Wednesday, March 18, 2015

California is running low on water and looks to the sea for help

The Guardian recently ran a headline story informing us that California has only a year of water left. This picture of the very lean snowpack on the mountains is not very encouraging, perhaps even a bit unnerving.



Yet, there are some who say that the situation in California isn't all that dire. Weather.com is running a story on the same subject and here is what Jay Lund, director at the UC Davis Center for Watershed Sciences, has to say: "It's not the right impression (to say) that one more year of this and we're toast. There's quite a bit more water left in groundwater, but a little bit less every year, because they're pumping it out to make up for the drought."

So water desalination is reaching the top of the to-do list again. In Carlsbad, California, after nearly a decade of political fighting, permitting and lawsuits, a water desalination plant is preparing for production. The plant is controversial for many reasons, the primary one being that it will be energy intensive and much more expensive than other means of fresh water production. After all, Nature already knows how to make fresh, potable water.

Water desalination has other problems. like what to do with the salt. I like sea salt, really. But what are we going to do with the brine that comes from desalination? I think that is a minor problem compared to the other problem, where are we going to get the green energy to support such efforts.

Yes, we could use solar power, but in my search for solar powered desalination projects, I could not find a single commercial scale plant in operation yet. Most are still in development or testing stages. Although it seems possible to supply water to many people just for desalination, I don't see that happening on a large scale with solar power.

Ultimately, we will need a compact, small footprint solution to power desalination. Alvin Weinberg, invented the light water nuclear reactor and the molten salt nuclear reactor. Seawater desalination is one of the uses he had in mind for waste heat from a molten salt reactor. The reactor would run on thorium, an element that is plentiful in the crust of the earth. There are many benefits to thorium reactors and they are far cleaner than coal or gas fired power plants. There is even one company that claims that with modular power plant construction, energy production would be cheaper than coal in about 4 years.

The use of waste heat from nuclear power plants for industrial uses, like desalination, doesn't get much press. That's because the vast majority of power plants are light water reactors. Thorium molten salt reactors run at temperatures far higher than light water reactors. This can provide the excess heat needed to desalinate water. All Generation IV reactors are being designed to run at a higher temperature for greater efficiency. The higher temperatures will allow for excess heat to be used for industrial processes. But thorium, being far more abundant, holds a definite advantage. The main obstacle holding it back in the US is a regulatory framework that would permit its use as a nuclear fuel.

New desalination techniques hold promise for greater efficiency and waste management. Here is one that relies on a temperature differential between the sea water and cold distilled water. Other processes rely upon pressure to pass the water through a filter. Either way, energy is required to separate the salt from the water. The concentrated brines are a problem, but they can be a solution. In fact they have many environmentally friendly industrial uses, described here. We may find that desalination is better than mining, after all.

Perhaps now, with the impending water crisis on the horizon, the political will to bring thorium molten salt reactors online for seawater desalination will appear. Just in time.
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