Wednesday, May 06, 2009

Depleted Cranium on Nuclear Desalination Plants

Here are some interesting facts on the potential of nuclear desalination plants:

Assuming that the same efficiency as the BN350 [reactor] setup were achieved in a conventional regenerative steam distillation plant, such a two-reactor [8-9 GW thermal APWR and EPR] driven desalination plant could therefore deliver about one million cubic meters of water per day (over one quarter of a billion US gallons), as well as more than half a gigawatt of electricity - more than enough for all plant operations as well as activities like pumping water, operating equipment and other internal activities.

To put this another way, since one acre-foot is equal to 1234 cubic meters, such a desalination plant could produce 810 acre-feet of water per day or about 283,500 acre-feet per year. What that equates to: Slightly less than half the water consumed by the entire city of Los Angeles.
Facts like these make me believe that we won't have serious water consumption problems in the future. If we run out of fresh water, the technology is already there for us to easily adapt to desalinating sea water.

Also worth noting, the proposed EPR unit at Calvert Cliffs, besides producing electricity, will be a desalination plant, though the water will only be used for plant purposes:
Unique to Unit 3 will be a desalination plant to produce potable water using reverse osmosis. The desalination plant will produce up to 1,250,000 gallon of potable water per day for Unit 3 and supporting facilities with total dissolved solids (TDS) less than 400 parts per million (ppm). The source for the desalination plant will be the brackish bay water from the makeup supply to the circulating water system. The TDS for the brackish bay water runs 10,000-15,000 ppm. The potable water will be distributed as makeup water for the demineralized water system, miscellaneous potable water services, fire protection and source water for the four ultimate heatsink cooling towers used during normal shutdown and power operation.

5 comments:

Jose C said...

big deal on the RO unit at Calvert - we did the same at the JEA for our plants back in the 70's, and they were oil fired. Just needed real clean make up water for the system, and it was cheaper than boiling the river water we used as a source.

George Carty said...

What about solar desalination? I'm surprised there isn't more interest, given the following factors:

1) Intermittency isn't the killer that it is for grid generation, because the final product (fresh water) can be stored in lieu of the energy used to produce it.

2) The areas that are in the greatest need of desalinated water are in deserts, where solar energy shines best

3) Many of these areas are in the Middle East, and Arab governments may be reluctant to build nuclear reactors for fear that Israel will bomb them (a la Osirak)

Thoughts?

perdajz said...

George,

The same argument that goes against solar power in the production of electricity applies to the solar production of anything. Even more so, in this case, because as you correctly point out, storage and transmission of water are not nearly the problem that storage and transmission of electricity is. Instead of tapping into hundreds of watts/m^2 with solar power, you can tap into hundreds of thousands of watt/m^2 with nuclear power. As with anything, if it were possible to do it with solar power, it would have been done centuries ago. It's not like you're the first person to have this idea, and noone ever imagined using the sun for energy before. Its just that solar power is quite feeble in relation to desalination needs.

Also, reactors can be built in deserts, just like Palo Verde.

George Carty said...

As with anything, if it were possible to do it with solar power, it would have been done centuries ago.Good point, especially as unlike solar electricity generation, solar desalination does not require any exotic technology.

Perhaps it was not used for historical reasons? Thinking of the Middle East again, it only became sufficiently populous to need desalination in the 20th century, at which point using the vast oil reserves of the area - both to power desalination directly and to pay for imported food to reduce the need for water - for this purpose was too tempting to resist.

Also, reactors can be built in deserts, just like Palo Verde.I never said they couldn't - I was merely saying that solar power does best in deserts.

I wonder if I was motivated by some fundamentally irrational concern about an energy monoculture. (Maybe it won't be so much of an issue in the future if we end the LWR monoculture within nuclear energy...)

George Carty said...

Incidentally, how can the efficacy of renewable energy sources (which is naturally measured in power per unit area), be compared with that of non-renewable energy sources (which is naturally measured in energy per unit mass)?