California City Considers Restarting Desalination Plant To Fight Drought 420
First time accepted submitter SaraLast (3619459) writes in with news about Santa Barbara considering the restart of its desalination plant. "This seaside city thought it had the perfect solution the last time California withered in a severe drought more than two decades ago: Tap the ocean to turn salty seawater to fresh water. The $34 million desalination plant was fired up for only three months and mothballed after a miracle soaking of rain. As the state again grapples with historic dryness, the city nicknamed the "American Riviera" has its eye on restarting the idled facility to hedge against current and future droughts. "We were so close to running out of water during the last drought. It was frightening," said Joshua Haggmark, interim water resources manager. "Desalination wasn't a crazy idea back then." Removing salt from ocean water is not a far-out idea, but it's no quick drought-relief option. It takes years of planning and overcoming red tape to launch a project. Santa Barbara is uniquely positioned with a desalination plant in storage. But getting it humming again won't be as simple as flipping a switch."
Re:California = 1D10T Errors (Score:5, Informative)
Agriculture in the southwest (i.e. in the desert) is being killed by the lack of rainfall, which seems to have caught everyone by surprise. They're idiots first, farmers second.
Science is hard (Score:5, Informative)
It's that little bit about boiling the water. Converting water from liquid to gaseous phase (aka boiling) is energy intensive (read:expensive). To go from room temp water (we'll say 20C) to all of it vaporized and ready for condensation takes about 0.72kWh for each liter of water. So before you run the plant, pump the water, cool the condensate, and prep it for delivery, you've got that much energy going in. Even if you had no other costs, and you paid the lowest (tier 1) residential rates from So Cal Edison, you're looking at $0.36/gal for water. Add processing, markup, delivery...you're north of $1/gal, I'd bet.
Of course, that's why they don't generally use distillation, but even in your scenario the cost of "just boiling the water" adds up very, very quickly.
Re:now I never looked into it (Score:5, Informative)
To me all you need to do is boil water to strip the salt, you sell the salt and the water back.
The difficulty is not the ability to do it, it is that the energy requirements make it economically uncompetitive. Boiling that much water and then collecting the condensation generally takes a LOT of energy which is quite expensive in most cases. Places with a desert like climate and abundant energy resources (like the Middle East) can result in desalinization plants that are economically sensible but in much of the world it's just not competitive. Theoretically you could have a nuclear powered desalinization plant that might be economically competitive but I'm not aware that anyone has done this yet.
you sell the salt and the water back.
Doesn't work when it cost you more to get the salt and water than it costs to truck/pipe it in from elsewhere. Salt in this case is a byproduct but you wouldn't be able to sell it profitably or even on a breakeven basis given current prices in most places. Same with the water if it is being sold to farmers. It makes their crops economically uncompetitive with those from areas not experiencing drought.
Obviously it is more proccessing, and more expensive than getting just ground water or rain water because of that but how much more expensive can it really be?
Consult wikipedia [wikipedia.org] for a quick answer.
could it not be done in a way where we use the salt water in a new type of energy generating plant, that collects the steam and makes it usable?
There are waste heat desalinization plants being experimented with.
Re:now I never looked into it (Score:5, Informative)
Desalination plants don't boil water to filter the salt out. They use reverse osmosis, which typically requires about 3 kWh of electricity per cubic metre of water processed due to the very high pressure pumps required to force the water through the filters.
Re:now I never looked into it (Score:4, Informative)
As has been pointed out, desalination plants don't typically use distillation, they use reverse osmosis. That is to say that they use very high-pressure pumps to force the water through a membrane which rejects salt. Energy consumption is currently at about 3 kWh per cubic metre, although that's falling over time was membrane technology improves (the less pressure required, the lower the cost).
That works out to about 3 watt-hours per litre. Where I live, industrial power rates put that at $0.0001056 CAD per litre. Or $0.1056 CAD per cubic metre of water (thousand litres) if you prefer.
Obviously, if you live in a place that charges more for power (industrial power is $0.0352 per kWh here), that cost goes up.
Re:Science is hard (Score:5, Informative)
You may be unaware, but the density of solar radiation is only about 6 kWh per meter square per day. That means that each parabolic trench of a square meter is capable of producing only about 10 liters per day. You'd need 100 square meters to provide the water needs of a single ordinary house. And that's assuming 100% efficiency; it's more likely to be at least twice that and quite possibly an order of magnitude, by the time you've shipped it. Then you've got to clean up the gunk, and amortize in the costs of the setup.
I'm all for more solar powered stuff, but it's not the automatic, easy win we'd like it to be, even for something as simple as this. Heating water to the boiling point, only to recondense it a moment later, is expensive. I'm sure that clever design could reuse that heat and reduce the costs, but it's still going to be far from free.
Distillation versus Reverse Osmosis (Score:5, Informative)
Desalination plants don't boil water to filter the salt out
Incorrect. Quite a few of them do boil the water. Some through vaccuum distillation [wikipedia.org] which lowers the energy requirements but it still is boiling the water. Reverse osmosis is the principle competitive technology to distillation methods but both exist.
Re:California = 1D10T Errors (Score:4, Informative)
Why can't food be grown in the Great Plains instead of the Mojave Desert?
It is grown there. However we're draining a lot of the aquifers in the Great Plains too since we plant crops like corn that use a LOT of water.
Re:now I never looked into it (Score:5, Informative)
I'm not trolling. I just don't think you understand the scale of the problem.
To give the entire Sahara 28 inches of rainfall (which is the low end of what Iowa gets annually), you need 5.4 billion acre feet of water. By mass, that's 67 times the total amount of oil produced since 1850*. If you think the water business is the problem now, just wait until you see the management for that size of operation.
So where exactly do we get these 15,000,000,000,000,000 pounds of water? We could drain half of Lake Superior, but you specified rain barrels. That makes the math easy. Cherrapunji is often regarded as the wettest place on Earth, recording 1,041.75 inches of rainfall in a calendar year, which is 37 times what Iowa gets. That means we'd only need to cover an area 1/37th the size of the Sahara to get enough water, assuming it all has the same rainfall as Cherrapunji. Our total rain-barrel area is then only about 95,000 square miles, which would cover about half the area of France.
I guess you're right: The problem is politics and business. No government or corporation wants to try to build a rain-barrel raft half the size of France (or larger, since it won't all receive 1000 inches of rainfall per year).
* Wolfram Alpha is great for perspective.
Re:A drop in the bucket. (Score:4, Informative)
That means some rich guy will dictate who gets water.
Under the current system, rich farmers get subsidized water, while poor people in the cities pay high rates to fund those subsidies. It is almost inconceivable that any market based system could be more unfair than the current system designed by politicians.
What's that? CA votes dem? well, no water for you.
California as a whole votes Dem. Most of the Central Valley, which receives the water subsidies, votes Rep.
Re:And with that yoiu get POWER! (Score:5, Informative)
I guess the initial costs might be quite a big higher than just getting a pump and a semi-permeable membrane.
It takes an average of 3kwh to desalinate 1 m^3 of water via reverse osmosis. Per this report [worldwaterweek.org] it's 4-12 kwh of thermal energy to distill 1 m^3, plus 1.5-3.5 kwh of electricity.
If we figure on 10 kwh of thermal and we're setting stuff up so that we're down near 1.5 kwh of electric*, then consult a solar map [nrel.gov], we're looking at needing 2-3 m^2 of collector per m^3 of production a day(at 90% or so efficiency), and it only cuts electric costs in half.
That's 264 gallons of water/day, roughly enough for 2.5 people [wikipedia.org]. Household useage, not commercial or industrial.
Please note that these are using near optimal assumptions, I wouldn't be surprised if you need 2-10 times as much collector as what I've estimated.
*Pumping and such.
Re:A drop in the bucket. (Score:5, Informative)
So what you are objecting to the the Practice of Water Rights
Water Rights are a legal principle, not Federal Micromanagement. The water belongs to the person with the oldest rights to it first. Need isn't part of the equation.
The person who's water rights were established in 1849 have priority to the person who's water rights were established in 1999.
First come first served. Water Rights are inheritable and sellable. Those farmers have water rights that are older than the residents in the Cities. That is why they get first dibs. Not because they are propped up by the Federal Government. But because the process of water rights was established by Common Law, and supported by California and Federal Courts.
Re:And with that yoiu get POWER! (Score:5, Informative)
Their mothballed desalination plant won't be a reverse osmosis system. It will be an older flash distillation plant.
Probably steam powered. I ran and supervised the operation of 2 multi-stage 100,000 gallon per day flash distillation plants in the Navy. They have very few moving parts and were very reliable. They just took a ton of steam to operate. Steam for the ejectors that pulled the vacuum, and steam for the heating elements. Lots of electricity for the pumps.
But they are talking about a plant that can produce millions of gallons per day of fresh water. It will be very clean and soft too. Expect 0 hardness on the output. They probably will be adding minerals so the output has good flavor.
Re:And with that yoiu get POWER! (Score:5, Informative)