3) There definitely isn't, and won't be, enough excess renewable capacity to distill even a fraction of the fresh water consumed. You don't need to distill 100% of freshwater, you just need to make up the difference between what is naturally available and what is used. The difference is generally small, especially when combined with water conservation methods. California's water shortfall could be covered by using just 6% of it's current annualized electricity generating capacity for desalination. > 4) This means that you still have to calculate a per kWh cost for the energy consumed to distill salt water to fresh water. The average kWh might not be the same as the market average kWh price, since if you make your distillation plants oversized so you can utilize any spare energy production, but there will still be a price. You would presumably locate your desalination plant in an appropriate location and operate it at appropriate times such that your cost per kwh is substantially below normal market rate. > 5) This price will most likely mean that the per gallon cost of distilled water will be higher than RO, or water pumped through a pipeline. RO would be desalination. A pipeline is still taking water from somewhere else, the price depending heavily on where you're getting it from and the geography between you and the source. In many cases there isn't a suitable freshwater source to pull from. Certainly there are no fresh water sources so limitless and readily accessible as the world's oceans.