Dealing with Drought

13.11.2007

It's kind of talking-pointy, but Daniel Weiss and Zoe Brown have a nice analysis of the ongoing droughts in both the Southeast and Southwest. Beyond flogging the usual (sensible!) conservation measures, they also make the good point that energy use is a major culprit here:

Power plants are voracious water users. Nuclear plants use 830 gallons of water per megawatt hour, and coal plants are right behind at 750 gallons per megawatt hour. If current power generation and energy demand trends continue, power plants will use 7.3 billion gallons a day by 2030. The Department of Energy reports that this equals all U.S. water consumption a decade ago.

The Atlanta Journal-Constitution caught onto this a few weeks ago, arguing that, seeing as how Atlanta's Lake Lanier is drying up, maybe it wasn't such a keen idea for the state to grant permits for a new coal plant that will consume "nearly 20 million gallons of water a day" from the Chattahoochee River, "putting an additional strain on metro Atlanta's major source of drinking water." (There's also that whole global warming thing, which is only going to dry out the region further.)

Conversely, wind and solar power use little water. But many states in the Southeast have strongly opposed renewable energy mandates—claiming that they can't live without coal. Georgia Governor Sonny Perdue commissioned an energy task force last year that, in the end, recommended a big push toward renewable power, but that proposal's now gathering dust in a filing cabinet. I wonder, though—if the AJC's any indication—if the water crisis could finally prompt folks to rethink their energy stance. (OK, more likely, they'll just conjure up a way to cool power plants without using so much water, but one can always hope...)

--Bradford Plumer

Posted: Tuesday, November 13, 2007 6:37 PM with 6 comment(s)

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stgla said:

I'm no scientist and I did not click your links, but is water use by power plants really using it up? It's like a water fountain -- looks like it's wasting water but it's the same water being pumped through the system over and over. And once you finish with it, you can still irrigate with it or whatever (assuming it's not contaminated).

November 13, 2007 2:16 PM

Brad Plumer said:

stgla -- A lot of water is lost due to evaporative heat loss during cooling. I assume that's what the AJC meant by "consumed" (i.e., they weren't including the water that's treated and then returned to the river).

November 13, 2007 2:30 PM

mjmckay said:

so how much would it add to costs to reclaim through closed circuit condensation and heat exchange?

I'm not an engineer, but could that be done or would the heat-exchanging efficiency of open evaporation be too difficult to make up in a closed system?

November 13, 2007 2:48 PM

mjmckay -- I've been curious about that too. Apparently there are some high-temperature reactors that can, in theory, be air-cooled, although it's not something I've really looked into (and don't know what the costs would be…)

As for coal, Duke Energy recently proposed an expansion to a coal plant in Charlotte and promised the new plant would draw 88 percent less water from the river, but still consume an additional 10 million gallons a day, so I wonder if that's still the best that can be done for now...

November 13, 2007 2:57 PM

thnx Brad-

your reply about air-cooled reactors prompts an odd thought that many in the CO2/Global Warming trenches have undoubtedly already considered: what are the global warming impacts of nuclear power?

If the heat generated by a reactor is dissipated into the atmosphere as IR radiation is that also just adding to the GW problem? The most basic problem with global warming is that CO2 (and other GW gases) are transparent to higher frequency electromagnetic radiation (sunlight) but opaque to lower frequency EM (infra-red released by the sunlight-warmed Earth). The energy comes in but it can't get out.

Now the nuclear industry has recently been touting nuclear generated electricity as a green, emissions-free power source. Many on the environmental left have also come around to accept that a large portion of the power grid will need to come from nuclear (at least in the mid-term). But have these advocates taken the contribution of nuclear power's thermal output into the equation? How much does adding thermal input (active warming) affect the picture? Or is it negligible?

Like many on the left, I was not a fan of corporatist nuclear power, but have recently been coming around to accept that it will need to play a bigger and bigger part in power generation, now this...

Just wonderin'

November 13, 2007 8:30 PM

dbhuff said:

Nuclear thermal loads on the planet would be miniscule. For instance, it is estimated that 10,000 sq miles of solar panels would be enough to completely replace all other sources of electrical power in the US. From this, one can conclude that the thermal load due to the sun (over 200,000,000 sq miles) would be minute in comparison.

Re: water use, solar photovoltaic doesn't use water, but the most efficient high capacity solar plants are thermal solar. These heat a working fluid and use that to drive a turbine, and they need cooling too, alas. While a lot of power plant water is returned, warmed, to the environment, even that has to be pretty cool in order not to mess up the environment. Cooling condensors would require a cold working fluid, and that would require energy, so it isn't very efficient to recapture the water. This doesn't mean it won't be done someday...depends how desparate we get.

November 14, 2007 2:24 PM