Fresh Water from Nuclear Desalination Plants

[Paulanddiw]

Yeah we’re running out of gasoline and diesel and, yeah, we’re converting more and more of our food into fuel, but the real problem is shortage of water. Turning corn into gasohol will raise corn prices which will make more farmers plant corn. There are lots of farmers and lots of land. But, planting more corn diverts irrigations water that once grew food to growing gasohol. We need more fresh water. Some places need it to drink. But, if we are to grow gasohol, we’ll need a whole lot more than that.

We need nuclear power plants which dedicate their power to desalination plants. Imagine 20 nuclear-desalination installations on the east coast of the Sea of Cortez (Gulf of California) in Mexico. Each nuclear-desalination plant could produce about as much fresh water as the Grand Coulee Dam irrigation district which irrigates about ¼ of the state of Washington. Twenty nuclear-desalination plants on the Sea of Cortez could convert the Sonora Desert into lush farm land – where they'd grow sugar cane, corn, jerusalem artichokes, or what ever for gasohol. (Besides, the spin-off for trees, lawns, consumer lighting, etc. would be insignificant.)

It would be green. For every gigawat-hour nuclear produced, we’d be able to capture a lot more energy from the sun raising crops in what used to be desert.

 

[anorlunda]

Many here would agree with you.

 

[phyzguy]

Like @anorlunda said, many of us (including me) agree with you. It would also be much greener to expand our nuclear capability to generate greenhouse gas free electric power. Sadly, with the current public perception of nuclear power, making any of this a reality seems impossible.

 

[gmax137]

Each nuclear-desalination plant could produce about as much fresh water as the Grand Coulee Dam irrigation district which irrigates about ¼ of the state of Washington.

Can you show us the basis for this? I am not doubting it, rather I am curious as to the numbers used to come up it.

 

[artis]

@gmax137 maybe something is wrong with my browser but it seems the original poster posted the thread in 2008, and hasn't logged in since.

Nevermind, must be a glitch on my side as all posters today seem like they last logged in a decade ago.

PS.There was a experimental reactor made by Soviets in Kazakhstan which produced both electricity and provided heat for desalination (as I suppose the desalination plant was merged with the reactor as a unit)
https://en.wikipedia.org/wiki/BN-350_reactor

 

[anorlunda]

@gmax137 maybe something is wrong with my browser but it seems the original poster posted the thread in 2008, and hasn't logged in since.

Nothing wrong. We are cleaning up old threads with zero replies. When I posted a reply to this one, it pushed it to the top of the most recently updated list. There will be more in coming days.

Most desalinization plants today use reverse osmosis. But to do that with nuclear means throwing away 2/3 of the energy first to make electricity. Direct evaporation may be more attractive in the nuclear case. Or as you suggest, a combined solution electric+heat.

 

[gmax137]

Oops, sorry for the necroposting. I think we all do that, once in a while

 

[BWV]

So what is the cost relative to other sources of energy?

not sure if my conversions are correct:
quick googling finds

10-13 kilowatt hours (kwh) per every thousand gallons (https://www.energycentral.com/c/ec/desalination-and-energy-consumption)

EIA estimates (see the other thread on nuclear economics) list overnight construction costs of $5K per / kwh,

so $50K in upfront capital to produce a 1000 gallons/hr plus operating costs of $0.05 / kwh

I bet PV along the sea of Cortez would be cheaper - the same EIA numbers have $1.6-1.8K overnight construction and lower operating costs

but recycling might be even cheaper

Funny though the 2008 OP mentioned the whole purpose of the nuclear desalination was to raise crops for biofuels because oil for gas and diesel was going to run out. So the whole scenario was ridiculous. Not only was peak oil wrong, it would be much better to generate electricity for EVs than to use it to desalinate water to grow crops for biofuels.

 

[artis]

exactly because a nuclear plant is only max 30/35% efficient if it uses water/steam cycle and needs to produce electricity, so then using that electricity to get fresh water again there are some efficiency matters and then growing biofuels and we know that a small car engine is only some 10-14% efficient for gasoline and some 20% for diesel (or something along those lines) so in the end we spend a "ton" of nuclear energy to produce some biofuels which then are very inefficient themselves.

Maybe this whole thing look a bit better if the heat from the reactor is used directly for water production although I don't know the efficiency then I assume it is also not 100%.

 

[anorlunda]

This source gives a table.

MSF=multi stage flash
MED-TVC=Multiple Effect Distillation with Thermal Vapour Compression
MED=Multiple Effect Distillation
RO=reverse osmosis

RO appears to be the lowest. However the RO number does not include the thermal energy needed to produce the electricity. In the case of nuclear, multiply by 3, so that RO takes 9-10.5.

In rough numbers, it sounds like about roughly equal. Use nuclear heat to evaporate water directly, or use it to generate electricity and use the electric for RO desalinization.

But in terms of money rather than energy, using nuclear heat directly without steam, without a turbine, without a generator would be much cheaper.

Don't forget solar desalinization both direct and indirect. There are several schemes for that.
https://en.wikipedia.org/wiki/Solar_desalination

 

[DEvens]

A kw hour is about 10 cents to 15 cents. So 1000 gallons requires something in the range of $1 to $2 of electricity.

So it requires 27,154 gallons to water 1 acre of land to a depth of 1 inch. Call it $50. Yes, I hit the high end.

Corn needs about 25 such irrigation to grow.

https://articles.extension.org/pages/14080/corn-water-requirements
So one acre of corn, in a completely arid location, would require about $1250 worth of water.

Iowa's average yield for corn is 166 bushels per acre. Meaning the cost of electricity for irrigation is round about $7.5 per bushel.

https://crops.extension.iastate.edu/are-we-capable-producing-300-buacre-corn-yields

The maximum price for corn was about $8, and it it is currently sitting around $4.

https://www.macrotrends.net/2532/corn-prices-historical-chart-data
So, it's not absolutely impossible to grow corn this way. It would just require a lot of improvements to make it economical. Growing corn in places where it rains at least some of the time, and where you can get irrigation water from a river or lake, seems to be a lot cheaper. Maybe it makes sense to have it do a "tickle" and get you over the hump.

 

[PeterDonis]

yeah, we’re converting more and more of our food into fuel

This was true at the time of the OP (2008), but it is not true now; we finally seem to have figured out that it is more economical to use food as, well, food, instead of burning it as fuel.

This doesn't change the more general point that having nuclear-generated electricity displace fossil fuel-generated electricity has a number of advantages.